linux-kernel - Re: [PATCH] spi: spi-geni-qcom: Don't wait to start 1st transfer if transmitting

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Message-ID: <838a6074-73e6-a48b-2684-5ea2ebff443a@codeaurora.org>
Date:   Mon, 14 Sep 2020 18:39:25 +0530
From:   Akash Asthana <akashast@...eaurora.org>
To:     Douglas Anderson <dianders@...omium.org>,
        Mark Brown <broonie@...nel.org>
Cc:     swboyd@...omium.org, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-spi@...r.kernel.org
Subject: Re: [PATCH] spi: spi-geni-qcom: Don't wait to start 1st transfer if
 transmitting


On 9/12/2020 11:47 PM, Douglas Anderson wrote:
> If we're sending bytes over SPI, we know the FIFO is empty at the
> start of the transfer.  There's no reason to wait for the interrupt
> telling us to start--we can just start right away.  Then if we
> transmit everything in one swell foop we don't even need to bother
> listening for TX interrupts.
>
> In a test of "flashrom -p ec -r /tmp/foo.bin" interrupts were reduced
> from ~30560 to ~29730, about a 3% savings.
>
> This patch looks bigger than it is because I moved a few functions
> rather than adding a forward declaration.  The only actual change to
> geni_spi_handle_tx() was to make it return a bool indicating if there
> is more to tx.
Reviewed-by: Akash Asthana <akashast@...eaurora.org>
> Signed-off-by: Douglas Anderson<dianders@...omium.org>

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