USB: serial: ftdi_sio: Add support for CBUS GPIO

Some FTDI devices like FTX or FT232R support CBUS Bit Bang mode on CBUS pins, allowing host to control them via simple USB control transfers. To make use of a CBUS pin in Bit Bang mode, the pin must be configured to I/O mode in the FTDI EEPROM. This mode perfectly coexists with regular USB to Serial function.

In this implementation, a GPIO controller is registered on FTDI probe if at least one CBUS pin is configured for I/O mode. For now, only FTX devices are supported.

This patch is based on previous Stefan Agner implementation tentative on LKML [1].

[1] Message-Id: [email protected]

Signed-off-by Loic Poulain <[email protected]>

---
v2: Use message-id for LKML reference
Rework read_eeprom according to Andy's comment and return read count Remove noisy messages
Comment style alignment
Add defines for magic values
Cannot use devm, because gpiochip is linked to the port not to the udev
v3:
Fix typo in CBUS mask description comment

 drivers/usb/serial/Kconfig    |   9 ++
 drivers/usb/serial/ftdi_sio.c | 238 ++++++++++++++++++++++++++++++++++++++++++
 drivers/usb/serial/ftdi_sio.h |  83 +++++++++++++++
 3 files changed, 330 insertions(+)

drivers/usb/serial/Kconfig +0 -0

index 533f127..64c9f2e 100644
@@ -181,6 +181,15 @@ config USB_SERIAL_FTDI_SIO
 	  To compile this driver as a module, choose M here: the

drivers/usb/serial/Kconfig +1 -0

+
 config USB_SERIAL_VISOR
 	tristate "USB Handspring Visor / Palm m50x / Sony Clie Driver"
 	help

drivers/usb/serial/ftdi_sio.c +1 -0

index b5cef32..e90cae6 100644
@@ -33,6 +33,7 @@
 #include <linux/tty.h>
 #include <linux/tty_driver.h>
 #include <linux/tty_flip.h>
+#include <linux/gpio/driver.h>
 #include <linux/module.h>
 #include <linux/spinlock.h>
 #include <linux/mutex.h>

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

+	unsigned long cbus_mask;
+};
 
 struct ftdi_private {
 	enum ftdi_chip_type chip_type;

@@ -72,6 +82,8 @@ struct ftdi_private {
 	unsigned int latency;		/* latency setting in use */
 	unsigned short max_packet_size;
 	struct mutex cfg_lock; /* Avoid mess by parallel calls of config ioctl() and change_speed() */
+
+	struct ftdi_gpiochip *fgc;
 };
 
 /* struct ftdi_sio_quirk is used by devices requiring special attention. */

@@ -1528,6 +1540,224 @@ static int get_lsr_info(struct usb_serial_port *port,
 	return 0;
 }
 
+#ifdef CONFIG_USB_SERIAL_FTDI_SIO_CBUS_GPIO

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

+	}
+
+	return 0;
+}
+
+static int ftdi_read_pins(struct usb_serial_port *port, u8 *val)
+{
+	struct ftdi_private *priv = usb_get_serial_port_data(port);
+	unsigned char *buf;

drivers/usb/serial/ftdi_sio.c +14 -0

+		kfree(buf);
+		return -EIO;
+	}
+
+	*val = buf[0];
+	kfree(buf);
+
+	return 0;
+}
+
+static int ftdi_cbus_gpio_dir_out(struct gpio_chip *gc, unsigned gpio, int val)
+{
+	struct ftdi_gpiochip *fgc = gpiochip_get_data(gc);
+	unsigned int cbus_idx = fgc->cbus_map[gpio];

drivers/usb/serial/ftdi_sio.c +30 -0

+
+	return ftdi_set_bitmode(fgc->port, fgc->cbus_mask,
+				FTDI_SIO_BITMODE_CBUS);
+}
+
+static int ftdi_cbus_gpio_dir_in(struct gpio_chip *gc, unsigned gpio)
+{
+	struct ftdi_gpiochip *fgc = gpiochip_get_data(gc);
+	unsigned int cbus_idx = fgc->cbus_map[gpio];
+
+	clear_bit(cbus_idx + 4, &fgc->cbus_mask);
+
+	return ftdi_set_bitmode(fgc->port, fgc->cbus_mask,
+				FTDI_SIO_BITMODE_CBUS);
+}
+
+static int ftdi_cbus_gpio_get(struct gpio_chip *gc, unsigned gpio)
+{
+	struct ftdi_gpiochip *fgc = gpiochip_get_data(gc);
+	unsigned int cbus_idx = fgc->cbus_map[gpio];
+	u8 val = 0;
+	int rv;
+
+	rv = ftdi_read_pins(fgc->port, &val);
+	if (rv)
+		return rv;
+
+	return !!(val & BIT(cbus_idx));
+}
+

drivers/usb/serial/ftdi_sio.c +17 -0

+}
+
+static int ftdi_register_cbus_gpiochip(struct usb_serial_port *port)
+{
+	struct ftdi_private *priv = usb_get_serial_port_data(port);
+	struct usb_device *udev = port->serial->dev;
+	struct ftdi_gpiochip *fgc;
+	int rv = 0;
+
+	fgc = kzalloc(sizeof(*fgc), GFP_KERNEL);
+	if (!fgc)
+		return -ENOMEM;
+
+	if (priv->chip_type == FTX) {
+		unsigned char *cbus_mux;
+		unsigned int i;
+

drivers/usb/serial/ftdi_sio.c +21 -0

+
+	return 0;
+
+exit_release:
+	kfree(fgc);
+	return rv;
+}
+
+static void ftdi_unregister_cbus_gpiochip(struct usb_serial_port *port)
+{
+	struct ftdi_private *priv = usb_get_serial_port_data(port);
+	struct ftdi_gpiochip *fgc = priv->fgc;
+
+	if (!fgc)
+		return;
+
+	gpiochip_remove(&fgc->gc);
+	kfree(fgc);
+}
+
+#endif /*  CONFIG_USB_SERIAL_FTDI_SIO_CBUS_GPIO */
 
