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) Zdenek
