linux-kernel - Re: [PATCH 3/3] clk: qcom: gcc-sc7280: Update the .pwrsts for usb gdsc

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Message-ID: <YyNWOJerkZcqgx5h@google.com>
Date:   Thu, 15 Sep 2022 16:43:36 +0000
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Rajendra Nayak <quic_rjendra@...cinc.com>
Cc:     Johan Hovold <johan@...nel.org>, andersson@...nel.org,
        agross@...nel.org, konrad.dybcio@...ainline.org,
        mturquette@...libre.com, sboyd@...nel.org, johan+linaro@...nel.org,
        quic_kriskura@...cinc.com, dianders@...omium.org,
        linux-clk@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] clk: qcom: gcc-sc7280: Update the .pwrsts for usb
 gdsc

On Thu, Sep 15, 2022 at 06:59:36PM +0530, Rajendra Nayak wrote:
> 
> On 9/15/2022 12:55 PM, Rajendra Nayak wrote:
> > 
> > 
> > On 9/15/2022 2:53 AM, Matthias Kaehlcke wrote:
> > > On Wed, Sep 14, 2022 at 09:12:36AM +0200, Johan Hovold wrote:
> > > > On Thu, Sep 01, 2022 at 09:04:55AM -0700, Matthias Kaehlcke wrote:
> > > > > On Thu, Sep 01, 2022 at 03:47:56PM +0530, Rajendra Nayak wrote:
> > > > > > USB on sc7280 cannot support wakeups from low power states
> > > > > > if the GDSC is turned OFF. Update the .pwrsts for usb GDSC so it
> > > > > > only transitions to RET in low power.
> > > > > > 
> > > > > > Signed-off-by: Rajendra Nayak <quic_rjendra@...cinc.com>
> > > > > 
> > > > > Reviewed-by: Matthias Kaehlcke <mka@...omium.org>
> > > > > Tested-by: Matthias Kaehlcke <mka@...omium.org>
> > > > 
> > > > Did you confirm that you actually hit the retention state?
> > > 
> > > No, how would I do that?
> > > 
> > > > IIUC, this series is equivalent to using ALWAYS_ON unless CX is actually
> > > > powered off during suspend.
> > > 
> > > The count in /sys/kernel/debug/qcom_stats/cxsd increses with each suspend,
> > > however it also does that with the GDSC configured as ALWAYS_ON and with
> > > Rajendra's "arm64: dts: qcom: sc7280: Add required-opps for USB" [1], so
> > 
> > hmm, that's really not expected. With my above patch and with the GDSC as
> > ALWAYS_ON there is a cx vote in suspend preventing cxsd so the counter
> > should not go up.
> 
> Perhaps you are missing '1b771839: clk: qcom: gdsc: enable optional power domain support'
> in your tree?

Indeed, that patch was missing in our tree, thanks for the pointer!

With it the CXSD count does not increase when the GDSC is configured as
ALWAYS_ON.