linux-kernel - Re: [PATCH v3 1/2] clk: qcom: camcc-sm6350: add pm

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Message-ID: <CAA8EJpotZjNqo72xhNVS+Fq7gbdADVF+tq8Ph4+tnPyO3HyQoA@mail.gmail.com>
Date:   Tue, 7 Mar 2023 17:06:56 +0200
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Luca Weiss <luca.weiss@...rphone.com>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        ~postmarketos/upstreaming@...ts.sr.ht, phone-devel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v3 1/2] clk: qcom: camcc-sm6350: add pm_runtime support

On Tue, 7 Mar 2023 at 16:54, Luca Weiss <luca.weiss@...rphone.com> wrote:
>
> On Tue Feb 14, 2023 at 1:32 PM CET, Dmitry Baryshkov wrote:
> > On Tue, 14 Feb 2023 at 13:01, Luca Weiss <luca.weiss@...rphone.com> wrote:
> > >
> > > Make sure that we can enable and disable the power domains used for
> > > camcc when the clocks are and aren't used.
> > >
> > > Signed-off-by: Luca Weiss <luca.weiss@...rphone.com>
> > > ---
> > >  drivers/clk/qcom/camcc-sm6350.c | 25 ++++++++++++++++++++++++-
> > >  1 file changed, 24 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/clk/qcom/camcc-sm6350.c b/drivers/clk/qcom/camcc-sm6350.c
> > > index acba9f99d960..fc5532e2ee5b 100644
> > > --- a/drivers/clk/qcom/camcc-sm6350.c
> > > +++ b/drivers/clk/qcom/camcc-sm6350.c
> > > @@ -7,6 +7,8 @@
> > >  #include <linux/clk-provider.h>
> > >  #include <linux/module.h>
> > >  #include <linux/platform_device.h>
> > > +#include <linux/pm_clock.h>
> > > +#include <linux/pm_runtime.h>
> > >  #include <linux/regmap.h>
> > >
> > >  #include <dt-bindings/clock/qcom,sm6350-camcc.h>
> > > @@ -1869,6 +1871,19 @@ MODULE_DEVICE_TABLE(of, camcc_sm6350_match_table);
> > >  static int camcc_sm6350_probe(struct platform_device *pdev)
> > >  {
> > >         struct regmap *regmap;
> > > +       int ret;
> > > +
> > > +       ret = devm_pm_runtime_enable(&pdev->dev);
> > > +       if (ret < 0)
> > > +               return ret;
> > > +
> > > +       ret = devm_pm_clk_create(&pdev->dev);
> > > +       if (ret < 0)
> > > +               return ret;
> >
> > This makes me wonder, what is the use for the pm_clk in your case? The
> > driver doesn't seem to use of_pm_clk_add_clk(), of_pm_clk_add_clks()
> > or pm_clk_add_clk(). So pm_clk_suspend() and pm_clk_resume() do
> > nothing.
>
> You're right that we're not using any of these functions in the driver.
> However still when camcc is not used, the associated power domain turns
> off correctly so that part works as expected.
>
> Honestly these lines have been copied from a different driver and I'm
> not familiar enough with the pm_runtime APIs to know what to use here
> without using the pm_clk* and pm_clk_suspend.

Please don't blindly C&P code.

>
> Basically we need, if any clock is being used in the driver, the
> power-domain needs to be enabled as well, and if nothing is used the
> power-domain can be disabled again.

Adding power-domains to the camcc node and calling
devm_pm_runtime_enable() should be enough. Please see how this is
managed for dispcc on sm8250.

-- 
With best wishes
Dmitry