> I'm having a similar issue with my shiny new 17" Powerbook G4. The > radeon chip works fine with framebuffer in 2.6.12.4 _with_ PREEMPT, > but not in 2.6.13-rc5 _with_ PREEMPT (configs are virtually identical). > I'll try your idea this afternoon when I get the chance.
Note that PREEMPT is known to cause problems on ppc32 ... I'm not sure what's up yet. (Random SIGILLs/SEGVs in userland typically) > I wonder if perhaps some code in radeonfb is used under the BKL, which > is now preemptable (Or maybe an ordinary spinlock changed or went > away?), because I also set PREEMPT_BKL. radeonfb should only rely on the console semaphore.... > I've got an LCD, and on mine > it looks like every third pixel-line gets shifted about 32-64 pixels to > the left, and they move with display refresh. My guess is that > something is interrupting radeonfb during a critical time in display > syncing and forcing the video card to wait too far into the next line > before sending pixels. radeonfb is mostly inactive after it has setup the framebuffer and unless you actually draw something, in which case, accel code is called. _However_ there is an unrelated problem with some panels, including some of the 17": The panel doesn't always "sync" properly. This seem to be related to some subtle timing issue in the LVDS code but I don't know exactly what yet. You can usually get it back by repeately turning the backlight all the way down (which shuts the panel off) and back up until it "catches". > One other data point, I've seen something like this, except not nearly > as bad, is stock debian 2.6.8 vs. stock debian 2.6.11 on powerpc. The > former exhibits some similar (but not nearly as bad) symptoms. (Same > Powerbook), whereas 2.6.11 doesn't. In that case, neither has PREEMPT. > I'll run more tests this afternoon/evening, to try to track it down. > > Cheers, > Kyle Moffett > > -- > There are two ways of constructing a software design. One way is to > make it so > simple that there are obviously no deficiencies. And the other way is > to make > it so complicated that there are no obvious deficiencies. The first > method is > far more difficult. > -- C.A.R. Hoare > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
