linux-kernel - [PATCH 2/4] drm/panel: otm8009a: fix glitches by moving backlight enable to otm8009a

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Date:   Mon, 23 Apr 2018 16:10:51 +0200
From:   Philippe Cornu <philippe.cornu@...com>
To:     Thierry Reding <thierry.reding@...il.com>,
        David Airlie <airlied@...ux.ie>,
        <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
CC:     Andrzej Hajda <a.hajda@...sung.com>,
        Yannick Fertre <yannick.fertre@...com>,
        Philippe Cornu <philippe.cornu@...com>,
        "Benjamin Gaignard" <benjamin.gaignard@...aro.org>,
        Vincent Abriou <vincent.abriou@...com>,
        Alexandre Torgue <alexandre.torgue@...com>
Subject: [PATCH 2/4] drm/panel: otm8009a: fix glitches by moving backlight enable to otm8009a_enable()

The backlight 1st update was in the otm8009a_prepare() function
for a bad reason: backlight was not working in video mode and the
otm8009a_prepare() is in command mode for the init sequence. As the
backlight is now fixed (no lpm), it is good to put it back in the
otm8009a_enable() function, avoiding also image glitches visible
on some "slow" devices.

Signed-off-by: Philippe Cornu <philippe.cornu@...com>
---
 drivers/gpu/drm/panel/panel-orisetech-otm8009a.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/panel/panel-orisetech-otm8009a.c b/drivers/gpu/drm/panel/panel-orisetech-otm8009a.c
index 0fd2e0144d2b..de4a16d5275c 100644
--- a/drivers/gpu/drm/panel/panel-orisetech-otm8009a.c
+++ b/drivers/gpu/drm/panel/panel-orisetech-otm8009a.c
@@ -330,13 +330,6 @@ static int otm8009a_prepare(struct drm_panel *panel)
 
 	ctx->prepared = true;
 
-	/*
-	 * Power on the backlight. Note: end-user still controls brightness
-	 * Note: ctx->prepared must be true before updating the backlight.
-	 */
-	ctx->bl_dev->props.power = FB_BLANK_UNBLANK;
-	backlight_update_status(ctx->bl_dev);
-
 	return 0;
 }
 
@@ -344,6 +337,16 @@ static int otm8009a_enable(struct drm_panel *panel)
 {
 	struct otm8009a *ctx = panel_to_otm8009a(panel);
 
+	if (ctx->enabled)
+		return 0;
+
+	/*
+	 * Power on the backlight. Note: end-user still controls brightness
+	 * Note: ctx->prepared must be true before updating the backlight.
+	 */
+	ctx->bl_dev->props.power = FB_BLANK_UNBLANK;
+	backlight_update_status(ctx->bl_dev);
+
 	ctx->enabled = true;
 
 	return 0;
-- 
2.15.1