linux-kernel - Re: [RESEND PATCH v2 4/7] clk: qcom: gdsc: enable optional power domain support

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Date:   Fri, 9 Jul 2021 11:32:40 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Taniya Das <tdas@...eaurora.org>,
        Jonathan Marek <jonathan@...ek.ca>,
        Michael Turquette <mturquette@...libre.com>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>,
        linux-clk <linux-clk@...r.kernel.org>,
        "Bryan O'Donoghue" <bryan.odonoghue@...aro.org>,
        Mark Brown <broonie@...nel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [RESEND PATCH v2 4/7] clk: qcom: gdsc: enable optional power
 domain support

On Fri, 9 Jul 2021 at 06:32, Dmitry Baryshkov
<dmitry.baryshkov@...aro.org> wrote:
>
> On sm8250 dispcc and videocc registers are powered up by the MMCX power
> domain. Currently we used a regulator to enable this domain on demand,
> however this has some consequences, as genpd code is not reentrant.
>
> Teach Qualcomm clock controller code about setting up power domains and
> using them for gdsc control.
>
> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>

[...]

> diff --git a/drivers/clk/qcom/gdsc.c b/drivers/clk/qcom/gdsc.c
> index 51ed640e527b..9401d01533c8 100644
> --- a/drivers/clk/qcom/gdsc.c
> +++ b/drivers/clk/qcom/gdsc.c
> @@ -427,6 +427,7 @@ int gdsc_register(struct gdsc_desc *desc,
>                         continue;
>                 scs[i]->regmap = regmap;
>                 scs[i]->rcdev = rcdev;
> +               scs[i]->pd.dev.parent = desc->dev;
>                 ret = gdsc_init(scs[i]);
>                 if (ret)
>                         return ret;
> @@ -439,6 +440,8 @@ int gdsc_register(struct gdsc_desc *desc,
>                         continue;
>                 if (scs[i]->parent)
>                         pm_genpd_add_subdomain(scs[i]->parent, &scs[i]->pd);
> +               else if (!IS_ERR_OR_NULL(dev->pm_domain))

So dev_pm_domain_attach() (which calls genpd_dev_pm_attach() is being
called for gdsc platform device from the platform bus', to try to
attach the device to its corresponding PM domain.

Looking a bit closer to genpd_dev_pm_attach(), I realize that we
shouldn't really try to attach a device to its PM domain, when its OF
node (dev->of_node) contains a "#power-domain-cells" specifier. This
is because it indicates that the device belongs to a genpd provider
itself. In this case, a "power-domains" specifier tells that it has a
parent domain.

I will post a patch that fixes this asap.

> +                       pm_genpd_add_subdomain(pd_to_genpd(dev->pm_domain), &scs[i]->pd);
>         }
>
>         return of_genpd_add_provider_onecell(dev->of_node, data);
> @@ -457,6 +460,8 @@ void gdsc_unregister(struct gdsc_desc *desc)
>                         continue;
>                 if (scs[i]->parent)
>                         pm_genpd_remove_subdomain(scs[i]->parent, &scs[i]->pd);
> +               else if (!IS_ERR_OR_NULL(dev->pm_domain))

Ditto.

> +                       pm_genpd_remove_subdomain(pd_to_genpd(dev->pm_domain), &scs[i]->pd);
>         }
>         of_genpd_del_provider(dev->of_node);
>  }
> --
> 2.30.2
>

Kind regards
Uffe