linux-kernel - Re: [PATCH] arm64: dts: qcom: sc8280xp: Flush RSC sleep & wake votes

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Message-ID: <ZGIc8SPNy0oqCqjR@hovoldconsulting.com>
Date:   Mon, 15 May 2023 13:52:17 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] arm64: dts: qcom: sc8280xp: Flush RSC sleep & wake votes

On Fri, May 12, 2023 at 08:04:25AM -0700, Bjorn Andersson wrote:
> The rpmh driver will cache sleep and wake votes until the cluster
> power-domain is about to enter idle, to avoid unnecessary writes. So
> associate the apps_rsc with the cluster pd, so that it can be notified
> about this event.
> 
> Without this, only AMC votes are being commited.

I'm sure I'm missing some details here, but from reading (and tracing)
the code it looks like the cached votes are still being flushed albeit
via rpmh_rsc_cpu_pm_callback() as the individual CPUs go down.

There wasn't really any obvious motivation in the series adding support
for the cluster domain as to why the new mechanism is preferred (e.g. if
this is an actual fix or just an optimisation done to align with
downstream):

	https://lore.kernel.org/all/20221018152837.619426-1-ulf.hansson@linaro.org/

Either way, this appears to work as intended even if it does not in
itself have any significant effect on the X13s power consumption (in
idle or suspend).

> Signed-off-by: Bjorn Andersson <quic_bjorande@...cinc.com>

Reviewed-by: Johan Hovold <johan+linaro@...nel.org>
Tested-by: Johan Hovold <johan+linaro@...nel.org>

Johan