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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAJZ5v0jtck8SYvXE2Env36MkK8zvK==U_7CANNrQWxFuQf2rWg@mail.gmail.com>
Date: Tue, 30 Dec 2025 17:17:44 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Geert Uytterhoeven <geert@...ux-m68k.org>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>, 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

On Tue, Dec 30, 2025 at 11:54 AM Geert Uytterhoeven
<geert@...ux-m68k.org> wrote:
>
> On Tue, 30 Dec 2025 at 11:34, Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> > 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).
>
> On R-Car Gen3, there are no such messages, as e.g.
> drivers/phy/renesas/phy-rcar-gen3-usb2.c does support Runtime PM.
> R-Car Gen2 uses drivers/phy/renesas/phy-rcar-gen2.c, which does not
> use Runtime PM yet, but still relies on explicit clock management.
>
> > > --- 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?

Sorry for breaking this!

> I assume the PHY core should support both drivers that do and do not
> support Runtime PM.

Yes, it should be sufficient to restore the pm_runtime_enabled() check.