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From: Maxime Ripard <maxime.ripard@bootlin.com>
To: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Sean Paul <seanpaul@chromium.org>,
	Maxime Ripard <maxime.ripard@bootlin.com>
Cc: bbrezillon@kernel.org, dri-devel@lists.freedesktop.org,
	Paul Kocialkowski <paul.kocialkowski@bootlin.com>,
	Chen-Yu Tsai <wens@csie.org>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	Jagan Teki <jagan@openedev.com>,
	linux-arm-kernel@lists.infradead.org
Subject: [PATCH v3 2/8] drm/sun4i: dsi: Change the start delay calculation
Date: Mon, 11 Feb 2019 15:41:23 +0100
Message-ID: <6e5f72e68f47ca0223877464bf12f0c3f3978de8.1549896081.git-series.maxime.ripard@bootlin.com> (raw)
In-Reply-To: <cover.f28d9994585553a089a519392616b0d26ed54af1.1549896081.git-series.maxime.ripard@bootlin.com>

The current calculation for the video start delay in the current DSI driver
is that it is the total vertical size, minus the front porch and sync length,
plus 1. This equals to the active vertical size plus the back porch plus 1.

That 1 is coming in the Allwinner BSP from an variable that is set to 1.
However, if we look at the Allwinner BSP more closely, and especially in
the "legacy" code for the display (in drivers/video/sunxi/legacy/), we can
see that this variable is actually computed from the porches and the sync
minus 10, clamped between 8 and 100.

This fixes the start delay symptom we've seen on some panels (vblank
timeouts with vertical white stripes at the bottom of the panel).

Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
---
 drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
index 380fc527a707..9471fa695ec7 100644
--- a/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
+++ b/drivers/gpu/drm/sun4i/sun6i_mipi_dsi.c
@@ -357,7 +357,9 @@ static void sun6i_dsi_inst_init(struct sun6i_dsi *dsi,
 static u16 sun6i_dsi_get_video_start_delay(struct sun6i_dsi *dsi,
 					   struct drm_display_mode *mode)
 {
-	return mode->vtotal - (mode->vsync_end - mode->vdisplay) + 1;
+	u16 start = clamp(mode->vtotal - mode->vdisplay - 10, 8, 100);
+
+	return mode->vtotal - (mode->vsync_end - mode->vdisplay) + start;
 }
 
 static void sun6i_dsi_setup_burst(struct sun6i_dsi *dsi,
-- 
git-series 0.9.1

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  parent reply index

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-11 14:41 [PATCH v3 0/8] drm/sun4i: dsi: Add burst mode support Maxime Ripard
2019-02-11 14:41 ` [PATCH v3 1/8] drm/sun4i: dsi: Restrict DSI tcon clock divider Maxime Ripard
2019-02-11 14:41 ` Maxime Ripard [this message]
2019-02-12 15:28   ` [PATCH v3 2/8] drm/sun4i: dsi: Change the start delay calculation Paul Kocialkowski
2019-02-12 15:45     ` Maxime Ripard
2019-02-11 14:41 ` [PATCH v3 3/8] drm/sun4i: dsi: Enforce boundaries on the start delay Maxime Ripard
2019-02-12 15:30   ` Paul Kocialkowski
2019-02-14  9:21     ` Maxime Ripard
2019-02-11 14:41 ` [PATCH v3 4/8] drm/sun4i: dsi: Fix front vs back porch calculation Maxime Ripard
2019-02-12 15:41   ` Paul Kocialkowski
2019-02-11 14:41 ` [PATCH v3 5/8] drm/sun4i: dsi: Fix DRQ calculation Maxime Ripard
2019-02-13 14:33   ` Paul Kocialkowski
2019-02-14  9:23     ` Maxime Ripard
2019-02-11 14:41 ` [PATCH v3 6/8] drm/sun4i: dsi: Rework a bit the hblk calculation Maxime Ripard
2019-02-13 14:41   ` Paul Kocialkowski
2019-02-11 14:41 ` [PATCH v3 7/8] drm/sun4i: dsi: Add burst support Maxime Ripard
2019-02-13 14:36   ` Paul Kocialkowski
2019-02-14  9:15     ` Maxime Ripard
2019-02-11 14:41 ` [PATCH v3 8/8] drm/panel: Add Ronbo RB070D30 panel Maxime Ripard
2019-02-11 15:13   ` Sam Ravnborg
2019-02-13 14:26   ` Paul Kocialkowski
2019-02-14 11:07     ` Re[2]: " Konstantin Sudakov
2019-02-12 10:32 ` [PATCH v3 0/8] drm/sun4i: dsi: Add burst mode support Jagan Teki
2019-02-15 14:12 ` Maxime Ripard
     [not found]   ` <CAMty3ZAA90-fHPADJSE3ht9CiYWA3yBoyEy7wVv9=6C5JiaTVw@mail.gmail.com>
2019-02-15 17:07     ` Jagan Teki
2019-02-18  8:26       ` Paul Kocialkowski
2019-02-18 10:31         ` Jagan Teki
2019-02-20 16:35           ` Maxime Ripard
2019-02-26  6:48             ` Jagan Teki

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