linux-kernel - [PATCH v3 1/4] drm/msm/mdss: correct HBB programmed on UBWC 5.x and 6.x devices

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Message-Id: <20260119-msm-ubwc-fixes-v3-1-34aaa672c829@oss.qualcomm.com>
Date: Mon, 19 Jan 2026 10:17:14 +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>,
        Konrad Dybcio <konrad.dybcio@....qualcomm.com>,
        Konrad Dybcio <konradybcio@...nel.org>, Vinod Koul <vkoul@...nel.org>,
        Stephan Gerhold <stephan.gerhold@...aro.org>
Cc: linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Val Packett <val@...kett.cool>
Subject: [PATCH v3 1/4] drm/msm/mdss: correct HBB programmed on UBWC 5.x
 and 6.x devices

As in the previous generations, on UBWC 5.x and 6.x devices the Highest
Bank Bit value should be programmed into the hardware with the offset of
-13.  Correct the value written into the register to prevent
unpredictable results.

Fixes: 227d4ce0b09e ("drm/msm: Offset MDSS HBB value by 13")
Tested-by: Val Packett <val@...kett.cool> # x1e80100-dell-latitude-7455
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
---
 drivers/gpu/drm/msm/msm_mdss.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/msm_mdss.c b/drivers/gpu/drm/msm/msm_mdss.c
index bf9a33e925ac..910242f5a71f 100644
--- a/drivers/gpu/drm/msm/msm_mdss.c
+++ b/drivers/gpu/drm/msm/msm_mdss.c
@@ -229,7 +229,7 @@ static void msm_mdss_setup_ubwc_dec_50(struct msm_mdss *msm_mdss)
 {
 	const struct qcom_ubwc_cfg_data *data = msm_mdss->mdss_data;
 	u32 value = MDSS_UBWC_STATIC_UBWC_SWIZZLE(data->ubwc_swizzle) |
-		    MDSS_UBWC_STATIC_HIGHEST_BANK_BIT(data->highest_bank_bit);
+		    MDSS_UBWC_STATIC_HIGHEST_BANK_BIT(data->highest_bank_bit - 13);
 
 	if (data->ubwc_bank_spread)
 		value |= MDSS_UBWC_STATIC_UBWC_BANK_SPREAD;

-- 
2.47.3