On Thu, May 24, 2012 at 04:21:48PM +0200, Zdenek Kabelac wrote: > 2012/5/23 Daniel Vetter <daniel at ffwll.ch>: > > On Wed, May 23, 2012 at 01:48:41PM +0200, Zdenek Kabelac wrote: > >> 2012/5/23 Daniel Vetter <daniel at ffwll.ch>: > >> > On Wed, May 23, 2012 at 09:07:28AM +0200, Daniel Vetter wrote: > >> >> On Wed, May 23, 2012 at 08:59:07AM +0200, Zdenek Kabelac wrote: > >> >> > Hmm I've been using i915.lvds_downclock=1 on grub command line, and > >> >> > haven't noticed any visible problems with 3.3 kernel. So I'd rather > >> >> > ask if the problematic patch isn't doing downclocking in a wrong way? > >> >> > Or maybe detection that downclocking is not supported properly is not > >> >> > correct now ? > >> >> > >> >> Nope, Sean's analysis is pretty much correct, that patch only makes > >> >> downclocking possible in more circumstances. And downclocking can > >> >> certainly explain what you're seeing, the backlight pwm signal is driven > >> >> off the panel dotclock, so if we change that we can very likely cause some > >> >> funny interference. I guess we could frob the backligth control settings > >> >> and adjust them for the change in clockspeed, but the current backlight > >> >> code is a bit a mess. So right now I suggest you just drop that option - > >> >> there are reasons it's not the default ;-) > >> > > >> > Quick question: What's the frequency of the brightness change? And how > >> > regular are the changes? > >> > -Daniel > >> > >> > >> Now when it's obvious it's related to powersaving ?- it's probably > >> much easier to explain, > >> that I've been observing those changes when some activity was happing - > >> i.e. opening ?picture - and after like 1 second image has flashed, - > >> then I've moved the mouse > >> stopped - and again image has flashed with brightness a bit. > >> > >> The issue would be probably far less noticeable if the period of time > >> of idle GPU would have to be > >> much longer (i.e. in minute range) > > > > Hm, that sounds more like something ugly is happening when we switch > > frequencies as opposed to the different frequency causing interference > > with the backlight. Just to check: You only see a quick flash, then > > brightness is back to normal? > > In fact I'm not really noticing the moment it goes back to normal - > I'll notice when it gets darker. > i.e. when I open picture with 'qiv' - after a second I notice that > picture becomes a bit darker. > If I do not move with anything - it stays this way. > > > > > If that's the case, please try Chris' fastboot branch. vsyncing the > > frequency change might indeed fix this. > > > > I've tried to compile, but compilation finished with some errors - so > I've tried to rebase branch on master 3.4 - tried to resolve some > error - but probably in a wrong thus resulted kernel given me just > black screen when X has been initialized. So I'll try to remove some > config options and I'll try to rebuild original fastboot branch later. Hm, maybe attach your .config and yell at Chris a bit to fix up his branch. -Daniel -- Daniel Vetter Mail: daniel at ffwll.ch Mobile: +41 (0)79 365 57 48
