linux-kernel - [PATCH AUTOSEL 6.6 28/40] drm/panel: st7703: Pick different reset sequence

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Date:   Tue,  7 Nov 2023 07:16:30 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Ondrej Jirman <megi@....cz>, Frank Oltmanns <frank@...manns.dev>,
        Samuel Holland <samuel@...lland.org>,
        Guido Günther <agx@...xcpu.org>,
        Sasha Levin <sashal@...nel.org>, neil.armstrong@...aro.org,
        maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
        tzimmermann@...e.de, airlied@...il.com, daniel@...ll.ch,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 6.6 28/40] drm/panel: st7703: Pick different reset sequence

From: Ondrej Jirman <megi@....cz>

[ Upstream commit d12d635bb03c7cb4830acb641eb176ee9ff2aa89 ]

Switching to a different reset sequence, enabling IOVCC before enabling
VCC.

There also needs to be a delay after enabling the supplies and before
deasserting the reset. The datasheet specifies 1ms after the supplies
reach the required voltage. Use 10-20ms to also give the power supplies
some time to reach the required voltage, too.

This fixes intermittent panel initialization failures and screen
corruption during resume from sleep on panel xingbangda,xbd599 (e.g.
used in PinePhone).

Signed-off-by: Ondrej Jirman <megi@....cz>
Signed-off-by: Frank Oltmanns <frank@...manns.dev>
Reported-by: Samuel Holland <samuel@...lland.org>
Reviewed-by: Guido Günther <agx@...xcpu.org>
Tested-by: Guido Günther <agx@...xcpu.org>
Signed-off-by: Guido Günther <agx@...xcpu.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230211171748.36692-2-frank@oltmanns.dev
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/panel/panel-sitronix-st7703.c | 25 ++++++++++---------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/panel/panel-sitronix-st7703.c b/drivers/gpu/drm/panel/panel-sitronix-st7703.c
index 6a39456395350..7bb723d445ade 100644
--- a/drivers/gpu/drm/panel/panel-sitronix-st7703.c
+++ b/drivers/gpu/drm/panel/panel-sitronix-st7703.c
@@ -506,29 +506,30 @@ static int st7703_prepare(struct drm_panel *panel)
 		return 0;
 
 	dev_dbg(ctx->dev, "Resetting the panel\n");
-	ret = regulator_enable(ctx->vcc);
+	gpiod_set_value_cansleep(ctx->reset_gpio, 1);
+
+	ret = regulator_enable(ctx->iovcc);
 	if (ret < 0) {
-		dev_err(ctx->dev, "Failed to enable vcc supply: %d\n", ret);
+		dev_err(ctx->dev, "Failed to enable iovcc supply: %d\n", ret);
 		return ret;
 	}
-	ret = regulator_enable(ctx->iovcc);
+
+	ret = regulator_enable(ctx->vcc);
 	if (ret < 0) {
-		dev_err(ctx->dev, "Failed to enable iovcc supply: %d\n", ret);
-		goto disable_vcc;
+		dev_err(ctx->dev, "Failed to enable vcc supply: %d\n", ret);
+		regulator_disable(ctx->iovcc);
+		return ret;
 	}
 
-	gpiod_set_value_cansleep(ctx->reset_gpio, 1);
-	usleep_range(20, 40);
+	/* Give power supplies time to stabilize before deasserting reset. */
+	usleep_range(10000, 20000);
+
 	gpiod_set_value_cansleep(ctx->reset_gpio, 0);
-	msleep(20);
+	usleep_range(15000, 20000);
 
 	ctx->prepared = true;
 
 	return 0;
-
-disable_vcc:
-	regulator_disable(ctx->vcc);
-	return ret;
 }
 
 static const u32 mantix_bus_formats[] = {
-- 
2.42.0