Linux 4.4.4 [regression]

[Linus Torvalds]

On Mon, Mar 7, 2016 at 6:20 AM, Jörg-Volker Peetz <jvpeetz at web.de> wrote:
>
> This same problem with X does happen in 4.5-rc7. And removing the line
> introduced by patch b36e52c44ce6728824546d8b5f05b844cede96f1 makes X go again on
> my laptop.

Ok, so that's dbb17a21c131eca94eb31136eee9a7fe5aff00d9 in mainline.

Dave, Alex: that commit makes Jörg-Volker's HP Pavilion dv7 with
hybrid graphics (AMD HD 4200 - AMD 5400) unable to run X. No
suspend/resume in sight, just starting X hangs.

I'd guess it's the "radeon_switcheroo_set_state()" craziness (based on
that hybrid graphics thing), but we need to do something since this is
a regression.

Just revert for now? Or do you have other suggestions for Jörg-Volker to test?

Maybe that call to drm_helper_hpd_irq_event() should be purely in the
real resume path?

Or maybe there is something that the switcheroo code does that just
interacts badly with the code in drm_helper_hpd_irq_event()? Deadlock
on mode_config.mutex or something?

I suspect we just need to revert, but if somebody who knows the code
sees some obvious fix, holler quickly, please.

                        Linus