linux-kernel - Re: [PATCH v1 15/23] phy: core: Discard pm_runtime

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Message-ID: <CAMuHMdVMFQebA43FJ53PBnd67C8fxWAC21cr4jWTGDwg-HV53w@mail.gmail.com>
Date: Tue, 30 Dec 2025 11:34:01 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: Linux PM <linux-pm@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, 
	Ulf Hansson <ulf.hansson@...aro.org>, Brian Norris <briannorris@...omium.org>, 
	Vinod Koul <vkoul@...nel.org>, Neil Armstrong <neil.armstrong@...aro.org>, 
	linux-phy@...ts.infradead.org, 
	Linux-Renesas <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH v1 15/23] phy: core: Discard pm_runtime_put() return values

Hi Rafael,

On Mon, 22 Dec 2025 at 21:40, Rafael J. Wysocki <rafael@...nel.org> wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> The PHY core defines phy_pm_runtime_put() to return an int, but that
> return value is never used.  It also passes the return value of
> pm_runtime_put() to the caller which is not very useful.
>
> Returning an error code from pm_runtime_put() merely means that it has
> not queued up a work item to check whether or not the device can be
> suspended and there are many perfectly valid situations in which that
> can happen, like after writing "on" to the devices' runtime PM "control"
> attribute in sysfs for one example.
>
> Modify phy_pm_runtime_put() to discard the pm_runtime_put() return
> value and change its return type to void.  Also drop the redundant
> pm_runtime_enabled() call from there.
>
> No intentional functional impact.
>
> This will facilitate a planned change of the pm_runtime_put() return
> type to void in the future.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Thanks for your patch, which is now commit caad07ae07e3fb17 ("phy:
core: Discard pm_runtime_put() return values") in phy/next.

This is causing several messages like

    phy phy-e6590100.usb-phy-controller.2: Runtime PM usage count underflow!

during boot, and s2ram on Koelsch (R-Car M2-W).

Reverting this commit fixes the issue.

> --- a/drivers/phy/phy-core.c
> +++ b/drivers/phy/phy-core.c
> @@ -190,15 +190,12 @@ int phy_pm_runtime_get_sync(struct phy *
>  }
>  EXPORT_SYMBOL_GPL(phy_pm_runtime_get_sync);
>
> -int phy_pm_runtime_put(struct phy *phy)
> +void phy_pm_runtime_put(struct phy *phy)
>  {
>         if (!phy)
> -               return 0;
> +               return;
>
> -       if (!pm_runtime_enabled(&phy->dev))
> -               return -ENOTSUPP;

Adding some instrumentation shows that this branch was taken before,
thus skipping the call to pm_runtime_put().

Can I just put the check back, or is there an underlying problem that
should be fixed instead?
Thanks!

> -
> -       return pm_runtime_put(&phy->dev);
> +       pm_runtime_put(&phy->dev);
>  }
>  EXPORT_SYMBOL_GPL(phy_pm_runtime_put);
>

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds