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

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Message-Id: <20240927135306.857617-1-hugo@hugovil.com>
Date: Fri, 27 Sep 2024 09:53:05 -0400
From: Hugo Villeneuve <hugo@...ovil.com>
To: Jagan Teki <jagan@...eble.ai>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	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@...ovil.com,
	Hugo Villeneuve <hvilleneuve@...onoff.com>,
	stable@...r.kernel.org,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] drm: panel: jd9365da-h3: fix reset signal polarity

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().

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
-- 
2.39.5