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>
---
v3 -> v4 changelog:
* RTS_AT_AUART() and CTS_AT_AUART() macro defined
* DMA engine disabled if RTS or CTS is GPIO line
* warn if fsl,uart-has-rtscts and RTS/CTS via GPIO are mixed
* CTSEN can't be enabled for hardware flow control block
if CTS is defined as GPIO line
* RTSEN can be enabled for hardware flow control block
even if RTS is defined as GPIO line.
RTS pin depends on pinctrl configuration which
selects RTS output from hardware flow control block or GPIO line.
* mxs_auart_settermios(): RTS_AT_AUART() and CTS_AT_AUART() used
* mxs_auart_irq_handle(): CTS_AT_AUART() used
* mxs_auart_init_gpios() returns true(success)/false(failure)
* dev_err() message fixed in mxs_auart_probe()
v2 -> v3 changelog:
* mctrl_gpio_free() removed to simplify:
mctrl_gpio_free() is not necessary in mxs_auart_probe() and
mxs_auart_remove() because mctrl_gpio_init() does all
allocations with devm_* functions.
(see Documentation/serial/driver since kernel 3.16)
* DMA on HW flow control comment updated, still not sure about the comment
* mxs_auart_modem_status() removed from mxs_auart_get_mctrl():
mctrl_gpio_get() does not clear gpio interrupt pendings like
8250_core.c does with MSR.
* mxs_auart_modem_status() moved to [3/4]
If enable_ms() is not called, uart_handle_cts_change()
shouldn't be called.
---
.../devicetree/bindings/serial/fsl-mxs-auart.txt | 10 ++++-
drivers/tty/serial/Kconfig | 1 +
drivers/tty/serial/mxs-auart.c | 50 +++++++++++++++++++---
3 files changed, 55 insertions(+), 6 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 2d49901..8bbcfd1 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);
@@ -416,17 +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);
--
1.7.11.3
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