Add support for MaxLinear/Exar USB to serial converters

Add support for MaxLinear/Exar USB to Serial converters. This driver only supports XR21V141X series but it can be extended to other series from Exar as well in future.

This driver is inspired from the initial one submitted by Patong Yang:

https://lore.kernel.org/linux-usb/20180404070634.nhspvmxcjwfgjkcv@advantechmxl-desktop

While the initial driver was a custom tty USB driver exposing whole new serial interface ttyXRUSBn, this version is completely based on USB serial core thus exposing the interfaces as ttyUSBn. This will avoid the overhead of exposing a new USB serial interface which the userspace tools are unaware of.

Signed-off-by Manivannan Sadhasivam <[email protected]>

---
 drivers/usb/serial/Kconfig     |   9 +
 drivers/usb/serial/Makefile    |   1 +
 drivers/usb/serial/xr_serial.c | 599 +++++++++++++++++++++++++++++++++
 3 files changed, 609 insertions(+)
 create mode 100644 drivers/usb/serial/xr_serial.c

drivers/usb/serial/Kconfig +9 -0

index 4007fa25a8ff..32595acb1d1d 100644
@@ -644,6 +644,15 @@ config USB_SERIAL_UPD78F0730
 	  To compile this driver as a module, choose M here: the
 	  module will be called upd78f0730.
 
+config USB_SERIAL_XR
+	tristate "USB MaxLinear/Exar USB to Serial driver"
+	help
+	  Say Y here if you want to use MaxLinear/Exar USB to Serial converter
+	  devices.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called xr_serial.
+
 config USB_SERIAL_DEBUG
 	tristate "USB Debugging Device"
 	help

drivers/usb/serial/Makefile +1 -0

index 2d491e434f11..4f69c2a3aff3 100644
@@ -62,4 +62,5 @@ obj-$(CONFIG_USB_SERIAL_VISOR)			+= visor.o
 obj-$(CONFIG_USB_SERIAL_WISHBONE)		+= wishbone-serial.o
 obj-$(CONFIG_USB_SERIAL_WHITEHEAT)		+= whiteheat.o
 obj-$(CONFIG_USB_SERIAL_XIRCOM)			+= keyspan_pda.o
+obj-$(CONFIG_USB_SERIAL_XR)			+= xr_serial.o
 obj-$(CONFIG_USB_SERIAL_XSENS_MT)		+= xsens_mt.o

drivers/usb/serial/xr_serial.c new file +0 -0

new file mode 100644
index 000000000000..e166916554d6

drivers/usb/serial/xr_serial.c new file +91 -0

+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/tty.h>
+#include <linux/usb.h>
+#include <linux/usb/serial.h>
+
+struct xr_txrx_clk_mask {
+	u16 tx;
+	u16 rx0;
+	u16 rx1;
+};
+
+#define XR_INT_OSC_HZ			48000000U
+#define XR21V141X_MIN_SPEED		46U
+#define XR21V141X_MAX_SPEED		XR_INT_OSC_HZ
+
+/* USB Requests */
+#define XR21V141X_SET_REQ		0
+#define XR21V141X_GET_REQ		1
+
+#define XR21V141X_CLOCK_DIVISOR_0	0x04
+#define XR21V141X_CLOCK_DIVISOR_1	0x05
+#define XR21V141X_CLOCK_DIVISOR_2	0x06
+#define XR21V141X_TX_CLOCK_MASK_0	0x07
+#define XR21V141X_TX_CLOCK_MASK_1	0x08
+#define XR21V141X_RX_CLOCK_MASK_0	0x09
+#define XR21V141X_RX_CLOCK_MASK_1	0x0a
+
+/* XR21V141X register blocks */
+#define XR21V141X_UART_REG_BLOCK	0
+#define XR21V141X_UM_REG_BLOCK		4
+#define XR21V141X_UART_CUSTOM_BLOCK	0x66
+
+/* XR21V141X UART Manager Registers */
+#define XR21V141X_UM_FIFO_ENABLE_REG	0x10
+#define XR21V141X_UM_ENABLE_TX_FIFO	0x01
+#define XR21V141X_UM_ENABLE_RX_FIFO	0x02
+
+#define XR21V141X_UM_RX_FIFO_RESET	0x18
+#define XR21V141X_UM_TX_FIFO_RESET	0x1c
+
+#define XR21V141X_UART_ENABLE_TX	0x1
+#define XR21V141X_UART_ENABLE_RX	0x2
+
+#define XR21V141X_UART_MODE_RI		BIT(0)
+#define XR21V141X_UART_MODE_CD		BIT(1)
+#define XR21V141X_UART_MODE_DSR		BIT(2)
+#define XR21V141X_UART_MODE_DTR		BIT(3)
+#define XR21V141X_UART_MODE_CTS		BIT(4)
+#define XR21V141X_UART_MODE_RTS		BIT(5)
+
+#define XR21V141X_UART_BREAK_ON		0xff
+#define XR21V141X_UART_BREAK_OFF	0
+
+#define XR21V141X_UART_DATA_MASK	GENMASK(3, 0)
+#define XR21V141X_UART_DATA_7		0x7
+#define XR21V141X_UART_DATA_8		0x8
+
+#define XR21V141X_UART_PARITY_MASK	GENMASK(6, 4)
+#define XR21V141X_UART_PARITY_SHIFT	0x4
+#define XR21V141X_UART_PARITY_NONE	0x0
+#define XR21V141X_UART_PARITY_ODD	0x1
+#define XR21V141X_UART_PARITY_EVEN	0x2
+#define XR21V141X_UART_PARITY_MARK	0x3
+#define XR21V141X_UART_PARITY_SPACE	0x4
+
+#define XR21V141X_UART_STOP_MASK	BIT(7)
+#define XR21V141X_UART_STOP_SHIFT	0x7
+#define XR21V141X_UART_STOP_1		0x0
+#define XR21V141X_UART_STOP_2		0x1
+
+#define XR21V141X_UART_FLOW_MODE_NONE	0x0
+#define XR21V141X_UART_FLOW_MODE_HW	0x1
+#define XR21V141X_UART_FLOW_MODE_SW	0x2
+
+#define XR21V141X_UART_MODE_GPIO_MASK	GENMASK(2, 0)
+#define XR21V141X_UART_MODE_RTS_CTS	0x1
+#define XR21V141X_UART_MODE_DTR_DSR	0x2
+#define XR21V141X_UART_MODE_RS485	0x3
+#define XR21V141X_UART_MODE_RS485_ADDR	0x4
+
+#define XR21V141X_REG_ENABLE		0x03
+#define XR21V141X_REG_FORMAT		0x0b
+#define XR21V141X_REG_FLOW_CTRL		0x0c
+#define XR21V141X_REG_XON_CHAR		0x10
+#define XR21V141X_REG_XOFF_CHAR		0x11
+#define XR21V141X_REG_LOOPBACK		0x12
+#define XR21V141X_REG_TX_BREAK		0x14

drivers/usb/serial/xr_serial.c new file +91 -0

+			      reg | (block << 8), NULL, 0,
+			      USB_CTRL_SET_TIMEOUT);
+	if (ret < 0) {
+		dev_err(&port->dev, "Failed to set reg 0x%02x: %d\n", reg, ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int xr_get_reg(struct usb_serial_port *port, u8 block, u8 reg,
+		      u8 *val)
+{
+	struct usb_serial *serial = port->serial;
+	u8 *dmabuf;
+	int ret;
+
+	dmabuf = kmalloc(1, GFP_KERNEL);
+	if (!dmabuf)
+		return -ENOMEM;
+
+	ret = usb_control_msg(serial->dev,
+			      usb_rcvctrlpipe(serial->dev, 0),
+			      XR21V141X_GET_REQ,
+			      USB_DIR_IN | USB_TYPE_VENDOR, 0,
+			      reg | (block << 8), dmabuf, 1,
+			      USB_CTRL_GET_TIMEOUT);
+	if (ret == 1) {
+		*val = *dmabuf;
+		ret = 0;
+	} else {
+		dev_err(&port->dev, "Failed to get reg 0x%02x: %d\n", reg, ret);
+		if (ret >= 0)
+			ret = -EIO;
+	}
+
+	kfree(dmabuf);
+
+	return ret;
+}
+
+static int xr_set_reg_uart(struct usb_serial_port *port, u8 reg, u8 val)
+{
+	return xr_set_reg(port, XR21V141X_UART_REG_BLOCK, reg, val);
+}
+
+static int xr_get_reg_uart(struct usb_serial_port *port, u8 reg, u8 *val)
+{
+	return xr_get_reg(port, XR21V141X_UART_REG_BLOCK, reg, val);
+}
+
+static int xr_set_reg_um(struct usb_serial_port *port, u8 reg, u8 val)
+{
+	return xr_set_reg(port, XR21V141X_UM_REG_BLOCK, reg, val);
+}
+
+/* Tx and Rx clock mask values obtained from section 3.3.4 of datasheet */
+static const struct xr_txrx_clk_mask xr21v141x_txrx_clk_masks[] = {
+	{ 0x000, 0x000, 0x000 },
+	{ 0x000, 0x000, 0x000 },
+	{ 0x100, 0x000, 0x100 },
+	{ 0x020, 0x400, 0x020 },
+	{ 0x010, 0x100, 0x010 },
+	{ 0x208, 0x040, 0x208 },
+	{ 0x104, 0x820, 0x108 },
+	{ 0x844, 0x210, 0x884 },
+	{ 0x444, 0x110, 0x444 },
+	{ 0x122, 0x888, 0x224 },
+	{ 0x912, 0x448, 0x924 },
+	{ 0x492, 0x248, 0x492 },
+	{ 0x252, 0x928, 0x292 },
+	{ 0x94a, 0x4a4, 0xa52 },
+	{ 0x52a, 0xaa4, 0x54a },
+	{ 0xaaa, 0x954, 0x4aa },
+	{ 0xaaa, 0x554, 0xaaa },
+	{ 0x555, 0xad4, 0x5aa },
+	{ 0xb55, 0xab4, 0x55a },
+	{ 0x6b5, 0x5ac, 0xb56 },
+	{ 0x5b5, 0xd6c, 0x6d6 },
+	{ 0xb6d, 0xb6a, 0xdb6 },
+	{ 0x76d, 0x6da, 0xbb6 },
+	{ 0xedd, 0xdda, 0x76e },
+	{ 0xddd, 0xbba, 0xeee },
+	{ 0x7bb, 0xf7a, 0xdde },
+	{ 0xf7b, 0xef6, 0x7de },
+	{ 0xdf7, 0xbf6, 0xf7e },
+	{ 0x7f7, 0xfee, 0xefe },
+	{ 0xfdf, 0xfbe, 0x7fe },
+	{ 0xf7f, 0xefe, 0xffe },
+	{ 0xfff, 0xffe, 0xffd },
+};

drivers/usb/serial/xr_serial.c new file +5 -0

+		rx_mask = xr21v141x_txrx_clk_masks[idx].rx1;
+	else
+		rx_mask = xr21v141x_txrx_clk_masks[idx].rx0;
+
+	dev_dbg(&port->dev, "Setting baud rate: %u\n", baud);

drivers/usb/serial/xr_serial.c new file +71 -0

+	if (ret)
+		return ret;
+
+	ret = xr_set_reg_uart(port, XR21V141X_CLOCK_DIVISOR_2, ((divisor >> 16) & 0xff));
+	if (ret)
+		return ret;
+
+	ret = xr_set_reg_uart(port, XR21V141X_TX_CLOCK_MASK_0, (tx_mask & 0xff));
+	if (ret)
+		return ret;
+
+	ret = xr_set_reg_uart(port, XR21V141X_TX_CLOCK_MASK_1, ((tx_mask >>  8) & 0xff));
+	if (ret)
+		return ret;
+
+	ret = xr_set_reg_uart(port, XR21V141X_RX_CLOCK_MASK_0, (rx_mask & 0xff));
+	if (ret)
+		return ret;
+
+	ret = xr_set_reg_uart(port, XR21V141X_RX_CLOCK_MASK_1, ((rx_mask >>  8) & 0xff));
+
+	tty_encode_baud_rate(tty, baud, baud);
+
+	return ret;
+}
+
+/*
+ * According to datasheet, below is the recommended sequence for enabling UART
+ * module in XR21V141X:
+ *
+ * Enable Tx FIFO
+ * Enable Tx and Rx
+ * Enable Rx FIFO
+ */
+static int xr_uart_enable(struct usb_serial_port *port)
+{
+	int ret;
+
+	ret = xr_set_reg_um(port, XR21V141X_UM_FIFO_ENABLE_REG, XR21V141X_UM_ENABLE_TX_FIFO);
+	if (ret)
+		return ret;
+
+	ret = xr_set_reg_uart(port, XR21V141X_REG_ENABLE,
+			      XR21V141X_UART_ENABLE_TX | XR21V141X_UART_ENABLE_RX);
+	if (ret)
+		return ret;
+
+	ret = xr_set_reg_um(port, XR21V141X_UM_FIFO_ENABLE_REG,
+			    XR21V141X_UM_ENABLE_TX_FIFO | XR21V141X_UM_ENABLE_RX_FIFO);
+
+	if (ret)
+		xr_set_reg_uart(port, XR21V141X_REG_ENABLE, 0);
+
+	return ret;
+}
+
+static int xr_uart_disable(struct usb_serial_port *port)
+{
+	int ret;
+
+	ret = xr_set_reg_uart(port, XR21V141X_REG_ENABLE, 0);
+	if (ret)
+		return ret;
+
+	ret = xr_set_reg_um(port, XR21V141X_UM_FIFO_ENABLE_REG, 0);
+
+	return ret;
+}
+
+static void xr_set_flow_mode(struct tty_struct *tty,
+			     struct usb_serial_port *port)

