serial: mxs-auart: use mctrl_gpio helpers for handling modem signals

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>
Reviewed-by: Richard Genoud <richard.genoud@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/Documentation/devicetree/bindings/serial/fsl-mxs-auart.txt b/Documentation/devicetree/bindings/serial/fsl-mxs-auart.txt
index 59a40f1..7c408c8 100644 (file)
--- 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@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"

diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 649b784..4e6a0ba 100644 (file)
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -1408,6 +1408,7 @@ 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 907c3e5..5922cb4 100644 (file)
--- a/drivers/tty/serial/mxs-auart.c
+++ b/drivers/tty/serial/mxs-auart.c
@@ -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);
@@ -416,17 +423,20 @@ 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);
        u32 mctrl = 0;
 
        if (stat & AUART_STAT_CTS)
                mctrl |= TIOCM_CTS;
 
-       return mctrl;
+       return mctrl_gpio_get(s->gpios, &mctrl);
 }
 
 static int mxs_auart_dma_prep_rx(struct mxs_auart_port *s);
@@ -554,6 +564,10 @@ err_out:
 
 }
 
+#define RTS_AT_AUART() IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(s->gpios,    \
+                                                       UART_GPIO_RTS))
+#define CTS_AT_AUART() IS_ERR_OR_NULL(mctrl_gpio_to_gpiod(s->gpios,    \
+                                                       UART_GPIO_CTS))
 static void mxs_auart_settermios(struct uart_port *u,
                                 struct ktermios *termios,
                                 struct ktermios *old)
@@ -630,6 +644,7 @@ static void mxs_auart_settermios(struct uart_port *u,
                ctrl |= AUART_LINECTRL_STP2;
 
        /* figure out the hardware flow control settings */
+       ctrl2 &= ~(AUART_CTRL2_CTSEN | AUART_CTRL2_RTSEN);
        if (cflag & CRTSCTS) {
                /*
                 * The DMA has a bug(see errata:2836) in mx23.
@@ -644,9 +659,11 @@ static void mxs_auart_settermios(struct uart_port *u,
                                ctrl2 |= AUART_CTRL2_TXDMAE | AUART_CTRL2_RXDMAE
                                       | AUART_CTRL2_DMAONERR;
                }
-               ctrl2 |= AUART_CTRL2_CTSEN | AUART_CTRL2_RTSEN;
-       } else {
-               ctrl2 &= ~(AUART_CTRL2_CTSEN | AUART_CTRL2_RTSEN);
+               /* Even if RTS is GPIO line RTSEN can be enabled because
+                * the pinctrl configuration decides about RTS pin function */
+               ctrl2 |= AUART_CTRL2_RTSEN;
+               if (CTS_AT_AUART())
+                       ctrl2 |= AUART_CTRL2_CTSEN;
        }
 
        /* set baud rate */
@@ -690,7 +707,9 @@ 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 (CTS_AT_AUART())
+                       uart_handle_cts_change(&s->port,
+                                       stat & AUART_STAT_CTS);
                writel(AUART_INTR_CTSMIS,
                                s->port.membase + AUART_INTR_CLR);
                istat &= ~AUART_INTR_CTSMIS;
@@ -1014,6 +1033,23 @@ static int serial_mxs_probe_dt(struct mxs_auart_port *s,
        return 0;
 }
 
+static bool 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 false;
+
+       /* Block (enabled before) DMA option if RTS or CTS is GPIO line */
+       if (!RTS_AT_AUART() || !CTS_AT_AUART()) {
+               if (test_bit(MXS_AUART_RTSCTS, &s->flags))
+                       dev_warn(dev,
+                                "DMA and flow control via gpio may cause some problems. DMA disabled!\n");
+               clear_bit(MXS_AUART_RTSCTS, &s->flags);
+       }
+
+       return true;
+}
+
 static int mxs_auart_probe(struct platform_device *pdev)
 {
        const struct of_device_id *of_id =
@@ -1069,6 +1105,10 @@ static int mxs_auart_probe(struct platform_device *pdev)
 
        platform_set_drvdata(pdev, s);
 
+       if (!mxs_auart_init_gpios(s, &pdev->dev))
+               dev_err(&pdev->dev,
+                       "Failed to initialize GPIOs. The serial port may not work as expected\n");
+
        auart_port[s->port.line] = s;
 
        mxs_auart_reset(&s->port);