serial: mxs-auart: gpios as modem signals (dirty)

The ctrl variable duplicated mctrl, member of uart_port structure in serial_core.h.
The code duplicated uart_update_mctrl() and uart_tiocmget() in serial_core.c.
mxs_auart_get_mctrl() reads back RTS line. It could be removed too but not sure.

Dedicated CTS and RTS pins are unusable together with a lot of other peripherals because they share the same line. Pinctrl is limited.

Moreover, the AUART controller doesn't handle DTR/DSR/DCD/RI signals, so we have to control them via GPIO.

This patch permits to use GPIOs to control the CTS/RTS/DTR/DSR/DCD/RI signals.

Signed-off-by Janusz Uzycki <[email protected]>

---
  .../devicetree/bindings/serial/fsl-mxs-auart.txt   | 10 +++++-
  drivers/tty/serial/Kconfig           |  1 +
  drivers/tty/serial/mxs-auart.c       | 37 ++++++++++++++++++++--
  3 files changed, 44 insertions(+), 4 deletions(-)

Documentation/devicetree/bindings/serial/fsl-mxs-auart.txt +9 -1

index 59a40f1..7c408c8 100644
@@ -11,8 +11,13 @@ Required properties:
  - dma-names: "rx" for RX channel, "tx" for TX channel.
 
  Optional properties:
-- fsl,uart-has-rtscts : Indicate the UART has RTS and CTS lines,
+- fsl,uart-has-rtscts : Indicate the UART has RTS and CTS lines
+  for hardware flow control,
  	it also means you enable the DMA support for this UART.
+- {rts,cts,dtr,dsr,rng,dcd}-gpios: specify a GPIO for RTS/CTS/DTR/DSR/RI/DCD
+  line respectively. It will use specified PIO instead of the peripheral
+  function pin for the USART feature.
+  If unsure, don't specify this property.
 
  Example:
  auart0: serial@8006a000 {

@@ -21,6 +26,9 @@ auart0: serial@8006a000 {
  	interrupts = <112>;
  	dmas = <&dma_apbx 8>, <&dma_apbx 9>;
  	dma-names = "rx", "tx";
+	cts-gpios = <&gpio1 15 GPIO_ACTIVE_LOW>;
+	dsr-gpios = <&gpio1 16 GPIO_ACTIVE_LOW>;
+	dcd-gpios = <&gpio1 17 GPIO_ACTIVE_LOW>;
  };
 
  Note: Each auart port should have an alias correctly numbered in "aliases"

drivers/tty/serial/Kconfig +1 -0

index 4fe8ca1..90e8516 100644
@@ -1357,6 +1357,7 @@ config SERIAL_MXS_AUART
  	depends on ARCH_MXS
  	tristate "MXS AUART support"
  	select SERIAL_CORE
+	select SERIAL_MCTRL_GPIO if GPIOLIB
  	help
  	  This driver supports the MXS Application UART (AUART) port.
 

drivers/tty/serial/mxs-auart.c +34 -3

index c712108..fdfa8a9 100644
@@ -42,6 +42,9 @@
 
  #include <asm/cacheflush.h>
 
+#include <linux/err.h>
+#include "serial_mctrl_gpio.h"
+
  #define MXS_AUART_PORTS 5
  #define MXS_AUART_FIFO_SIZE		16
 

@@ -158,6 +161,8 @@ struct mxs_auart_port {
  	struct scatterlist rx_sgl;
  	struct dma_chan	*rx_dma_chan;
  	void *rx_dma_buf;
+
+	struct mctrl_gpios	*gpios;
  };
 
  static struct platform_device_id mxs_auart_devtype[] = {

@@ -405,6 +410,8 @@ static void mxs_auart_release_port(struct uart_port *u)
 
  static void mxs_auart_set_mctrl(struct uart_port *u, unsigned mctrl)
  {
+	struct mxs_auart_port *s = to_auart_port(u);
+
  	u32 ctrl = readl(u->membase + AUART_CTRL2);
 
  	ctrl &= ~(AUART_CTRL2_RTSEN | AUART_CTRL2_RTS);

@@ -416,10 +423,13 @@ static void mxs_auart_set_mctrl(struct uart_port *u, unsigned mctrl)
  	}
 
  	writel(ctrl, u->membase + AUART_CTRL2);
+
+	mctrl_gpio_set(s->gpios, mctrl);
  }
 
  static u32 mxs_auart_get_mctrl(struct uart_port *u)
  {
+	struct mxs_auart_port *s = to_auart_port(u);
  	u32 stat = readl(u->membase + AUART_STAT);
  	int ctrl2 = readl(u->membase + AUART_CTRL2);
  	u32 mctrl = 0;

