linux-kernel - Re: [PATCH v5 0/5] spi: Add DMA mode support to spi-qcom-qspi

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Date:   Thu, 25 May 2023 07:25:45 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Vijaya Krishna Nivarthi <quic_vnivarth@...cinc.com>,
        andersson@...nel.org
Cc:     agross@...nel.org, konrad.dybcio@...aro.org, broonie@...nel.org,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        cros-qcom-dts-watchers@...omium.org, linux-arm-msm@...r.kernel.org,
        linux-spi@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, quic_msavaliy@...cinc.com,
        mka@...omium.org, swboyd@...omium.org, quic_vtanuku@...cinc.com
Subject: Re: [PATCH v5 0/5] spi: Add DMA mode support to spi-qcom-qspi

Hi Bjorn,

On Mon, Apr 24, 2023 at 2:32 AM Vijaya Krishna Nivarthi
<quic_vnivarth@...cinc.com> wrote:
>
> There are large number of QSPI irqs that fire during boot/init and later
> on every suspend/resume.
> This could be made faster by doing DMA instead of PIO.
> Below is comparison for number of interrupts raised in 2 scenarios...
> Boot up and stabilise
> Suspend/Resume
>
> Sequence   PIO    DMA
> =======================
> Boot-up    69088  19284
> S/R        5066   3430
>
> Speed test results...
> spi-nor read times in sec after 2 min uptime
> ============================================
> PIO - Iterations-1000, min=3.18, max=3.74, avg=3.53
> DMA - Iterations-1000, min=1.21, max=2.28, avg=1.79
>
> spi-nor write times in sec after 2 min uptime
> =============================================
> PIO - Iterations-1000, min=3.20, max=8.24, avg=3.58
> DMA - Iterations-1000, min=1.25, max=5.13, avg=1.82
>
> Further testing performed...
> a) multiple entries in sgt (simulated by max_dma_len = 1024)
> b) fallback to pio (simulated by dma setup failure)
>
> Vijaya Krishna Nivarthi (5):
>   spi: dt-bindings: qcom,spi-qcom-qspi: Add iommus
>   arm64: dts: qcom: sc7180: Add stream-id of qspi to iommus
>   arm64: dts: qcom: sc7280: Add stream-id of qspi to iommus
>   arm64: dts: qcom: sdm845: Add stream-id of qspi to iommus
>   spi: spi-qcom-qspi: Add DMA mode support

Mark has landed the bindings / code changes:

b5762d95607e spi: spi-qcom-qspi: Add DMA mode support
64c05eb3a0f4 spi: dt-bindings: qcom,spi-qcom-qspi: Add iommus

...so I think the dts changes here are ready for you to land. There
are no hard dependencies here so you can land the dts without needing
the code changes.

Thanks!

-Doug