linux-kernel - Re: [PATCH v1 5/5] driver core: Set fw

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Date:   Wed, 10 Feb 2021 12:52:29 -0800
From:   Saravana Kannan <saravanak@...gle.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Android Kernel Team <kernel-team@...roid.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Jisheng Zhang <Jisheng.Zhang@...aptics.com>,
        Kevin Hilman <khilman@...libre.com>,
        John Stultz <john.stultz@...aro.org>,
        Nicolas Saenz Julienne <nsaenzjulienne@...e.de>,
        Marc Zyngier <maz@...nel.org>
Subject: Re: [PATCH v1 5/5] driver core: Set fw_devlink=on by default

On Wed, Feb 10, 2021 at 7:10 AM Guenter Roeck <linux@...ck-us.net> wrote:
>
> On 2/10/21 12:20 AM, Saravana Kannan wrote:
> > On Tue, Feb 9, 2021 at 9:54 PM Guenter Roeck <linux@...ck-us.net> wrote:
> >>
> >> On Thu, Dec 17, 2020 at 07:17:03PM -0800, Saravana Kannan wrote:
> >>> Cyclic dependencies in some firmware was one of the last remaining
> >>> reasons fw_devlink=on couldn't be set by default. Now that cyclic
> >>> dependencies don't block probing, set fw_devlink=on by default.
> >>>
> >>> Setting fw_devlink=on by default brings a bunch of benefits (currently,
> >>> only for systems with device tree firmware):
> >>> * Significantly cuts down deferred probes.
> >>> * Device probe is effectively attempted in graph order.
> >>> * Makes it much easier to load drivers as modules without having to
> >>>   worry about functional dependencies between modules (depmod is still
> >>>   needed for symbol dependencies).
> >>>
> >>> If this patch prevents some devices from probing, it's very likely due
> >>> to the system having one or more device drivers that "probe"/set up a
> >>> device (DT node with compatible property) without creating a struct
> >>> device for it.  If we hit such cases, the device drivers need to be
> >>> fixed so that they populate struct devices and probe them like normal
> >>> device drivers so that the driver core is aware of the devices and their
> >>> status. See [1] for an example of such a case.
> >>>
> >>> [1] - https://lore.kernel.org/lkml/CAGETcx9PiX==mLxB9PO8Myyk6u2vhPVwTMsA5NkD-ywH5xhusw@mail.gmail.com/
> >>> Signed-off-by: Saravana Kannan <saravanak@...gle.com>
> >>
> >> This patch breaks nios2 boot tests in qemu. The system gets stuck when
> >> trying to reboot. Reverting this patch fixes the problem. Bisect log
> >> is attached.
> >
> > Thanks for the report Guenter. Can you please try this series?
> > https://lore.kernel.org/lkml/20210205222644.2357303-1-saravanak@google.com/
> >
>
> Not this week. I have lots of reviews to complete before the end of the week,
> with the 5.12 commit window coming up.

Ok. By next week, all the fixes should be in linux-next too. So it
should be easier if you choose to test.

> Given the number of problems observed, I personally think that it is way
> too early for this patch. We'll have no end of problems if it is applied
> to the upstream kernel in the next commit window. Of course, that is just
> my personal opinion.

You had said "with 115 of 430 boot tests failing in -next" earlier.
Just to be sure I understand it right, you are not saying this patch
caused them all right? You are just saying that 115 general boot
failures that might mask fw_devlink issues in some of them, right?

Thanks,
Saravana