linux-kernel - [PATCH 5.11 213/342] drm/msm/mdp5: Configure PP_SYNC

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Date:   Mon, 10 May 2021 12:20:03 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        Rob Clark <robdclark@...omium.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.11 213/342] drm/msm/mdp5: Configure PP_SYNC_HEIGHT to double the vtotal

From: Marijn Suijten <marijn.suijten@...ainline.org>

[ 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 <angelogioacchino.delregno@...ainline.org>
Signed-off-by: Marijn Suijten <marijn.suijten@...ainline.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...ainline.org>
Link: https://lore.kernel.org/r/20210406214726.131534-2-marijn.suijten@somainline.org
Signed-off-by: Rob Clark <robdclark@...omium.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 ff2c1d583c79..f6df4d3b1406 100644
--- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_cmd_encoder.c
+++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_cmd_encoder.c
@@ -49,9 +49,17 @@ static int pingpong_tearcheck_setup(struct drm_encoder *encoder,
 		| MDP5_PP_SYNC_CONFIG_VSYNC_IN_EN;
 	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);
 	mdp5_write(mdp5_kms,
-		REG_MDP5_PP_SYNC_CONFIG_HEIGHT(pp_id), 0xfff0);
+		REG_MDP5_PP_SYNC_CONFIG_HEIGHT(pp_id), (2 * mode->vtotal));
+
 	mdp5_write(mdp5_kms,
 		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);
-- 
2.30.2