Re: [PATCH] drm/bridge: it6505: Fix inverted reset polarity

[Neil Armstrong <neil.armstrong@linaro.org>]

On 29/10/2024 10:54, Chen-Yu Tsai wrote:
> The IT6505 bridge chip has a active low reset line. Since it is a
> "reset" and not an "enable" line, the GPIO should be asserted to
> put it in reset and deasserted to bring it out of reset during
> the power on sequence.
> 
> The polarity was inverted when the driver was first introduced, likely
> because the device family that was targeted had an inverting level
> shifter on the reset line.
> 
> The MT8186 Corsola devices already have the IT6505 in their device tree,
> but the whole display pipeline is actually disabled and won't be enabled
> until some remaining issues are sorted out. The other known user is
> the MT8183 Kukui / Jacuzzi family; their device trees currently do not
> have the IT6505 included.
> 
> Fix the polarity in the driver while there are no actual users.
> 
> Fixes: b5c84a9edcd4 ("drm/bridge: add it6505 driver")
> Cc: <stable@vger.kernel.org>
> Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
> ---
>   drivers/gpu/drm/bridge/ite-it6505.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/bridge/ite-it6505.c b/drivers/gpu/drm/bridge/ite-it6505.c
> index 7502a5f81557..df7ecdf0f422 100644
> --- a/drivers/gpu/drm/bridge/ite-it6505.c
> +++ b/drivers/gpu/drm/bridge/ite-it6505.c
> @@ -2618,9 +2618,9 @@ static int it6505_poweron(struct it6505 *it6505)
>   	/* time interval between OVDD and SYSRSTN at least be 10ms */
>   	if (pdata->gpiod_reset) {
>   		usleep_range(10000, 20000);
> -		gpiod_set_value_cansleep(pdata->gpiod_reset, 0);
> -		usleep_range(1000, 2000);
>   		gpiod_set_value_cansleep(pdata->gpiod_reset, 1);
> +		usleep_range(1000, 2000);
> +		gpiod_set_value_cansleep(pdata->gpiod_reset, 0);
>   		usleep_range(25000, 35000);
>   	}
>   
> @@ -2651,7 +2651,7 @@ static int it6505_poweroff(struct it6505 *it6505)
>   	disable_irq_nosync(it6505->irq);
>   
>   	if (pdata->gpiod_reset)
> -		gpiod_set_value_cansleep(pdata->gpiod_reset, 0);
> +		gpiod_set_value_cansleep(pdata->gpiod_reset, 1);
>   
>   	if (pdata->pwr18) {
>   		err = regulator_disable(pdata->pwr18);
> @@ -3205,7 +3205,7 @@ static int it6505_init_pdata(struct it6505 *it6505)
>   		return PTR_ERR(pdata->ovdd);
>   	}
>   
> -	pdata->gpiod_reset = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
> +	pdata->gpiod_reset = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
>   	if (IS_ERR(pdata->gpiod_reset)) {
>   		dev_err(dev, "gpiod_reset gpio not found");
>   		return PTR_ERR(pdata->gpiod_reset);

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>