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

[Marc Zyngier]

Hi Geert,

On 2021-01-18 17:39, Geert Uytterhoeven wrote:
> Hi Saravana,
>
> On Fri, Dec 18, 2020 at 4:34 AM Saravana Kannan <saravanak@xxxxxxxxxx> 
> 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@xxxxxxxxxxxxxx/
> > Signed-off-by: Saravana Kannan <saravanak@xxxxxxxxxx>
>
> Shimoda-san reported that next-20210111 and later fail to boot
> on Renesas R-Car Gen3 platforms. No output is seen, unless earlycon
> is enabled.
>
> I have bisected this to commit e590474768f1cc04 ("driver core: Set
> fw_devlink=on by default").

There is a tentative patch from Saravana here[1], which works around
some issues on my RK3399 platform, and it'd be interesting to find
out whether that helps on your system.

Thanks,

        M.

[1] 
https://lore.kernel.org/r/20210116011412.3211292-1-saravanak@xxxxxxxxxx
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