[PATCH v4 2/4] serial: mxs-auart: use mctrl_gpio helpers for handling modem signals
Janusz Użycki
j.uzycki at elproma.com.pl
Fri Oct 24 08:51:08 PDT 2014
W dniu 2014-10-24 o 17:32, Richard Genoud pisze:
> On 10/10/2014 18:53, Janusz Uzycki wrote:
>> 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 at elproma.com.pl>
>> ---
>> 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 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 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 */
> This is confusing, so I think some more comments won't be too much.
> Something like:
> /*
> * The DMA only work if the lines CTS/RTS are handled by the controller
> * cf. 8418e67d9523 serial: mxs: enable the DMA only when the RTS/CTS is
> valid
> * So, If the CTS/RTS lines are controlled via GPIO the MXS_AUART_RTSCTS
> bit should be
> * cleaned to indicate that the RTS/CTS lines are not handled by the
> controller.
> */
> (If I understood correctly what is done here.)
This is not clear in the driver. If hardware RTS/CTS (non-gpio) is not
defined in DT
only DMA is not used. It is still possible to use hardware RTS/CTS lines
if you set hw-flowcontrol in termios. So it is also possible to mix
hardware RTS/CTS
and gpio RTS/CTS. In mixed or gpio case the code blocks/disables DMA.
I know my comment is not clear but the reason is in the earlier code.
Can you propose better solution?
After review and small fixes requested new version is required for a
patchset
or rather patch resend?
kind regards
Janusz
>> + 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);
>>
> Reviewed-by: Richard Genoud <richard.genoud at gmail.com>
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