Re: [PATCH v1 5/5] driver core: Set fw_devlink=on by default

From: Saravana Kannan <saravanak@google.com>
To: Guenter Roeck <linux@roeck-us.net>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	Android Kernel Team <kernel-team@android.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Jisheng Zhang <Jisheng.Zhang@synaptics.com>,
	Kevin Hilman <khilman@baylibre.com>,
	John Stultz <john.stultz@linaro.org>,
	Nicolas Saenz Julienne <nsaenzjulienne@suse.de>,
	Marc Zyngier <maz@kernel.org>
Subject: Re: [PATCH v1 5/5] driver core: Set fw_devlink=on by default
Date: Tue, 16 Feb 2021 18:39:55 -0800	[thread overview]
Message-ID: <CAGETcx-fQWJUyDS9HbHzBpb-1dSNX1B7jqOF9696D0rZXnBHFQ@mail.gmail.com> (raw)
In-Reply-To: <db598d8c-cf59-8478-2248-2ad2ab065c37@roeck-us.net>

On Wed, Feb 10, 2021 at 1:21 PM Guenter Roeck <linux@roeck-us.net> wrote:
>
> On 2/10/21 12:52 PM, Saravana Kannan wrote:
> > On Wed, Feb 10, 2021 at 7:10 AM Guenter Roeck <linux@roeck-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@roeck-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@google.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?
> >
>
> Correct.

Is it right to assume [1] fixed all known boot issues due to fw_devlink=on?
[1] - https://lore.kernel.org/lkml/20210215224258.1231449-1-saravanak@google.com/

-Saravana