drivers/usb/serial/xr_serial.c new file +70 -0

+		gpio_mode |= XR21V141X_UART_MODE_RTS_CTS;
+		flow = XR21V141X_UART_FLOW_MODE_HW;
+	} else if (I_IXON(tty)) {
+		u8 start_char = START_CHAR(tty);
+		u8 stop_char = STOP_CHAR(tty);
+
+		dev_dbg(&port->dev, "Enabling sw flow ctrl\n");
+		flow = XR21V141X_UART_FLOW_MODE_SW;
+
+		xr_set_reg_uart(port, XR21V141X_REG_XON_CHAR, start_char);
+		xr_set_reg_uart(port, XR21V141X_REG_XOFF_CHAR, stop_char);
+	} else {
+		dev_dbg(&port->dev, "Disabling flow ctrl\n");
+		flow = XR21V141X_UART_FLOW_MODE_NONE;
+	}
+
+	/*
+	 * As per the datasheet, UART needs to be disabled while writing to
+	 * FLOW_CONTROL register.
+	 */
+	xr_uart_disable(port);
+	xr_set_reg_uart(port, XR21V141X_REG_FLOW_CTRL, flow);
+	xr_uart_enable(port);
+
+	xr_set_reg_uart(port, XR21V141X_REG_GPIO_MODE, gpio_mode);
+}
+
+static int xr_tiocmset_port(struct usb_serial_port *port,
+			    unsigned int set, unsigned int clear)
+{
+	u8 gpio_set = 0;
+	u8 gpio_clr = 0;
+	int ret = 0;
+
+	/* Modem control pins are active low, so set & clr are swapped */
+	if (set & TIOCM_RTS)
+		gpio_clr |= XR21V141X_UART_MODE_RTS;
+	if (set & TIOCM_DTR)
+		gpio_clr |= XR21V141X_UART_MODE_DTR;
+	if (clear & TIOCM_RTS)
+		gpio_set |= XR21V141X_UART_MODE_RTS;
+	if (clear & TIOCM_DTR)
+		gpio_set |= XR21V141X_UART_MODE_DTR;
+
+	/* Writing '0' to gpio_{set/clr} bits has no effect, so no need to do */
+	if (gpio_clr)
+		ret = xr_set_reg_uart(port, XR21V141X_REG_GPIO_CLR, gpio_clr);
+
+	if (gpio_set)
+		ret = xr_set_reg_uart(port, XR21V141X_REG_GPIO_SET, gpio_set);
+
+	return ret;
+}
+
+static int xr_tiocmset(struct tty_struct *tty,
+		       unsigned int set, unsigned int clear)
+{
+	struct usb_serial_port *port = tty->driver_data;
+
+	return xr_tiocmset_port(port, set, clear);
+}
+
+static void xr_dtr_rts(struct usb_serial_port *port, int on)
+{
+	if (on)
+		xr_tiocmset_port(port, TIOCM_DTR | TIOCM_RTS, 0);
+	else
+		xr_tiocmset_port(port, 0, TIOCM_DTR | TIOCM_RTS);
+}
+

drivers/usb/serial/xr_serial.c new file +13 -0

+	case CS6:
+		/* CS5 and CS6 are not supported, so just restore old setting */
+		termios->c_cflag &= ~CSIZE;
+		if (old_termios)
+			termios->c_cflag |= old_termios->c_cflag & CSIZE;
+		else
+			bits |= XR21V141X_UART_DATA_8;
+		break;
+	case CS7:
+		bits |= XR21V141X_UART_DATA_7;
+		break;
+	case CS8:
+	fallthrough;

drivers/usb/serial/xr_serial.c new file +15 -0

+			else
+				bits |= XR21V141X_UART_PARITY_SPACE <<
+					XR21V141X_UART_PARITY_SHIFT;
+		} else {
+			if (C_PARODD(tty))
+				bits |= XR21V141X_UART_PARITY_ODD <<
+					XR21V141X_UART_PARITY_SHIFT;
+			else
+				bits |= XR21V141X_UART_PARITY_EVEN <<
+					XR21V141X_UART_PARITY_SHIFT;
+		}
+	}
+
+	if (C_CSTOPB(tty))
+		bits |= XR21V141X_UART_STOP_2 << XR21V141X_UART_STOP_SHIFT;

drivers/usb/serial/xr_serial.c new file +27 -0

+
+	xr_set_flow_mode(tty, port);
+}
+
+static int xr_open(struct tty_struct *tty, struct usb_serial_port *port)
+{
+	int ret;
+
+	ret = xr_uart_enable(port);
+	if (ret) {
+		dev_err(&port->dev, "Failed to enable UART\n");
+		return ret;
+	}
+
+	/* Setup termios */
+	if (tty)
+		xr_set_termios(tty, port, NULL);
+
+	ret = usb_serial_generic_open(tty, port);
+	if (ret) {
+		xr_uart_disable(port);
+		return ret;
+	}
+
+	return 0;
+}
+

drivers/usb/serial/xr_serial.c new file +42 -0

+
+	return 0;
+}
+
+static int xr_tiocmget(struct tty_struct *tty)
+{
+	struct usb_serial_port *port = tty->driver_data;
+	u8 status;
+	int ret;
+
+	ret = xr_get_reg_uart(port, XR21V141X_REG_GPIO_STATUS, &status);
+	if (ret)
+		return ret;
+
+	/*
+	 * Modem control pins are active low, so reading '0' means it is active
+	 * and '1' means not active.
+	 */
+	ret = ((status & XR21V141X_UART_MODE_DTR) ? 0 : TIOCM_DTR) |
+	      ((status & XR21V141X_UART_MODE_RTS) ? 0 : TIOCM_RTS) |
+	      ((status & XR21V141X_UART_MODE_CTS) ? 0 : TIOCM_CTS) |
+	      ((status & XR21V141X_UART_MODE_DSR) ? 0 : TIOCM_DSR) |
+	      ((status & XR21V141X_UART_MODE_RI) ? 0 : TIOCM_RI) |
+	      ((status & XR21V141X_UART_MODE_CD) ? 0 : TIOCM_CD);
+
+	return ret;
+}
+
+static void xr_break_ctl(struct tty_struct *tty, int break_state)
+{
+	struct usb_serial_port *port = tty->driver_data;
+	u8 state;
+
+	if (break_state == 0)
+		state = XR21V141X_UART_BREAK_OFF;
+	else
+		state = XR21V141X_UART_BREAK_ON;
+
+	dev_dbg(&port->dev, "Turning break %s\n",
+		state == XR21V141X_UART_BREAK_OFF ? "off" : "on");
+	xr_set_reg_uart(port, XR21V141X_REG_TX_BREAK, state);
+}

drivers/usb/serial/xr_serial.c new file +25 -0

+
+static const struct usb_device_id id_table[] = {
+	{ USB_DEVICE(0x04e2, 0x1410) }, /* XR21V141X */
+	{ }
+};
+MODULE_DEVICE_TABLE(usb, id_table);
+
+static struct usb_serial_driver xr_device = {
+	.driver = {
+		.owner = THIS_MODULE,
+		.name =	"xr_serial",
+	},
+	.id_table		= id_table,
+	.num_ports		= 1,
+	.open			= xr_open,
+	.close			= xr_close,
+	.break_ctl		= xr_break_ctl,
+	.set_termios		= xr_set_termios,
+	.tiocmget		= xr_tiocmget,
+	.tiocmset		= xr_tiocmset,
+	.probe			= xr_probe,
+	.port_probe		= xr_port_probe,
+	.port_remove		= xr_port_remove,
+	.dtr_rts		= xr_dtr_rts
+};

Quoted 3 lines · Manivannan Sadhasivam

Add support for MaxLinear/Exar USB to Serial converters. This driver only supports XR21V141X series but it can be extended to other series from Exar as well in future.

There are still a few issues with this driver, but I really don't want to have to review it again in a couple of months so I've fixed it up myself this time.

The trivial stuff I folded into this patch, and I'll submit a follow-on series for the rest.

Quoted 3 lines

This driver is inspired from the initial one submitted by Patong Yang:

https://lore.kernel.org/linux-usb/20180404070634.nhspvmxcjwfgjkcv@advantechmxl-desktop

Using /r/ is shorter.

Quoted 5 lines

While the initial driver was a custom tty USB driver exposing whole new serial interface ttyXRUSBn, this version is completely based on USB serial core thus exposing the interfaces as ttyUSBn. This will avoid the overhead of exposing a new USB serial interface which the userspace tools are unaware of.

I added a comment about the two driver modes here (ACM and "custom").

Quoted 44 lines

Signed-off-by Manivannan Sadhasivam <[email protected]>

---
 drivers/usb/serial/Kconfig     |   9 +
 drivers/usb/serial/Makefile    |   1 +
 drivers/usb/serial/xr_serial.c | 599 +++++++++++++++++++++++++++++++++
 3 files changed, 609 insertions(+)
 create mode 100644 drivers/usb/serial/xr_serial.c

drivers/usb/serial/Kconfig +9 -0

index 4007fa25a8ff..32595acb1d1d 100644
@@ -644,6 +644,15 @@ config USB_SERIAL_UPD78F0730
 	  To compile this driver as a module, choose M here: the
 	  module will be called upd78f0730.
 
+config USB_SERIAL_XR
+	tristate "USB MaxLinear/Exar USB to Serial driver"
+	help
+	  Say Y here if you want to use MaxLinear/Exar USB to Serial converter
+	  devices.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called xr_serial.
+
 config USB_SERIAL_DEBUG
 	tristate "USB Debugging Device"
 	help

drivers/usb/serial/Makefile +1 -0

index 2d491e434f11..4f69c2a3aff3 100644
@@ -62,4 +62,5 @@ obj-$(CONFIG_USB_SERIAL_VISOR)			+= visor.o
 obj-$(CONFIG_USB_SERIAL_WISHBONE)		+= wishbone-serial.o
 obj-$(CONFIG_USB_SERIAL_WHITEHEAT)		+= whiteheat.o
 obj-$(CONFIG_USB_SERIAL_XIRCOM)			+= keyspan_pda.o
+obj-$(CONFIG_USB_SERIAL_XR)			+= xr_serial.o
 obj-$(CONFIG_USB_SERIAL_XSENS_MT)		+= xsens_mt.o

drivers/usb/serial/xr_serial.c new file +0 -0

new file mode 100644
index 000000000000..e166916554d6

drivers/usb/serial/xr_serial.c line 9

Quoted 9 lines

drivers/usb/serial/xr_serial.c new file +9 -0

@@ -0,0 +1,599 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * MaxLinear/Exar USB to Serial driver
+ *
+ * Based on the initial driver written by Patong Yang:
+ * https://lore.kernel.org/linux-usb/20180404070634.nhspvmxcjwfgjkcv@advantechmxl-desktop
+ *
+ * Copyright (c) 2018 Patong Yang <[email protected]>
+ * Copyright (c) 2020 Manivannan Sadhasivam <[email protected]>

I moved your copyright notice under "MaxLinear..." so that it's clear who claims what copyright.

Quoted 91 lines

drivers/usb/serial/xr_serial.c new file +91 -0

+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/tty.h>
+#include <linux/usb.h>
+#include <linux/usb/serial.h>
+
+struct xr_txrx_clk_mask {
+	u16 tx;
+	u16 rx0;
+	u16 rx1;
+};
+
+#define XR_INT_OSC_HZ			48000000U
+#define XR21V141X_MIN_SPEED		46U
+#define XR21V141X_MAX_SPEED		XR_INT_OSC_HZ
+
+/* USB Requests */
+#define XR21V141X_SET_REQ		0
+#define XR21V141X_GET_REQ		1
+
+#define XR21V141X_CLOCK_DIVISOR_0	0x04
+#define XR21V141X_CLOCK_DIVISOR_1	0x05
+#define XR21V141X_CLOCK_DIVISOR_2	0x06
+#define XR21V141X_TX_CLOCK_MASK_0	0x07
+#define XR21V141X_TX_CLOCK_MASK_1	0x08
+#define XR21V141X_RX_CLOCK_MASK_0	0x09
+#define XR21V141X_RX_CLOCK_MASK_1	0x0a
+
+/* XR21V141X register blocks */
+#define XR21V141X_UART_REG_BLOCK	0
+#define XR21V141X_UM_REG_BLOCK		4
+#define XR21V141X_UART_CUSTOM_BLOCK	0x66
+
+/* XR21V141X UART Manager Registers */
+#define XR21V141X_UM_FIFO_ENABLE_REG	0x10
+#define XR21V141X_UM_ENABLE_TX_FIFO	0x01
+#define XR21V141X_UM_ENABLE_RX_FIFO	0x02
+
+#define XR21V141X_UM_RX_FIFO_RESET	0x18
+#define XR21V141X_UM_TX_FIFO_RESET	0x1c
+
+#define XR21V141X_UART_ENABLE_TX	0x1
+#define XR21V141X_UART_ENABLE_RX	0x2
+
+#define XR21V141X_UART_MODE_RI		BIT(0)
+#define XR21V141X_UART_MODE_CD		BIT(1)
+#define XR21V141X_UART_MODE_DSR		BIT(2)
+#define XR21V141X_UART_MODE_DTR		BIT(3)
+#define XR21V141X_UART_MODE_CTS		BIT(4)
+#define XR21V141X_UART_MODE_RTS		BIT(5)
+
+#define XR21V141X_UART_BREAK_ON		0xff
+#define XR21V141X_UART_BREAK_OFF	0
+
+#define XR21V141X_UART_DATA_MASK	GENMASK(3, 0)
+#define XR21V141X_UART_DATA_7		0x7
+#define XR21V141X_UART_DATA_8		0x8
+
+#define XR21V141X_UART_PARITY_MASK	GENMASK(6, 4)
+#define XR21V141X_UART_PARITY_SHIFT	0x4
+#define XR21V141X_UART_PARITY_NONE	0x0
+#define XR21V141X_UART_PARITY_ODD	0x1
+#define XR21V141X_UART_PARITY_EVEN	0x2
+#define XR21V141X_UART_PARITY_MARK	0x3
+#define XR21V141X_UART_PARITY_SPACE	0x4
+
+#define XR21V141X_UART_STOP_MASK	BIT(7)
+#define XR21V141X_UART_STOP_SHIFT	0x7
+#define XR21V141X_UART_STOP_1		0x0
+#define XR21V141X_UART_STOP_2		0x1
+
+#define XR21V141X_UART_FLOW_MODE_NONE	0x0
+#define XR21V141X_UART_FLOW_MODE_HW	0x1
+#define XR21V141X_UART_FLOW_MODE_SW	0x2
+
+#define XR21V141X_UART_MODE_GPIO_MASK	GENMASK(2, 0)
+#define XR21V141X_UART_MODE_RTS_CTS	0x1
+#define XR21V141X_UART_MODE_DTR_DSR	0x2
+#define XR21V141X_UART_MODE_RS485	0x3
+#define XR21V141X_UART_MODE_RS485_ADDR	0x4
+
+#define XR21V141X_REG_ENABLE		0x03
+#define XR21V141X_REG_FORMAT		0x0b
+#define XR21V141X_REG_FLOW_CTRL		0x0c
+#define XR21V141X_REG_XON_CHAR		0x10
+#define XR21V141X_REG_XOFF_CHAR		0x11
+#define XR21V141X_REG_LOOPBACK		0x12
+#define XR21V141X_REG_TX_BREAK		0x14

