linux-kernel - Re: [PATCH v2 1/2] clk: mediatek: Introduce need_pm_runtime to mtk_clk

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Message-ID: <CAGXv+5F1AjQYf0qVd5PwZobkvHLCczX_KcGEebNP5JvJCHb9rw@mail.gmail.com>
Date: Wed, 3 Jan 2024 15:45:17 +0800
From: Chen-Yu Tsai <wenst@...omium.org>
To: Pin-yen Lin <treapking@...omium.org>
Cc: Michael Turquette <mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>, 
	Matthias Brugger <matthias.bgg@...il.com>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
	linux-arm-kernel@...ts.infradead.org, linux-clk@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Weiyi Lu <weiyi.lu@...iatek.com>, 
	linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v2 1/2] clk: mediatek: Introduce need_pm_runtime to mtk_clk_desc

On Tue, Jan 2, 2024 at 4:14 PM Pin-yen Lin <treapking@...omium.org> wrote:
>
> Introduce a new need_pm_runtime variable to mtk_clk_desc to indicate
> this clock needs a runtime PM get on the clock controller during the
> probing stage.

No. The flag indicates that the clock controller needs runtime PM
for its operation, likely because it needs some power domain enabled.

The runtime PM get during the probe phase is a workaround to prevent
a deadlock in clk_register.

These are two separate things. The second part also should be documented
in the code with a comment, i.e. a comment should be placed before
pm_runtime_resume_and_get().

ChenYu

> Signed-off-by: Pin-yen Lin <treapking@...omium.org>
> ---
>
> 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 | 15 +++++++++++++++
>  drivers/clk/mediatek/clk-mtk.h |  2 ++
>  2 files changed, 17 insertions(+)
>
> diff --git a/drivers/clk/mediatek/clk-mtk.c b/drivers/clk/mediatek/clk-mtk.c
> index 2e55368dc4d8..c31e535909c8 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 +495,14 @@ 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);
> +               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 +583,9 @@ 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 +616,9 @@ 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
>