[PATCH 1/4] serial: mxs-auart: use mctrl_gpio helpers for handling modem signals (v2.2c)

[PATCH 1/4] serial: mxs-auart: use mctrl_gpio helpers for handling modem signals (v2.2c)

[Janusz Uzycki]

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 <j.uzycki@elproma.com.pl>
---
 .../devicetree/bindings/serial/fsl-mxs-auart.txt   | 10 ++-
 drivers/tty/serial/Kconfig           |  1 +
 drivers/tty/serial/mxs-auart.c       | 77 +++++++++++++++++++++-
 3 files changed, 84 insertions(+), 4 deletions(-)

diff --git a/Documentation/devicetree/bindings/serial/fsl-mxs-auart.txt b/Documentation/devicetree/bindings/serial/fsl-mxs-auart.txt
index 59a40f1..7c408c8 100644
--- a/Documentation/devicetree/bindings/serial/fsl-mxs-auart.txt
+++ b/Documentation/devicetree/bindings/serial/fsl-mxs-auart.txt
@@ -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 at 8006a000 {
@@ -21,6 +26,9 @@ auart0: serial at 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"
diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 4fe8ca1..90e8516 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -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.
 
diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auart.c
index 52d14e3..4690200 100644
--- a/drivers/tty/serial/mxs-auart.c
+++ b/drivers/tty/serial/mxs-auart.c
@@ -38,6 +38,9 @@
 
 #include <asm/cacheflush.h>
 
+#include <linux/err.h>
+#include "serial_mctrl_gpio.h"
+
 #define MXS_AUART_MAJOR 242
 #define MXS_AUART_PORTS 5
 #define MXS_AUART_FIFO_SIZE		16
@@ -156,6 +159,8 @@ 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[] = {
@@ -415,8 +420,43 @@ static void mxs_auart_set_mctrl(struct uart_port *u, unsigned mctrl)
 			ctrl |= AUART_CTRL2_RTS;
 	}
 
+	/* Does tty layer modify mctrl for input lines
+	 * and the code below is required? */
+#if 0
 	s->ctrl = mctrl;
+#else
+	s->ctrl &= ~(TIOCM_RTS | TIOCM_DTR);
+	s->ctrl |= mctrl & (TIOCM_RTS | TIOCM_DTR);
+#endif
 	writel(ctrl, u->membase + AUART_CTRL2);
+
+	mctrl_gpio_set(s->gpios, mctrl);
+}
+
+/* mxs_auart_modem_status() based on 8250.c,
+ * similar function could be as serial's helper... */
+#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->ctrl;
+	s->ctrl = mctrl;
+	if (mctrl_diff & MCTRL_ANY_DELTA &&
+			/*interrupt_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)
@@ -433,7 +473,9 @@ static u32 mxs_auart_get_mctrl(struct uart_port *u)
 	if (ctrl2 & AUART_CTRL2_RTS)
 		mctrl |= TIOCM_RTS;
 
-	return mctrl;
+	/* should mxs_auart_modem_status() be in interrupt only? */
+	return mxs_auart_modem_status(s,
+			mctrl_gpio_get(s->gpios, &mctrl));
 }
 
 static int mxs_auart_dma_prep_rx(struct mxs_auart_port *s);
@@ -637,7 +679,12 @@ static void mxs_auart_settermios(struct uart_port *u,
 		ctrl |= AUART_LINECTRL_STP2;
 
 	/* figure out the hardware flow control settings */
-	if (cflag & CRTSCTS) {
+	/*FIXME: DMA for hardware flow control only? */
+	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,
@@ -696,8 +743,14 @@ static irqreturn_t mxs_auart_irq_handle(int irq, void *context)
 		| AUART_INTR_CTSMIS),
 			s->port.membase + AUART_INTR_CLR);
 
+	mxs_auart_modem_status(s,
+			mctrl_gpio_get(s->gpios, &s->ctrl));
+
 	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;
@@ -758,6 +811,8 @@ 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->ctrl);
 	return 0;
 }
 
