Subject: [PATCH 1/4] serial: mxs-auart: use mctrl_gpio helpers for handling modem signals (v2.2c)

From: [email-masked] (Janusz Użycki)
Date: Tue, 23 Sep 2014 18:18:33 +0200

Please for comments in order to resend clean patches.
4/4: can be applied separately

TODO:
- tx_empty fix
- port.lock
- pm support

best regards
Janusz

W dniu 2014-09-19 20:13, Janusz Uzycki pisze:
> 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 <[email-masked]>
> ---
>   .../devicetree/bindings/serial/fsl-mxs-auart.txt   | 10 ++-
>   drivers/tty/serial/Kconfig           |  1 +
>   drivers/tty/serial/mxs-auart.c       | 77 +++++++++++++++++++++-
>   3 files changed, 84 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 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 52d14e3..4690200 100644
> --- a/drivers/tty/serial/mxs-auart.c
> +++ b/drivers/tty/serial/mxs-auart.c
> @@ -38,6 +38,9 @@
>   
>   #include <asm/cacheflush.h>
>   
> +#include <linux/err.h>
> +#include "serial_mctrl_gpio.h"
> +
>   #define MXS_AUART_MAJOR 242
>   #define MXS_AUART_PORTS 5
>   #define MXS_AUART_FIFO_SIZE		16
> @@ -156,6 +159,8 @@ 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[] = {
> @@ -415,8 +420,43 @@ static void mxs_auart_set_mctrl(struct uart_port *u, unsigned mctrl)
>   			ctrl |= AUART_CTRL2_RTS;
>   	}
>   
> +	/* Does tty layer modify mctrl for input lines
> +	 * and the code below is required? */
> +#if 0
>   	s->ctrl = mctrl;
> +#else
> +	s->ctrl &= ~(TIOCM_RTS | TIOCM_DTR);
> +	s->ctrl |= mctrl & (TIOCM_RTS | TIOCM_DTR);
> +#endif
>   	writel(ctrl, u->membase + AUART_CTRL2);
> +
> +	mctrl_gpio_set(s->gpios, mctrl);
> +}
> +
> +/* mxs_auart_modem_status() based on 8250.c,
> + * similar function could be as serial's helper... */
> +#define MCTRL_ANY_DELTA        (TIOCM_RI | TIOCM_DSR | TIOCM_CD | TIOCM_CTS)
> +static u32 mxs_auart_modem_status(struct mxs_auart_port *s, u32 mctrl)
> +{
> +	u32 mctrl_diff;
> +
> +	mctrl_diff = mctrl ^ s->ctrl;
> +	s->ctrl = mctrl;
> +	if (mctrl_diff & MCTRL_ANY_DELTA &&
> +			/*interrupt_enabled &&*/
> +			s->port.state != NULL) {
> +		if (mctrl_diff & TIOCM_RI)
> +			s->port.icount.rng++;
> +		if (mctrl_diff & TIOCM_DSR)
> +			s->port.icount.dsr++;
> +		if (mctrl_diff & TIOCM_CD)
> +			uart_handle_dcd_change(&s->port, mctrl & TIOCM_CD);
> +		if (mctrl_diff & TIOCM_CTS)
> +			uart_handle_cts_change(&s->port, mctrl & TIOCM_CTS);
> +
> +		wake_up_interruptible(&s->port.state->port.delta_msr_wait);
> +	}
> +	return mctrl;
>   }
>   
>   static u32 mxs_auart_get_mctrl(struct uart_port *u)
> @@ -433,7 +473,9 @@ static u32 mxs_auart_get_mctrl(struct uart_port *u)
>   	if (ctrl2 & AUART_CTRL2_RTS)
>   		mctrl |= TIOCM_RTS;
>   
> -	return mctrl;
> +	/* should mxs_auart_modem_status() be in interrupt only? */
> +	return mxs_auart_modem_status(s,
> +			mctrl_gpio_get(s->gpios, &mctrl));
>   }
>   
>   static int mxs_auart_dma_prep_rx(struct mxs_auart_port *s);
> @@ -637,7 +679,12 @@ static void mxs_auart_settermios(struct uart_port *u,
>   		ctrl |= AUART_LINECTRL_STP2;
>   
>   	/* figure out the hardware flow control settings */
> -	if (cflag & CRTSCTS) {
> +	/*FIXME: DMA for hardware flow control only? */
> +	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,
> @@ -696,8 +743,14 @@ static irqreturn_t mxs_auart_irq_handle(int irq, void *context)
>   		| AUART_INTR_CTSMIS),
>   			s->port.membase + AUART_INTR_CLR);
>   
> +	mxs_auart_modem_status(s,
> +			mctrl_gpio_get(s->gpios, &s->ctrl));
> +
>   	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;
> @@ -758,6 +811,8 @@ static int mxs_auart_startup(struct uart_port *u)
>   	 */
>   	writel(AUART_LINECTRL_FEN, u->membase + AUART_LINECTRL_SET);
>   
> +	/* get initial status of modem lines */
> +	mctrl_gpio_get(s->gpios, &s->ctrl);
>   	return 0;
>   }
>   
> @@ -1021,6 +1076,14 @@ 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 =
> @@ -1078,6 +1141,11 @@ 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);
> @@ -1094,6 +1162,7 @@ static int mxs_auart_probe(struct platform_device *pdev)
>   	return 0;
>   
>   out_free_irq:
> +	mctrl_gpio_free(&pdev->dev, s->gpios);	/*useless?*/
>   	auart_port[pdev->id] = NULL;
>   	free_irq(s->irq, s);
>   out_free_clk:
> @@ -1112,6 +1181,8 @@ static int mxs_auart_remove(struct platform_device *pdev)
>   
>   	auart_port[pdev->id] = NULL;
>   
> +	mctrl_gpio_free(&pdev->dev, s->gpios);	/*useless?*/
> +
>   	clk_put(s->clk);
>   	free_irq(s->irq, s);
>   	kfree(s);