drivers/usb/serial/xr_serial.c line 110

Quoted 10 lines

drivers/usb/serial/xr_serial.c new file +10 -0

+#define XR21V141X_REG_RS845_DELAY	0x15
+#define XR21V141X_REG_GPIO_MODE		0x1a
+#define XR21V141X_REG_GPIO_DIR		0x1b
+#define XR21V141X_REG_GPIO_INT_MASK	0x1c
+#define XR21V141X_REG_GPIO_SET		0x1d
+#define XR21V141X_REG_GPIO_CLR		0x1e
+#define XR21V141X_REG_GPIO_STATUS	0x1f
+
+static int xr_set_reg(struct usb_serial_port *port, u8 block, u8 reg,
+		      u8 val)

No need for line breaks.

drivers/usb/serial/xr_serial.c line 118

Quoted 8 lines

drivers/usb/serial/xr_serial.c new file +8 -0

+{
+	struct usb_serial *serial = port->serial;
+	int ret;
+
+	ret = usb_control_msg(serial->dev,
+			      usb_sndctrlpipe(serial->dev, 0),
+			      XR21V141X_SET_REQ,
+			      USB_DIR_OUT | USB_TYPE_VENDOR, val,

The request-type should include USB_RECIP_DEVICE (0) as well.

Quoted 91 lines

drivers/usb/serial/xr_serial.c new file +91 -0

+			      reg | (block << 8), NULL, 0,
+			      USB_CTRL_SET_TIMEOUT);
+	if (ret < 0) {
+		dev_err(&port->dev, "Failed to set reg 0x%02x: %d\n", reg, ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+static int xr_get_reg(struct usb_serial_port *port, u8 block, u8 reg,
+		      u8 *val)
+{
+	struct usb_serial *serial = port->serial;
+	u8 *dmabuf;
+	int ret;
+
+	dmabuf = kmalloc(1, GFP_KERNEL);
+	if (!dmabuf)
+		return -ENOMEM;
+
+	ret = usb_control_msg(serial->dev,
+			      usb_rcvctrlpipe(serial->dev, 0),
+			      XR21V141X_GET_REQ,
+			      USB_DIR_IN | USB_TYPE_VENDOR, 0,
+			      reg | (block << 8), dmabuf, 1,
+			      USB_CTRL_GET_TIMEOUT);
+	if (ret == 1) {
+		*val = *dmabuf;
+		ret = 0;
+	} else {
+		dev_err(&port->dev, "Failed to get reg 0x%02x: %d\n", reg, ret);
+		if (ret >= 0)
+			ret = -EIO;
+	}
+
+	kfree(dmabuf);
+
+	return ret;
+}
+
+static int xr_set_reg_uart(struct usb_serial_port *port, u8 reg, u8 val)
+{
+	return xr_set_reg(port, XR21V141X_UART_REG_BLOCK, reg, val);
+}
+
+static int xr_get_reg_uart(struct usb_serial_port *port, u8 reg, u8 *val)
+{
+	return xr_get_reg(port, XR21V141X_UART_REG_BLOCK, reg, val);
+}
+
+static int xr_set_reg_um(struct usb_serial_port *port, u8 reg, u8 val)
+{
+	return xr_set_reg(port, XR21V141X_UM_REG_BLOCK, reg, val);
+}
+
+/* Tx and Rx clock mask values obtained from section 3.3.4 of datasheet */
+static const struct xr_txrx_clk_mask xr21v141x_txrx_clk_masks[] = {
+	{ 0x000, 0x000, 0x000 },
+	{ 0x000, 0x000, 0x000 },
+	{ 0x100, 0x000, 0x100 },
+	{ 0x020, 0x400, 0x020 },
+	{ 0x010, 0x100, 0x010 },
+	{ 0x208, 0x040, 0x208 },
+	{ 0x104, 0x820, 0x108 },
+	{ 0x844, 0x210, 0x884 },
+	{ 0x444, 0x110, 0x444 },
+	{ 0x122, 0x888, 0x224 },
+	{ 0x912, 0x448, 0x924 },
+	{ 0x492, 0x248, 0x492 },
+	{ 0x252, 0x928, 0x292 },
+	{ 0x94a, 0x4a4, 0xa52 },
+	{ 0x52a, 0xaa4, 0x54a },
+	{ 0xaaa, 0x954, 0x4aa },
+	{ 0xaaa, 0x554, 0xaaa },
+	{ 0x555, 0xad4, 0x5aa },
+	{ 0xb55, 0xab4, 0x55a },
+	{ 0x6b5, 0x5ac, 0xb56 },
+	{ 0x5b5, 0xd6c, 0x6d6 },
+	{ 0xb6d, 0xb6a, 0xdb6 },
+	{ 0x76d, 0x6da, 0xbb6 },
+	{ 0xedd, 0xdda, 0x76e },
+	{ 0xddd, 0xbba, 0xeee },
+	{ 0x7bb, 0xf7a, 0xdde },
+	{ 0xf7b, 0xef6, 0x7de },
+	{ 0xdf7, 0xbf6, 0xf7e },
+	{ 0x7f7, 0xfee, 0xefe },
+	{ 0xfdf, 0xfbe, 0x7fe },
+	{ 0xf7f, 0xefe, 0xffe },
+	{ 0xfff, 0xffe, 0xffd },
+};

drivers/usb/serial/xr_serial.c line 219

Quoted 10 lines

drivers/usb/serial/xr_serial.c new file +10 -0

+
+static int xr_set_baudrate(struct tty_struct *tty,
+			   struct usb_serial_port *port)
+{
+	u32 divisor, baud, idx;
+	u16 tx_mask, rx_mask;
+	int ret;
+
+	baud = clamp(tty->termios.c_ospeed, XR21V141X_MIN_SPEED,
+		     XR21V141X_MAX_SPEED);

You shouldn't report back anything else but B0 if that's requested, the actual rate can be left unchanged.

drivers/usb/serial/xr_serial.c line 224

Quoted 5 lines

drivers/usb/serial/xr_serial.c new file +5 -0

+	divisor = XR_INT_OSC_HZ / baud;
+	idx = ((32 * XR_INT_OSC_HZ) / baud) & 0x1f;
+	tx_mask = xr21v141x_txrx_clk_masks[idx].tx;
+
+	if (divisor & 1)

Nit: 0x01 since bitmask.

Quoted 5 lines

drivers/usb/serial/xr_serial.c new file +5 -0

+		rx_mask = xr21v141x_txrx_clk_masks[idx].rx1;
+	else
+		rx_mask = xr21v141x_txrx_clk_masks[idx].rx0;
+
+	dev_dbg(&port->dev, "Setting baud rate: %u\n", baud);

drivers/usb/serial/xr_serial.c line 239

Quoted 10 lines

drivers/usb/serial/xr_serial.c new file +10 -0

+	/*
+	 * XR21V141X uses fractional baud rate generator with 48MHz internal
+	 * oscillator and 19-bit programmable divisor. So theoretically it can
+	 * generate most commonly used baud rates with high accuracy.
+	 */
+	ret = xr_set_reg_uart(port, XR21V141X_CLOCK_DIVISOR_0, (divisor & 0xff));
+	if (ret)
+		return ret;
+
+	ret = xr_set_reg_uart(port, XR21V141X_CLOCK_DIVISOR_1, ((divisor >>  8) & 0xff));

I broke these long lines again.

Quoted 71 lines

drivers/usb/serial/xr_serial.c new file +71 -0

+	if (ret)
+		return ret;
+
+	ret = xr_set_reg_uart(port, XR21V141X_CLOCK_DIVISOR_2, ((divisor >> 16) & 0xff));
+	if (ret)
+		return ret;
+
+	ret = xr_set_reg_uart(port, XR21V141X_TX_CLOCK_MASK_0, (tx_mask & 0xff));
+	if (ret)
+		return ret;
+
+	ret = xr_set_reg_uart(port, XR21V141X_TX_CLOCK_MASK_1, ((tx_mask >>  8) & 0xff));
+	if (ret)
+		return ret;
+
+	ret = xr_set_reg_uart(port, XR21V141X_RX_CLOCK_MASK_0, (rx_mask & 0xff));
+	if (ret)
+		return ret;
+
+	ret = xr_set_reg_uart(port, XR21V141X_RX_CLOCK_MASK_1, ((rx_mask >>  8) & 0xff));
+
+	tty_encode_baud_rate(tty, baud, baud);
+
+	return ret;
+}
+
+/*
+ * According to datasheet, below is the recommended sequence for enabling UART
+ * module in XR21V141X:
+ *
+ * Enable Tx FIFO
+ * Enable Tx and Rx
+ * Enable Rx FIFO
+ */
+static int xr_uart_enable(struct usb_serial_port *port)
+{
+	int ret;
+
+	ret = xr_set_reg_um(port, XR21V141X_UM_FIFO_ENABLE_REG, XR21V141X_UM_ENABLE_TX_FIFO);
+	if (ret)
+		return ret;
+
+	ret = xr_set_reg_uart(port, XR21V141X_REG_ENABLE,
+			      XR21V141X_UART_ENABLE_TX | XR21V141X_UART_ENABLE_RX);
+	if (ret)
+		return ret;
+
+	ret = xr_set_reg_um(port, XR21V141X_UM_FIFO_ENABLE_REG,
+			    XR21V141X_UM_ENABLE_TX_FIFO | XR21V141X_UM_ENABLE_RX_FIFO);
+
+	if (ret)
+		xr_set_reg_uart(port, XR21V141X_REG_ENABLE, 0);
+
+	return ret;
+}
+
+static int xr_uart_disable(struct usb_serial_port *port)
+{
+	int ret;
+
+	ret = xr_set_reg_uart(port, XR21V141X_REG_ENABLE, 0);
+	if (ret)
+		return ret;
+
+	ret = xr_set_reg_um(port, XR21V141X_UM_FIFO_ENABLE_REG, 0);
+
+	return ret;
+}
+
+static void xr_set_flow_mode(struct tty_struct *tty,
+			     struct usb_serial_port *port)

drivers/usb/serial/xr_serial.c line 320

Quoted 10 lines

drivers/usb/serial/xr_serial.c new file +10 -0

+{
+	unsigned int cflag = tty->termios.c_cflag;
+	int ret;
+	u8 flow, gpio_mode;
+
+	ret = xr_get_reg_uart(port, XR21V141X_REG_GPIO_MODE, &gpio_mode);
+	if (ret)
+		return;
+
+	if (cflag & CRTSCTS) {

C_CRTSCTS(tty)

drivers/usb/serial/xr_serial.c line 327

Quoted 7 lines

drivers/usb/serial/xr_serial.c new file +7 -0

+		dev_dbg(&port->dev, "Enabling hardware flow ctrl\n");
+
+		/*
+		 * RTS/CTS is the default flow control mode, so set GPIO mode
+		 * for controlling the pins manually by default.
+		 */
+		gpio_mode &= ~XR21V141X_UART_MODE_GPIO_MASK;

This needs to be done before the conditional so that GPIO mode is again selected when disabling flow control, otherwise your break RTS control.

Also you never configure DTR/RTS as outputs despite all pins being inputs by default according to the datasheet. Effectively, DTR control is currently broken and RTS can only be used for automatic flow control.

Did you not test these signals separately?

