linux-kernel - [PATCH v7 4/8] drm/panel: sw43408: Separate reset sequence into own function

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Message-Id: <20251214-pixel-3-v7-4-b1c0cf6f224d@ixit.cz>
Date: Sun, 14 Dec 2025 15:51:20 +0100
From: David Heidelberg via B4 Relay <devnull+david.ixit.cz@...nel.org>
To: Bjorn Andersson <andersson@...nel.org>, 
 Konrad Dybcio <konradybcio@...nel.org>, Rob Herring <robh@...nel.org>, 
 Krzysztof Kozlowski <krzk+dt@...nel.org>, 
 Conor Dooley <conor+dt@...nel.org>, Sumit Semwal <sumit.semwal@...aro.org>, 
 Casey Connolly <casey.connolly@...aro.org>, 
 Neil Armstrong <neil.armstrong@...aro.org>, 
 Jessica Zhang <jesszhan0024@...il.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>, 
 Marijn Suijten <marijn.suijten@...ainline.org>, 
 Dmitry Baryshkov <lumag@...nel.org>, Vinod Koul <vkoul@...nel.org>, 
 Petr Hodina <phodina@...tonmail.com>, 
 Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org, 
 linux-kernel@...r.kernel.org, phone-devel@...r.kernel.org, 
 dri-devel@...ts.freedesktop.org, David Heidelberg <david@...t.cz>
Subject: [PATCH v7 4/8] drm/panel: sw43408: Separate reset sequence into
 own function

From: David Heidelberg <david@...t.cz>

Splitting reset() from prepare() follows clean coding practices and lets
us potentially make reset optional in the future for flicker-less
takeover from a bootloader or framebuffer driver where the panel is
already configured.

Signed-off-by: David Heidelberg <david@...t.cz>
---
 drivers/gpu/drm/panel/panel-lg-sw43408.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/panel/panel-lg-sw43408.c b/drivers/gpu/drm/panel/panel-lg-sw43408.c
index dcca7873acf8e..ed9c7452ea846 100644
--- a/drivers/gpu/drm/panel/panel-lg-sw43408.c
+++ b/drivers/gpu/drm/panel/panel-lg-sw43408.c
@@ -119,6 +119,16 @@ static int sw43408_program(struct drm_panel *panel)
 	return ctx.accum_err;
 }
 
+static void sw43408_reset(struct sw43408_panel *ctx)
+{
+	gpiod_set_value(ctx->reset_gpio, 0);
+	usleep_range(9000, 10000);
+	gpiod_set_value(ctx->reset_gpio, 1);
+	usleep_range(1000, 2000);
+	gpiod_set_value(ctx->reset_gpio, 0);
+	usleep_range(9000, 10000);
+}
+
 static int sw43408_prepare(struct drm_panel *panel)
 {
 	struct sw43408_panel *ctx = to_panel_info(panel);
@@ -130,12 +140,7 @@ static int sw43408_prepare(struct drm_panel *panel)
 
 	usleep_range(5000, 6000);
 
-	gpiod_set_value(ctx->reset_gpio, 0);
-	usleep_range(9000, 10000);
-	gpiod_set_value(ctx->reset_gpio, 1);
-	usleep_range(1000, 2000);
-	gpiod_set_value(ctx->reset_gpio, 0);
-	usleep_range(9000, 10000);
+	sw43408_reset(ctx);
 
 	ret = sw43408_program(panel);
 	if (ret)

-- 
2.51.0