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* [PATCH AUTOSEL 4.19 29/35] drm/msm/mdp5: Configure PP_SYNC_HEIGHT to double the vtotal
       [not found] <>
@ 2021-05-03 16:41 ` Sasha Levin
  0 siblings, 0 replies; only message in thread
From: Sasha Levin @ 2021-05-03 16:41 UTC (permalink / raw)
  To: linux-kernel, stable
  Cc: Marijn Suijten, AngeloGioacchino Del Regno, Rob Clark,
	Sasha Levin, linux-arm-msm, dri-devel, freedreno

From: Marijn Suijten <>

[ Upstream commit 2ad52bdb220de5ab348098e3482b01235d15a842 ]

Leaving this at a close-to-maximum register value 0xFFF0 means it takes
very long for the MDSS to generate a software vsync interrupt when the
hardware TE interrupt doesn't arrive.  Configuring this to double the
vtotal (like some downstream kernels) leads to a frame to take at most
twice before the vsync signal, until hardware TE comes up.

In this case the hardware interrupt responsible for providing this
signal - "disp-te" gpio - is not hooked up to the mdp5 vsync/pp logic at
all.  This solves severe panel update issues observed on at least the
Xperia Loire and Tone series, until said gpio is properly hooked up to
an irq.

Suggested-by: AngeloGioacchino Del Regno <>
Signed-off-by: Marijn Suijten <>
Reviewed-by: AngeloGioacchino Del Regno <>
Signed-off-by: Rob Clark <>
Signed-off-by: Sasha Levin <>
 drivers/gpu/drm/msm/disp/mdp5/mdp5_cmd_encoder.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/disp/mdp5/mdp5_cmd_encoder.c b/drivers/gpu/drm/msm/disp/mdp5/mdp5_cmd_encoder.c
index d6f79dc755b4..14e2ce87bab1 100644
--- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_cmd_encoder.c
+++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_cmd_encoder.c
@@ -78,9 +78,17 @@ static int pingpong_tearcheck_setup(struct drm_encoder *encoder,
 	cfg |= MDP5_PP_SYNC_CONFIG_VSYNC_COUNT(vclks_line);
+	/*
+	 * Tearcheck emits a blanking signal every vclks_line * vtotal * 2 ticks on
+	 * the vsync_clk equating to roughly half the desired panel refresh rate.
+	 * This is only necessary as stability fallback if interrupts from the
+	 * panel arrive too late or not at all, but is currently used by default
+	 * because these panel interrupts are not wired up yet.
+	 */
 	mdp5_write(mdp5_kms, REG_MDP5_PP_SYNC_CONFIG_VSYNC(pp_id), cfg);
-		REG_MDP5_PP_SYNC_CONFIG_HEIGHT(pp_id), 0xfff0);
+		REG_MDP5_PP_SYNC_CONFIG_HEIGHT(pp_id), (2 * mode->vtotal));
 		REG_MDP5_PP_VSYNC_INIT_VAL(pp_id), mode->vdisplay);
 	mdp5_write(mdp5_kms, REG_MDP5_PP_RD_PTR_IRQ(pp_id), mode->vdisplay + 1);

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