[PATCH v4 2/4] serial: mxs-auart: use mctrl_gpio helpers for handling modem signals
Janusz Użycki
j.uzycki at elproma.com.pl
Thu Nov 6 03:13:27 PST 2014
Any news?
best regards
Janusz
W dniu 2014-10-31 o 09:48, Richard Genoud pisze:
> 2014-10-24 17:51 GMT+02:00 Janusz Użycki <j.uzycki at elproma.com.pl>:
>> 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?
> Maybe Huang Shijie knows more on this DMA vs RTS/CTS incompatibility.
> [added Huang Shijie in Cc ]
>
>> After review and small fixes requested new version is required for a
>> patchset
>> or rather patch resend?
> It's better to resend the whole patchset (after giving some time for
> Huang Shijie to give its thoughts )
>
>> 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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