linux-kernel - Re: [PATCH 2/2] clk: qcom: gcc-sc7280: Keep USB GDSC power domains on when USB wakeup is enabled

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Message-ID: <YwhyS7a8djIFPSOq@hovoldconsulting.com>
Date:   Fri, 26 Aug 2022 09:12:11 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, linux-arm-msm@...r.kernel.org,
        Johan Hovold <johan+linaro@...nel.org>,
        Douglas Anderson <dianders@...omium.org>,
        Krishna Kurapati <quic_kriskura@...cinc.com>,
        linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Subject: Re: [PATCH 2/2] clk: qcom: gcc-sc7280: Keep USB GDSC power domains
 on when USB wakeup is enabled

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:
> > On Tue, Aug 23, 2022 at 09:42:53AM -0700, Matthias Kaehlcke wrote:
> > > On Tue, Aug 23, 2022 at 01:16:36PM +0200, Johan Hovold wrote:
> > > > On Mon, Aug 22, 2022 at 11:53:11AM -0700, Matthias Kaehlcke wrote:
> > > > > Set GENPD_FLAG_ACTIVE_WAKEUP for the USB GDSC power domains of SC7280.
> > > > > 
> > > > > Suggested-by: Johan Hovold <johan+linaro@...nel.org>
> > > > > Signed-off-by: Matthias Kaehlcke <mka@...omium.org>
> > > > > ---
> > > > > 
> > > > >  drivers/clk/qcom/gcc-sc7280.c | 2 ++
> > > > >  1 file changed, 2 insertions(+)
> > > > > 
> > > > > diff --git a/drivers/clk/qcom/gcc-sc7280.c b/drivers/clk/qcom/gcc-sc7280.c
> > > > > index 7ff64d4d5920..4ff855269467 100644
> > > > > --- a/drivers/clk/qcom/gcc-sc7280.c
> > > > > +++ b/drivers/clk/qcom/gcc-sc7280.c
> > > > > @@ -3125,6 +3125,7 @@ static struct gdsc gcc_usb30_prim_gdsc = {
> > > > >  	.gdscr = 0xf004,
> > > > >  	.pd = {
> > > > >  		.name = "gcc_usb30_prim_gdsc",
> > > > > +		.flags = GENPD_FLAG_ACTIVE_WAKEUP,
> > > > 
> > > > Have you verified that the power-domain doesn't need to remain on also
> > > > when USB isn't used for wakeup?
> > > 
> > > So far I haven't observed issues with this on sc7180 and sc7280 when USB
> > > wakeup is disabled.
> > 
> > Ok, good.
> > 
> > I would have assumed that it needed to stay always-on before the
> > s/device_can_wakeup/device_may_wakeup/ change as before that the PHYs
> > would be left on regardless of the (sysfs) wakeup setting.
> 
> That make sense, not sure why GENPD_FLAG_ACTIVE_WAKEUP works with wakeup
> disabled.
> 
> In any case setting the genpd flags directly in the gdsc descriptor doesn't
> seem to be the right thing to do. With GENPD_FLAG_ALWAYS_ON my sc7280 system
> stalls at boot. It boots when ALWAYS_ON is set in the gdsc flags, which ends
> up setting GENPD_FLAG_ALWAYS_ON of the genpd. I'll send a new version of this
> series which sets the correct flag.

Yes, GENPD_FLAG_ALWAYS_ON needs to be set via the gdsc ALWAYS_ON flag as
genpd expects the PD to be on when registered or else it silently errors
out...

	https://lore.kernel.org/all/20220805121250.10347-3-johan+linaro@kernel.org/

> > > > This is the case for sc8280xp and indicates that there are further
> > > > missing pieces here (at least for that platform).
> > > 
> > > What are you observing on sc8280xp when wakeup is disabled?
> > 
> > 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.

Thanks for confirming.
 
> 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 wonder what the status on other QC platforms is, from a quick grep it
> seems only msm8953 sets the USB gdsc to ALWAYS_ON.

Yes, this is likely needed on other platforms as well.

Johan