linux-kernel - Re: [PATCH v3 2/2] clk: mediatek: mt8183: Enable need_runtime

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Date: Fri, 23 Feb 2024 12:43:39 +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>, Weiyi Lu <weiyi.lu@...iatek.com>, 
	linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org, 
	linux-mediatek@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 2/2] clk: mediatek: mt8183: Enable need_runtime_pm on mt8183-mfgcfg

On Mon, Jan 8, 2024 at 4:18 PM Pin-yen Lin <treapking@...omium.org> wrote:
>
> mt8183-mfgcfg has a mutual dependency with genpd during the probing
> stage, so enable need_runtim_pm to prevent a deadlock in the following
> call stack:
>
> CPU0:  genpd_lock --> clk_prepare_lock
> genpd_power_off_work_fn()
>  genpd_lock()
>  generic_pm_domain::power_off()
>     clk_unprepare()
>       clk_prepare_lock()
>
> CPU1: clk_prepare_lock --> genpd_lock
> clk_register()
>   __clk_core_init()
>     clk_prepare_lock()
>     clk_pm_runtime_get()
>       genpd_lock()
>
> Do a runtime PM get at the probe function to make sure clk_register()
> won't acquire the genpd lock.
>
> Fixes: acddfc2c261b ("clk: mediatek: Add MT8183 clock support")
> Signed-off-by: Pin-yen Lin <treapking@...omium.org>

Reviewed-by: Chen-Yu Tsai <wenst@...omium.org>

Note that this compliments a patch [1] adding the power domain for the mfgcfg
clock controller node, which has been floating around for almost 3 years.

[1] https://lore.kernel.org/linux-mediatek/20210414073108.3899082-1-ikjn@chromium.org/

> ---
>
> (no changes since v1)
>
>  drivers/clk/mediatek/clk-mt8183-mfgcfg.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/clk/mediatek/clk-mt8183-mfgcfg.c b/drivers/clk/mediatek/clk-mt8183-mfgcfg.c
> index ba504e19d420..62d876e150e1 100644
> --- a/drivers/clk/mediatek/clk-mt8183-mfgcfg.c
> +++ b/drivers/clk/mediatek/clk-mt8183-mfgcfg.c
> @@ -29,6 +29,7 @@ static const struct mtk_gate mfg_clks[] = {
>  static const struct mtk_clk_desc mfg_desc = {
>         .clks = mfg_clks,
>         .num_clks = ARRAY_SIZE(mfg_clks),
> +       .need_runtime_pm = true,
>  };
>
>  static const struct of_device_id of_match_clk_mt8183_mfg[] = {
> --
> 2.43.0.472.g3155946c3a-goog
>