Quoted 70 lines

drivers/usb/serial/xr_serial.c new file +70 -0

+		gpio_mode |= XR21V141X_UART_MODE_RTS_CTS;
+		flow = XR21V141X_UART_FLOW_MODE_HW;
+	} else if (I_IXON(tty)) {
+		u8 start_char = START_CHAR(tty);
+		u8 stop_char = STOP_CHAR(tty);
+
+		dev_dbg(&port->dev, "Enabling sw flow ctrl\n");
+		flow = XR21V141X_UART_FLOW_MODE_SW;
+
+		xr_set_reg_uart(port, XR21V141X_REG_XON_CHAR, start_char);
+		xr_set_reg_uart(port, XR21V141X_REG_XOFF_CHAR, stop_char);
+	} else {
+		dev_dbg(&port->dev, "Disabling flow ctrl\n");
+		flow = XR21V141X_UART_FLOW_MODE_NONE;
+	}
+
+	/*
+	 * As per the datasheet, UART needs to be disabled while writing to
+	 * FLOW_CONTROL register.
+	 */
+	xr_uart_disable(port);
+	xr_set_reg_uart(port, XR21V141X_REG_FLOW_CTRL, flow);
+	xr_uart_enable(port);
+
+	xr_set_reg_uart(port, XR21V141X_REG_GPIO_MODE, gpio_mode);
+}
+
+static int xr_tiocmset_port(struct usb_serial_port *port,
+			    unsigned int set, unsigned int clear)
+{
+	u8 gpio_set = 0;
+	u8 gpio_clr = 0;
+	int ret = 0;
+
+	/* Modem control pins are active low, so set & clr are swapped */
+	if (set & TIOCM_RTS)
+		gpio_clr |= XR21V141X_UART_MODE_RTS;
+	if (set & TIOCM_DTR)
+		gpio_clr |= XR21V141X_UART_MODE_DTR;
+	if (clear & TIOCM_RTS)
+		gpio_set |= XR21V141X_UART_MODE_RTS;
+	if (clear & TIOCM_DTR)
+		gpio_set |= XR21V141X_UART_MODE_DTR;
+
+	/* Writing '0' to gpio_{set/clr} bits has no effect, so no need to do */
+	if (gpio_clr)
+		ret = xr_set_reg_uart(port, XR21V141X_REG_GPIO_CLR, gpio_clr);
+
+	if (gpio_set)
+		ret = xr_set_reg_uart(port, XR21V141X_REG_GPIO_SET, gpio_set);
+
+	return ret;
+}
+
+static int xr_tiocmset(struct tty_struct *tty,
+		       unsigned int set, unsigned int clear)
+{
+	struct usb_serial_port *port = tty->driver_data;
+
+	return xr_tiocmset_port(port, set, clear);
+}
+
+static void xr_dtr_rts(struct usb_serial_port *port, int on)
+{
+	if (on)
+		xr_tiocmset_port(port, TIOCM_DTR | TIOCM_RTS, 0);
+	else
+		xr_tiocmset_port(port, 0, TIOCM_DTR | TIOCM_RTS);
+}
+

drivers/usb/serial/xr_serial.c line 407

Quoted 10 lines

drivers/usb/serial/xr_serial.c new file +10 -0

+static void xr_set_termios(struct tty_struct *tty,
+			   struct usb_serial_port *port,
+			   struct ktermios *old_termios)
+{
+	struct ktermios *termios = &tty->termios;
+	int ret;
+	u8 bits = 0;
+
+	if ((old_termios && tty->termios.c_ospeed != old_termios->c_ospeed) ||
+	    !old_termios)

This can be simplified.

drivers/usb/serial/xr_serial.c line 412

Quoted 5 lines

drivers/usb/serial/xr_serial.c new file +5 -0

+		xr_set_baudrate(tty, port);
+
+	switch (C_CSIZE(tty)) {
+	case CS5:
+	fallthrough;

No need for fallthrough for empty cases.

Quoted 13 lines

drivers/usb/serial/xr_serial.c new file +13 -0

+	case CS6:
+		/* CS5 and CS6 are not supported, so just restore old setting */
+		termios->c_cflag &= ~CSIZE;
+		if (old_termios)
+			termios->c_cflag |= old_termios->c_cflag & CSIZE;
+		else
+			bits |= XR21V141X_UART_DATA_8;
+		break;
+	case CS7:
+		bits |= XR21V141X_UART_DATA_7;
+		break;
+	case CS8:
+	fallthrough;

drivers/usb/serial/xr_serial.c line 435

Quoted 10 lines

drivers/usb/serial/xr_serial.c new file +10 -0

+	default:
+		bits |= XR21V141X_UART_DATA_8;
+		break;
+	}
+
+	if (C_PARENB(tty)) {
+		if (C_CMSPAR(tty)) {
+			if (C_PARODD(tty))
+				bits |= XR21V141X_UART_PARITY_MARK <<
+					XR21V141X_UART_PARITY_SHIFT;

I'd prefer just shifting the values when defining them, which is more consistent with how CSIZE is handled too.

Quoted 15 lines

drivers/usb/serial/xr_serial.c new file +15 -0

+			else
+				bits |= XR21V141X_UART_PARITY_SPACE <<
+					XR21V141X_UART_PARITY_SHIFT;
+		} else {
+			if (C_PARODD(tty))
+				bits |= XR21V141X_UART_PARITY_ODD <<
+					XR21V141X_UART_PARITY_SHIFT;
+			else
+				bits |= XR21V141X_UART_PARITY_EVEN <<
+					XR21V141X_UART_PARITY_SHIFT;
+		}
+	}
+
+	if (C_CSTOPB(tty))
+		bits |= XR21V141X_UART_STOP_2 << XR21V141X_UART_STOP_SHIFT;

drivers/usb/serial/xr_serial.c line 460

Quoted 10 lines

drivers/usb/serial/xr_serial.c new file +10 -0

+	else
+		bits |= XR21V141X_UART_STOP_1 << XR21V141X_UART_STOP_SHIFT;
+
+	ret = xr_set_reg_uart(port, XR21V141X_REG_FORMAT, bits);
+	if (ret)
+		return;
+
+	/* If baud rate is B0, clear DTR and RTS */
+	if (C_BAUD(tty) == B0)
+		xr_dtr_rts(port, 0);

This isn't sufficient; RTS will not be dropped when CRTSCTS is enabled, and we should reassert the lines when moving from B0 too.

Quoted 27 lines

drivers/usb/serial/xr_serial.c new file +27 -0

+
+	xr_set_flow_mode(tty, port);
+}
+
+static int xr_open(struct tty_struct *tty, struct usb_serial_port *port)
+{
+	int ret;
+
+	ret = xr_uart_enable(port);
+	if (ret) {
+		dev_err(&port->dev, "Failed to enable UART\n");
+		return ret;
+	}
+
+	/* Setup termios */
+	if (tty)
+		xr_set_termios(tty, port, NULL);
+
+	ret = usb_serial_generic_open(tty, port);
+	if (ret) {
+		xr_uart_disable(port);
+		return ret;
+	}
+
+	return 0;
+}
+

drivers/usb/serial/xr_serial.c line 497

Quoted 10 lines

drivers/usb/serial/xr_serial.c new file +10 -0

+static void xr_close(struct usb_serial_port *port)
+{
+	usb_serial_generic_close(port);
+
+	xr_uart_disable(port);
+}
+
+static int xr_probe(struct usb_serial *serial, const struct usb_device_id *id)
+{
+	struct usb_device *usb_dev = interface_to_usbdev(serial->interface);

You can just use serial->dev directly.

drivers/usb/serial/xr_serial.c line 507

Quoted 10 lines

drivers/usb/serial/xr_serial.c new file +10 -0

+	struct usb_driver *driver = serial->type->usb_driver;
+	struct usb_interface *control_interface;
+	int ret;
+
+	/* Don't bind to control interface */
+	if (serial->interface->cur_altsetting->desc.bInterfaceNumber == 0)
+		return -ENODEV;
+
+	/* But claim the control interface during data interface probe */
+	control_interface = usb_ifnum_to_if(usb_dev, 0);

You must check for NULL here since a device may not have an interface 0 in case you'll oops here. This can be triggered by a malicious device or when fuzzing USB descriptors.

drivers/usb/serial/xr_serial.c line 512

Quoted 5 lines

drivers/usb/serial/xr_serial.c new file +5 -0

+	ret = usb_driver_claim_interface(driver, control_interface, NULL);
+	if (ret) {
+		dev_err(&serial->interface->dev, "Can't claim control interface\n");
+		return ret;
+	}

And you must release the control interface again when unbinding the driver to avoid leaking resources and to allow the driver to be rebound.

Quoted 42 lines

drivers/usb/serial/xr_serial.c new file +42 -0

+
+	return 0;
+}
+
+static int xr_tiocmget(struct tty_struct *tty)
+{
+	struct usb_serial_port *port = tty->driver_data;
+	u8 status;
+	int ret;
+
+	ret = xr_get_reg_uart(port, XR21V141X_REG_GPIO_STATUS, &status);
+	if (ret)
+		return ret;
+
+	/*
+	 * Modem control pins are active low, so reading '0' means it is active
+	 * and '1' means not active.
+	 */
+	ret = ((status & XR21V141X_UART_MODE_DTR) ? 0 : TIOCM_DTR) |
+	      ((status & XR21V141X_UART_MODE_RTS) ? 0 : TIOCM_RTS) |
+	      ((status & XR21V141X_UART_MODE_CTS) ? 0 : TIOCM_CTS) |
+	      ((status & XR21V141X_UART_MODE_DSR) ? 0 : TIOCM_DSR) |
+	      ((status & XR21V141X_UART_MODE_RI) ? 0 : TIOCM_RI) |
+	      ((status & XR21V141X_UART_MODE_CD) ? 0 : TIOCM_CD);
+
+	return ret;
+}
+
+static void xr_break_ctl(struct tty_struct *tty, int break_state)
+{
+	struct usb_serial_port *port = tty->driver_data;
+	u8 state;
+
+	if (break_state == 0)
+		state = XR21V141X_UART_BREAK_OFF;
+	else
+		state = XR21V141X_UART_BREAK_ON;
+
+	dev_dbg(&port->dev, "Turning break %s\n",
+		state == XR21V141X_UART_BREAK_OFF ? "off" : "on");
+	xr_set_reg_uart(port, XR21V141X_REG_TX_BREAK, state);
+}

drivers/usb/serial/xr_serial.c line 564

Quoted 10 lines

drivers/usb/serial/xr_serial.c new file +10 -0

+
+static int xr_port_probe(struct usb_serial_port *port)
+{
+	return 0;
+}
+
+static int xr_port_remove(struct usb_serial_port *port)
+{
+	return 0;
+}

Again, don't add these until you need them.

Quoted 25 lines

drivers/usb/serial/xr_serial.c new file +25 -0

+
+static const struct usb_device_id id_table[] = {
+	{ USB_DEVICE(0x04e2, 0x1410) }, /* XR21V141X */
+	{ }
+};
+MODULE_DEVICE_TABLE(usb, id_table);
+
+static struct usb_serial_driver xr_device = {
+	.driver = {
+		.owner = THIS_MODULE,
+		.name =	"xr_serial",
+	},
+	.id_table		= id_table,
+	.num_ports		= 1,
+	.open			= xr_open,
+	.close			= xr_close,
+	.break_ctl		= xr_break_ctl,
+	.set_termios		= xr_set_termios,
+	.tiocmget		= xr_tiocmget,
+	.tiocmset		= xr_tiocmset,
+	.probe			= xr_probe,
+	.port_probe		= xr_port_probe,
+	.port_remove		= xr_port_remove,
+	.dtr_rts		= xr_dtr_rts
+};

drivers/usb/serial/xr_serial.c line 599

Quoted 10 lines

drivers/usb/serial/xr_serial.c new file +10 -0

+
+static struct usb_serial_driver * const serial_drivers[] = {
+	&xr_device, NULL
+};
+
+module_usb_serial_driver(serial_drivers, id_table);
+
+MODULE_AUTHOR("Manivannan Sadhasivam <[email protected]>");
+MODULE_DESCRIPTION("MaxLinear/Exar USB to Serial driver");
+MODULE_LICENSE("GPL");

Looks good overall otherwise.

I've applied this one now, and will follow up with a series addressing the non-trivial bits pointed out below.

Johan

Quoted 9 lines · Johan Hovold

Quoted 3 lines · Manivannan Sadhasivam

Add support for MaxLinear/Exar USB to Serial converters. This driver only supports XR21V141X series but it can be extended to other series from Exar as well in future.

There are still a few issues with this driver, but I really don't want to have to review it again in a couple of months so I've fixed it up myself this time.

Quoted 3 lines

The trivial stuff I folded into this patch, and I'll submit a follow-on series for the rest.

Many thanks for doing this! These days it is really difficult to find time for spare time stuffs.

And all of your fixes makes sense to me.

Quoted 14 lines · Johan Hovold

Quoted 12 lines · Manivannan Sadhasivam

Quoted 3 lines

Add support for MaxLinear/Exar USB to Serial converters. This driver only supports XR21V141X series but it can be extended to other series from Exar as well in future.

There are still a few issues with this driver, but I really don't want to have to review it again in a couple of months so I've fixed it up myself this time.

The trivial stuff I folded into this patch, and I'll submit a follow-on series for the rest.

Quoted 4 lines

Many thanks for doing this! These days it is really difficult to find time for spare time stuffs.

And all of your fixes makes sense to me.

Thanks for taking a look!

Hi Johan,

Em Tue, 26 Jan 2021 17:26:36 +0100
Johan Hovold <[email protected]> escreveu:

Quoted 6 lines · Manivannan Sadhasivam

Quoted 5 lines · Johan Hovold

Quoted 4 lines · Manivannan Sadhasivam

Quoted 3 lines

Add support for MaxLinear/Exar USB to Serial converters. This driver only supports XR21V141X series but it can be extended to other series from Exar as well in future.

I'm now facing an issue with this driver. I have here two different boards with those USB UART from MaxLinear/Exar.

The first one is identical to Mani's one:

	USB_DEVICE(0x04e2, 0x1411)
The second one is a different version of it:
	USB_DEVICE(0x04e2, 0x1424)

By looking at the final driver merged at linux-next, it sounds that somewhere during the review of this series, it lost the priv struct, and the xr_probe function. It also lost support for all MaxLinear/Exar devices, except for just one model (04e2:1411).

