[PATCH 5/9] drm/panfrost: Add HW_ISSUE_TTRX_3485 quirk

[Alyssa Rosenzweig]

> > TTRX_3485 requires the infamous "dummy job" workaround. I have this
> > workaround implemented in a local branch, but I have not yet hit a case
> > that requires it so I cannot test whether the implementation is correct.
> > In the mean time, add the quirk bit so we can document which platforms
> > may need it in the future.
> 
> This one is hideous ;) Although to me this isn't the 'infamous' one as
> it's not the earliest example of a dummy job.

Terrifying. I guess we narrowly avoided the 'replay' workaround which
was far worse than this one...

> However... I believe as Panfrost currently stands this is probably not
> very possible to hit. It requires a job to be stopped (soft or hard) at
> a critical point during submission - which at the moment Panfrost
> basically never does (the exception is if you close the fd immediately
> while a job is in progress). And of course the timing has to be 'just
> right' to hit the bug.

OK, that's good to know. Still "should" be fixed but that definitely
lowers the priority of it. Frankly the multithreading bugs we have on
the CPU side would hang the machine sooner...