On Tue, Feb 23, 2016 at 08:44:49PM +0100, Tore Anderson wrote: > Hi Ville, > > > "The monitor is connected with a DP+-to-HDMI cable" > > This and some reading of the DP dual mode spec gave me another idea; > > The DP->HDMI adaptor may simply be degrading the signal quality too > > much. According to the DP dual mode spec we're supposed to limit the > > TMDS clock based on the type of adapter used, but currently we have > > no code to do that. I've cooked up a few patches that should do what > > we want: > > git://github.com/vsyrjala/linux.git dp_dual_mode > > > > I've quickly tested it locally, and it seemed to do the right thing > > with a few different types of adaptors. > > I've run 32fa589 for a few hours now and it have not seen a single > blank or flicker. So it seems you've nailed it - thanks a lot! Excellent. > > Let me know if you want me to test more patches, post debug logs, or > anything else. Well, just to check the details of your particular cable/dongle, maybe you can post the dmesg with drm.debug=0xe with my branch? Or at least the parts that refer to DP dual mode adaptors. > > BTW, also discovered right before you sent that e-mail that downgrading > to a 1920x1080i mode (rather than the monitor's native 1920x1080) would > also stop the flickering. I'd assume that also fits well with your > diagnosis (less bandwidth needed => better tolerance for degraded signal > quality), but I thought I'd let you know in case not. Yeah, interlaced requires half the bandwidth of progressive, so it should then fit comfortably within the 165MHz limit of the adaptor. > > > > By the way: Is it possible to disable HDMI 12bpc in a way that > > > doesn't require me to patch and rebuild the kernel drivers, such as > > > a kernel module parameter or sysfs setting? (I prefer to simply use > > > the upstream Fedora kernel RPMs, but this issue is currently making > > > that impossible.) > > > > We don't have any knob to control this. > > I don't need it anymore, so no worries. ;-) > > Tore -- Ville Syrjälä Intel OTC _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