The original submission:

	https://lore.kernel.org/linux-usb/20180404070634.nhspvmxcjwfgjkcv@advantechmxl-desktop

And the manufacturer's Linux driver on their website:

https://www.maxlinear.com/support/design-tools/software-drivers

Had support for other 12 different models of the MaxLinear/Exar USB UART.

Those are grouped into 5 different major types:

	+	init_xr2280x_reg_map();
	+	init_xr21b142x_reg_map();
	+	init_xr21b1411_reg_map();
	+	init_xr21v141x_reg_map();
	+
	+	if ((xrusb->DeviceProduct & 0xfff0) == 0x1400)
	+		memcpy(&(xrusb->reg_map), &xr2280x_reg_map,
	+			sizeof(struct reg_addr_map));
	+	else if ((xrusb->DeviceProduct & 0xFFF0) == 0x1420)
	+		memcpy(&(xrusb->reg_map), &xr21b142x_reg_map,
	+			sizeof(struct reg_addr_map));
	+	else if (xrusb->DeviceProduct == 0x1411)
	+		memcpy(&(xrusb->reg_map), &xr21b1411_reg_map,
	+			sizeof(struct reg_addr_map));
	+	else if ((xrusb->DeviceProduct & 0xfff0) == 0x1410)
	+		memcpy(&(xrusb->reg_map), &xr21v141x_reg_map,
	+			sizeof(struct reg_addr_map));
	+	else
	+		rv = -1;

Note: Please don't be confused by "reg_map" name. This has nothing
to do with Linux regmap API ;-)

What happens is that different USB IDs have different values for each register. So, for instance, the UART enable register is set to either one of the following values, depending on the value of udev->descriptor.idProduct:

	xr21b140x_reg_map.uart_enable_addr = 0x00;
	xr21b1411_reg_map.uart_enable_addr = 0xc00;
	xr21v141x_reg_map.uart_enable_addr = 0x03;
	xr21b142x_reg_map.uart_enable_addr = 0x00;

There are other values that depend on the probing time detection, based on other USB descriptors. Those set several fields at the priv data that would allow to properly map the registers.

Also, there are 4 models that support multiple channels. On those, there are one pair of register get/set for each channel.

-

In summary, while supporting just 04e2:1411 there's no need for a private struct, in order to properly support the other models, some autodetection is needed. The best way of doing that is to re-add the .probe method and adding a priv struct.

As I dunno why this was dropped in the first place, I'm wondering if it would be ok to re-introduce them.

To be clear: my main focus here is just to avoid needing to use Windows in order to use the serial console of the hardware with the 0x1424 variant ;-)

I can't test the driver with the other hardware, but, IMHO, instead of adding a hack to support 0x1424, the better (but more painful) would be to re-add the auto-detection part and support for the other models.

Quoted 27 lines

Hi Johan,

Em Tue, 26 Jan 2021 17:26:36 +0100
Johan Hovold <[email protected]> escreveu:

Quoted 6 lines · Manivannan Sadhasivam

Quoted 5 lines · Johan Hovold

Quoted 4 lines · Manivannan Sadhasivam

Quoted 3 lines

Add support for MaxLinear/Exar USB to Serial converters. This driver only supports XR21V141X series but it can be extended to other series from Exar as well in future.

I'm now facing an issue with this driver. I have here two different boards with those USB UART from MaxLinear/Exar.

The first one is identical to Mani's one:

	USB_DEVICE(0x04e2, 0x1411)
The second one is a different version of it:
	USB_DEVICE(0x04e2, 0x1424)

By looking at the final driver merged at linux-next, it sounds that somewhere during the review of this series, it lost the priv struct, and the xr_probe function. It also lost support for all MaxLinear/Exar devices, except for just one model (04e2:1411).

The original submission:

Quoted 8 lines

	https://lore.kernel.org/linux-usb/20180404070634.nhspvmxcjwfgjkcv@advantechmxl-desktop

And the manufacturer's Linux driver on their website:

https://www.maxlinear.com/support/design-tools/software-drivers

Had support for other 12 different models of the MaxLinear/Exar USB UART.

IIRC Manivannan only had access to one of these models and his original submission (based on the patch you link to above) didn't include support for the others. And keeping the type abstraction didn't make sense for just one model.

Quoted 44 lines

Those are grouped into 5 different major types:

	+	init_xr2280x_reg_map();
	+	init_xr21b142x_reg_map();
	+	init_xr21b1411_reg_map();
	+	init_xr21v141x_reg_map();
	+
	+	if ((xrusb->DeviceProduct & 0xfff0) == 0x1400)
	+		memcpy(&(xrusb->reg_map), &xr2280x_reg_map,
	+			sizeof(struct reg_addr_map));
	+	else if ((xrusb->DeviceProduct & 0xFFF0) == 0x1420)
	+		memcpy(&(xrusb->reg_map), &xr21b142x_reg_map,
	+			sizeof(struct reg_addr_map));
	+	else if (xrusb->DeviceProduct == 0x1411)
	+		memcpy(&(xrusb->reg_map), &xr21b1411_reg_map,
	+			sizeof(struct reg_addr_map));
	+	else if ((xrusb->DeviceProduct & 0xfff0) == 0x1410)
	+		memcpy(&(xrusb->reg_map), &xr21v141x_reg_map,
	+			sizeof(struct reg_addr_map));
	+	else
	+		rv = -1;

Note: Please don't be confused by "reg_map" name. This has nothing
to do with Linux regmap API ;-)

What happens is that different USB IDs have different values for each register. So, for instance, the UART enable register is set to either one of the following values, depending on the value of udev->descriptor.idProduct:

	xr21b140x_reg_map.uart_enable_addr = 0x00;
	xr21b1411_reg_map.uart_enable_addr = 0xc00;
	xr21v141x_reg_map.uart_enable_addr = 0x03;
	xr21b142x_reg_map.uart_enable_addr = 0x00;

There are other values that depend on the probing time detection, based on other USB descriptors. Those set several fields at the priv data that would allow to properly map the registers.

Also, there are 4 models that support multiple channels. On those, there are one pair of register get/set for each channel.

-

Quoted 7 lines

In summary, while supporting just 04e2:1411 there's no need for a private struct, in order to properly support the other models, some autodetection is needed. The best way of doing that is to re-add the .probe method and adding a priv struct.

As I dunno why this was dropped in the first place, I'm wondering if it would be ok to re-introduce them.

Sure. It was just not needed if we were only going to support one model.

Quoted 4 lines

To be clear: my main focus here is just to avoid needing to use Windows in order to use the serial console of the hardware with the 0x1424 variant ;-)

Quoted 4 lines

I can't test the driver with the other hardware, but, IMHO, instead of adding a hack to support 0x1424, the better (but more painful) would be to re-add the auto-detection part and support for the other models.

Sounds good to me.

Quoted 27 lines

Hi Johan,

Em Tue, 26 Jan 2021 17:26:36 +0100
Johan Hovold <[email protected]> escreveu:

Quoted 6 lines · Manivannan Sadhasivam

Quoted 5 lines · Johan Hovold

Quoted 4 lines · Manivannan Sadhasivam

Quoted 3 lines

Add support for MaxLinear/Exar USB to Serial converters. This driver only supports XR21V141X series but it can be extended to other series from Exar as well in future.

I'm now facing an issue with this driver. I have here two different boards with those USB UART from MaxLinear/Exar.

The first one is identical to Mani's one:

	USB_DEVICE(0x04e2, 0x1411)
The second one is a different version of it:
	USB_DEVICE(0x04e2, 0x1424)

By looking at the final driver merged at linux-next, it sounds that somewhere during the review of this series, it lost the priv struct, and the xr_probe function. It also lost support for all MaxLinear/Exar devices, except for just one model (04e2:1411).

The original submission:

Quoted 8 lines

	https://lore.kernel.org/linux-usb/20180404070634.nhspvmxcjwfgjkcv@advantechmxl-desktop

And the manufacturer's Linux driver on their website:

https://www.maxlinear.com/support/design-tools/software-drivers

Had support for other 12 different models of the MaxLinear/Exar USB UART.

IIRC Manivannan only had access to one of these models and his original submission (based on the patch you link to above) didn't include support for the others. And keeping the type abstraction didn't make sense for just one model.

Quoted 44 lines

Those are grouped into 5 different major types:

	+	init_xr2280x_reg_map();
	+	init_xr21b142x_reg_map();
	+	init_xr21b1411_reg_map();
	+	init_xr21v141x_reg_map();
	+
	+	if ((xrusb->DeviceProduct & 0xfff0) == 0x1400)
	+		memcpy(&(xrusb->reg_map), &xr2280x_reg_map,
	+			sizeof(struct reg_addr_map));
	+	else if ((xrusb->DeviceProduct & 0xFFF0) == 0x1420)
	+		memcpy(&(xrusb->reg_map), &xr21b142x_reg_map,
	+			sizeof(struct reg_addr_map));
	+	else if (xrusb->DeviceProduct == 0x1411)
	+		memcpy(&(xrusb->reg_map), &xr21b1411_reg_map,
	+			sizeof(struct reg_addr_map));
	+	else if ((xrusb->DeviceProduct & 0xfff0) == 0x1410)
	+		memcpy(&(xrusb->reg_map), &xr21v141x_reg_map,
	+			sizeof(struct reg_addr_map));
	+	else
	+		rv = -1;

Note: Please don't be confused by "reg_map" name. This has nothing
to do with Linux regmap API ;-)

What happens is that different USB IDs have different values for each register. So, for instance, the UART enable register is set to either one of the following values, depending on the value of udev->descriptor.idProduct:

	xr21b140x_reg_map.uart_enable_addr = 0x00;
	xr21b1411_reg_map.uart_enable_addr = 0xc00;
	xr21v141x_reg_map.uart_enable_addr = 0x03;
	xr21b142x_reg_map.uart_enable_addr = 0x00;

There are other values that depend on the probing time detection, based on other USB descriptors. Those set several fields at the priv data that would allow to properly map the registers.

Also, there are 4 models that support multiple channels. On those, there are one pair of register get/set for each channel.

-

Quoted 7 lines

In summary, while supporting just 04e2:1411 there's no need for a private struct, in order to properly support the other models, some autodetection is needed. The best way of doing that is to re-add the .probe method and adding a priv struct.

As I dunno why this was dropped in the first place, I'm wondering if it would be ok to re-introduce them.

Sure. It was just not needed if we were only going to support one model.

Quoted 4 lines

To be clear: my main focus here is just to avoid needing to use Windows in order to use the serial console of the hardware with the 0x1424 variant ;-)

Quoted 4 lines

I can't test the driver with the other hardware, but, IMHO, instead of adding a hack to support 0x1424, the better (but more painful) would be to re-add the auto-detection part and support for the other models.

Sounds good to me.

Em Mon, 22 Feb 2021 16:47:36 +0100
Johan Hovold <[email protected]> escreveu:

Quoted 100 lines · Mauro Carvalho Chehab

Quoted 27 lines

Hi Johan,

Em Tue, 26 Jan 2021 17:26:36 +0100
Johan Hovold <[email protected]> escreveu:

Quoted 6 lines · Manivannan Sadhasivam

Quoted 5 lines · Johan Hovold

Quoted 4 lines · Manivannan Sadhasivam

Quoted 3 lines

Add support for MaxLinear/Exar USB to Serial converters. This driver only supports XR21V141X series but it can be extended to other series from Exar as well in future.

I'm now facing an issue with this driver. I have here two different boards with those USB UART from MaxLinear/Exar.

The first one is identical to Mani's one:

	USB_DEVICE(0x04e2, 0x1411)
The second one is a different version of it:
	USB_DEVICE(0x04e2, 0x1424)

By looking at the final driver merged at linux-next, it sounds that somewhere during the review of this series, it lost the priv struct, and the xr_probe function. It also lost support for all MaxLinear/Exar devices, except for just one model (04e2:1411).

The original submission:

Quoted 8 lines

	https://lore.kernel.org/linux-usb/20180404070634.nhspvmxcjwfgjkcv@advantechmxl-desktop

And the manufacturer's Linux driver on their website:

https://www.maxlinear.com/support/design-tools/software-drivers

Had support for other 12 different models of the MaxLinear/Exar USB UART.

IIRC Manivannan only had access to one of these models and his original submission (based on the patch you link to above) didn't include support for the others. And keeping the type abstraction didn't make sense for just one model.

Quoted 44 lines

Those are grouped into 5 different major types:

	+	init_xr2280x_reg_map();
	+	init_xr21b142x_reg_map();
	+	init_xr21b1411_reg_map();
	+	init_xr21v141x_reg_map();
	+
	+	if ((xrusb->DeviceProduct & 0xfff0) == 0x1400)
	+		memcpy(&(xrusb->reg_map), &xr2280x_reg_map,
	+			sizeof(struct reg_addr_map));
	+	else if ((xrusb->DeviceProduct & 0xFFF0) == 0x1420)
	+		memcpy(&(xrusb->reg_map), &xr21b142x_reg_map,
	+			sizeof(struct reg_addr_map));
	+	else if (xrusb->DeviceProduct == 0x1411)
	+		memcpy(&(xrusb->reg_map), &xr21b1411_reg_map,
	+			sizeof(struct reg_addr_map));
	+	else if ((xrusb->DeviceProduct & 0xfff0) == 0x1410)
	+		memcpy(&(xrusb->reg_map), &xr21v141x_reg_map,
	+			sizeof(struct reg_addr_map));
	+	else
	+		rv = -1;

Note: Please don't be confused by "reg_map" name. This has nothing
to do with Linux regmap API ;-)

What happens is that different USB IDs have different values for each register. So, for instance, the UART enable register is set to either one of the following values, depending on the value of udev->descriptor.idProduct:

	xr21b140x_reg_map.uart_enable_addr = 0x00;
	xr21b1411_reg_map.uart_enable_addr = 0xc00;
	xr21v141x_reg_map.uart_enable_addr = 0x03;
	xr21b142x_reg_map.uart_enable_addr = 0x00;

There are other values that depend on the probing time detection, based on other USB descriptors. Those set several fields at the priv data that would allow to properly map the registers.

