linux-kernel - [PATCH] drm/msm/dpu: Add missing safe_lut

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Date:   Mon, 30 Oct 2023 16:23:20 -0700
From:   Bjorn Andersson <quic_bjorande@...cinc.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>,
        Daniel Vetter <daniel@...ll.ch>,
        "Bjorn Andersson" <andersson@...nel.org>,
        Kuogee Hsieh <quic_khsieh@...cinc.com>
CC:     Johan Hovold <johan@...nel.org>, <linux-arm-msm@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
        <stable@...r.kernel.org>, Doug Anderson <dianders@...omium.org>,
        Rob Clark <robdclark@...omium.org>,
        Bjorn Andersson <quic_bjorande@...cinc.com>
Subject: [PATCH] drm/msm/dpu: Add missing safe_lut_tbl in sc8280xp catalog

During USB transfers on the SC8280XP __arm_smmu_tlb_sync() is seen to
typically take 1-2ms to complete. As expected this results in poor
performance, something that has been mitigated by proposing running the
iommu in non-strict mode (boot with iommu.strict=0).

This turns out to be related to the SAFE logic, and programming the QOS
SAFE values in the DPU (per suggestion from Rob and Doug) reduces the
TLB sync time to below 10us, which means significant less time spent
with interrupts disabled and a significant boost in throughput.

Fixes: 4a352c2fc15a ("drm/msm/dpu: Introduce SC8280XP")
Cc: stable@...r.kernel.org
Suggested-by: Doug Anderson <dianders@...omium.org>
Suggested-by: Rob Clark <robdclark@...omium.org>
Signed-off-by: Bjorn Andersson <quic_bjorande@...cinc.com>
---
 drivers/gpu/drm/msm/disp/dpu1/catalog/dpu_8_0_sc8280xp.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/drm/msm/disp/dpu1/catalog/dpu_8_0_sc8280xp.h b/drivers/gpu/drm/msm/disp/dpu1/catalog/dpu_8_0_sc8280xp.h
index 1ccd1edd693c..4c0528794e7a 100644
--- a/drivers/gpu/drm/msm/disp/dpu1/catalog/dpu_8_0_sc8280xp.h
+++ b/drivers/gpu/drm/msm/disp/dpu1/catalog/dpu_8_0_sc8280xp.h
@@ -406,6 +406,7 @@ static const struct dpu_perf_cfg sc8280xp_perf_data = {
 	.min_llcc_ib = 0,
 	.min_dram_ib = 800000,
 	.danger_lut_tbl = {0xf, 0xffff, 0x0},
+	.safe_lut_tbl = {0xfe00, 0xfe00, 0xffff},
 	.qos_lut_tbl = {
 		{.nentry = ARRAY_SIZE(sc8180x_qos_linear),
 		.entries = sc8180x_qos_linear

---
base-commit: c503e3eec382ac708ee7adf874add37b77c5d312
change-id: 20231030-sc8280xp-dpu-safe-lut-9769027b8452

Best regards,
-- 
Bjorn Andersson <quic_bjorande@...cinc.com>