@@ -431,7 +441,7 @@ static u32 mxs_auart_get_mctrl(struct uart_port *u)
  	if (ctrl2 & AUART_CTRL2_RTS)
  		mctrl |= TIOCM_RTS;
 
-	return mctrl;
+	return mctrl_gpio_get(s->gpios, &mctrl);
  }
 
  static int mxs_auart_dma_prep_rx(struct mxs_auart_port *s);

@@ -635,7 +645,12 @@ static void mxs_auart_settermios(struct uart_port *u,
  		ctrl |= AUART_LINECTRL_STP2;
 
  	/* figure out the hardware flow control settings */
-	if (cflag & CRTSCTS) {
+	/* FIXME: Likely DMA could be enabled not only for HW flow control */
+	if (cflag & CRTSCTS &&
+			(IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(s->gpios,
+					 UART_GPIO_RTS)) ||
+			 IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(s->gpios,
+					 UART_GPIO_CTS)))) {
  		/*
  		 * The DMA has a bug(see errata:2836) in mx23.
  		 * So we can not implement the DMA for auart in mx23,

@@ -695,7 +710,10 @@ static irqreturn_t mxs_auart_irq_handle(int irq, void *context)
  			s->port.membase + AUART_INTR_CLR);
 
  	if (istat & AUART_INTR_CTSMIS) {
-		uart_handle_cts_change(&s->port, stat & AUART_STAT_CTS);
+		if (IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(s->gpios,
+						UART_GPIO_CTS)))
+			uart_handle_cts_change(&s->port,
+					stat & AUART_STAT_CTS);
  		writel(AUART_INTR_CTSMIS,
  				s->port.membase + AUART_INTR_CLR);
  		istat &= ~AUART_INTR_CTSMIS;

@@ -1019,6 +1037,14 @@ static int serial_mxs_probe_dt(struct mxs_auart_port *s,
  	return 0;
  }
 
+static int mxs_auart_init_gpios(struct mxs_auart_port *s, struct device *dev)
+{
+	s->gpios = mctrl_gpio_init(dev, 0);
+	if (IS_ERR_OR_NULL(s->gpios))
+		return -1;
+	return 0;
+}
+
  static int mxs_auart_probe(struct platform_device *pdev)
  {
  	const struct of_device_id *of_id =

@@ -1074,6 +1100,11 @@ static int mxs_auart_probe(struct platform_device *pdev)
 
  	platform_set_drvdata(pdev, s);
 
+	ret = mxs_auart_init_gpios(s, &pdev->dev);
+	if (ret < 0)
+		dev_err(&pdev->dev, "%s",
+			"Failed to initialize GPIOs. The serial port may not work as expected");
+
  	auart_port[s->port.line] = s;
 
  	mxs_auart_reset(&s->port);

Could somebody comment if DMA could be enabled also if CTS/RTS is supported by GPIOs? Is it safe?
It would allow me to avoid ugly code in mxs_auart_settermios(), as commented Russel King.

Otherwise I have to keep backward compatibility on DMA and HW flow control, and fix the ugly code.

Marek Vasut:
"Why do you think DMA would do any good on long transfers without flowcontrol."

Quoted 4 lines

Could somebody comment if DMA could be enabled also if CTS/RTS is supported by GPIOs? Is it safe?
It would allow me to avoid ugly code in mxs_auart_settermios(), as commented Russel King.

Russel*L* please, otherwise you are giving me implicit permission to mis-spell your name.

Quoted 6 lines

Otherwise I have to keep backward compatibility on DMA and HW flow control, and fix the ugly code.

Marek Vasut:
"Why do you think DMA would do any good on long transfers without flowcontrol."

The problem with DMA without hardware flow control is that the UART transmission will run at full speed, with characters back to back.

You will have a variable amount of latency when dealing with the CTS signal - interrupt handling latency in Linux can be quite variable. (I'm not sure whether this has improved recently, USB used to be particularly bad, causing 3+ ms latencies.)

