Re: [PATCH 1/4] ARM/serial: at91: move machine quirk into machine

[Nicolas Ferre <nicolas.ferre@atmel.com>]

On 05/11/2013 10:28, Linus Walleij :
> This removes the dependency on <mach/gpio.h> from the AT91 serial
> driver by adding an mctrl callback quirk.
>
> Long term it is better if the driver calls the generic GPIO
> interface (gpio_set_value()), but this gets a hairy cross-depency
> into the machine-local headers out of the way for now.
>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

Linus,

I do think that we have to remove this dependency but the only thing 
that embarrasses me is that your change only allows non-DT at91rm9200 to 
work well with its RTS line.
If we use Device Tree with this product (which is actually possible) we 
don't have this feature available anymore...

A possible solution can be to give an optional RTS pin specification to 
the DT binding and to the pdata structure, if defined it can be used in 
the atmel_set_mctrl() function. This way we do not have a special 
behavior for at91rm9200 anymore. For the use of specialized AT91 gpio 
functions, well, we can implement the move to gpiolib.

What do you think Linus? Is there a trend to remove the calls to GPIO 
functions in drivers?

Best regards,

> ---
> Greg, if you're OK with this approach please give me an ACK
> so I can take this through the ARM SoC or GPIO tree in the end.
> ---
>   arch/arm/mach-at91/at91rm9200_devices.c | 14 ++++++++++++++
>   drivers/tty/serial/atmel_serial.c       | 19 ++++---------------
>   include/linux/platform_data/atmel.h     |  1 +
>   3 files changed, 19 insertions(+), 15 deletions(-)
>
> diff --git a/arch/arm/mach-at91/at91rm9200_devices.c b/arch/arm/mach-at91/at91rm9200_devices.c
> index 3ebc9792560c..3ce6ba6341ed 100644
> --- a/arch/arm/mach-at91/at91rm9200_devices.c
> +++ b/arch/arm/mach-at91/at91rm9200_devices.c
> @@ -12,6 +12,7 @@
>    */
>   #include <asm/mach/arch.h>
>   #include <asm/mach/map.h>
> +#include <asm/termios.h>
>
>   #include <linux/dma-mapping.h>
>   #include <linux/gpio.h>
> @@ -957,9 +958,22 @@ static struct resource uart0_resources[] = {
>   	},
>   };
>
> +static void uart0_set_mctrl(unsigned int mctrl)
> +{
> +	/*
> +	 * AT91RM9200 Errata #39: RTS0 is not internally connected
> +	 * to PA21. We need to drive the pin manually.
> +	 */
> +	if (mctrl & TIOCM_RTS)
> +		at91_set_gpio_value(AT91_PIN_PA21, 0);
> +	else
> +		at91_set_gpio_value(AT91_PIN_PA21, 1);
> +}
> +
>   static struct atmel_uart_data uart0_data = {
>   	.use_dma_tx	= 1,
>   	.use_dma_rx	= 1,
> +	.set_mctrl	= uart0_set_mctrl,
>   };
>
>   static u64 uart0_dmamask = DMA_BIT_MASK(32);
> diff --git a/drivers/tty/serial/atmel_serial.c b/drivers/tty/serial/atmel_serial.c
> index d067285a2d20..5b29e3152d7e 100644
> --- a/drivers/tty/serial/atmel_serial.c
> +++ b/drivers/tty/serial/atmel_serial.c
> @@ -47,7 +47,6 @@
>
>   #ifdef CONFIG_ARM
>   #include <mach/cpu.h>
> -#include <asm/gpio.h>
>   #endif
>
>   #define PDC_BUFFER_SIZE		512
> @@ -176,6 +175,7 @@ struct atmel_uart_port {
>   	void (*schedule_tx)(struct uart_port *port);
>   	void (*release_rx)(struct uart_port *port);
>   	void (*release_tx)(struct uart_port *port);
> +	void (*set_mctrl)(unsigned int mctrl);
>   };
>
>   static struct atmel_uart_port atmel_ports[ATMEL_MAX_UART];
> @@ -300,20 +300,8 @@ static void atmel_set_mctrl(struct uart_port *port, u_int mctrl)
>   	unsigned int mode;
>   	struct atmel_uart_port *atmel_port = to_atmel_uart_port(port);
>
> -#ifdef CONFIG_ARCH_AT91RM9200
> -	if (cpu_is_at91rm9200()) {

By removing this call, you can also remove
    #include <mach/cpu.h>

as well (maybe in another patch).


> -		/*
> -		 * AT91RM9200 Errata #39: RTS0 is not internally connected
> -		 * to PA21. We need to drive the pin manually.
> -		 */
> -		if (port->mapbase == AT91RM9200_BASE_US0) {
> -			if (mctrl & TIOCM_RTS)
> -				at91_set_gpio_value(AT91_PIN_PA21, 0);
> -			else
> -				at91_set_gpio_value(AT91_PIN_PA21, 1);
> -		}
> -	}
> -#endif
> +	if (atmel_port->set_mctrl)
> +		atmel_port->set_mctrl(mctrl);
>
>   	if (mctrl & TIOCM_RTS)
>   		control |= ATMEL_US_RTSEN;
> @@ -2365,6 +2353,7 @@ static int atmel_serial_probe(struct platform_device *pdev)
>   	port = &atmel_ports[ret];
>   	port->backup_imr = 0;
>   	port->uart.line = ret;
> +	port->set_mctrl = pdata->set_mctrl;
>
>   	ret = atmel_init_port(port, pdev);
>   	if (ret)
> diff --git a/include/linux/platform_data/atmel.h b/include/linux/platform_data/atmel.h
> index cea9f70133c5..59991aae0217 100644
> --- a/include/linux/platform_data/atmel.h
> +++ b/include/linux/platform_data/atmel.h
> @@ -84,6 +84,7 @@ struct atmel_uart_data {
>   	short			use_dma_rx;	/* use receive DMA? */
>   	void __iomem		*regs;		/* virt. base address, if any */
>   	struct serial_rs485	rs485;		/* rs485 settings */
> +	void (*set_mctrl)(unsigned int mctrl);	/* mctrl callback */
>   };
>
>    /* Touchscreen Controller */
>


-- 
Nicolas Ferre