@@ -1021,6 +1076,14 @@ 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 =
@@ -1078,6 +1141,11 @@ 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);
@@ -1094,6 +1162,7 @@ static int mxs_auart_probe(struct platform_device *pdev)
 	return 0;
 
 out_free_irq:
+	mctrl_gpio_free(&pdev->dev, s->gpios);	/*useless?*/
 	auart_port[pdev->id] = NULL;
 	free_irq(s->irq, s);
 out_free_clk:
@@ -1112,6 +1181,8 @@ static int mxs_auart_remove(struct platform_device *pdev)
 
 	auart_port[pdev->id] = NULL;
 
+	mctrl_gpio_free(&pdev->dev, s->gpios);	/*useless?*/
+
 	clk_put(s->clk);
 	free_irq(s->irq, s);
 	kfree(s);
-- 
1.7.11.3

[PATCH 2/4] serial: mxs-auart: add interrupts for modem control lines

[Janusz Uzycki]

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

Signed-off-by: Janusz Uzycki <j.uzycki@elproma.com.pl>
---
 drivers/tty/serial/mxs-auart.c | 146 ++++++++++++++++++++++++++-
 1 file changed, 143 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auart.c
index 4690200..c2f24f8 100644
--- a/drivers/tty/serial/mxs-auart.c
+++ b/drivers/tty/serial/mxs-auart.c
@@ -38,7 +38,10 @@
 
 #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_MAJOR 242
@@ -161,6 +164,8 @@ 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[] = {
@@ -478,6 +483,64 @@ static u32 mxs_auart_get_mctrl(struct uart_port *u)
 			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]);
+	/* otherwise: shouldn't be AUART_INTR_CTSMIEN enabled here? (FIXME) */
+
+	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]);
+	/* otherwise: shouldn't be AUART_INTR_CTSMIEN disabled here? (FIXME) */
+
+	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)
 {
@@ -726,6 +789,12 @@ 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)
@@ -743,8 +812,15 @@ static irqreturn_t mxs_auart_irq_handle(int irq, void *context)
 		| AUART_INTR_CTSMIS),
 			s->port.membase + AUART_INTR_CLR);
 
-	mxs_auart_modem_status(s,
-			mctrl_gpio_get(s->gpios, &s->ctrl));
+	/*
+	 * 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->ctrl));
 
 	if (istat & AUART_INTR_CTSMIS) {
 		if (IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(s->gpios,
@@ -813,6 +889,8 @@ static int mxs_auart_startup(struct uart_port *u)
 
 	/* get initial status of modem lines */
 	mctrl_gpio_get(s->gpios, &s->ctrl);
+
+	s->ms_irq_enabled = false;
 	return 0;
 }
 
@@ -820,6 +898,8 @@ 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);
 
@@ -876,6 +956,7 @@ 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,
@@ -1078,12 +1159,61 @@ 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 =
@@ -1146,13 +1276,20 @@ 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",
@@ -1161,6 +1298,8 @@ static int mxs_auart_probe(struct platform_device *pdev)
 
 	return 0;
 
+out_free_gpio_irq:
+	mxs_auart_free_gpio_irq(s);
 out_free_irq:
 	mctrl_gpio_free(&pdev->dev, s->gpios);	/*useless?*/
 	auart_port[pdev->id] = NULL;
@@ -1181,6 +1320,7 @@ static int mxs_auart_remove(struct platform_device *pdev)
 
 	auart_port[pdev->id] = NULL;
 
+	mxs_auart_free_gpio_irq(s);
 	mctrl_gpio_free(&pdev->dev, s->gpios);	/*useless?*/
 
 	clk_put(s->clk);
-- 
1.7.11.3

[PATCH 3/4] serial: mxs-auart: enable PPS support

[Janusz Uzycki]

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

Signed-off-by: Janusz Uzycki <j.uzycki@elproma.com.pl>
---
 drivers/tty/serial/mxs-auart.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auart.c
index c2f24f8..9381732 100644
--- a/drivers/tty/serial/mxs-auart.c
+++ b/drivers/tty/serial/mxs-auart.c
@@ -797,6 +797,15 @@ static void mxs_auart_settermios(struct uart_port *u,
 		mxs_auart_disable_ms(u);
 }
 