When CTS is deasserted, you have to pause the transmission as soon as possible to avoid overflowing the remote end. At 115200 baud, each character takes around 90us to be transmitted. If you are delayed in handling the CTS interrupt for 3ms, then you will have transmitted around 35 characters in that time, which could be enough to cause an overflow at the remote end.

Since the idea of flow control is to prevent overruns/overflow at the receiver, this is far from ideal.

If Linux had a way to handle flow control interrupts as a higher priority than other interrupts (especially interrupting an already in-progress interrupt handler) then having GPIOs as flow control signals would be a much saner proposition.

Unfortunately, lockdep completely gets in the way of that.

It means it is possible but not in Linux today?

I think the problem is not interrupt delay, which is often much below 100us (we get ~10us delay on DCD).

Isn't the problem rather how to break DMA transmission fast?

Hardware flow control not always requires to stop transmission immediately.

Usually delay of some chars is acceptable if remote receiver implements low/high water mark (overflow trigger lower than RX FIFO size).

Handle CTS/DSR/RI/DCD GPIO interrupts in mxs-auart.

Signed-off-by Janusz Uzycki <[email protected]>

---
 drivers/tty/serial/mxs-auart.c | 176 ++++++++++++++++++++++++++-
 1 file changed, 174 insertions(+), 2 deletions(-)

drivers/tty/serial/mxs-auart.c +173 -2

index fdfa8a9..ab127a2 100644
@@ -42,7 +42,10 @@
 
 #include <asm/cacheflush.h>
 
+#include <linux/gpio.h>
+#include <linux/gpio/consumer.h>
 #include <linux/err.h>
+#include <linux/irq.h>
 #include "serial_mctrl_gpio.h"
 
 #define MXS_AUART_PORTS 5

@@ -146,6 +149,7 @@ struct mxs_auart_port {
 #define MXS_AUART_DMA_RX_READY	3  /* bit 3 */
 #define MXS_AUART_RTSCTS	4  /* bit 4 */
 	unsigned long flags;
+	unsigned int mctrl_prev;
 	enum mxs_auart_type devtype;
 
 	unsigned int irq;

@@ -163,6 +167,8 @@ struct mxs_auart_port {
 	void *rx_dma_buf;
 
 	struct mctrl_gpios	*gpios;
+	int			gpio_irq[UART_GPIO_MAX];
+	bool			ms_irq_enabled;
 };
 
 static struct platform_device_id mxs_auart_devtype[] = {

@@ -427,6 +433,29 @@ static void mxs_auart_set_mctrl(struct uart_port *u, unsigned mctrl)
 	mctrl_gpio_set(s->gpios, mctrl);
 }
 
+#define MCTRL_ANY_DELTA        (TIOCM_RI | TIOCM_DSR | TIOCM_CD | TIOCM_CTS)
+static u32 mxs_auart_modem_status(struct mxs_auart_port *s, u32 mctrl)
+{
+	u32 mctrl_diff;
+
+	mctrl_diff = mctrl ^ s->mctrl_prev;
+	s->mctrl_prev = mctrl;
+	if (mctrl_diff & MCTRL_ANY_DELTA && s->ms_irq_enabled &&
+						s->port.state != NULL) {
+		if (mctrl_diff & TIOCM_RI)
+			s->port.icount.rng++;
+		if (mctrl_diff & TIOCM_DSR)
+			s->port.icount.dsr++;
+		if (mctrl_diff & TIOCM_CD)
+			uart_handle_dcd_change(&s->port, mctrl & TIOCM_CD);
+		if (mctrl_diff & TIOCM_CTS)
+			uart_handle_cts_change(&s->port, mctrl & TIOCM_CTS);
+
+		wake_up_interruptible(&s->port.state->port.delta_msr_wait);
+	}
+	return mctrl;
+}
+
 static u32 mxs_auart_get_mctrl(struct uart_port *u)
 {
 	struct mxs_auart_port *s = to_auart_port(u);

@@ -444,6 +473,64 @@ static u32 mxs_auart_get_mctrl(struct uart_port *u)
 	return mctrl_gpio_get(s->gpios, &mctrl);
 }
 
