linux-kernel - Re: [PATCH 2/3] clk: qcom: lpass-sc7180: Fix pm

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Message-ID: <CAD=FV=VSh90tdSDaxThoGaE_uYWPTMrGYBMM0UqcH=HUZaScNg@mail.gmail.com>
Date:   Fri, 4 Nov 2022 15:08:12 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Bjorn Andersson <andersson@...nel.org>,
        Taniya Das <quic_tdas@...cinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Judy Hsiao <judyhsiao@...omium.org>,
        Srinivasa Rao Mandadapu <quic_srivasam@...cinc.com>,
        Matthias Kaehlcke <mka@...omium.org>,
        Andy Gross <agross@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, linux-arm-msm@...r.kernel.org,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] clk: qcom: lpass-sc7180: Fix pm_runtime usage

Hi,

On Fri, Nov 4, 2022 at 2:19 PM Stephen Boyd <swboyd@...omium.org> wrote:
>
> Quoting Douglas Anderson (2022-11-04 06:56:29)
> > The sc7180 lpass clock controller's pm_runtime usage wasn't broken
> > quite as spectacularly as the sc7280's pm_runtime usage, but it was
> > still broken. Putting some printouts in at boot showed me this (with
> > serial console enabled, which makes the prints slow and thus changes
> > timing):
> >   [    3.109951] DOUG: my_pm_clk_resume, usage=1
> >   [    3.114767] DOUG: my_pm_clk_resume, usage=1
> >   [    3.664443] DOUG: my_pm_clk_suspend, usage=0
> >   [    3.897566] DOUG: my_pm_clk_suspend, usage=0
> >   [    3.910137] DOUG: my_pm_clk_resume, usage=1
> >   [    3.923217] DOUG: my_pm_clk_resume, usage=0
> >   [    4.440116] DOUG: my_pm_clk_suspend, usage=-1
> >   [    4.444982] DOUG: my_pm_clk_suspend, usage=0
> >   [   14.170501] DOUG: my_pm_clk_resume, usage=1
> >   [   14.176245] DOUG: my_pm_clk_resume, usage=0
> >
> > ...or this w/out serial console:
> >   [    0.556139] DOUG: my_pm_clk_resume, usage=1
> >   [    0.556279] DOUG: my_pm_clk_resume, usage=1
> >   [    1.058422] DOUG: my_pm_clk_suspend, usage=-1
> >   [    1.058464] DOUG: my_pm_clk_suspend, usage=0
> >   [    1.186250] DOUG: my_pm_clk_resume, usage=1
> >   [    1.186292] DOUG: my_pm_clk_resume, usage=0
> >   [    1.731536] DOUG: my_pm_clk_suspend, usage=-1
> >   [    1.731557] DOUG: my_pm_clk_suspend, usage=0
> >   [   10.288910] DOUG: my_pm_clk_resume, usage=1
> >   [   10.289496] DOUG: my_pm_clk_resume, usage=0
> >
> > It seems to be doing roughly the right sequence of calls, but just
> > like with sc7280 this is more by luck than anything. Having a usage of
> > -1 is just not OK.
> >
> > Let's fix this like we did with sc7280.
>
> Any Fixes tag?

Ah, right. I guess the most obvious one is actually:

Fixes: ce8c195e652f ("clk: qcom: lpasscc: Introduce pm autosuspend for SC7180")

That's what got us going negative. One could _sorta_ make the argument
for a "Fixes" tag all the way to the start of the driver, though. The
driver never did a pm_runtime_get() during probe and so there was (I
guess) a chance that some of the bare register writes in probe could
have been unclocked. I'm not aware of that ever being a problem, so I
guess just the above "Fixes" is fine.


> > Signed-off-by: Douglas Anderson <dianders@...omium.org>
> > ---
>
> Reviewed-by: Stephen Boyd <swboyd@...omium.org>

Thanks! Yell if you want me to spin a v2 with the Fixes in place.

-Doug