Lockdep reports a possible circular locking dependency when attaching
devices to an MDLC PM domain:

  - During creation of the singleton PM domain:
      A. r8a78000_genpd_always_on_singleton() takes r8a78000_mdlc_lock,
      B. pm_genpd_init() takes gpd_list_lock.

  - During attachment of devices to PM domains:
      A. pm_genpd_add_device() takes gpd_list_lock,
      B. r8a78000_mdlc_attach_dev() takes r8a78000_mdlc_lock.

As the former is done only once, before any devices are attached, such a
AB-BA deadlock cannot really happen.  Fix this false positive by
introducing a separate lock to protect the creation of the singleton
domain.

Fixes: 89e6a71b35703f10 ("pmdomain: renesas: Add R-Car X5H MDLC driver")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
 drivers/pmdomain/renesas/r8a78000-mdlc.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/pmdomain/renesas/r8a78000-mdlc.c b/drivers/pmdomain/renesas/r8a78000-mdlc.c
index 2668fc2ac9cbd388..1fd71bb3da776eb1 100644
--- a/drivers/pmdomain/renesas/r8a78000-mdlc.c
+++ b/drivers/pmdomain/renesas/r8a78000-mdlc.c
@@ -45,8 +45,9 @@ struct r8a78000_mdlc_priv {
 };
 
 static struct generic_pm_domain *r8a78000_genpd_always_on;
+
 static HLIST_HEAD(r8a78000_mdlc_list);
-static DEFINE_MUTEX(r8a78000_mdlc_lock);	/* protects the two above */
+static DEFINE_MUTEX(r8a78000_mdlc_lock);	/* protects the list above */
 
 static struct generic_pm_domain *r8a78000_genpd_xlate(
 			const struct of_phandle_args *spec, void *data)
@@ -191,10 +192,11 @@ static void r8a78000_genpd_del_provider(void *data)
 
 static int r8a78000_genpd_always_on_singleton(struct device *dev)
 {
+	static DEFINE_MUTEX(singleton_lock);
 	struct generic_pm_domain *genpd;
 	int ret;
 
-	guard(mutex)(&r8a78000_mdlc_lock);
+	guard(mutex)(&singleton_lock);
 
 	if (r8a78000_genpd_always_on)
 		return 0;
-- 
2.43.0

On Mon, Sep 7, 2026 at 4:32 PM Geert Uytterhoeven
<geert+renesas@glider.be> wrote:
>
> Lockdep reports a possible circular locking dependency when attaching
> devices to an MDLC PM domain:
>
>   - During creation of the singleton PM domain:
>       A. r8a78000_genpd_always_on_singleton() takes r8a78000_mdlc_lock,
>       B. pm_genpd_init() takes gpd_list_lock.
>
>   - During attachment of devices to PM domains:
>       A. pm_genpd_add_device() takes gpd_list_lock,
>       B. r8a78000_mdlc_attach_dev() takes r8a78000_mdlc_lock.
>
> As the former is done only once, before any devices are attached, such a
> AB-BA deadlock cannot really happen.  Fix this false positive by
> introducing a separate lock to protect the creation of the singleton
> domain.
>
> Fixes: 89e6a71b35703f10 ("pmdomain: renesas: Add R-Car X5H MDLC driver")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Applied for next, thanks!

Kind regards
Uffe


> ---
>  drivers/pmdomain/renesas/r8a78000-mdlc.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pmdomain/renesas/r8a78000-mdlc.c b/drivers/pmdomain/renesas/r8a78000-mdlc.c
> index 2668fc2ac9cbd388..1fd71bb3da776eb1 100644
> --- a/drivers/pmdomain/renesas/r8a78000-mdlc.c
> +++ b/drivers/pmdomain/renesas/r8a78000-mdlc.c
> @@ -45,8 +45,9 @@ struct r8a78000_mdlc_priv {
>  };
>
>  static struct generic_pm_domain *r8a78000_genpd_always_on;
> +
>  static HLIST_HEAD(r8a78000_mdlc_list);
> -static DEFINE_MUTEX(r8a78000_mdlc_lock);       /* protects the two above */
> +static DEFINE_MUTEX(r8a78000_mdlc_lock);       /* protects the list above */
>
>  static struct generic_pm_domain *r8a78000_genpd_xlate(
>                         const struct of_phandle_args *spec, void *data)
> @@ -191,10 +192,11 @@ static void r8a78000_genpd_del_provider(void *data)
>
>  static int r8a78000_genpd_always_on_singleton(struct device *dev)
>  {
> +       static DEFINE_MUTEX(singleton_lock);
>         struct generic_pm_domain *genpd;
>         int ret;
>
> -       guard(mutex)(&r8a78000_mdlc_lock);
> +       guard(mutex)(&singleton_lock);
>
>         if (r8a78000_genpd_always_on)
>                 return 0;
> --
> 2.43.0
>

On 26-09-07 16:32:01, Geert Uytterhoeven wrote:
> Lockdep reports a possible circular locking dependency when attaching
> devices to an MDLC PM domain:
> 
>   - During creation of the singleton PM domain:
>       A. r8a78000_genpd_always_on_singleton() takes r8a78000_mdlc_lock,
>       B. pm_genpd_init() takes gpd_list_lock.
> 
>   - During attachment of devices to PM domains:
>       A. pm_genpd_add_device() takes gpd_list_lock,
>       B. r8a78000_mdlc_attach_dev() takes r8a78000_mdlc_lock.
> 
> As the former is done only once, before any devices are attached, such a
> AB-BA deadlock cannot really happen.  Fix this false positive by
> introducing a separate lock to protect the creation of the singleton
> domain.
> 
> Fixes: 89e6a71b35703f10 ("pmdomain: renesas: Add R-Car X5H MDLC driver")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Looks OK to me, so:

Reviewed-by: Abel Vesa <abel.vesa@oss.qualcomm.com>