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

[Rob Herring <robh@xxxxxxxxxx>]

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?

Rob