On Sun, Nov 11, 2018 at 9:26 PM Rob Herring <[email protected]> wrote: > On Sun, Nov 11, 2018 at 7:04 AM Andy Shevchenko > <[email protected]> wrote:
> > I seems Grant's mail delivery bounces messages. I delibirately reduced > > the Cc list for sake of ping Grant in case it would pass. > > That would be because he is not at Linaro anymore. Added his ARM account. Thanks! > > On Sat, Nov 10, 2018 at 8:12 PM Andy Shevchenko > > <[email protected]> wrote: > > > > > > Consider the following scenario. > > > > > > There are two independent devices coupled together by functional > > > dependencies: > > > - USB OTG (dwc3-pci) > > > - extcon (tested with extcon-intel-mrfld, not yet in upstream) > > > > > > Each of the driver services a corresponding device is built as a module. > > > In the > > > Buildroot environment the modules are probed by alphabetical ordering of > > > their > > > modaliases. The latter comes to the case when USB OTG driver will be > > > probed > > > first followed by extcon one. > > > > > > So, if the platform anticipates extcon device to be appeared, in the > > > above case > > > we will get deferred probe of USB OTG, because of ordering. > > > > > > Now, a cherry on top of the cake, the deferred probing list contains > > > the only two modules, i.e. USB OTG and extcon. Due to above circumstances, > > > values in the local_trigger_count and deferred_trigger_count are not the > > > same, > > > and thus provokes deferred probe triggering again and again. > > > > > > ... > > > [ 20.678332] platform dwc3.0.auto: Retrying from deferred list > > > [ 20.694743] platform dwc3.0.auto: Driver dwc3 requests probe deferral > > > [ 20.701254] platform dwc3.0.auto: Added to deferred list > > > [ 20.706620] platform dwc3.0.auto: driver_deferred_probe_add_trigger 1 2 > > > [ 20.713732] platform dwc3.0.auto: Retrying from deferred list > > > [ 20.730035] platform dwc3.0.auto: Driver dwc3 requests probe deferral > > > [ 20.736540] platform dwc3.0.auto: Added to deferred list > > > [ 20.741889] platform dwc3.0.auto: driver_deferred_probe_add_trigger 3 4 > > > [ 20.748991] platform dwc3.0.auto: Retrying from deferred list > > > [ 20.765416] platform dwc3.0.auto: Driver dwc3 requests probe deferral > > > [ 20.771914] platform dwc3.0.auto: Added to deferred list > > > [ 20.777279] platform dwc3.0.auto: driver_deferred_probe_add_trigger 5 6 > > > ... > > > > > > Deeper investigation shows the culprit commit 58b116bce136 > > > ("drivercore: deferral race condition fix") which was dedicated to fix > > > some > > > other issue while bringing a regression. > > > > > > This reverts commit 58b116bce13612e5aa6fcd49ecbd4cf8bb59e835 for good > > > until > > > we will have better solution. > > How is behavior that's been there for 4.5 years a regression? Aren't > we going to break Davinci that this commit was supposed to fix? What > else could be relying on current behavior? I guess we are purerly on a side of luck. I don't remember people build usb and extcon as modules and using Buildroot, or anything that probes modules let's say,in "arbitrary" way. (That is one of the reason why I didn't dare to put Fixes tag there). Nevertheless, I have actual issue. I'm all ears to know about another possibility how to fix the issue on my side. -- With Best Regards, Andy Shevchenko
