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c76fbefaf9
commit a9193983f4 upstream.
The overlay on the i830M has a peculiar failure mode: It works the
first time around after boot-up, but consistenly hangs the second time
it's used.
Chris Wilson has dug out a nice errata:
"1.5.12 Clock Gating Disable for Display Register
Address Offset: 06200h–06203h
"Bit 3
Ovrunit Clock Gating Disable.
0 = Clock gating controlled by unit enabling logic
1 = Disable clock gating function
DevALM Errata ALM049: Overlay Clock Gating Must be Disabled: Overlay
& L2 Cache clock gating must be disabled in order to prevent device
hangs when turning off overlay.SW must turn off Ovrunit clock gating
(6200h) and L2 Cache clock gating (C8h)."
Now I've nowhere found that 0xc8 register and hence couldn't apply the
l2 cache workaround. But I've remembered that part of the magic that
the OVERLAY_ON/OFF commands are supposed to do is to rearrange cache
allocations so that the overlay scaler has some scratch space.
And while pondering how that could explain the hang the 2nd time we
enable the overlay, I've remembered that the old ums overlay code did
_not_ issue the OVERLAY_OFF cmd.
And indeed, disabling the OFF cmd results in the overlay working
flawlessly, so I guess we can workaround the lack of the above
workaround by simply never disabling the overlay engine once it's
enabled.
Note that we have the first part of the above w/a already implemented
in i830_init_clock_gating - leave that as-is to avoid surprises.
v2: Add a comment in the code.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=47827
Tested-by: Rhys <rhyspuk@gmail.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
[bwh: Backported to 3.2:
- Adjust context
- s/intel_ring_emit(ring, /OUT_RING(/]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
************************************************************
* 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