+static void mxs_auart_set_ldisc(struct uart_port *port, int new)
+{
+	if (new == N_PPS) {
+		port->flags |= UPF_HARDPPS_CD;
+		mxs_auart_enable_ms(port);
+	} else
+		port->flags &= ~UPF_HARDPPS_CD;
+}
+
 static irqreturn_t mxs_auart_irq_handle(int irq, void *context)
 {
 	u32 istat;
@@ -963,6 +972,7 @@ static struct uart_ops mxs_auart_ops = {
 	.startup	= mxs_auart_startup,
 	.shutdown       = mxs_auart_shutdown,
 	.set_termios    = mxs_auart_settermios,
+	.set_ldisc      = mxs_auart_set_ldisc,
 	.type	   	= mxs_auart_type,
 	.release_port   = mxs_auart_release_port,
 	.request_port   = mxs_auart_request_port,
-- 
1.7.11.3

[PATCH 4/4] serial: mxs-auart: add sysrq support

[Janusz Uzycki]

When using mxs-auart based console, sometime we need the sysrq function
to help debugging kernel. The sysrq code is basically there,
this patch just simply enable it.

Signed-off-by: Janusz Uzycki <j.uzycki@elproma.com.pl>
---
 drivers/tty/serial/mxs-auart.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auart.c
index 9381732..b144382 100644
--- a/drivers/tty/serial/mxs-auart.c
+++ b/drivers/tty/serial/mxs-auart.c
@@ -14,6 +14,12 @@
  * http://www.gnu.org/copyleft/gpl.html
  */
 
+#if defined(CONFIG_SERIAL_MXS_AUART_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
+#include <linux/sysrq.h>
+/* define before linux/serial_core.h */
+#define SUPPORT_SYSRQ
+#endif
+
 #include <linux/kernel.h>
 #include <linux/errno.h>
 #include <linux/init.h>
-- 
1.7.11.3

[PATCH 1/4] serial: mxs-auart: use mctrl_gpio helpers for handling modem signals (v2.2c)

[Janusz Użycki]

Please for comments in order to resend clean patches.
4/4: can be applied separately

