Re: [PATCH v3] driver core: Break infinite loop when deferred probe can't be satisfied

[Grant Likely]

On 26/03/2020 12:03, Andy Shevchenko wrote:
> On Thu, Mar 26, 2020 at 11:45:18AM +0200, Peter Ujfalusi wrote:
> > On 26/03/2020 10.39, Rafael J. Wysocki wrote:
> > > On Wed, Mar 25, 2020 at 11:09 PM Saravana Kannan <saravanak@xxxxxxxxxx> wrote:
> > > > On Wed, Mar 25, 2020 at 5:51 AM Andy Shevchenko
> > > > <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
>
> ...
>
> > > OK, so the situation right now is that commit 58b116bce136 has
> > > introduced a regression and so it needs to be fixed or reverted.  The
> > > cases that were previously broken and were unbroken by that commit
> > > don't matter here, so you cannot argue that they would be "broken".
> >
> > commit 58b116bce136 is from 2014 and the whole ULPI support for dwc3
> > came in a year later.
> > While I agree that 58b116bce136 fail to handle came a year later, but
> > technically it did not introduced a regression.
> >
> > The revert on the other hand is going to introduce a regression as
> > things were working fine since 2014. Not sure why the dwc3 issue got
> > this long to be noticed as the 58b116bce136 was already in kernel when
> > the ULPI support was added...
>
> I dare to say that is luck based on people's laziness to figure out the root
> cause. As I pointed out in email to Saravana the issue is not limited to USB
> case and, if my memory doesn't trick me out, I suffered from it approximately
> in ~2014-2015 with pin control tables.

I've not been involved in this for a very long time, but from our past 
conversations and the description that is given here I still feel that 
this problem is a design bug on the dwc3 driver dependencies rather than 
a failure with driver core. dwc3 is doing something rather convoluted 
and it would be worth reevaluating how probe failures are unwound on 
that particular driver stack.

g.