linux-kernel - [PATCH 1/3] drm/msm/mdp5: Configure PP_SYNC

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Date:   Tue,  6 Apr 2021 23:47:24 +0200
From:   Marijn Suijten <marijn.suijten@...ainline.org>
To:     phone-devel@...r.kernel.org
Cc:     ~postmarketos/upstreaming@...ts.sr.ht,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Martin Botka <martin.botka@...ainline.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        Rob Clark <robdclark@...il.com>, Sean Paul <sean@...rly.run>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
        linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] drm/msm/mdp5: Configure PP_SYNC_HEIGHT to double the vtotal

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>
---
 drivers/gpu/drm/msm/disp/mdp5/mdp5_cmd_encoder.c | 2 +-
 1 file changed, 1 insertion(+), 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..2d5ac03dbc17 100644
--- a/drivers/gpu/drm/msm/disp/mdp5/mdp5_cmd_encoder.c
+++ b/drivers/gpu/drm/msm/disp/mdp5/mdp5_cmd_encoder.c
@@ -51,7 +51,7 @@ static int pingpong_tearcheck_setup(struct drm_encoder *encoder,
 
 	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);
-- 
2.31.1