linux-kernel - [PATCH v2 2/2] drm/msm/disp: Correct porch timing for SDM845

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Message-Id: <20250212-sdm845_dp-v2-2-4954e51458f4@gmail.com>
Date: Wed, 12 Feb 2025 15:03:47 -0800
From: "James A. MacInnes" <james.a.macinnes@...il.com>
To: Rob Clark <robdclark@...il.com>, 
 Abhinav Kumar <quic_abhinavk@...cinc.com>, 
 Dmitry Baryshkov <dmitry.baryshkov@...aro.org>, Sean Paul <sean@...rly.run>, 
 Marijn Suijten <marijn.suijten@...ainline.org>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 Chandan Uddaraju <chandanu@...eaurora.org>, 
 Stephen Boyd <swboyd@...omium.org>, Vara Reddy <quic_varar@...cinc.com>, 
 Tanmay Shah <tanmay@...eaurora.org>
Cc: linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
 freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
 Guenter Roeck <groeck@...omium.org>, Rob Clark <robdclark@...omium.org>, 
 "James A. MacInnes" <james.a.macinnes@...il.com>
Subject: [PATCH v2 2/2] drm/msm/disp: Correct porch timing for SDM845

Type-C DisplayPort inoperable due to incorrect porch settings.
- Re-used wide_bus_en as flag to prevent porch shifting

Fixes: c943b4948b58 ("drm/msm/dp: add displayPort driver support")
Signed-off-by: James A. MacInnes <james.a.macinnes@...il.com>
---
 drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c
index abd6600046cb..a21addc4794f 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c
@@ -94,17 +94,21 @@ static void drm_mode_to_intf_timing_params(
 		timing->vsync_polarity = 0;
 	}

-	/* for DP/EDP, Shift timings to align it to bottom right */
-	if (phys_enc->hw_intf->cap->type == INTF_DP) {
+	timing->wide_bus_en = dpu_encoder_is_widebus_enabled(phys_enc->parent);
+	timing->compression_en = dpu_encoder_is_dsc_enabled(phys_enc->parent);
+
+	/*
+	 *  For DP/EDP, Shift timings to align it to bottom right.
+	 *  wide_bus_en is set for everything excluding SDM845 &
+	 *  porch changes cause DisplayPort failure and HDMI tearing.
+	 */
+	if (phys_enc->hw_intf->cap->type == INTF_DP && timing->wide_bus_en) {
 		timing->h_back_porch += timing->h_front_porch;
 		timing->h_front_porch = 0;
 		timing->v_back_porch += timing->v_front_porch;
 		timing->v_front_porch = 0;
 	}

-	timing->wide_bus_en = dpu_encoder_is_widebus_enabled(phys_enc->parent);
-	timing->compression_en = dpu_encoder_is_dsc_enabled(phys_enc->parent);
-
 	/*
 	 * for DP, divide the horizonal parameters by 2 when
 	 * widebus is enabled

-- 
2.43.0