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

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Date:   Wed, 15 Nov 2023 10:41:15 -0800
From:   Abhinav Kumar <quic_abhinavk@...cinc.com>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>,
        Rob Clark <robdclark@...il.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>
Subject: Re: [PATCH] drm/msm/dpu: Add missing safe_lut_tbl in sc8280xp catalog



On 10/30/2023 4:23 PM, Bjorn Andersson wrote:
> 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>
> ---

Matches what we have in downstream DT, hence

Reviewed-by: Abhinav Kumar <quic_abhinavk@...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,