TODO:
- tx_empty fix
- port.lock
- pm support

best regards
Janusz

W dniu 2014-09-19 20:13, Janusz Uzycki pisze:
> 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 <j.uzycki@elproma.com.pl>
> ---
>   .../devicetree/bindings/serial/fsl-mxs-auart.txt   | 10 ++-
>   drivers/tty/serial/Kconfig           |  1 +
>   drivers/tty/serial/mxs-auart.c       | 77 +++++++++++++++++++++-
>   3 files changed, 84 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/serial/fsl-mxs-auart.txt b/Documentation/devicetree/bindings/serial/fsl-mxs-auart.txt
> index 59a40f1..7c408c8 100644
> --- a/Documentation/devicetree/bindings/serial/fsl-mxs-auart.txt
> +++ b/Documentation/devicetree/bindings/serial/fsl-mxs-auart.txt
> @@ -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 at 8006a000 {
> @@ -21,6 +26,9 @@ auart0: serial at 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"
> diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
> index 4fe8ca1..90e8516 100644
> --- a/drivers/tty/serial/Kconfig
> +++ b/drivers/tty/serial/Kconfig
> @@ -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.
>   
> diff --git a/drivers/tty/serial/mxs-auart.c b/drivers/tty/serial/mxs-auart.c
> index 52d14e3..4690200 100644
> --- a/drivers/tty/serial/mxs-auart.c
> +++ b/drivers/tty/serial/mxs-auart.c
> @@ -38,6 +38,9 @@
>   
>   #include <asm/cacheflush.h>
>   
> +#include <linux/err.h>
> +#include "serial_mctrl_gpio.h"
> +
>   #define MXS_AUART_MAJOR 242
>   #define MXS_AUART_PORTS 5
>   #define MXS_AUART_FIFO_SIZE		16
> @@ -156,6 +159,8 @@ 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[] = {
> @@ -415,8 +420,43 @@ static void mxs_auart_set_mctrl(struct uart_port *u, unsigned mctrl)
>   			ctrl |= AUART_CTRL2_RTS;
>   	}
>   
> +	/* Does tty layer modify mctrl for input lines
> +	 * and the code below is required? */
> +#if 0
>   	s->ctrl = mctrl;
> +#else
> +	s->ctrl &= ~(TIOCM_RTS | TIOCM_DTR);
> +	s->ctrl |= mctrl & (TIOCM_RTS | TIOCM_DTR);
> +#endif
>   	writel(ctrl, u->membase + AUART_CTRL2);
> +
> +	mctrl_gpio_set(s->gpios, mctrl);
> +}
> +
> +/* mxs_auart_modem_status() based on 8250.c,
> + * similar function could be as serial's helper... */
> +#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->ctrl;
> +	s->ctrl = mctrl;
> +	if (mctrl_diff & MCTRL_ANY_DELTA &&
> +			/*interrupt_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)
> @@ -433,7 +473,9 @@ static u32 mxs_auart_get_mctrl(struct uart_port *u)
>   	if (ctrl2 & AUART_CTRL2_RTS)
>   		mctrl |= TIOCM_RTS;
>   
> -	return mctrl;
> +	/* should mxs_auart_modem_status() be in interrupt only? */
> +	return mxs_auart_modem_status(s,
> +			mctrl_gpio_get(s->gpios, &mctrl));
>   }
>   
>   static int mxs_auart_dma_prep_rx(struct mxs_auart_port *s);
> @@ -637,7 +679,12 @@ static void mxs_auart_settermios(struct uart_port *u,
>   		ctrl |= AUART_LINECTRL_STP2;
>   
>   	/* figure out the hardware flow control settings */
> -	if (cflag & CRTSCTS) {
> +	/*FIXME: DMA for hardware flow control only? */
> +	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,
> @@ -696,8 +743,14 @@ static irqreturn_t mxs_auart_irq_handle(int irq, void *context)
>   		| AUART_INTR_CTSMIS),
>   			s->port.membase + AUART_INTR_CLR);
>   
> +	mxs_auart_modem_status(s,
> +			mctrl_gpio_get(s->gpios, &s->ctrl));
> +
>   	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;
> @@ -758,6 +811,8 @@ 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->ctrl);
>   	return 0;
>   }
>   
> @@ -1021,6 +1076,14 @@ 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 =
> @@ -1078,6 +1141,11 @@ 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);
> @@ -1094,6 +1162,7 @@ static int mxs_auart_probe(struct platform_device *pdev)
>   	return 0;
>   
>   out_free_irq:
> +	mctrl_gpio_free(&pdev->dev, s->gpios);	/*useless?*/
>   	auart_port[pdev->id] = NULL;
>   	free_irq(s->irq, s);
>   out_free_clk:
> @@ -1112,6 +1181,8 @@ static int mxs_auart_remove(struct platform_device *pdev)
>   
>   	auart_port[pdev->id] = NULL;
>   
> +	mctrl_gpio_free(&pdev->dev, s->gpios);	/*useless?*/
> +
>   	clk_put(s->clk);
>   	free_irq(s->irq, s);
>   	kfree(s);

[PATCH 1/4] serial: mxs-auart: use mctrl_gpio helpers for handling modem signals (v2.2c)

[Janusz Użycki]

W dniu 2014-09-25 17:29, Richard Genoud pisze:
> 2014-09-20 10:08 GMT+02:00 Janusz U?ycki <j.uzycki@elproma.com.pl>:
> Hi,
Hi Richard,

first, thanks for the very useful answers.

>> Could you look on my patch series [1...4]
>> serial: mxs-auart:
>> use mctrl_gpio helpers for handling modem signals (v2.2c)
>> at http://news.gmane.org/gmane.linux.serial ?
> If you resend them, put me in the CC list.
> That will be easier for me to have a look at them.

sure

>> I added some comments in patch's code.
>> In atmel_serial mctrl_gpio_free() is ommited,
>> is it useless?
> If you take a look at mctrl_gpio_init(), you'll see that all the
> allocations are done with devm_* functions.
> So that they are automatically deallocated when the module unloads.
> I still wrote mctrl_gpio_free() for some cases where we want to free
> memory without unloading the module.
>
> So you don't have to call mctrl_gpio_free() at the end of
> mxs_auart_probe() and mxs_auart_remove()
> (cf Documentation/serial/driver )

It is clear now, thanks.

>> Atmel_serial also does not parse modem
>> line status in mxs_auart_get_mctrl(),
>> 8250 driver does it. Which solution is ok?
> Well, in atmel_get_mctrl(), we have to retrieve the line status from
> the uart controller :
> that's done with :
> status = UART_GET_CSR(port);
> Then, for the lines controlled via GPIO, we are calling
> mctrl_gpio_get() that updates the mctrl flags with gpios states.
>
> It doesn't seems different from 8250.

