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Date:   Fri, 26 Aug 2022 06:33:56 -0700
From:   Matthias Kaehlcke <mka@chromium.org>
To:     Johan Hovold <johan@kernel.org>
Cc:     Andy Gross <agross@kernel.org>,
        Bjorn Andersson <andersson@kernel.org>,
        Konrad Dybcio <konrad.dybcio@somainline.org>,
        Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>, linux-arm-msm@vger.kernel.org,
        Johan Hovold <johan+linaro@kernel.org>,
        Douglas Anderson <dianders@chromium.org>,
        Krishna Kurapati <quic_kriskura@quicinc.com>,
        linux-kernel@vger.kernel.org, linux-clk@vger.kernel.org,
        Bjorn Andersson <bjorn.andersson@linaro.org>
Subject: Re: [PATCH 2/2] clk: qcom: gcc-sc7280: Keep USB GDSC power domains
 on when USB wakeup is enabled
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On Fri, Aug 26, 2022 at 03:26:51PM +0200, Johan Hovold wrote:
> On Fri, Aug 26, 2022 at 06:24:37AM -0700, Matthias Kaehlcke wrote:
> > On Fri, Aug 26, 2022 at 06:19:37AM -0700, Matthias Kaehlcke wrote:
> > > On Fri, Aug 26, 2022 at 03:12:05PM +0200, Johan Hovold wrote:
> > > > On Fri, Aug 26, 2022 at 06:05:19AM -0700, Matthias Kaehlcke wrote:
> > > > > On Thu, Aug 25, 2022 at 03:16:58PM -0700, Matthias Kaehlcke wrote:
> > > > > > On Wed, Aug 24, 2022 at 10:47:44AM +0200, Johan Hovold wrote:
> > > > 
> > > > > > > The wakeup setting doesn't seem to have anything to do with the genpd
> > > > > > > issues on sc8280xp and the controller doesn't resume properly regardless
> > > > > > > of whether the PHYs have been disabled or not during suspend unless the
> > > > > > > PD is left on.
> > > > > > 
> > > > > > I'm essentially seeing the same. USB is hosed after resume unless the PD
> > > > > > is left on.
> > > > > > 
> > > > > > On Chrome OS we currently work around that with a version of commit
> > > > > > d9be8d5c5b03 ("usb: dwc3: qcom: Keep power domain on to retain controller
> > > > > > status") which was reverted upstream. I'm not sure whether USB worked after
> > > > > > resume before we enabled wakeup support. I would have sworn it did, but we
> > > > > > landed an old version of the wakeup patches a long time ago, so my
> > > > > > memory might be failing me.
> > > > > 
> > > > > I need to remind myself that keeping the GDSC on is only needed when the PHYs
> > > > > are kept on. The PHYs were always off before wakeup support was added, which
> > > > > is why USB wasn't broken after suspend in the pre-wakeup days.
> > > > 
> > > > Ok, so to be clear: if you disable wakeup with my patches applied so
> > > > that the PD is actually turned off, USB still resumes with only
> > > > GENPD_FLAG_ACTIVE_WAKEUP set?
> > 
> > Actually without GENPD_FLAG_ACTIVE_WAKEUP
> 
> Sure, that only comes into play with wakeup enabled. I assume you still
> need it for USB wakeup to work?

Yes, for USB wakeup to work either setting the above genpd flag or (better)
the ALWAYS_ON flag of the GDSC is needed.