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

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Message-ID: <c2c802e0-73fb-a362-7e46-f6a7ec40d6b1@quicinc.com>
Date:   Wed, 12 Apr 2023 20:58:32 +0530
From:   Vijaya Krishna Nivarthi <quic_vnivarth@...cinc.com>
To:     Stephen Boyd <swboyd@...omium.org>, <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

Thank you for the review...


On 4/5/2023 2:00 AM, Stephen Boyd wrote:
> 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?

We have not made measurements but the change is expected to improve 
performance.

Testing revealed no regressions.