linux-kernel - [PATCH v3 2/3] drm/msm/dpu: filter writeback modes using writeback maxlinewidth

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Message-Id: <20260112-max-mixer-width-v3-2-f98063ea21f5@oss.qualcomm.com>
Date: Mon, 12 Jan 2026 05:11:30 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Rob Clark <robin.clark@....qualcomm.com>,
        Dmitry Baryshkov <lumag@...nel.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jesszhan0024@...il.com>, Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>
Cc: linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Jessica Zhang <jessica.zhang@....qualcomm.com>
Subject: [PATCH v3 2/3] drm/msm/dpu: filter writeback modes using writeback
 maxlinewidth

From: Jessica Zhang <jessica.zhang@....qualcomm.com>

Maximum width of the writeback mode is limited by the hardware buffer in
the WB block rather than by the LM properties (LM doesn't have an actual
buffer). Use the actual hardware limit (the writeback maxlinewidth) to
filter modes.

Signed-off-by: Jessica Zhang <jessica.zhang@....qualcomm.com>
[DB: fixed commit message]
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
---
 drivers/gpu/drm/msm/disp/dpu1/dpu_writeback.c | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_writeback.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_writeback.c
index 7545c0293efb..209b1e27a84b 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_writeback.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_writeback.c
@@ -14,14 +14,7 @@ static int dpu_wb_conn_get_modes(struct drm_connector *connector)
 	struct msm_drm_private *priv = dev->dev_private;
 	struct dpu_kms *dpu_kms = to_dpu_kms(priv->kms);
 
-	/*
-	 * We should ideally be limiting the modes only to the maxlinewidth but
-	 * on some chipsets this will allow even 4k modes to be added which will
-	 * fail the per SSPP bandwidth checks. So, till we have dual-SSPP support
-	 * and source split support added lets limit the modes based on max_mixer_width
-	 * as 4K modes can then be supported.
-	 */
-	return drm_add_modes_noedid(connector, dpu_kms->catalog->caps->max_mixer_width,
+	return drm_add_modes_noedid(connector, dpu_kms->catalog->wb->maxlinewidth,
 			dev->mode_config.max_height);
 }
 

-- 
2.47.3