[Bug 72864] [HSW ULT/BDW]igt/kms_cursor_crc fails with eDP

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=72864

--- Comment #18 from Paulo Zanoni <przanoni at gmail.com> ---
Ok, so I did some more investigation... The problem only appears to happen on
pipe A. Arthur suggested that some package C state may be interfering with
memory/caches, and the HW is calculating CRC the result based on a wrong input.

So I did some test, and if we keep the i915_forcewake_user file open, the
problem _does not_ happen.

The easiest way I found to test this is:

- open a terminal
- become root
- run "irb"
- on its prompt, type: "a =
File.open("/sys/kernel/debug/dri/0/i915_forcewake_user")"
- leave this terminal as it is
- open a new terminal
- run sudo ./kms_cursor_crc

The test will succeed!

For the real fix, I guess we have to find a way to prevent deep PC states
whenever we're calculating CRCs for pipe A...

-- 
You are receiving this mail because:
You are the QA Contact for the bug.
You are on the CC list for the bug.
You are the assignee for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.freedesktop.org/archives/intel-gfx-bugs/attachments/20141010/afe45a7d/attachment.html>