+/*
+ * Enable modem status interrupts
+ */
+static void mxs_auart_enable_ms(struct uart_port *port)
+{
+	struct mxs_auart_port *s = to_auart_port(port);
+
+	/*
+	 * Interrupt should not be enabled twice
+	 */
+	if (s->ms_irq_enabled)
+		return;
+
+	s->ms_irq_enabled = true;
+
+	if (s->gpio_irq[UART_GPIO_CTS] >= 0)
+		enable_irq(s->gpio_irq[UART_GPIO_CTS]);
+	/* TODO: enable AUART_INTR_CTSMIEN otherwise */
+
+	if (s->gpio_irq[UART_GPIO_DSR] >= 0)
+		enable_irq(s->gpio_irq[UART_GPIO_DSR]);
+
+	if (s->gpio_irq[UART_GPIO_RI] >= 0)
+		enable_irq(s->gpio_irq[UART_GPIO_RI]);
+
+	if (s->gpio_irq[UART_GPIO_DCD] >= 0)
+		enable_irq(s->gpio_irq[UART_GPIO_DCD]);
+}
+
+/*
+ * Disable modem status interrupts
+ */
+static void mxs_auart_disable_ms(struct uart_port *port)
+{
+	struct mxs_auart_port *s = to_auart_port(port);
+
+	/*
+	 * Interrupt should not be disabled twice
+	 */
+	if (!s->ms_irq_enabled)
+		return;
+
+	s->ms_irq_enabled = false;
+
+	if (s->gpio_irq[UART_GPIO_CTS] >= 0)
+		disable_irq(s->gpio_irq[UART_GPIO_CTS]);
+	/* TODO: disable AUART_INTR_CTSMIEN otherwise */
+
+	if (s->gpio_irq[UART_GPIO_DSR] >= 0)
+		disable_irq(s->gpio_irq[UART_GPIO_DSR]);
+
+	if (s->gpio_irq[UART_GPIO_RI] >= 0)
+		disable_irq(s->gpio_irq[UART_GPIO_RI]);
+
+	if (s->gpio_irq[UART_GPIO_DCD] >= 0)
+		disable_irq(s->gpio_irq[UART_GPIO_DCD]);
+}
+
 static int mxs_auart_dma_prep_rx(struct mxs_auart_port *s);
 static void dma_rx_callback(void *arg)
 {

@@ -692,6 +779,12 @@ static void mxs_auart_settermios(struct uart_port *u,
 			dev_err(s->dev, "We can not start up the DMA.\n");
 		}
 	}
+
+	/* CTS flow-control and modem-status interrupts */
+	if (UART_ENABLE_MS(u, termios->c_cflag))
+		mxs_auart_enable_ms(u);
+	else
+		mxs_auart_disable_ms(u);
 }
 
 static irqreturn_t mxs_auart_irq_handle(int irq, void *context)

@@ -709,9 +802,20 @@ static irqreturn_t mxs_auart_irq_handle(int irq, void *context)
 		| AUART_INTR_CTSMIS),
 			s->port.membase + AUART_INTR_CLR);
 
+	/*
+	 * Dealing with GPIO interrupt
+	 */
+	if (irq == s->gpio_irq[UART_GPIO_CTS] ||
+	    irq == s->gpio_irq[UART_GPIO_DCD] ||
+	    irq == s->gpio_irq[UART_GPIO_DSR] ||
+	    irq == s->gpio_irq[UART_GPIO_RI])
+		mxs_auart_modem_status(s,
+				mctrl_gpio_get(s->gpios, &s->mctrl_prev));
+
 	if (istat & AUART_INTR_CTSMIS) {
 		if (IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(s->gpios,
-						UART_GPIO_CTS)))
+							UART_GPIO_CTS))
+						&& s->ms_irq_enabled)
 			uart_handle_cts_change(&s->port,
 					stat & AUART_STAT_CTS);
 		writel(AUART_INTR_CTSMIS,

@@ -774,6 +878,10 @@ static int mxs_auart_startup(struct uart_port *u)
 	 */
 	writel(AUART_LINECTRL_FEN, u->membase + AUART_LINECTRL_SET);
 
+	/* get initial status of modem lines */
+	mctrl_gpio_get(s->gpios, &s->mctrl_prev);
+
+	s->ms_irq_enabled = false;
 	return 0;
 }
 

@@ -781,6 +889,8 @@ static void mxs_auart_shutdown(struct uart_port *u)
 {
 	struct mxs_auart_port *s = to_auart_port(u);
 
+	mxs_auart_disable_ms(u);
+
 	if (auart_dma_enabled(s))
 		mxs_auart_dma_exit(s);
 