Also, there are 4 models that support multiple channels. On those, there are one pair of register get/set for each channel.

-

Quoted 7 lines

In summary, while supporting just 04e2:1411 there's no need for a private struct, in order to properly support the other models, some autodetection is needed. The best way of doing that is to re-add the .probe method and adding a priv struct.

As I dunno why this was dropped in the first place, I'm wondering if it would be ok to re-introduce them.

Sure. It was just not needed if we were only going to support one model.

Quoted 4 lines

To be clear: my main focus here is just to avoid needing to use Windows in order to use the serial console of the hardware with the 0x1424 variant ;-)

Quoted 6 lines

Quoted 4 lines

I can't test the driver with the other hardware, but, IMHO, instead of adding a hack to support 0x1424, the better (but more painful) would be to re-add the auto-detection part and support for the other models.

Sounds good to me.

While testing the xr_serial (as currently merged), I opted to apply the patches on the top of vanilla Kernel 5.11 - as it sounds too risky to use linux-next so early on a new development cycle :-)

There, I'm getting an OOPS:

	[   30.261291] BUG: kernel NULL pointer dereference, address: 00000000000000a8
	[   30.261375] #PF: supervisor write access in kernel mode
	[   30.261438] #PF: error_code(0x0002) - not-present page
	[   30.261500] PGD 0 P4D 0 
	[   30.261539] Oops: 0002 [#1] SMP PTI
	[   30.261586] CPU: 2 PID: 686 Comm: kworker/2:3 Not tainted 5.11.0+ #14
	[   30.261666] Hardware name:  /NUC5i7RYB, BIOS RYBDWi35.86A.0380.2019.0517.1530 05/17/2019
	[   30.261757] Workqueue: usb_hub_wq hub_event
	[   30.261816] RIP: 0010:mutex_lock+0x1e/0x40
	[   30.261875] Code: c3 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 55 48 89 e5 41 54 49 89 fc e8 8d dd ff ff 31 c0 65 48 8b 14 25 c0 7b 01 00 <f0> 49 0f b1 14 24 75 04 41 5c 5d c3 4c 89 e7 e8 ae ff ff ff 41 5c
	[   30.262076] RSP: 0018:ffffb937c0767b70 EFLAGS: 00010246
	[   30.262140] RAX: 0000000000000000 RBX: ffff95e71ef75430 RCX: 0000000000000027
	[   30.262223] RDX: ffff95e70597b000 RSI: 00000000ffffdfff RDI: 00000000000000a8
	[   30.262305] RBP: ffffb937c0767b78 R08: ffff95ea76d18ac0 R09: ffffb937c0767948
	[   30.262387] R10: 0000000000000001 R11: 0000000000000001 R12: 00000000000000a8
	[   30.262469] R13: 0000000000000000 R14: ffff95e71ef75400 R15: 0000000000000000
	[   30.262551] FS:  0000000000000000(0000) GS:ffff95ea76d00000(0000) knlGS:0000000000000000
	[   30.262645] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
	[   30.262713] CR2: 00000000000000a8 CR3: 000000042be0a002 CR4: 00000000003706e0
	[   30.262796] Call Trace:
	[   30.262832]  usb_serial_disconnect+0x33/0x140
	[   30.262897]  usb_unbind_interface+0x8c/0x260
	[   30.262957]  device_release_driver_internal+0x103/0x1d0
	[   30.263026]  device_release_driver+0x12/0x20
	[   30.263083]  bus_remove_device+0xe1/0x150
	[   30.263140]  device_del+0x192/0x3f0
	[   30.263188]  ? usb_remove_ep_devs+0x1f/0x30
	[   30.263244]  usb_disable_device+0x95/0x1c0
	[   30.263300]  usb_disconnect+0xc0/0x270
	[   30.263350]  hub_event+0xa2e/0x1620

After adding this hack:

<snip>

drivers/usb/serial/usb-serial.c +5 -0

@@ -1081,6 +1081,11 @@ static void usb_serial_disconnect(struct usb_interface *interface)
        struct usb_serial_port *port;
        struct tty_struct *tty;
 
+       if (!serial) {
+               dev_err(dev, "%s: Serial pointer is NULL!!!\n", __func__);
+               return;
+       }
+
        usb_serial_console_disconnect(serial);
 
        mutex_lock(&serial->disc_mutex);

</snip>

It works fine:

	[  283.005625] xr_serial 2-1:1.1: xr_serial converter detected
	[  283.005868] usb 2-1: xr_serial converter now attached to ttyUSB0
	[  283.007284] printk: console [ttyUSB0] enabled
	[  284.444419] usb 2-1: USB disconnect, device number 5
	[  284.444520] xr_serial 2-1:1.0: usb_serial_disconnect: Serial pointer is NULL!!!
	[  284.444894] printk: console [ttyUSB0] disabled
	[  284.445091] xr_serial ttyUSB0: xr_serial converter now disconnected from ttyUSB0
	[  284.445141] xr_disconnect
	[  284.445156] xr_serial 2-1:1.1: device disconnected

I'm not sure if the bug is at xr_serial or if it is inside usb-serial.c.

Any ideas?

Em Thu, 25 Feb 2021 18:58:20 +0100
Mauro Carvalho Chehab <[email protected]> escreveu:

Quoted 59 lines

While testing the xr_serial (as currently merged), I opted to apply the patches on the top of vanilla Kernel 5.11 - as it sounds too risky to use linux-next so early on a new development cycle :-)

There, I'm getting an OOPS:

	[   30.261291] BUG: kernel NULL pointer dereference, address: 00000000000000a8
	[   30.261375] #PF: supervisor write access in kernel mode
	[   30.261438] #PF: error_code(0x0002) - not-present page
	[   30.261500] PGD 0 P4D 0 
	[   30.261539] Oops: 0002 [#1] SMP PTI
	[   30.261586] CPU: 2 PID: 686 Comm: kworker/2:3 Not tainted 5.11.0+ #14
	[   30.261666] Hardware name:  /NUC5i7RYB, BIOS RYBDWi35.86A.0380.2019.0517.1530 05/17/2019
	[   30.261757] Workqueue: usb_hub_wq hub_event
	[   30.261816] RIP: 0010:mutex_lock+0x1e/0x40

	[   30.262796] Call Trace:
	[   30.262832]  usb_serial_disconnect+0x33/0x140
	[   30.262897]  usb_unbind_interface+0x8c/0x260
	[   30.262957]  device_release_driver_internal+0x103/0x1d0
	[   30.263026]  device_release_driver+0x12/0x20
	[   30.263083]  bus_remove_device+0xe1/0x150
	[   30.263140]  device_del+0x192/0x3f0
	[   30.263188]  ? usb_remove_ep_devs+0x1f/0x30
	[   30.263244]  usb_disable_device+0x95/0x1c0
	[   30.263300]  usb_disconnect+0xc0/0x270
	[   30.263350]  hub_event+0xa2e/0x1620

After adding this hack:

<snip>

drivers/usb/serial/usb-serial.c +5 -0

@@ -1081,6 +1081,11 @@ static void usb_serial_disconnect(struct usb_interface *interface)
        struct usb_serial_port *port;
        struct tty_struct *tty;
 
+       if (!serial) {
+               dev_err(dev, "%s: Serial pointer is NULL!!!\n", __func__);
+               return;
+       }
+
        usb_serial_console_disconnect(serial);
 
        mutex_lock(&serial->disc_mutex);

</snip>

It works fine:

	[  283.005625] xr_serial 2-1:1.1: xr_serial converter detected
	[  283.005868] usb 2-1: xr_serial converter now attached to ttyUSB0
	[  283.007284] printk: console [ttyUSB0] enabled
	[  284.444419] usb 2-1: USB disconnect, device number 5
	[  284.444520] xr_serial 2-1:1.0: usb_serial_disconnect: Serial pointer is NULL!!!
	[  284.444894] printk: console [ttyUSB0] disabled
	[  284.445091] xr_serial ttyUSB0: xr_serial converter now disconnected from ttyUSB0
	[  284.445141] xr_disconnect
	[  284.445156] xr_serial 2-1:1.1: device disconnected

Quoted 3 lines

I'm not sure if the bug is at xr_serial or if it is inside usb-serial.c.

Any ideas?

Answering myself, as those devices may have two different interfaces (one for control and another one for data), I suspect that the driver needs to manually call usb_set_intfdata() after detecting the data interface.

Quoted 62 lines

Em Thu, 25 Feb 2021 18:58:20 +0100
Mauro Carvalho Chehab <[email protected]> escreveu:

Quoted 59 lines

While testing the xr_serial (as currently merged), I opted to apply the patches on the top of vanilla Kernel 5.11 - as it sounds too risky to use linux-next so early on a new development cycle :-)

There, I'm getting an OOPS:

	[   30.261291] BUG: kernel NULL pointer dereference, address: 00000000000000a8
	[   30.261375] #PF: supervisor write access in kernel mode
	[   30.261438] #PF: error_code(0x0002) - not-present page
	[   30.261500] PGD 0 P4D 0 
	[   30.261539] Oops: 0002 [#1] SMP PTI
	[   30.261586] CPU: 2 PID: 686 Comm: kworker/2:3 Not tainted 5.11.0+ #14
	[   30.261666] Hardware name:  /NUC5i7RYB, BIOS RYBDWi35.86A.0380.2019.0517.1530 05/17/2019
	[   30.261757] Workqueue: usb_hub_wq hub_event
	[   30.261816] RIP: 0010:mutex_lock+0x1e/0x40  

	[   30.262796] Call Trace:
	[   30.262832]  usb_serial_disconnect+0x33/0x140
	[   30.262897]  usb_unbind_interface+0x8c/0x260
	[   30.262957]  device_release_driver_internal+0x103/0x1d0
	[   30.263026]  device_release_driver+0x12/0x20
	[   30.263083]  bus_remove_device+0xe1/0x150
	[   30.263140]  device_del+0x192/0x3f0
	[   30.263188]  ? usb_remove_ep_devs+0x1f/0x30
	[   30.263244]  usb_disable_device+0x95/0x1c0
	[   30.263300]  usb_disconnect+0xc0/0x270
	[   30.263350]  hub_event+0xa2e/0x1620

After adding this hack:

<snip>

drivers/usb/serial/usb-serial.c +5 -0

@@ -1081,6 +1081,11 @@ static void usb_serial_disconnect(struct usb_interface *interface)
        struct usb_serial_port *port;
        struct tty_struct *tty;
 
+       if (!serial) {
+               dev_err(dev, "%s: Serial pointer is NULL!!!\n", __func__);
+               return;
+       }
+
        usb_serial_console_disconnect(serial);
 
        mutex_lock(&serial->disc_mutex);

</snip>

It works fine:

	[  283.005625] xr_serial 2-1:1.1: xr_serial converter detected
	[  283.005868] usb 2-1: xr_serial converter now attached to ttyUSB0
	[  283.007284] printk: console [ttyUSB0] enabled
	[  284.444419] usb 2-1: USB disconnect, device number 5
	[  284.444520] xr_serial 2-1:1.0: usb_serial_disconnect: Serial pointer is NULL!!!
	[  284.444894] printk: console [ttyUSB0] disabled
	[  284.445091] xr_serial ttyUSB0: xr_serial converter now disconnected from ttyUSB0
	[  284.445141] xr_disconnect
	[  284.445156] xr_serial 2-1:1.1: device disconnected

Quoted 8 lines

Quoted 3 lines

I'm not sure if the bug is at xr_serial or if it is inside usb-serial.c.

Any ideas?

Answering myself, as those devices may have two different interfaces (one for control and another one for data), I suspect that the driver needs to manually call usb_set_intfdata() after detecting the data interface.

Thanks for reporting this.

I'm afraid it's a bit more involved than that; we'd need to add support to USB-serial core for managing a sibling interface and either one being disconnected first. This has implications for suspend as well.

I think we should just not claim the control interface for now since it not currently used by the driver. I'll send a fix.

Add gpiochip support for Maxlinear/Exar USB to serial converter for controlling the available gpios.

Inspired from cp210x usb to serial converter driver.

Cc Linus Walleij <[email protected]>

Cc [email protected]

Signed-off-by Manivannan Sadhasivam <[email protected]>

Quoted 2 lines · Manivannan Sadhasivam

Add gpiochip support for Maxlinear/Exar USB to serial converter for controlling the available gpios.

One minor notice:

drivers/usb/serial/xr_serial.c line 29

Quoted 9 lines

drivers/usb/serial/xr_serial.c +9 -0

+enum gpio_pins {
+       GPIO_RI = 0,
+       GPIO_CD,
+       GPIO_DSR,
+       GPIO_DTR,
+       GPIO_CTS,
+       GPIO_RTS,
+       GPIO_MAX,
+};

You know the names of the pins...

drivers/usb/serial/xr_serial.c static void xr_break_ctl(struct tty_struct *tty, int break_state) · line 755

Quoted 13 lines

drivers/usb/serial/xr_serial.c +13 -0

+       port_priv->gc.ngpio = 6;
+       port_priv->gc.label = "xr_gpios";
+       port_priv->gc.request = xr_gpio_request;
+       port_priv->gc.free = xr_gpio_free;
+       port_priv->gc.get_direction = xr_gpio_direction_get;
+       port_priv->gc.direction_input = xr_gpio_direction_input;
+       port_priv->gc.direction_output = xr_gpio_direction_output;
+       port_priv->gc.get = xr_gpio_get;
+       port_priv->gc.set = xr_gpio_set;
+       port_priv->gc.owner = THIS_MODULE;
+       port_priv->gc.parent = &port->dev;
+       port_priv->gc.base = -1;
+       port_priv->gc.can_sleep = true;

So assign port_priv->gc.names here as well with an array of strings with the names ("RI", "CD", ... etc). This makes it look really nice in userspace if you do e.g. "lsgpio".

