[Intel-gfx] [PATCH] drm/i915/vlv: reset VLV media force wake request register

[Darren Hart]

On 5/9/14, 5:41, "Jani Nikula" <jani.nikula at intel.com> wrote:

>Media force wake get hangs the machine when the system is booted without
>displays attached. The assumption is that (at least some versions of)
>the firmware has skipped some initialization in that case.
>
>Empirical evidence suggests we need to reset the media force wake
>request register in addition to the render one to avoid hangs.
>
>Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=75895
>Reported-by: Imre Deak <imre.deak at intel.com>
>Reported-by: Darren Hart <dvhart at linux.intel.com>
>Cc: stable at vger.kernel.org
>Signed-off-by: Jani Nikula <jani.nikula at intel.com>

Applied to 3.14.2 and tested on MinnowBoardMax A0 hardware (BayTrail-I,
Atom E3825).

* With no display connected, the boot no longer hangs and DRM prints
sensible messages during boot:
[    5.968837] [drm] GMBUS [i915 gmbus vga] timed out, falling back to bit
banging on pin 2
[    5.988037] i915 0000:00:02.0: No connectors reported connected with
modes
[    5.995744] [drm] Cannot find any crtc or sizes - going 1024x768
[    6.004716] fbcon: inteldrmfb (fb0) is primary device
[    6.013066] Console: switching to colour frame buffer device 128x48
[    6.034147] i915 0000:00:02.0: fb0: inteldrmfb frame buffer device
[    6.041168] i915 0000:00:02.0: registered panic notifier
[    6.049820] ACPI: Video Device [GFX0] (multi-head: yes  rom: no  post:
no)
[    6.058788] acpi device:30: registered as cooling_device3
[    6.065111] input: Video Bus as
/devices/LNXSYSTM:00/device:00/PNP0A08:00/LNXVIDEO:00/input/input4
[    6.075370] [drm] Initialized i915 1.6.0 20080730 for 0000:00:02.0 on
minor 0


* If a display is subsequently connected and X is restarted, it behaves as
expected.

* Booting with a display connected continue to work as expected.

Tested-by: Darren Hart <dvhart at linux.intel.com>

Thank you very much Jani!

-- 
Darren Hart					Open Source Technology Center
darren.hart at intel.com				            Intel Corporation