@@ -837,6 +947,7 @@ static struct uart_ops mxs_auart_ops = {
 	.start_tx       = mxs_auart_start_tx,
 	.stop_tx	= mxs_auart_stop_tx,
 	.stop_rx	= mxs_auart_stop_rx,
+	.enable_ms      = mxs_auart_enable_ms,
 	.break_ctl      = mxs_auart_break_ctl,
 	.set_mctrl	= mxs_auart_set_mctrl,
 	.get_mctrl      = mxs_auart_get_mctrl,

@@ -1039,12 +1150,61 @@ static int serial_mxs_probe_dt(struct mxs_auart_port *s,
 
 static int mxs_auart_init_gpios(struct mxs_auart_port *s, struct device *dev)
 {
+	enum mctrl_gpio_idx i;
+	struct gpio_desc *gpiod;
+
 	s->gpios = mctrl_gpio_init(dev, 0);
 	if (IS_ERR_OR_NULL(s->gpios))
 		return -1;
+
+	for (i = 0; i < UART_GPIO_MAX; i++) {
+		gpiod = mctrl_gpio_to_gpiod(s->gpios, i);
+		if (gpiod && (gpiod_get_direction(gpiod) == GPIOF_DIR_IN))
+			s->gpio_irq[i] = gpiod_to_irq(gpiod);
+		else
+			s->gpio_irq[i] = -EINVAL;
+	}
+
 	return 0;
 }
 
+static void mxs_auart_free_gpio_irq(struct mxs_auart_port *s)
+{
+	enum mctrl_gpio_idx i;
+
+	for (i = 0; i < UART_GPIO_MAX; i++)
+		if (s->gpio_irq[i] >= 0)
+			free_irq(s->gpio_irq[i], s);
+}
+
+static int mxs_auart_request_gpio_irq(struct mxs_auart_port *s)
+{
+	int *irq = s->gpio_irq;
+	enum mctrl_gpio_idx i;
+	int err = 0;
+
+	for (i = 0; (i < UART_GPIO_MAX) && !err; i++) {
+		if (irq[i] < 0)
+			continue;
+
+		irq_set_status_flags(irq[i], IRQ_NOAUTOEN);
+		err = request_irq(irq[i], mxs_auart_irq_handle,
+				IRQ_TYPE_EDGE_BOTH, dev_name(s->dev), s);
+		if (err)
+			dev_err(s->dev, "%s - Can't get %d irq\n",
+				__func__, irq[i]);
+	}
+
+	/*
+	 * If something went wrong, rollback.
+	 */
+	while (err && (--i >= 0))
+		if (irq[i] >= 0)
+			free_irq(irq[i], s);
+
+	return err;
+}
+
 static int mxs_auart_probe(struct platform_device *pdev)
 {
 	const struct of_device_id *of_id =

@@ -1092,6 +1252,8 @@ static int mxs_auart_probe(struct platform_device *pdev)
 	s->port.type = PORT_IMX;
 	s->port.dev = s->dev = &pdev->dev;
 
+	s->mctrl_prev = 0;
+
 	s->irq = platform_get_irq(pdev, 0);
 	s->port.irq = s->irq;
 	ret = request_irq(s->irq, mxs_auart_irq_handle, 0, dev_name(&pdev->dev), s);

@@ -1105,13 +1267,20 @@ static int mxs_auart_probe(struct platform_device *pdev)
 		dev_err(&pdev->dev, "%s",
 			"Failed to initialize GPIOs. The serial port may not work as expected");
 
+	/*
+	 * Get the GPIO lines IRQ
+	 */
+	ret = mxs_auart_request_gpio_irq(s);
+	if (ret)
+		goto out_free_irq;
+
 	auart_port[s->port.line] = s;
 
 	mxs_auart_reset(&s->port);
 
 	ret = uart_add_one_port(&auart_driver, &s->port);
 	if (ret)
-		goto out_free_irq;
+		goto out_free_gpio_irq;
 
 	version = readl(s->port.membase + AUART_VERSION);
 	dev_info(&pdev->dev, "Found APPUART %d.%d.%d\n",

@@ -1120,6 +1289,8 @@ static int mxs_auart_probe(struct platform_device *pdev)
 
 	return 0;
 
+out_free_gpio_irq:
+	mxs_auart_free_gpio_irq(s);
 out_free_irq:
 	auart_port[pdev->id] = NULL;
 	free_irq(s->irq, s);

Quoted 301 lines

Handle CTS/DSR/RI/DCD GPIO interrupts in mxs-auart.

