Re: [Freedreno] [PATCH 1/3] drm/msm/mdp5: Configure PP_SYNC_HEIGHT to double the vtotal

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Hi Marijn

On 2021-04-06 14:47, Marijn Suijten wrote:
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.

The reason the CONFIG_HEIGHT was at such a high value is to make sure that we always get the TE only from the panel vsync and not false positives coming
from the tear check logic itself.

When you say that disp-te gpio is not hooked up, is it something incorrect with
the schematic OR panel is not generating the TE correctly?


Suggested-by: AngeloGioacchino Del Regno
<angelogioacchino.delregno@xxxxxxxxxxxxxx>
Signed-off-by: Marijn Suijten <marijn.suijten@xxxxxxxxxxxxxx>
Reviewed-by: AngeloGioacchino Del Regno
<angelogioacchino.delregno@xxxxxxxxxxxxxx>
---
 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);
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