On Mon, Oct 30, 2023 at 04:23:20PM -0700, 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@xxxxxxxxxxxxxxx
> Suggested-by: Doug Anderson <dianders@xxxxxxxxxxxx>
> Suggested-by: Rob Clark <robdclark@xxxxxxxxxxxx>
> Signed-off-by: Bjorn Andersson <quic_bjorande@xxxxxxxxxxx>
> ---
> 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},
What does these values represent? And how SAFE is to override the default QoS
values?
I'm not too familiar with the MSM DRM driver, so please excuse my ignorance.
- Mani
> .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@xxxxxxxxxxx>
>
--
மணிவண்ணன் சதாசிவம்