Signed-off-by Janusz Uzycki <[email protected]>

---
  drivers/tty/serial/mxs-auart.c | 176 ++++++++++++++++++++++++++-
  1 file changed, 174 insertions(+), 2 deletions(-)

drivers/tty/serial/mxs-auart.c +173 -2

index fdfa8a9..ab127a2 100644
@@ -42,7 +42,10 @@
 
  #include <asm/cacheflush.h>
 
+#include <linux/gpio.h>
+#include <linux/gpio/consumer.h>
  #include <linux/err.h>
+#include <linux/irq.h>
  #include "serial_mctrl_gpio.h"
 
  #define MXS_AUART_PORTS 5

@@ -146,6 +149,7 @@ struct mxs_auart_port {
  #define MXS_AUART_DMA_RX_READY	3  /* bit 3 */
  #define MXS_AUART_RTSCTS	4  /* bit 4 */
  	unsigned long flags;
+	unsigned int mctrl_prev;
  	enum mxs_auart_type devtype;
 
  	unsigned int irq;

@@ -163,6 +167,8 @@ struct mxs_auart_port {
  	void *rx_dma_buf;
 
  	struct mctrl_gpios	*gpios;
+	int			gpio_irq[UART_GPIO_MAX];
+	bool			ms_irq_enabled;
  };
 
  static struct platform_device_id mxs_auart_devtype[] = {

@@ -427,6 +433,29 @@ static void mxs_auart_set_mctrl(struct uart_port *u, unsigned mctrl)
  	mctrl_gpio_set(s->gpios, mctrl);
  }
 
+#define MCTRL_ANY_DELTA        (TIOCM_RI | TIOCM_DSR | TIOCM_CD | TIOCM_CTS)
+static u32 mxs_auart_modem_status(struct mxs_auart_port *s, u32 mctrl)
+{
+	u32 mctrl_diff;
+
+	mctrl_diff = mctrl ^ s->mctrl_prev;
+	s->mctrl_prev = mctrl;
+	if (mctrl_diff & MCTRL_ANY_DELTA && s->ms_irq_enabled &&
+						s->port.state != NULL) {
+		if (mctrl_diff & TIOCM_RI)
+			s->port.icount.rng++;
+		if (mctrl_diff & TIOCM_DSR)
+			s->port.icount.dsr++;
+		if (mctrl_diff & TIOCM_CD)
+			uart_handle_dcd_change(&s->port, mctrl & TIOCM_CD);
+		if (mctrl_diff & TIOCM_CTS)
+			uart_handle_cts_change(&s->port, mctrl & TIOCM_CTS);
+
+		wake_up_interruptible(&s->port.state->port.delta_msr_wait);
+	}
+	return mctrl;
+}
+
  static u32 mxs_auart_get_mctrl(struct uart_port *u)
  {
  	struct mxs_auart_port *s = to_auart_port(u);

@@ -444,6 +473,64 @@ static u32 mxs_auart_get_mctrl(struct uart_port *u)
  	return mctrl_gpio_get(s->gpios, &mctrl);
  }
 
+/*
+ * Enable modem status interrupts
+ */
+static void mxs_auart_enable_ms(struct uart_port *port)
+{
+	struct mxs_auart_port *s = to_auart_port(port);
+
+	/*
+	 * Interrupt should not be enabled twice
+	 */
+	if (s->ms_irq_enabled)
+		return;
+
+	s->ms_irq_enabled = true;
+
+	if (s->gpio_irq[UART_GPIO_CTS] >= 0)
+		enable_irq(s->gpio_irq[UART_GPIO_CTS]);
+	/* TODO: enable AUART_INTR_CTSMIEN otherwise */
+
+	if (s->gpio_irq[UART_GPIO_DSR] >= 0)
+		enable_irq(s->gpio_irq[UART_GPIO_DSR]);
+
+	if (s->gpio_irq[UART_GPIO_RI] >= 0)
+		enable_irq(s->gpio_irq[UART_GPIO_RI]);
+
+	if (s->gpio_irq[UART_GPIO_DCD] >= 0)
+		enable_irq(s->gpio_irq[UART_GPIO_DCD]);
+}
+
+/*
+ * Disable modem status interrupts
+ */
+static void mxs_auart_disable_ms(struct uart_port *port)
+{
+	struct mxs_auart_port *s = to_auart_port(port);
+
+	/*
+	 * Interrupt should not be disabled twice
+	 */
+	if (!s->ms_irq_enabled)
+		return;
+
+	s->ms_irq_enabled = false;
+
+	if (s->gpio_irq[UART_GPIO_CTS] >= 0)
+		disable_irq(s->gpio_irq[UART_GPIO_CTS]);
+	/* TODO: disable AUART_INTR_CTSMIEN otherwise */
+
+	if (s->gpio_irq[UART_GPIO_DSR] >= 0)
+		disable_irq(s->gpio_irq[UART_GPIO_DSR]);
+
+	if (s->gpio_irq[UART_GPIO_RI] >= 0)
+		disable_irq(s->gpio_irq[UART_GPIO_RI]);
+
+	if (s->gpio_irq[UART_GPIO_DCD] >= 0)
+		disable_irq(s->gpio_irq[UART_GPIO_DCD]);
+}
+
  static int mxs_auart_dma_prep_rx(struct mxs_auart_port *s);
  static void dma_rx_callback(void *arg)
  {

