linux-kernel - [PATCH 2/4] drm/msm/dpu: offset HBB values written to DPU by -13

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Message-Id: <20260117-msm-ubwc-fixes-v1-2-d5c65ea552c7@oss.qualcomm.com>
Date: Sat, 17 Jan 2026 08:35:55 +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
Subject: [PATCH 2/4] drm/msm/dpu: offset HBB values written to DPU by -13

As in all other places, 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")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
---
 drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp.c
index 6f1fc790ad6d..b66c4cb5760c 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp.c
+++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp.c
@@ -270,30 +270,32 @@ static void dpu_hw_sspp_setup_format(struct dpu_sw_pipe *pipe,
 		((fmt->bpp - 1) << 9);
 
 	if (fmt->fetch_mode != MDP_FETCH_LINEAR) {
+		u32 hbb = ctx->ubwc->highest_bank_bit - 13;
+
 		if (MSM_FORMAT_IS_UBWC(fmt))
 			opmode |= MDSS_MDP_OP_BWC_EN;
 		src_format |= (fmt->fetch_mode & 3) << 30; /*FRAME_FORMAT */
 		DPU_REG_WRITE(c, SSPP_FETCH_CONFIG,
 			DPU_FETCH_CONFIG_RESET_VALUE |
-			ctx->ubwc->highest_bank_bit << 18);
+			hbb << 18);
 		switch (ctx->ubwc->ubwc_enc_version) {
 		case UBWC_1_0:
 			fast_clear = fmt->alpha_enable ? BIT(31) : 0;
 			DPU_REG_WRITE(c, SSPP_UBWC_STATIC_CTRL,
 					fast_clear | (ctx->ubwc->ubwc_swizzle & 0x1) |
 					BIT(8) |
-					(ctx->ubwc->highest_bank_bit << 4));
+					(hbb << 4));
 			break;
 		case UBWC_2_0:
 			fast_clear = fmt->alpha_enable ? BIT(31) : 0;
 			DPU_REG_WRITE(c, SSPP_UBWC_STATIC_CTRL,
 					fast_clear | (ctx->ubwc->ubwc_swizzle) |
-					(ctx->ubwc->highest_bank_bit << 4));
+					(hbb << 4));
 			break;
 		case UBWC_3_0:
 			DPU_REG_WRITE(c, SSPP_UBWC_STATIC_CTRL,
 					BIT(30) | (ctx->ubwc->ubwc_swizzle) |
-					(ctx->ubwc->highest_bank_bit << 4));
+					(hbb << 4));
 			break;
 		case UBWC_4_0:
 			DPU_REG_WRITE(c, SSPP_UBWC_STATIC_CTRL,

-- 
2.47.3