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

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Message-ID: <16bd6bc2-8f10-4b99-9903-6e9f0f8778d8@linaro.org>
Date: Mon, 30 Sep 2024 18:24:44 +0200
From: neil.armstrong@...aro.org
To: Hugo Villeneuve <hugo@...ovil.com>
Cc: 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>,
 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

On 30/09/2024 17:05, Hugo Villeneuve wrote:
> On Mon, 30 Sep 2024 16:38:14 +0200
> Neil Armstrong <neil.armstrong@...aro.org> wrote:
> 
>> 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 ?
> 
> Hi Neil,
> I confirmed that no in-tree DTS is referencing this driver. I did a
> search of all the compatible strings defined in the
> "jadard,jd9365da-h3.yaml" file. I also did the same on Debian code
> search.


OK then:
Reviewed-by: Neil Armstrong <neil.armstrong@...aro.org>

> 
> Hugo.
> 
> 
>>
>> 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
>>
>>
> 
>