@@ -692,6 +779,12 @@ static void mxs_auart_settermios(struct uart_port *u,
  			dev_err(s->dev, "We can not start up the DMA.\n");
  		}
  	}
+
+	/* CTS flow-control and modem-status interrupts */
+	if (UART_ENABLE_MS(u, termios->c_cflag))
+		mxs_auart_enable_ms(u);
+	else
+		mxs_auart_disable_ms(u);
  }
 
  static irqreturn_t mxs_auart_irq_handle(int irq, void *context)

@@ -709,9 +802,20 @@ static irqreturn_t mxs_auart_irq_handle(int irq, void *context)
  		| AUART_INTR_CTSMIS),
  			s->port.membase + AUART_INTR_CLR);
 
+	/*
+	 * Dealing with GPIO interrupt
+	 */
+	if (irq == s->gpio_irq[UART_GPIO_CTS] ||
+	    irq == s->gpio_irq[UART_GPIO_DCD] ||
+	    irq == s->gpio_irq[UART_GPIO_DSR] ||
+	    irq == s->gpio_irq[UART_GPIO_RI])
+		mxs_auart_modem_status(s,
+				mctrl_gpio_get(s->gpios, &s->mctrl_prev));
+
  	if (istat & AUART_INTR_CTSMIS) {
  		if (IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(s->gpios,
-						UART_GPIO_CTS)))
+							UART_GPIO_CTS))
+						&& s->ms_irq_enabled)
  			uart_handle_cts_change(&s->port,
  					stat & AUART_STAT_CTS);
  		writel(AUART_INTR_CTSMIS,

@@ -774,6 +878,10 @@ static int mxs_auart_startup(struct uart_port *u)
  	 */
  	writel(AUART_LINECTRL_FEN, u->membase + AUART_LINECTRL_SET);
 
+	/* get initial status of modem lines */
+	mctrl_gpio_get(s->gpios, &s->mctrl_prev);
+
+	s->ms_irq_enabled = false;
  	return 0;
  }
 

@@ -781,6 +889,8 @@ static void mxs_auart_shutdown(struct uart_port *u)
  {
  	struct mxs_auart_port *s = to_auart_port(u);
 
+	mxs_auart_disable_ms(u);
+
  	if (auart_dma_enabled(s))
  		mxs_auart_dma_exit(s);
 

@@ -837,6 +947,7 @@ static struct uart_ops mxs_auart_ops = {
  	.start_tx       = mxs_auart_start_tx,
  	.stop_tx	= mxs_auart_stop_tx,
  	.stop_rx	= mxs_auart_stop_rx,
+	.enable_ms      = mxs_auart_enable_ms,
  	.break_ctl      = mxs_auart_break_ctl,
  	.set_mctrl	= mxs_auart_set_mctrl,
  	.get_mctrl      = mxs_auart_get_mctrl,

@@ -1039,12 +1150,61 @@ static int serial_mxs_probe_dt(struct mxs_auart_port *s,
 
  static int mxs_auart_init_gpios(struct mxs_auart_port *s, struct device *dev)
  {
+	enum mctrl_gpio_idx i;
+	struct gpio_desc *gpiod;
+
  	s->gpios = mctrl_gpio_init(dev, 0);
  	if (IS_ERR_OR_NULL(s->gpios))
  		return -1;
+
+	for (i = 0; i < UART_GPIO_MAX; i++) {
+		gpiod = mctrl_gpio_to_gpiod(s->gpios, i);
+		if (gpiod && (gpiod_get_direction(gpiod) == GPIOF_DIR_IN))
+			s->gpio_irq[i] = gpiod_to_irq(gpiod);
+		else
+			s->gpio_irq[i] = -EINVAL;
+	}
+
  	return 0;
  }
 
