<html> <head> <base href="https://bugs.freedesktop.org/" /> </head> <body> <div> <a class="bz_bug_link bz_status_ASSIGNED " title="ASSIGNED - [HSW ULT/BDW]igt/kms_cursor_crc fails with eDP" href="https://bugs.freedesktop.org/show_bug.cgi?id=72864#c18">Comment # 18</a> on <a class="bz_bug_link bz_status_ASSIGNED " title="ASSIGNED - [HSW ULT/BDW]igt/kms_cursor_crc fails with eDP" href="https://bugs.freedesktop.org/show_bug.cgi?id=72864">bug 72864</a> from <a class="email" href="mailto:przanoni@gmail.com" title="Paulo Zanoni <przanoni@gmail.com>"> Paulo Zanoni</a> <pre>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...</pre> </div> <hr> You are receiving this mail because: <ul> <li>You are the QA Contact for the bug.</li> <li>You are on the CC list for the bug.</li> <li>You are the assignee for the bug.</li> </ul> </body> </html>