linux-kernel - Re: [PATCH v2 1/9] PM: domains: Delete usage of driver_deferred_probe_check

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Message-ID: <CAGETcx_1USPRbFKV5j00qkQ-QXJkp7=FAfnFcfiNnM4J5KF1cQ@mail.gmail.com>
Date:   Tue, 21 Jun 2022 12:34:03 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Kevin Hilman <khilman@...nel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>, kernel-team@...roid.com,
        linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        iommu@...ts.linux-foundation.org, netdev@...r.kernel.org,
        linux-gpio@...r.kernel.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH v2 1/9] PM: domains: Delete usage of driver_deferred_probe_check_state()

On Tue, Jun 21, 2022 at 12:28 AM Tony Lindgren <tony@...mide.com> wrote:
>
> Hi,
>
> * Saravana Kannan <saravanak@...gle.com> [700101 02:00]:
> > Now that fw_devlink=on by default and fw_devlink supports
> > "power-domains" property, the execution will never get to the point
> > where driver_deferred_probe_check_state() is called before the supplier
> > has probed successfully or before deferred probe timeout has expired.
> >
> > So, delete the call and replace it with -ENODEV.
>
> Looks like this causes omaps to not boot in Linux next.

Can you please point me to an example DTS I could use for debugging
this? I'm assuming you are leaving fw_devlink=on and not turning it
off or putting it in permissive mode.

> With this
> simple-pm-bus fails to probe initially as the power-domain is not
> yet available.

Before we get to late_initcall(), I'd expect this series to not have
any impact because both fw_devlink and
driver_deferred_probe_check_state() should be causing the device's
probe to get deferred until the PM domain device comes up.

To double check this, without this series, can you give me the list of
"supplier:*" symlinks under a simple-pm-bus device's sysfs folder
that's having problems with this series? And for all those symlinks,
cat the "status" file under that directory?

In the system where this is failing, is the PM domain driver loaded as
a module at a later point?

Couple of other things to try (with the patches) to narrow this down:
* Can you set driver_probe_timeout=0 in the command line and see if that helps?
* Can you set it to something high like 30 or even larger and see if it helps?

> On platform_probe() genpd_get_from_provider() returns
> -ENOENT.

This error is with the series I assume?

> Seems like other stuff is potentially broken too, any ideas on
> how to fix this?

I'll want to understand the issue first. It's not yet clear to me why
fw_devlink isn't blocking the probe of the simple-pm-bus device until
the PM domain device shows up. And if it is not blocking, then why and
at what point in boot it's giving up and letting the probe get to this
point where there's an error.

-Saravana

>
>
> >
> > Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> > ---
> >  drivers/base/power/domain.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
> > index 739e52cd4aba..3e86772d5fac 100644
> > --- a/drivers/base/power/domain.c
> > +++ b/drivers/base/power/domain.c
> > @@ -2730,7 +2730,7 @@ static int __genpd_dev_pm_attach(struct device *dev, struct device *base_dev,
> >               mutex_unlock(&gpd_list_lock);
> >               dev_dbg(dev, "%s() failed to find PM domain: %ld\n",
> >                       __func__, PTR_ERR(pd));
> > -             return driver_deferred_probe_check_state(base_dev);
> > +             return -ENODEV;
> >       }
> >
> >       dev_dbg(dev, "adding to PM domain %s\n", pd->name);
> > --
> > 2.36.1.255.ge46751e96f-goog
> >
>
> --
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