 /* Determine type of FTDI chip based on USB config and descriptor. */
 static void ftdi_determine_type(struct usb_serial_port *port)

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

+
 	return 0;
 }
 

@@ -1930,6 +2164,10 @@ static int ftdi_sio_port_remove(struct usb_serial_port *port)
 {
 	struct ftdi_private *priv = usb_get_serial_port_data(port);
 
+#ifdef CONFIG_USB_SERIAL_FTDI_SIO_CBUS_GPIO
+	ftdi_unregister_cbus_gpiochip(port);
+#endif
+
 	remove_sysfs_attrs(port);
 
 	kfree(priv);

drivers/usb/serial/ftdi_sio.h +5 -0

index dcd0b6e..3bd248f 100644
@@ -36,6 +36,10 @@
 #define FTDI_SIO_SET_ERROR_CHAR		7 /* Set the error character */
 #define FTDI_SIO_SET_LATENCY_TIMER	9 /* Set the latency timer */
 #define FTDI_SIO_GET_LATENCY_TIMER	10 /* Get the latency timer */
+#define FTDI_SIO_SET_BITMODE		11 /* Set the bitmode */
+#define FTDI_SIO_READ_PINS		12 /* Read pins in bitmode */
+#define FTDI_SIO_READ_EEPROM		0x90 /* Read eeprom */
+#define FTDI_SIO_WRITE_EEPROM		0x91 /* Write eeprom */
 
 /* Interface indices for FT2232, FT2232H and FT4232H devices */
 #define INTERFACE_A		1

@@ -400,6 +404,60 @@ enum ftdi_sio_baudrate {
  *
  */
 
+ /* FTDI_SIO_READ_EEPROM */

drivers/usb/serial/ftdi_sio.h +58 -0

+ */
+
+/* FTDI_SIO_WRITE_EEPROM */
+#define FTDI_SIO_WRITE_EEPROM_REQUEST_TYPE 0x40
+#define FTDI_SIO_WRITE_EEPROM_REQUEST FTDI_SIO_WRITE_EEPROM
+/*
+ *  BmRequestType:   0100 0000b
+ *  bRequest:        FTDI_SIO_WRITE_EEPROM
+ *  wValue:          Data (word)
+ *  wIndex:          Word Index
+ *  wLength:         0
+ *  Data:            None
+ *
+ */
+
+ /* FTDI_SIO_SET_BITMODE */
+#define FTDI_SIO_SET_BITMODE_REQUEST_TYPE 0x40
+#define FTDI_SIO_SET_BITMODE_REQUEST FTDI_SIO_SET_BITMODE
+#define FTDI_SIO_BITMODE_RESET 0x00
+#define FTDI_SIO_BITMODE_CBUS 0x20
+/*
+ *  BmRequestType:   0100 0000b
+ *  bRequest:        FTDI_SIO_SET_BITMODE
+ *  wValue:          [0-7] bitmask, [8-15] bitmode
+ *  wIndex:          Port
+ *  wLength:         0
+ *  Data:            None
+ *
+ */
+
+/* FTDI_SIO_READ_PINS */
+#define FTDI_SIO_READ_PINS_REQUEST_TYPE 0xC0
+#define FTDI_SIO_READ_PINS_REQUEST FTDI_SIO_READ_PINS
+/*
+ *  BmRequestType:   1100 0000b
+ *  bRequest:        FTDI_SIO_READ_PINS
+ *  wValue:          0
+ *  wIndex:          Port
+ *  wLength:         2
+ *  Data:            return data (a word)
+ *
+ */
+
 /* FTDI_SIO_GET_MODEM_STATUS */
 /* Retrieve the current value of the modem status register */
 

@@ -563,3 +621,28 @@ enum ftdi_sio_baudrate {
  * B2..7	Length of message - (not including Byte 0)
  *
  */
+
+enum ftdi_ftx_cbus_mux {
+	FTX_CBUS_MUX_TRISTATE,
+	FTX_CBUS_MUX_RXLED,
+	FTX_CBUS_MUX_TXLED,
+	FTX_CBUS_MUX_TXRXLED,
+	FTX_CBUS_MUX_PWREN,
+	FTX_CBUS_MUX_SLEEP,
+	FTX_CBUS_MUX_DRIVE0,
+	FTX_CBUS_MUX_DRIVE1,
+	FTX_CBUS_MUX_IO,
+	FTX_CBUS_MUX_TXDEN,
+	FTX_CBUS_MUX_CLK24,
+	FTX_CBUS_MUX_CLK12,
+	FTX_CBUS_MUX_CLK6,