Apparently it's broken in the exact same way as the gmbus irq. For
reference of the full story see
commit c12aba5aa0
Author: Jiri Kosina <jkosina@suse.cz>
Date: Tue Mar 19 09:56:57 2013 +0100
drm/i915: stop using GMBUS IRQs on Gen4 chips
The effect is that we have a storm of unclaimed interrupts on the
legacy irq line. If that one is used by a different device then the
kernel will complain and rather quickly kill the irq source. Which
breaks any device trying to actually use the legacy irq line.
This regression has been introduced
commit 4aeebd7443
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date: Thu Oct 31 09:53:36 2013 +0100
drm/i915: dp aux irq support for g4x/vlv
Note that disabling MSI works around the issue, but we can't do that
since apparently then the hw will miss interrupts. At least if
relevant comments in i915_irq.c are accurate.
v2: Cross-reference dp aux and gmbus gen4 comments.
v3: Consolidate harder into i915_drv.h as suggested by Chris.
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Jiri Kosina <jkosina@suse.cz>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reported-and-tested-by: Jiri Kosina <jkosina@suse.cz>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
************************************************************
* For the very latest on DRI development, please see: *
* http://dri.freedesktop.org/ *
************************************************************
The Direct Rendering Manager (drm) is a device-independent kernel-level
device driver that provides support for the XFree86 Direct Rendering
Infrastructure (DRI).
The DRM supports the Direct Rendering Infrastructure (DRI) in four major
ways:
1. The DRM provides synchronized access to the graphics hardware via
the use of an optimized two-tiered lock.
2. The DRM enforces the DRI security policy for access to the graphics
hardware by only allowing authenticated X11 clients access to
restricted regions of memory.
3. The DRM provides a generic DMA engine, complete with multiple
queues and the ability to detect the need for an OpenGL context
switch.
4. The DRM is extensible via the use of small device-specific modules
that rely extensively on the API exported by the DRM module.
Documentation on the DRI is available from:
http://dri.freedesktop.org/wiki/Documentation
http://sourceforge.net/project/showfiles.php?group_id=387
http://dri.sourceforge.net/doc/
For specific information about kernel-level support, see:
The Direct Rendering Manager, Kernel Support for the Direct Rendering
Infrastructure
http://dri.sourceforge.net/doc/drm_low_level.html
Hardware Locking for the Direct Rendering Infrastructure
http://dri.sourceforge.net/doc/hardware_locking_low_level.html
A Security Analysis of the Direct Rendering Infrastructure
http://dri.sourceforge.net/doc/security_low_level.html
4e6b788c3f