+static void mxs_auart_free_gpio_irq(struct mxs_auart_port *s)
+{
+	enum mctrl_gpio_idx i;
+
+	for (i = 0; i < UART_GPIO_MAX; i++)
+		if (s->gpio_irq[i] >= 0)
+			free_irq(s->gpio_irq[i], s);
+}
+
+static int mxs_auart_request_gpio_irq(struct mxs_auart_port *s)
+{
+	int *irq = s->gpio_irq;
+	enum mctrl_gpio_idx i;
+	int err = 0;
+
+	for (i = 0; (i < UART_GPIO_MAX) && !err; i++) {
+		if (irq[i] < 0)
+			continue;
+
+		irq_set_status_flags(irq[i], IRQ_NOAUTOEN);
+		err = request_irq(irq[i], mxs_auart_irq_handle,
+				IRQ_TYPE_EDGE_BOTH, dev_name(s->dev), s);
+		if (err)
+			dev_err(s->dev, "%s - Can't get %d irq\n",
+				__func__, irq[i]);
+	}
+
+	/*
+	 * If something went wrong, rollback.
+	 */
+	while (err && (--i >= 0))
+		if (irq[i] >= 0)
+			free_irq(irq[i], s);
+
+	return err;
+}
+
  static int mxs_auart_probe(struct platform_device *pdev)
  {
  	const struct of_device_id *of_id =

@@ -1092,6 +1252,8 @@ static int mxs_auart_probe(struct platform_device *pdev)
  	s->port.type = PORT_IMX;
  	s->port.dev = s->dev = &pdev->dev;
 
+	s->mctrl_prev = 0;
+
  	s->irq = platform_get_irq(pdev, 0);
  	s->port.irq = s->irq;
  	ret = request_irq(s->irq, mxs_auart_irq_handle, 0, dev_name(&pdev->dev), s);

@@ -1105,13 +1267,20 @@ static int mxs_auart_probe(struct platform_device *pdev)
  		dev_err(&pdev->dev, "%s",
  			"Failed to initialize GPIOs. The serial port may not work as expected");
 
+	/*
+	 * Get the GPIO lines IRQ
+	 */
+	ret = mxs_auart_request_gpio_irq(s);
+	if (ret)
+		goto out_free_irq;
+
  	auart_port[s->port.line] = s;
 
  	mxs_auart_reset(&s->port);
 
  	ret = uart_add_one_port(&auart_driver, &s->port);
  	if (ret)
-		goto out_free_irq;
+		goto out_free_gpio_irq;
 
  	version = readl(s->port.membase + AUART_VERSION);
  	dev_info(&pdev->dev, "Found APPUART %d.%d.%d\n",

@@ -1120,6 +1289,8 @@ static int mxs_auart_probe(struct platform_device *pdev)
 
  	return 0;
 
+out_free_gpio_irq:
+	mxs_auart_free_gpio_irq(s);
  out_free_irq:
  	auart_port[pdev->id] = NULL;
  	free_irq(s->irq, s);

drivers/tty/serial/mxs-auart.c static int mxs_auart_remove(struct platform_device *pdev) · line 1316

Quoted 7 lines

drivers/tty/serial/mxs-auart.c +1 -0

@@ -1139,6 +1310,7 @@ static int mxs_auart_remove(struct platform_device *pdev)
 
  	auart_port[pdev->id] = NULL;
 
+	mxs_auart_free_gpio_irq(s);
  	clk_put(s->clk);
  	free_irq(s->irq, s);
  	kfree(s);

Seems also ok.
Janusz, will you provide a patch to complete {en,dis}able_ms functions for non-gpio ?

Reviewed-by Richard Genoud <[email protected]>

Enables PPS support in mxs-auart serial driver to make PPS API working.

Signed-off-by Janusz Uzycki <[email protected]>

---
  drivers/tty/serial/mxs-auart.c | 10 ++++++++++
  1 file changed, 10 insertions(+)

drivers/tty/serial/mxs-auart.c +0 -0

index ab127a2..4f1ab98 100644