<html> <head> <base href="https://bugs.freedesktop.org/"> </head> <body> <div> <a class="bz_bug_link bz_status_NEW " title="NEW - [KBL] "enable_rc6" parameter deprecation brings back freezing" href="https://bugs.freedesktop.org/show_bug.cgi?id=105962#c53">Comment # 53</a> on <a class="bz_bug_link bz_status_NEW " title="NEW - [KBL] "enable_rc6" parameter deprecation brings back freezing" href="https://bugs.freedesktop.org/show_bug.cgi?id=105962">bug 105962</a> from <a class="email" href="mailto:george.mccollister@gmail.com" title="George McCollister <george.mccollister@gmail.com>"> George McCollister</a> <pre>I'm able to reproduce this issue on five Atom E3845 based embedded systems in a lab. With intel_idle.max_cstate=0 processor.max_cstate=0 I can get all systems to restart due to watchdog reset overnight. Sometimes, but not always I have observed errors such as these on the serial console immediately prior to the system lockup/reboot: [144039.363431] [drm:vlv_set_power_well [i915]] *ERROR* timeout setting power well state 00000c00 (000ffc00) [144039.476432] [drm:vlv_set_power_well [i915]] *ERROR* timeout setting power well state 000000c0 (000ffcc0) [144039.589165] [drm:vlv_set_power_well [i915]] *ERROR* timeout setting power well state 00000000 (000fccc0) [144039.702190] [drm:vlv_set_power_well [i915]] *ERROR* timeout setting power well state 00000000 (000f0cc0) [144039.814669] [drm:vlv_set_power_well [i915]] *ERROR* timeout setting power well state 00000000 (000c0cc0) [144039.925749] [drm:vlv_set_power_well [i915]] *ERROR* timeout setting power well state 00000000 (00000cc0) [144040.120485] [drm:vlv_set_power_well [i915]] *ERROR* timeout setting power well state 00000c00 (00000cc0) [144040.233084] [drm:vlv_set_power_well [i915]] *ERROR* timeout setting power well state 000000c0 (00000cc0) [144040.388315] [drm:vlv_set_power_well [i915]] *ERROR* timeout setting power well state 000000c0 (00000cc0) [144040.607674] [drm:vlv_set_power_well [i915]] *ERROR* timeout setting power well state 000000c0 (00000cc0) Most commonly, only one of the above error messages (or none) is printed to the serial console. On 4.14.x, adding i915.enable_rc6=0 allows the systems to run 3+ days (until I stop the test). Hoping it would fix the problem I checked out and built kernel commit a75d035fedbdecf83f86767aa2e4d05c8c4ffd95. All systems still rebooted overnight. I've since found that using i915.disable_power_well=0 also prevents the problem from occurring on all tested kernel versions. Is this setting less disruptive to the operation than i915.enable_rc6=0? Is there also value in testing "enable_dc=0"? If any of the developers are working on this and think they have a fix, give me the URI of a git repo and the commit to use and I can build, test it in the lab. Also specify any kernel config settings and kernel command line arguments you want me to use. Since someone might ask I'm using "intel_idle.max_cstate=0 processor.max_cstate=0" since these systems require minimal scheduling latency. I also noticed they can prevent other i915 lockup issues. I can remove them for testing purposes upon request.</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> </ul> </body> </html>