Quoted 18 lines · Linus Walleij

On Sun, Nov 22, 2020 at 6:08 PM Manivannan Sadhasivam <[email protected]> wrote:

You know the names of the pins...

drivers/usb/serial/xr_serial.c static void xr_break_ctl(struct tty_struct *tty, int break_state) · line 755

Quoted 13 lines

drivers/usb/serial/xr_serial.c +13 -0

+       port_priv->gc.ngpio = 6;
+       port_priv->gc.label = "xr_gpios";
+       port_priv->gc.request = xr_gpio_request;
+       port_priv->gc.free = xr_gpio_free;
+       port_priv->gc.get_direction = xr_gpio_direction_get;
+       port_priv->gc.direction_input = xr_gpio_direction_input;
+       port_priv->gc.direction_output = xr_gpio_direction_output;
+       port_priv->gc.get = xr_gpio_get;
+       port_priv->gc.set = xr_gpio_set;
+       port_priv->gc.owner = THIS_MODULE;
+       port_priv->gc.parent = &port->dev;
+       port_priv->gc.base = -1;
+       port_priv->gc.can_sleep = true;

Quoted 4 lines

So assign port_priv->gc.names here as well with an array of strings with the names ("RI", "CD", ... etc). This makes it look really nice in userspace if you do e.g. "lsgpio".

Last time we tried that gpiolib still used a flat namespace so that you can't have have more than one device using the same names. Unless that has changed this is a no-go. See

        https://lore.kernel.org/r/[email protected]

for our previous discussion about this.

Quoted 24 lines · Johan Hovold

Quoted 18 lines · Linus Walleij

On Sun, Nov 22, 2020 at 6:08 PM Manivannan Sadhasivam <[email protected]> wrote:

You know the names of the pins...

drivers/usb/serial/xr_serial.c static void xr_break_ctl(struct tty_struct *tty, int break_state) · line 755

Quoted 13 lines

drivers/usb/serial/xr_serial.c +13 -0

+       port_priv->gc.ngpio = 6;
+       port_priv->gc.label = "xr_gpios";
+       port_priv->gc.request = xr_gpio_request;
+       port_priv->gc.free = xr_gpio_free;
+       port_priv->gc.get_direction = xr_gpio_direction_get;
+       port_priv->gc.direction_input = xr_gpio_direction_input;
+       port_priv->gc.direction_output = xr_gpio_direction_output;
+       port_priv->gc.get = xr_gpio_get;
+       port_priv->gc.set = xr_gpio_set;
+       port_priv->gc.owner = THIS_MODULE;
+       port_priv->gc.parent = &port->dev;
+       port_priv->gc.base = -1;
+       port_priv->gc.can_sleep = true;

Quoted 4 lines

So assign port_priv->gc.names here as well with an array of strings with the names ("RI", "CD", ... etc). This makes it look really nice in userspace if you do e.g. "lsgpio".

Quoted 7 lines

Last time we tried that gpiolib still used a flat namespace so that you can't have have more than one device using the same names. Unless that has changed this is a no-go. See

        https://lore.kernel.org/r/[email protected]

for our previous discussion about this.

Hm hm yeah we actually put in a nasty warning there since:

                gpio = gpio_name_to_desc(gc->names[i]);
                if (gpio)
                        dev_warn(&gdev->dev,
                                 "Detected name collision for GPIO name '%s'\n",
                                 gc->names[i]);

A better approach might be to create an array of names prepended with something device-unique like the USB bus topology? Or do we need a helper to help naming the GPIOs? What would be helpful here?

name = kasprintf(GFP_KERNEL, "%s-NAME", topology_str);

[Me]

Quoted 5 lines

A better approach might be to create an array of names prepended with something device-unique like the USB bus topology? Or do we need a helper to help naming the GPIOs? What would be helpful here?

Quoted 1 line

name = kasprintf(GFP_KERNEL, "%s-NAME", topology_str);

Well we started discussing this back when we only had the sysfs interface which suffered from the same problem. I thought the chardev interface was supposed to get rid of the assumption of a flat name space? Perhaps in v3 of the ABI. ;P

But what about any other non-pluggable
IC, which provides a few named GPIO lines and of which there could be more than one in a system?

The topology is already encoded in sysfs and it seems backwards to have each and every gpio driver reconstruct it.

Quoted 7 lines · Johan Hovold

[Me]

Quoted 5 lines

A better approach might be to create an array of names prepended with something device-unique like the USB bus topology? Or do we need a helper to help naming the GPIOs? What would be helpful here?

Quoted 6 lines

Quoted 1 line

name = kasprintf(GFP_KERNEL, "%s-NAME", topology_str);

Well we started discussing this back when we only had the sysfs interface which suffered from the same problem. I thought the chardev interface was supposed to get rid of the assumption of a flat name space? Perhaps in v3 of the ABI. ;P

It's "mostly true" that the line names are unique per-chip actually, because people don't like the nasty warning message. I wonder if anything would really break if I go in and make a patch to enforce it, since all drivers passing ->names in the gpiochip are in the kernel we can check them all.

If the names are unique-per-chip, we can add a restriction like this with the requirement:

depends on !GPIO_SYSFS

so it can't even be compiled in if someone is using the sysfs.

That should solve the situation where people are (ab)using the sysfs and getting name collisions as a result.

Then it should be fine for any driver to provide a names array provided all the names are unique on that gpiochip.

I doubt it would break anything, but let's see what Geert says. He has some special usecases in the gpio-aggregator driver which will incidentally look for just linenames when aggregating gpios, but I feel it is a bit thick for it to work with multiple hot-pluggable GPIO chips as well, I don't think that is its usecase. (We all want to be perfect but...)

Quoted 3 lines

But what about any other non-pluggable
IC, which provides a few named GPIO lines and of which there could be more than one in a system?

I think if there are such, and the lines are unique per-chip we should make the drivers depend on !GPIO_SYSFS.

Quoted 2 lines

The topology is already encoded in sysfs and it seems backwards to have each and every gpio driver reconstruct it.

I agree.

I think if this driver already has unique line-names per-gpiochip we could actually make it depend on !GPIO_SYSFS and just add the names.

Yours,
Linus Walleij

Quoted 5 lines · Linus Walleij

On Tue, Dec 8, 2020 at 10:57 AM Johan Hovold <[email protected]> wrote:

I think if this driver already has unique line-names per-gpiochip we could actually make it depend on !GPIO_SYSFS and just add the names.

Sure thing.

Johan, if you are okay with this I can resubmit incorporating Linus's suggestion.

Quoted 4 lines · Johan Hovold

Well we started discussing this back when we only had the sysfs interface which suffered from the same problem. I thought the chardev interface was supposed to get rid of the assumption of a flat name space? Perhaps in v3 of the ABI. ;P

It's "mostly true" that the line names are unique per-chip actually, because people don't like the nasty warning message. I wonder if anything would really break if I go in and make a patch to enforce it, since all drivers passing ->names in the gpiochip are in the kernel we can check them all.

If the names are unique-per-chip, we can add a restriction like this with the requirement:

depends on !GPIO_SYSFS

so it can't even be compiled in if someone is using the sysfs.

That should solve the situation where people are (ab)using the sysfs and getting name collisions as a result.

Then it should be fine for any driver to provide a names array provided all the names are unique on that gpiochip.

I doubt it would break anything, but let's see what Geert says. He has some special usecases in the gpio-aggregator driver which will incidentally look for just linenames when aggregating gpios, but I feel it is a bit thick for it to work with multiple hot-pluggable GPIO chips as well, I don't think that is its usecase. (We all want to be perfect but...)

Quoted 3 lines

But what about any other non-pluggable
IC, which provides a few named GPIO lines and of which there could be more than one in a system?

I think if there are such, and the lines are unique per-chip we should make the drivers depend on !GPIO_SYSFS.

Quoted 6 lines · Linus Walleij

depends on !GPIO_SYSFS

so it can't even be compiled in if someone is using the sysfs.

That should solve the situation where people are (ab)using the sysfs and getting name collisions as a result.

Would it possible to set a flag to suppress just the sysfs entry renaming instead?

Despite its flaws the sysfs interface is still very convenient and I'd prefer not to disable it just because of the line names.

Quoted 2 lines

Then it should be fine for any driver to provide a names array provided all the names are unique on that gpiochip.

So it sounds like there's nothing preventing per-chip-unique names in the rest of gpiolib and the new chardev interface then? Are the user-space libraries able to cope with it, etc?

Quoted 9 lines · Johan Hovold

Quoted 6 lines · Linus Walleij

depends on !GPIO_SYSFS

so it can't even be compiled in if someone is using the sysfs.

That should solve the situation where people are (ab)using the sysfs and getting name collisions as a result.

Quoted 2 lines

Would it possible to set a flag to suppress just the sysfs entry renaming instead?

Hm you mean that when a GPIO is "exported" in sysfs it should not get a symbolic name from the names but instead just the number?

I bet someone has written their scripts to take advantage of the symbolic names so I suspect the task becomes bigger like suppress the sysfs entry renaming if and only if there is a namespace collision.

But I think we can do that, doesn't seem too hard?

I just hacked up this:
https://lore.kernel.org/linux-gpio/[email protected]/T/#u

Quoted 2 lines

Despite its flaws the sysfs interface is still very convenient and I'd prefer not to disable it just because of the line names.

Would these conveniences be identical to those listed in my recent TODO entry?
https://lore.kernel.org/linux-gpio/[email protected]/

There are several other issues with the sysfs, so making it conflict with other drivers is almost plus in the direction of discouragement from the GPIO submaintainer point of view, but I do see that people like it for the reasons in the TODO. :/

I am strongly encouraging any developer with a few spare cycles on their hands to go and implement the debugfs facility because we can make it so much better than the sysfs, easier and more convenient for testing etc.

Quoted 6 lines

Quoted 2 lines

Then it should be fine for any driver to provide a names array provided all the names are unique on that gpiochip.

So it sounds like there's nothing preventing per-chip-unique names in the rest of gpiolib and the new chardev interface then? Are the user-space libraries able to cope with it, etc?

Yes the documentation refers to libgpiod a very well maintained library:
https://www.kernel.org/doc/html/latest/driver-api/gpio/using-gpio.html
https://git.kernel.org/pub/scm/libs/libgpiod/libgpiod.git/

Quoted 10 lines · Linus Walleij

Quoted 3 lines · Johan Hovold

So it sounds like there's nothing preventing per-chip-unique names in the rest of gpiolib and the new chardev interface then? Are the user-space libraries able to cope with it, etc?

Yes the documentation refers to libgpiod a very well maintained library:
https://www.kernel.org/doc/html/latest/driver-api/gpio/using-gpio.html
https://git.kernel.org/pub/scm/libs/libgpiod/libgpiod.git/

Just did a super quick check and it seems libgpiod still assumes a flat name space. For example, gpiod_chip_find_line() returns only the first line found that matches a name. Shouldn't be impossible to extend, but just want to make sure this flat namespace assumption hasn't been to heavily relied upon.

On Wed, Dec 09, 2020 at 05:25:32PM +0100, Linus Walleij wrote:

I just replied to that thread, but to summarize, you can't rely on having the sysfs code detect collisions since that will trigger a bunch of nasty warnings and backtraces. We also don't want the sysfs interface for a specific USB device to depend on probe order (only the first one plugged in gets to use the line names). And adding line names now could in fact be what breaks currently working scripts.

Quoted 4 lines

I am strongly encouraging any developer with a few spare cycles on their hands to go and implement the debugfs facility because we can make it so much better than the sysfs, easier and more convenient for testing etc.

Don't you run the risk of having people enable debugfs in production systems now just so they can use the old-style interface?

Side note: if you skip the "export" part of the interface, how would you indicate that a line is already in use or not available (e.g. gpio-range-reserved)?

Just did a super quick check and it seems libgpiod still assumes a flat name space. For example, gpiod_chip_find_line() returns only the first line found that matches a name. Shouldn't be impossible to extend, but just want to make sure this flat namespace assumption hasn't been to heavily relied upon.

Quoted 8 lines · Johan Hovold

On Wed, Dec 09, 2020 at 05:25:32PM +0100, Linus Walleij wrote:

I just replied to that thread, but to summarize, you can't rely on having the sysfs code detect collisions since that will trigger a bunch of nasty warnings and backtraces. We also don't want the sysfs interface for a specific USB device to depend on probe order (only the first one plugged in gets to use the line names). And adding line names now could in fact be what breaks currently working scripts.

Yes the sysfs ABI is very volatile and easy to break.

As pointed out in the other reply, sysfs base GPIO number is all wibbly-wobbly on anything hot-pluggable so in a way I feel it is the right thing to disallow sysfs altogether on hotpluggable devices.

Quoted 5 lines

Just did a super quick check and it seems libgpiod still assumes a flat name space. For example, gpiod_chip_find_line() returns only the first line found that matches a name. Shouldn't be impossible to extend, but just want to make sure this flat namespace assumption hasn't been to heavily relied upon.

The unique way to identify a GPIO is gpiochip instance (with topology from sysfs) and then a line number on that chip. This is done e.g. in the example tool tools/gpio/gpio-hammer.c

As you can see the tool doesn't use these line names.

The line names are really like symbolic links or something. But they are indeed in a flat namespace so we should try to at least make them unique if it turns out people love to use these.

As it is now system designers mostly use device tree to assign line names and they try to make these unique because they don't like the nasty warnings from gpiolib.

