linux-kernel - Re: [PATCH v2] pmdomain: mtk-pm-domains: improve spinlock recursion fix in probe with correcting reference count

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Message-ID: <CAPDyKFranQ=UU5waLcw27E4SG30bps80DmGs+zZs6N9=iZa_zg@mail.gmail.com>
Date: Sun, 28 Dec 2025 16:51:11 +0100
From: Ulf Hansson <ulf.hansson@...aro.org>
To: Macpaul Lin <macpaul.lin@...iatek.com>
Cc: Matthias Brugger <matthias.bgg@...il.com>, 
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>, 
	Nícolas F . R . A . Prado <nfraprado@...labora.com>, 
	Chen-Yu Tsai <wenst@...omium.org>, linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-mediatek@...ts.infradead.org, 
	Weiyi Lu <Weiyi.Lu@...iatek.com>, Jian Hui Lee <jianhui.lee@...onical.com>, 
	Irving-CH Lin <Irving-CH.Lin@...iatek.com>, conor@...nel.org, krzk@...nel.org, 
	Louis-Alexis Eyraud <louisalexis.eyraud@...labora.com>, Bear Wang <bear.wang@...iatek.com>, 
	Pablo Sun <pablo.sun@...iatek.com>, Ramax Lo <ramax.lo@...iatek.com>, 
	Macpaul Lin <macpaul@...il.com>, 
	MediaTek Chromebook Upstream <Project_Global_Chrome_Upstream_Group@...iatek.com>, Stable@...r.kernel.org
Subject: Re: [PATCH v2] pmdomain: mtk-pm-domains: improve spinlock recursion
 fix in probe with correcting reference count

On Fri, 28 Nov 2025 at 05:17, Macpaul Lin <macpaul.lin@...iatek.com> wrote:
>
> Remove scpsys_get_legacy_regmap(), replacing its usage with
> of_find_node_with_property().  Explicitly call of_node_get(np) before each
> of_find_node_with_property() to maintain correct node reference counting.
>
> The of_find_node_with_property() function "consumes" its input by calling
> of_node_put() internally, whether or not it finds a match.
> Currently, dev->of_node (np) is passed multiple times in sequence without
> incrementing its reference count, causing it to be decremented multiple times
> and risking early memory release.
>
> Adding of_node_get(np) before each call balances the reference count,
> preventing premature node release.
>
> Fixes: c1bac49fe91f ("pmdomains: mtk-pm-domains: Fix spinlock recursion in probe")
> Cc: Stable@...r.kernel.org
> Signed-off-by: Macpaul Lin <macpaul.lin@...iatek.com>
> Tested-by: Louis-Alexis Eyraud <louisalexis.eyraud@...labora.com>

Applied for fixes, thanks!

Kind regards
Uffe



> ---
>  drivers/pmdomain/mediatek/mtk-pm-domains.c | 21 ++++++---------------
>  1 file changed, 6 insertions(+), 15 deletions(-)
>
> Changes for v2:
>  - Rewording commit message.
>  - Add Fixes: and Tested-by: tag, thanks.
>
> diff --git a/drivers/pmdomain/mediatek/mtk-pm-domains.c b/drivers/pmdomain/mediatek/mtk-pm-domains.c
> index 80561d27f2b2..f64f24d520dd 100644
> --- a/drivers/pmdomain/mediatek/mtk-pm-domains.c
> +++ b/drivers/pmdomain/mediatek/mtk-pm-domains.c
> @@ -984,18 +984,6 @@ static void scpsys_domain_cleanup(struct scpsys *scpsys)
>         }
>  }
>
> -static struct device_node *scpsys_get_legacy_regmap(struct device_node *np, const char *pn)
> -{
> -       struct device_node *local_node;
> -
> -       for_each_child_of_node(np, local_node) {
> -               if (of_property_present(local_node, pn))
> -                       return local_node;
> -       }
> -
> -       return NULL;
> -}
> -
>  static int scpsys_get_bus_protection_legacy(struct device *dev, struct scpsys *scpsys)
>  {
>         const u8 bp_blocks[3] = {
> @@ -1017,7 +1005,8 @@ static int scpsys_get_bus_protection_legacy(struct device *dev, struct scpsys *s
>          * this makes it then possible to allocate the array of bus_prot
>          * regmaps and convert all to the new style handling.
>          */
> -       node = scpsys_get_legacy_regmap(np, "mediatek,infracfg");
> +       of_node_get(np);
> +       node = of_find_node_with_property(np, "mediatek,infracfg");
>         if (node) {
>                 regmap[0] = syscon_regmap_lookup_by_phandle(node, "mediatek,infracfg");
>                 of_node_put(node);
> @@ -1030,7 +1019,8 @@ static int scpsys_get_bus_protection_legacy(struct device *dev, struct scpsys *s
>                 regmap[0] = NULL;
>         }
>
> -       node = scpsys_get_legacy_regmap(np, "mediatek,smi");
> +       of_node_get(np);
> +       node = of_find_node_with_property(np, "mediatek,smi");
>         if (node) {
>                 smi_np = of_parse_phandle(node, "mediatek,smi", 0);
>                 of_node_put(node);
> @@ -1048,7 +1038,8 @@ static int scpsys_get_bus_protection_legacy(struct device *dev, struct scpsys *s
>                 regmap[1] = NULL;
>         }
>
> -       node = scpsys_get_legacy_regmap(np, "mediatek,infracfg-nao");
> +       of_node_get(np);
> +       node = of_find_node_with_property(np, "mediatek,infracfg-nao");
>         if (node) {
>                 regmap[2] = syscon_regmap_lookup_by_phandle(node, "mediatek,infracfg-nao");
>                 num_regmaps++;
> --
> 2.45.2
>