linux-kernel - Re: [PATCH 0/2] spi: Add DMA mode support to spi-qcom-qspi

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Date:   Tue, 4 Apr 2023 13:30:28 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Vijaya Krishna Nivarthi <quic_vnivarth@...cinc.com>,
        agross@...nel.org, andersson@...nel.org, broonie@...nel.org,
        devicetree@...r.kernel.org, konrad.dybcio@...aro.org,
        krzysztof.kozlowski+dt@...aro.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-spi@...r.kernel.org,
        robh+dt@...nel.org, vkoul@...nel.org
Cc:     quic_msavaliy@...cinc.com, dianders@...omium.org, mka@...omium.org,
        quic_vtanuku@...cinc.com
Subject: Re: [PATCH 0/2] spi: Add DMA mode support to spi-qcom-qspi

Quoting Vijaya Krishna Nivarthi (2023-04-04 11:03:18)
> 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 acenarios...
> Boot up and stabilise
> Suspend/Resume
>
> Sequence   PIO    DMA
> =======================
> Boot-up    69088  19284
> S/R        5066   3430
>

The interrupts are less, yes, but does it save time or power?