linux-kernel - Re: [PATCH] drm: panel: jd9365da-h3: fix reset signal polarity

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Message-ID: <f9b0cc53-00ae-4390-9ff9-1dac0c0804ba@linaro.org>
Date: Mon, 30 Sep 2024 16:38:14 +0200
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Hugo Villeneuve <hugo@...ovil.com>, Jagan Teki <jagan@...eble.ai>,
 Jessica Zhang <quic_jesszhan@...cinc.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Linus Walleij <linus.walleij@...aro.org>
Cc: Hugo Villeneuve <hvilleneuve@...onoff.com>, stable@...r.kernel.org,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm: panel: jd9365da-h3: fix reset signal polarity

Hi,

On 27/09/2024 15:53, Hugo Villeneuve wrote:
> From: Hugo Villeneuve <hvilleneuve@...onoff.com>
> 
> In jadard_prepare() a reset pulse is generated with the following
> statements (delays ommited for clarity):
> 
>      gpiod_set_value(jadard->reset, 1); --> Deassert reset
>      gpiod_set_value(jadard->reset, 0); --> Assert reset for 10ms
>      gpiod_set_value(jadard->reset, 1); --> Deassert reset
> 
> However, specifying second argument of "0" to gpiod_set_value() means to
> deassert the GPIO, and "1" means to assert it. If the reset signal is
> defined as GPIO_ACTIVE_LOW in the DTS, the above statements will
> incorrectly generate the reset pulse (inverted) and leave it asserted
> (LOW) at the end of jadard_prepare().

Did you check the polarity in DTS of _all_ users of this driver ?

Neil

> 
> Fix reset behavior by inverting gpiod_set_value() second argument
> in jadard_prepare(). Also modify second argument to devm_gpiod_get()
> in jadard_dsi_probe() to assert the reset when probing.
> 
> Do not modify it in jadard_unprepare() as it is already properly
> asserted with "1", which seems to be the intended behavior.
> 
> Fixes: 6b818c533dd8 ("drm: panel: Add Jadard JD9365DA-H3 DSI panel")
> Cc: <stable@...r.kernel.org>
> Signed-off-by: Hugo Villeneuve <hvilleneuve@...onoff.com>
> ---
>   drivers/gpu/drm/panel/panel-jadard-jd9365da-h3.c | 8 ++++----
>   1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panel/panel-jadard-jd9365da-h3.c b/drivers/gpu/drm/panel/panel-jadard-jd9365da-h3.c
> index 44897e5218a69..6fec99cf4d935 100644
> --- a/drivers/gpu/drm/panel/panel-jadard-jd9365da-h3.c
> +++ b/drivers/gpu/drm/panel/panel-jadard-jd9365da-h3.c
> @@ -110,13 +110,13 @@ static int jadard_prepare(struct drm_panel *panel)
>   	if (jadard->desc->lp11_to_reset_delay_ms)
>   		msleep(jadard->desc->lp11_to_reset_delay_ms);
>   
> -	gpiod_set_value(jadard->reset, 1);
> +	gpiod_set_value(jadard->reset, 0);
>   	msleep(5);
>   
> -	gpiod_set_value(jadard->reset, 0);
> +	gpiod_set_value(jadard->reset, 1);
>   	msleep(10);
>   
> -	gpiod_set_value(jadard->reset, 1);
> +	gpiod_set_value(jadard->reset, 0);
>   	msleep(130);
>   
>   	ret = jadard->desc->init(jadard);
> @@ -1131,7 +1131,7 @@ static int jadard_dsi_probe(struct mipi_dsi_device *dsi)
>   	dsi->format = desc->format;
>   	dsi->lanes = desc->lanes;
>   
> -	jadard->reset = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
> +	jadard->reset = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
>   	if (IS_ERR(jadard->reset)) {
>   		DRM_DEV_ERROR(&dsi->dev, "failed to get our reset GPIO\n");
>   		return PTR_ERR(jadard->reset);
> 
> base-commit: 18ba6034468e7949a9e2c2cf28e2e123b4fe7a50