Hi! > > With Device Trees (DT), the dependencies of the devices are defined in the > > DT, then the drivers parse that information to lookup the needed resources > > that have as dependencies. > > > > Since drivers and devices are registered in a non-deterministic way, it is > > possible that a device that is a dependency has not been registered yet by > > the time that is looked up. > > > > In this case the driver that requires this dependency cannot probe and has > > to defer it. So the driver core adds it to a list of deferred devices that > > is iterated again every time that a new driver is probed successfully. > > > > For debugging purposes it may be useful to know what are the devices whose > > probe function was deferred. Add a debugfs entry showing that information. > > > > $ cat /sys/kernel/debug/devices_deferred > > 48070000.i2c:twl@48:bci > > musb-hdrc.0.auto > > omapdrm.0 > > > > This information could be obtained partially by enabling debugging, but it > > means that the kernel log has to be parsed and the probe deferral balanced > > with the successes. This can be error probe and has to be done in a ad-hoc > > manner by everyone who needs to debug these kind of issues. > > > > Since the information is already known by the kernel, just show it to make > > it easier to debug. > > > > Signed-off-by: Javier Martinez Canillas <javi...@redhat.com> > > Reviewed-by: Andy Shevchenko <andy.shevche...@gmail.com> > > Reviewed-by: Mark Brown <broo...@kernel.org> > > Reviewed-by: Sebastian Reichel <sebastian.reic...@collabora.co.uk>
Thanks for doing this.
Note that it rejects on current -rc4, but solution is trivial.
Tested-by: Pavel Machek <pa...@ucw.cz>
Unfortunately, it does not help with pwm problem on Droid4, as nothing
is deffered:
user@devuan:/sys/bus/platform/drivers$ cat
/sys/kernel/debug/devices_deferred
user@devuan:/sys/bus/platform/drivers$
Pavel
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