If I google for the phrase "Detected name collision for GPIO name" I just find the code, our discussions and some USB serial devices warning about this so far.

Maybe we should just make a patch to disallow it?

Quoted 5 lines · Linus Walleij

If I google for the phrase "Detected name collision for GPIO name" I just find the code, our discussions and some USB serial devices warning about this so far.

Maybe we should just make a patch to disallow it?

That would make it impossible to provide name lines on hotpluggable controllers, which would be nice to support.

Quoted 8 lines · Johan Hovold

Quoted 5 lines · Linus Walleij

If I google for the phrase "Detected name collision for GPIO name" I just find the code, our discussions and some USB serial devices warning about this so far.

Maybe we should just make a patch to disallow it?

Quoted 2 lines

That would make it impossible to provide name lines on hotpluggable controllers, which would be nice to support.

I merged a patch for this now, let's tighten this loose end up.

Also: thanks for poking me about this, I should have looked into this ages ago :/ focus you know...

Quoted 8 lines · Manivannan Sadhasivam

Add gpiochip support for Maxlinear/Exar USB to serial converter for controlling the available gpios.

Inspired from cp210x usb to serial converter driver.

Cc Linus Walleij <[email protected]>

Cc [email protected]

Signed-off-by Manivannan Sadhasivam <[email protected]>

This looks good to me overall, provided that it plays well with the serial port.

One minor notice:

drivers/usb/serial/xr_serial.c line 29

Quoted 9 lines

drivers/usb/serial/xr_serial.c +9 -0

+enum gpio_pins {
+       GPIO_RI = 0,
+       GPIO_CD,
+       GPIO_DSR,
+       GPIO_DTR,
+       GPIO_CTS,
+       GPIO_RTS,
+       GPIO_MAX,
+};

You know the names of the pins...

drivers/usb/serial/xr_serial.c static void xr_break_ctl(struct tty_struct *tty, int break_state) · line 755

Quoted 13 lines

drivers/usb/serial/xr_serial.c +13 -0

+       port_priv->gc.ngpio = 6;
+       port_priv->gc.label = "xr_gpios";
+       port_priv->gc.request = xr_gpio_request;
+       port_priv->gc.free = xr_gpio_free;
+       port_priv->gc.get_direction = xr_gpio_direction_get;
+       port_priv->gc.direction_input = xr_gpio_direction_input;
+       port_priv->gc.direction_output = xr_gpio_direction_output;
+       port_priv->gc.get = xr_gpio_get;
+       port_priv->gc.set = xr_gpio_set;
+       port_priv->gc.owner = THIS_MODULE;
+       port_priv->gc.parent = &port->dev;
+       port_priv->gc.base = -1;
+       port_priv->gc.can_sleep = true;

So assign port_priv->gc.names here as well with an array of strings with the names ("RI", "CD", ... etc). This makes it look really nice in userspace if you do e.g. "lsgpio".

With that:

Reviewed-by Linus Walleij <[email protected]>

Yours,
Linus Walleij

Add gpiochip support for Maxlinear/Exar USB to serial converter for controlling the available gpios.

Inspired from cp210x usb to serial converter driver.

Cc Linus Walleij <[email protected]>

Cc [email protected]

Signed-off-by Manivannan Sadhasivam <[email protected]>

---
 drivers/usb/serial/xr_serial.c | 267 ++++++++++++++++++++++++++++++++-
 1 file changed, 261 insertions(+), 6 deletions(-)

drivers/usb/serial/xr_serial.c +8 -0

index e166916554d6..ca63527a5310 100644
@@ -9,6 +9,7 @@
  * Copyright (c) 2020 Manivannan Sadhasivam <[email protected]>
  */
 
+#include <linux/gpio/driver.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/slab.h>

@@ -16,6 +17,28 @@
 #include <linux/usb.h>
 #include <linux/usb/serial.h>
 
+#ifdef CONFIG_GPIOLIB
+enum gpio_pins {
+	GPIO_RI = 0,
+	GPIO_CD,
+	GPIO_DSR,
+	GPIO_DTR,
+	GPIO_CTS,

drivers/usb/serial/xr_serial.c +8 -0

+#endif
+	struct mutex gpio_lock;	/* protects GPIO state */
+	bool port_open;
+};
+
 struct xr_txrx_clk_mask {
 	u16 tx;
 	u16 rx0;

@@ -106,6 +129,8 @@ struct xr_txrx_clk_mask {
 #define XR21V141X_REG_GPIO_CLR		0x1e
 #define XR21V141X_REG_GPIO_STATUS	0x1f
 
+static int xr_cts_rts_check(struct xr_port_private *port_priv);
+
 static int xr_set_reg(struct usb_serial_port *port, u8 block, u8 reg,
 		      u8 val)
 {

@@ -309,6 +334,7 @@ static int xr_uart_disable(struct usb_serial_port *port)
 static void xr_set_flow_mode(struct tty_struct *tty,
 			     struct usb_serial_port *port)
 {
+	struct xr_port_private *port_priv = usb_get_serial_port_data(port);
 	unsigned int cflag = tty->termios.c_cflag;
 	int ret;
 	u8 flow, gpio_mode;

drivers/usb/serial/xr_serial.c +15 -5

+			flow = XR21V141X_UART_FLOW_MODE_NONE;
+			goto exit;
+		}
+
 		dev_dbg(&port->dev, "Enabling hardware flow ctrl\n");
 
 		/*

@@ -341,6 +378,7 @@ static void xr_set_flow_mode(struct tty_struct *tty,
 		flow = XR21V141X_UART_FLOW_MODE_NONE;
 	}
 
+exit:
 	/*
 	 * As per the datasheet, UART needs to be disabled while writing to
 	 * FLOW_CONTROL register.

@@ -355,18 +393,22 @@ static void xr_set_flow_mode(struct tty_struct *tty,
 static int xr_tiocmset_port(struct usb_serial_port *port,
 			    unsigned int set, unsigned int clear)
 {
+	struct xr_port_private *port_priv = usb_get_serial_port_data(port);
 	u8 gpio_set = 0;
 	u8 gpio_clr = 0;
 	int ret = 0;
 
-	/* Modem control pins are active low, so set & clr are swapped */
-	if (set & TIOCM_RTS)
+	/*
+	 * Modem control pins are active low, so set & clr are swapped. And
+	 * ignore the pins that are occupied by GPIOLIB.
+	 */
+	if ((set & TIOCM_RTS) && !(port_priv->pin_status[GPIO_RTS]))
 		gpio_clr |= XR21V141X_UART_MODE_RTS;
-	if (set & TIOCM_DTR)
+	if ((set & TIOCM_DTR) && !(port_priv->pin_status[GPIO_DTR]))
 		gpio_clr |= XR21V141X_UART_MODE_DTR;
-	if (clear & TIOCM_RTS)
+	if ((clear & TIOCM_RTS) && !(port_priv->pin_status[GPIO_RTS]))
 		gpio_set |= XR21V141X_UART_MODE_RTS;
-	if (clear & TIOCM_DTR)
+	if ((clear & TIOCM_DTR) && !(port_priv->pin_status[GPIO_DTR]))
 		gpio_set |= XR21V141X_UART_MODE_DTR;
 
 	/* Writing '0' to gpio_{set/clr} bits has no effect, so no need to do */

@@ -464,6 +506,7 @@ static void xr_set_termios(struct tty_struct *tty,
 
 static int xr_open(struct tty_struct *tty, struct usb_serial_port *port)
 {
+	struct xr_port_private *port_priv = usb_get_serial_port_data(port);
 	int ret;
 
 	ret = xr_uart_enable(port);

drivers/usb/serial/xr_serial.c +21 -1

+
 	return 0;
 }
 
 static void xr_close(struct usb_serial_port *port)
 {
+	struct xr_port_private *port_priv = usb_get_serial_port_data(port);
+
 	usb_serial_generic_close(port);
 
+	mutex_lock(&port_priv->gpio_lock);
+	port_priv->port_open = false;
+	mutex_unlock(&port_priv->gpio_lock);
+
 	xr_uart_disable(port);
 }
 

@@ -553,13 +606,215 @@ static void xr_break_ctl(struct tty_struct *tty, int break_state)
 	xr_set_reg_uart(port, XR21V141X_REG_TX_BREAK, state);
 }
 
-static int xr_port_probe(struct usb_serial_port *port)
+#ifdef CONFIG_GPIOLIB
+
+static int xr_cts_rts_check(struct xr_port_private *port_priv)
 {
+	if (port_priv->pin_status[GPIO_RTS] || port_priv->pin_status[GPIO_CTS])
+		return -EBUSY;
+
 	return 0;
 }
 
+static int xr_gpio_request(struct gpio_chip *gc, unsigned int offset)
+{
+	struct usb_serial_port *port = gpiochip_get_data(gc);
+	struct xr_port_private *port_priv = usb_get_serial_port_data(port);
+	int ret = 0;
+
+	mutex_lock(&port_priv->gpio_lock);
+	/*

drivers/usb/serial/xr_serial.c +12 -0

+
+err_out:
+	mutex_unlock(&port_priv->gpio_lock);
+
+	return ret;
+}
+
+static void xr_gpio_free(struct gpio_chip *gc, unsigned int offset)
+{
+	struct usb_serial_port *port = gpiochip_get_data(gc);
+	struct xr_port_private *port_priv = usb_get_serial_port_data(port);
+

From: Mauro Carvalho Chehab <[email protected]>

The RTS/CTS line discipline for this device doesn't follow the standard. So, in order to properly support TX, a separate driver is needed.

Ensure that cdc_acm will ignore it during probe time, if the Kernel is built with support for it.

Signed-off-by Mauro Carvalho Chehab <[email protected]>

Signed-off-by Manivannan Sadhasivam <[email protected]>

---
 drivers/usb/class/cdc-acm.c | 6 ++++++
 1 file changed, 6 insertions(+)

drivers/usb/class/cdc-acm.c +0 -0

index 30ef946a8e1a..719829e6b6db 100644
@@ -1890,6 +1890,12 @@ static const struct usb_device_id acm_ids[] = {
 	},
 #endif

From: Manivannan Sadhasivam <[email protected]>

Hello,

This series adds support for MaxLinear/Exar USB to serial converters. This driver only supports XR21V141X series but it can easily be extended to other series in future.

This driver is inspired from the initial one submitted by Patong Yang:
https://lore.kernel.org/linux-usb/20180404070634.nhspvmxcjwfgjkcv@advantechmxl-desktop

While the initial driver was a custom tty USB driver exposing whole new serial interface ttyXRUSBn, this version is completely based on USB serial core thus exposing the interfaces as ttyUSBn. This will avoid the overhead of exposing a new USB serial interface which the userspace tools are unaware of.

This series has been tested with Hikey970 board hosting XR21V141X chip.

NOTE: I've removed all reviews and tested-by tags as the code has gone through substantial rework. Greg, Linus, Mauro please consider reviewing again.

Thanks,
Mani

Changes in v5:

* Incorporated review comments from Johan. Noticeable ones are:
- Made serial and gpiolib support exclusive and used mutex to avoid race. The gpio requests from gpiolib will be rejected when serial port is in use.
- The driver only binds to data interface but claims both control and data interface.
- Handled B0 request
- Removed all reviews as the code has gone through substantial rework.

Changes in v4:

* Multiple improvements based on Johan's review. Noticeable ones are:
- Now the driver claims both control and data interfaces but only registers tty device for data interface.
- GPIO pin status is now shared between the console and gpiolib implementations. This is done to avoid changing the lines spuriously.
- A separate port_open flag is added to reject GPIO requests while the tty port is open.
- Removed padding PID to gpio device.
* Added Greg and Mauro's review and tested tags.
* Included a patch from Mauro to avoid the CDC-ACM driver to claim this device when this driver is built.

Changes in v3:

* Dropped the check for PID and also the reg_width property.

Changes in v2:

* Dropped the code related to handling variable register size. It's all u8 now.
* Dropped the header file and moved the contents to driver itself.
* Added Linus's reviewed-by tag for gpiochip patch.
* Added PID to gpiochip label
* Dropped gpiochip for interface 0

Manivannan Sadhasivam (2):
usb: serial: Add MaxLinear/Exar USB to Serial driver
usb: serial: xr_serial: Add gpiochip support

Mauro Carvalho Chehab (1):
usb: cdc-acm: Ignore Exar XR21V141X when serial driver is built

 drivers/usb/class/cdc-acm.c    |   6 +
 drivers/usb/serial/Kconfig     |   9 +
 drivers/usb/serial/Makefile    |   1 +
 drivers/usb/serial/xr_serial.c | 854 +++++++++++++++++++++++++++++++++
 4 files changed, 870 insertions(+)
 create mode 100644 drivers/usb/serial/xr_serial.c

Signature · 1 line

2.25.1

Quoted 17 lines · Manivannan Sadhasivam

From: Manivannan Sadhasivam <[email protected]>

Hello,

This series adds support for MaxLinear/Exar USB to serial converters. This driver only supports XR21V141X series but it can easily be extended to other series in future.

This driver is inspired from the initial one submitted by Patong Yang:
https://lore.kernel.org/linux-usb/20180404070634.nhspvmxcjwfgjkcv@advantechmxl-desktop

While the initial driver was a custom tty USB driver exposing whole new serial interface ttyXRUSBn, this version is completely based on USB serial core thus exposing the interfaces as ttyUSBn. This will avoid the overhead of exposing a new USB serial interface which the userspace tools are unaware of.

Quoted 6 lines

This series has been tested with Hikey970 board hosting XR21V141X chip.

NOTE: I've removed all reviews and tested-by tags as the code has gone through substantial rework. Greg, Linus, Mauro please consider reviewing again.

Any chance to get this series into v5.11?