Re: [PATCH v1] driver core: Extend deferred probe timeout on driver registration

[Rob Herring <robh@xxxxxxxxxx>]

On Fri, May 13, 2022 at 12:26 PM Saravana Kannan <saravanak@xxxxxxxxxx> wrote:
>
> On Fri, May 13, 2022 at 6:58 AM Rob Herring <robh@xxxxxxxxxx> wrote:
> >
> > On Fri, Apr 29, 2022 at 5:09 PM Saravana Kannan <saravanak@xxxxxxxxxx> wrote:
> > >
> > > The deferred probe timer that's used for this currently starts at
> > > late_initcall and runs for driver_deferred_probe_timeout seconds. The
> > > assumption being that all available drivers would be loaded and
> > > registered before the timer expires. This means, the
> > > driver_deferred_probe_timeout has to be pretty large for it to cover the
> > > worst case. But if we set the default value for it to cover the worst
> > > case, it would significantly slow down the average case. For this
> > > reason, the default value is set to 0.
> > >
> > > Also, with CONFIG_MODULES=y and the current default values of
> > > driver_deferred_probe_timeout=0 and fw_devlink=on, devices with missing
> > > drivers will cause their consumer devices to always defer their probes.
> > > This is because device links created by fw_devlink defer the probe even
> > > before the consumer driver's probe() is called.
> > >
> > > Instead of a fixed timeout, if we extend an unexpired deferred probe
> > > timer on every successful driver registration, with the expectation more
> > > modules would be loaded in the near future, then the default value of
> > > driver_deferred_probe_timeout only needs to be as long as the worst case
> > > time difference between two consecutive module loads.
> > >
> > > So let's implement that and set the default value to 10 seconds when
> > > CONFIG_MODULES=y.
> >
> > We had to revert a non-zero timeout before (issue with NFS root IIRC).
> > Does fw_devlink=on somehow fix that?
>
> If it's the one where ip autoconfig was timing out, then John Stultz
> fixed it by fixing wait_for_device_probe().
> https://lore.kernel.org/all/20200422203245.83244-4-john.stultz@xxxxxxxxxx/

Yeah, that was it.

Acked-by: Rob Herring <robh@xxxxxxxxxx>