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

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Message-Id: <20240930110537.dbbd51824c2bb68506e2f678@hugovil.com>
Date: Mon, 30 Sep 2024 11:05:37 -0400
From: Hugo Villeneuve <hugo@...ovil.com>
To: neil.armstrong@...aro.org
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 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.

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
> 
> 


-- 
Hugo Villeneuve