On Feb 28, 2013 5:20 PM, "Takashi Iwai" <<a href="mailto:tiwai@suse.de">tiwai@suse.de</a>> wrote: > > At Thu, 28 Feb 2013 17:33:56 +0200, > Jani Nikula wrote: > > > > On Thu, 28 Feb 2013, James Courtier-Dutton <<a href="mailto:james.dutton@gmail.com">james.dutton@gmail.com</a>> wrote: > > > Bisect done on tree: > > > git://<a href="http://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git">git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git</a> > > > Worked on 3.7. > > > Broken on 3.8 > > > > > > Problem: "Backlight not coming on after resume." > > > git finally bisected for my Samsung Serial 7 Laptop. > > > Bisecting: 0 revisions left to test after this (roughly 0 steps) > > > [cf0a6584aa6d382f802f2c3cacac23ccbccde0cd] drm/i915: write backlight > > > harder <- This is the problem commit. Seems that fixing some > > > machines breaks others, based on the existing comments on that patch. > > > > The backlight haunts us again. Could you post the dmesg with > > drm.debug=0xe module parameter, first running vanilla 3.8, and then with > > the bad commit reverted, please? > > > > Might not be a bad idea to file a bug on Product=DRI, > > Component=DRM/Intel at <a href="https://bugs.freedesktop.org">https://bugs.freedesktop.org</a> (see > > <a href="https://01.org/linuxgraphics/documentation/how-report-bugs-0">https://01.org/linuxgraphics/documentation/how-report-bugs-0</a> for > > details) and attach your bisect results and the dmesgs there. > > I'm afraid the patch doesn't do it right. It fixes for Dell, but the > old problem on others back by that. It was merged before actually > testing on the machines the original fix was intended for. > > Now I can confirm a problem (partially) with the latest Linus tree on > a new laptop. I write "partially" because it happens only during the > splash screen of S4 hibernation, so I've ignored, so far. > > James, try to revert that commit. Does it fix? > > If so, you should check the output of intel_reg_dumper at broken and > working states. > Can someone point me to a datasheet that relates to this bit of code, so i can understand what all the registers do. I would like to understand the code in order to suggest a better fix.