But serial8250_get_mctrl() in 8250_core.c calls serial8250_modem_status()
which calls eg. uart_handle_cts_change() even if enable_ms() wasn't called.
This is the difference.
The serial8250_modem_status() is also called in the interrupt
and, what I don't understand, in serial8250_console_write().

>> Do you happen to know if tty layer
>> modifies mctrl between mxs_auart_get_mctrl(),
>> mxs_auart_set_mctrl() and mxs_auart_get_mctrl() again?
> I don't quite understand what you mean.
> The only way for the kernel to get line status (DCD, CTS,DSR,RI) is
> via get_mctrl.
> And the only way for the kernel to set line status
> (RTS,DTR,out1,out2,loop) is via set_mctrl.

Yes, but:
* mxs_auart_set_mctrl() in the mxs-auart stores the lastest mctrl
    in private ctrl field
* the stored value is used to supply initial returned value
    by mxs_auart_get_mctrl()
* uart_update_mctrl() in serial_core.c modifies only selected bits
    in port->mctrl field - OK, input bits stay untouched
* uart_port_startup() in serial_code.c sets RTS and DTR
    and zeroes others (also input bits)
* uart_set_termios() in serial_core.c modifies the bits too
* uart_suspend_port() in serial_core.c sets all mctrl bits to 0

It looks that mxs_auart_set_mctrl() doesn't have to store mctrl at all
because uart_tiocmget() in serial_core.c restores the output bits
from port->mctrl field. So the code is duplicated.
Do you agree?
P.S. It was even implemented in serial_core.c in 2.6.12.

best regards
Janusz
> best regards,
> Richard.

[PATCH 1/4] serial: mxs-auart: use mctrl_gpio helpers for handling modem signals (v2.2c)

[Russell King - ARM Linux]

On Fri, Sep 26, 2014 at 02:59:18PM +0200, Janusz U?ycki wrote:
> But serial8250_get_mctrl() in 8250_core.c calls serial8250_modem_status()
> which calls eg. uart_handle_cts_change() even if enable_ms() wasn't called.
> This is the difference.
> The serial8250_modem_status() is also called in the interrupt
> and, what I don't understand, in serial8250_console_write().

Reading the MSR register clears the interrupts.  So, whenever MSR is read,
you have to deal with any state changes which _would_ have been passed
to the interrupt function.

Plus, it's not quite as you make out above.

If enable_ms() is not called, then UART_IER_MSI will not be set in up->ier.
Hence, uart_handle_cts_change() will not be called.

The reason for the call in the console function is to account for the
state changes during console write with CTS flow control - this again
needs the MSR register to be read, and we have to account for MSR state
changes after the console write has completed.

-- 
FTTC broadband for 0.8mile line: currently at 9.5Mbps down 400kbps up
according to speedtest.net.

[PATCH 1/4] serial: mxs-auart: use mctrl_gpio helpers for handling modem signals (v2.2c)

[Janusz Użycki]

W dniu 2014-09-26 15:11, Russell King - ARM Linux pisze:
> On Fri, Sep 26, 2014 at 02:59:18PM +0200, Janusz U?ycki wrote:
>> But serial8250_get_mctrl() in 8250_core.c calls serial8250_modem_status()
>> which calls eg. uart_handle_cts_change() even if enable_ms() wasn't called.
>> This is the difference.
>> The serial8250_modem_status() is also called in the interrupt
>> and, what I don't understand, in serial8250_console_write().
> Reading the MSR register clears the interrupts.  So, whenever MSR is read,
> you have to deal with any state changes which _would_ have been passed
> to the interrupt function.
>
> Plus, it's not quite as you make out above.
>
> If enable_ms() is not called, then UART_IER_MSI will not be set in up->ier.
> Hence, uart_handle_cts_change() will not be called.

Oh, now I understand the condition "up->ier & UART_IER_MSI"
in serial8250_modem_status().
So in case of gpio modem lines interrupt is the only right place like in 
atmel_serial.c.

> The reason for the call in the console function is to account for the
> state changes during console write with CTS flow control - this again
> needs the MSR register to be read, and we have to account for MSR state
> changes after the console write has completed.
It means that gpio modem lines does not support flow control for console
on the moment, right Richard?

best regards
Janusz