Re: [PATCH] gpio: sifive: use the correct register to read output values

[Damien Le Moal <damien.lemoal@xxxxxxxxxxxxxxxxxx>]

On 2/4/22 22:02, Niklas Cassel wrote:
> From: Niklas Cassel <niklas.cassel@xxxxxxx>
> 
> Setting the output of a GPIO to 1 using gpiod_set_value(), followed by
> reading the same GPIO using gpiod_get_value(), will currently yield an
> incorrect result.
> 
> This is because the SiFive GPIO device stores the output values in reg_set,
> not reg_dat.
> 
> Supply the flag BGPIOF_READ_OUTPUT_REG_SET to bgpio_init() so that the
> generic driver reads the correct register.
> 
> Signed-off-by: Niklas Cassel <niklas.cassel@xxxxxxx>

This probably needs a Fixes tag. I have not checked which patch though.

> ---
> The patch was tested on a canaan,k210 board (canaan,k210-gpiohs compatible
> string). It would be nice with a Tested-by from someone with a SiFive board.
> 
> However, the u-boot driver for this device already behaves exactly the same
> as this driver does after my patch, for all platforms using the driver.
> 
>  drivers/gpio/gpio-sifive.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpio/gpio-sifive.c b/drivers/gpio/gpio-sifive.c
> index 403f9e833d6a..7d82388b4ab7 100644
> --- a/drivers/gpio/gpio-sifive.c
> +++ b/drivers/gpio/gpio-sifive.c
> @@ -223,7 +223,7 @@ static int sifive_gpio_probe(struct platform_device *pdev)
>  			 NULL,
>  			 chip->base + SIFIVE_GPIO_OUTPUT_EN,
>  			 chip->base + SIFIVE_GPIO_INPUT_EN,
> -			 0);
> +			 BGPIOF_READ_OUTPUT_REG_SET);
>  	if (ret) {
>  		dev_err(dev, "unable to init generic GPIO\n");
>  		return ret;


-- 
Damien Le Moal
Western Digital Research