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@xxxxxxxxxxxxxx>
---
.../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(-)
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@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 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 c712108..fdfa8a9 100644
--- 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);
@@ -416,10 +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);
