linux-kernel - Re: Linux 4.4.4 [regression]

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Message-ID: <CA+55aFzGY59nx0woBDd98yX0oUN+xaXDa1_s4d371KajMst7Og@mail.gmail.com>
Date:	Mon, 7 Mar 2016 08:20:35 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Jörg-Volker Peetz <jvpeetz@....de>,
	Dave Airlie <airlied@...il.com>,
	DRI mailing list <dri-devel@...ts.freedesktop.org>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	stable <stable@...r.kernel.org>, lwn@....net,
	Jiri Slaby <jslaby@...e.cz>,
	Alex Deucher <alexander.deucher@....com>
Subject: Re: Linux 4.4.4 [regression]

On Mon, Mar 7, 2016 at 6:20 AM, Jörg-Volker Peetz <jvpeetz@....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