lockup on boot -- drm/i915/display: Force the state compute phase once to enable PSR

[Dominik Brodowski <linux@dominikbrodowski.net>]

On Mon, Feb 17, 2020 at 10:08:52PM +0100, Boris Brezillon wrote:
> On Mon, 17 Feb 2020 21:09:42 +0100
> Dominik Brodowski <linux@dominikbrodowski.net> wrote:
> 
> > On my old Dell XPS 13 laptop with
> > 
> > 00:00.0 Host bridge: Intel Corporation Broadwell-U Host Bridge -OPI (rev 09)
> > 00:02.0 VGA compatible controller: Intel Corporation HD Graphics 5500 (rev 09) (prog-if 00 [VGA controller])
> > 
> > booting 5.6-rc1 and -rc2 fails after the dmesg line
> > 
> > 	fb0: switching to inteldrmfb from simple
> > 
> > while the next lines should be something like (v5.5):
> > 
> > 	Console: switching to colour dummy device 80x25
> > 	i915 0000:00:02.0: vgaarb: deactivate vga console
> > 	[drm] ACPI BIOS requests an excessive sleep of 25000 ms, using 1500 ms instead
> > 	[drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
> > 	[drm] Driver supports precise vblank timestamp query.
> > 	i915 0000:00:02.0: vgaarb: changed VGA decodes: olddecodes=io+mem,decodes=io+mem:owns=io+mem
> > 
> > A git bisect lead to
> > 
> > 	commit b86d895524ab ("drm/bridge: Add an ->atomic_check() hook")
> 
> This commit has been reverted: you should ignore any failures between
> b86d895524ab ("drm/bridge: Add an ->atomic_check() hook") and
> 099126352303 ("Revert "drm/bridge: Add a drm_bridge_state object").

A new bisect now points to

	60c6a14b489b ("drm/i915/display: Force the state compute phase
	once to enable PSR").

Please note that bisecting this is quite a hassle, in particular due to
various reverts in between and back-merges (such as ec027b33c8bb, which has
two parents in "bad" state). As 60c6a14b489b does not revert cleanly, I
can't test a revert on top of 5.6-rc2.

Thanks,
	Dominik