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Subject: Re: [PATCH] soc: qcom-geni-se: Don't use relaxed writes when writing commands
From:   Stephen Boyd <swboyd@chromium.org>
Cc:     linux-arm-msm@vger.kernel.org,
        Rajendra Nayak <rnayak@codeaurora.org>,
        Akash Asthana <akashast@codeaurora.org>,
        Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>,
        Wolfram Sang <wsa@the-dreams.de>, msavaliy@codeaurora.org,
        Douglas Anderson <dianders@chromium.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Matthias Kaehlcke <mka@chromium.org>,
        linux-kernel@vger.kernel.org
To:     Andy Gross <agross@kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Douglas Anderson <dianders@chromium.org>
Date:   Wed, 22 Jul 2020 17:50:24 -0700
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Quoting Douglas Anderson (2020-07-22 15:01:20)
> Writing the command is the final step in kicking off a transfer.
> Let's use writel() to ensure that any other memory accesses are done
> before the command kicks off.  It's expected that this is mostly
> relevant if we're in DMA mode but since it doesn't appear to regress
> performance in a measurable way [1] even in PIO mode and it's easier
> to reason about then let's just always use it.
>=20
> NOTE: this patch came about due to code inspection.  No actual
> problems were observed that this patch fixes.
>=20
> [1] Tested by timing "flashrom -p ec" on a Chromebook which stresses
> GENI SPI a lot.
>=20
> Suggested-by: Stephen Boyd <swboyd@chromium.org>
> Signed-off-by: Douglas Anderson <dianders@chromium.org>
> ---

Reviewed-by: Stephen Boyd <swboyd@chromium.org>