Re: [PATCH v3 1/2] clk: mediatek: Introduce need_pm_runtime to mtk_clk_desc

[AngeloGioacchino Del Regno]

Il 23/02/24 05:27, Chen-Yu Tsai ha scritto:
> On Mon, Jan 8, 2024 at 4:18 PM Pin-yen Lin <treapking@xxxxxxxxxxxx> wrote:
> > Introduce a new need_pm_runtime variable to mtk_clk_desc to indicate
> > this clock controller needs runtime PM for its operations.
> > Also do a runtime PM get on the clock controller during the
> > probing stage to workaround a possible deadlock.
> >
> > Signed-off-by: Pin-yen Lin <treapking@xxxxxxxxxxxx>
>
> Reviewed-by: Chen-Yu Tsai <wenst@xxxxxxxxxxxx>
>
> The patch itself looks fine.
>
> Besides the MT8183 MFG clock issues, we do actually need this for the
> MT8192 ADSP clock. Its power domain is not enabled by default.

..but on MT8195 the ADSP clock works - because the ADSP node exists.

This poses a question: should we make clock controllers depend on power domains,
or should we keep everything powered off (hence clocks down - no power consumption)
*unless* the user exists?

For the second one, this means that the *device* gets the power domain (adsp), and
not the clock controller (which clocks are effectively useless if there's no user).

Angelo

> > ---
> >
> > Changes in v3:
> > - Update the commit message and the comments before runtime PM call
> >
> > Changes in v2:
> > - Fix the order of error handling
> > - Update the commit message and add a comment before the runtime PM call
> >
> >   drivers/clk/mediatek/clk-mtk.c | 19 +++++++++++++++++++
> >   drivers/clk/mediatek/clk-mtk.h |  2 ++
> >   2 files changed, 21 insertions(+)
> >
> > diff --git a/drivers/clk/mediatek/clk-mtk.c b/drivers/clk/mediatek/clk-mtk.c
> > index 2e55368dc4d8..ba1d1c495bc2 100644
> > --- a/drivers/clk/mediatek/clk-mtk.c
> > +++ b/drivers/clk/mediatek/clk-mtk.c
> > @@ -13,6 +13,7 @@
> >   #include <linux/of.h>
> >   #include <linux/of_address.h>
> >   #include <linux/platform_device.h>
> > +#include <linux/pm_runtime.h>
> >   #include <linux/slab.h>
> >
> >   #include "clk-mtk.h"
> > @@ -494,6 +495,18 @@ static int __mtk_clk_simple_probe(struct platform_device *pdev,
> >                          return IS_ERR(base) ? PTR_ERR(base) : -ENOMEM;
> >          }
> >
> > +
> > +       if (mcd->need_runtime_pm) {
> > +               devm_pm_runtime_enable(&pdev->dev);
> > +               /*
> > +                * Do a pm_runtime_resume_and_get() to workaround a possible
> > +                * deadlock between clk_register() and the genpd framework.
> > +                */
> > +               r = pm_runtime_resume_and_get(&pdev->dev);
> > +               if (r)
> > +                       return r;
> > +       }
> > +
> >          /* Calculate how many clk_hw_onecell_data entries to allocate */
> >          num_clks = mcd->num_clks + mcd->num_composite_clks;
> >          num_clks += mcd->num_fixed_clks + mcd->num_factor_clks;
> > @@ -574,6 +587,9 @@ static int __mtk_clk_simple_probe(struct platform_device *pdev,
> >                          goto unregister_clks;
> >          }
> >
> > +       if (mcd->need_runtime_pm)
> > +               pm_runtime_put(&pdev->dev);
> > +
> >          return r;
> >
> >   unregister_clks:
> > @@ -604,6 +620,9 @@ static int __mtk_clk_simple_probe(struct platform_device *pdev,
> >   free_base:
> >          if (mcd->shared_io && base)
> >                  iounmap(base);
> > +
> > +       if (mcd->need_runtime_pm)
> > +               pm_runtime_put(&pdev->dev);
> >          return r;
> >   }
> >
> > diff --git a/drivers/clk/mediatek/clk-mtk.h b/drivers/clk/mediatek/clk-mtk.h
> > index 22096501a60a..c17fe1c2d732 100644
> > --- a/drivers/clk/mediatek/clk-mtk.h
> > +++ b/drivers/clk/mediatek/clk-mtk.h
> > @@ -237,6 +237,8 @@ struct mtk_clk_desc {
> >
> >          int (*clk_notifier_func)(struct device *dev, struct clk *clk);
> >          unsigned int mfg_clk_idx;
> > +
> > +       bool need_runtime_pm;
> >   };
> >
> >   int mtk_clk_pdev_probe(struct platform_device *pdev);
> > --
> > 2.43.0.472.g3155946c3a-goog