On Thu, Oct 19, 2017 at 01:08:05PM -0400, Alex Deucher wrote: > On Thu, Oct 19, 2017 at 12:32 PM, Rob Clark <robdclark@xxxxxxxxx> wrote: > > On Wed, Oct 18, 2017 at 4:06 PM, Lloyd Atkinson <latkinso@xxxxxxxxxxxxxx> wrote: > >> Hi folks, > >> > >> We're looking at 4K HDMI mode support, and noticed aspect ratio support > >> is in flux. > >> > >> Aspect ratio parsing was added to the mode: > >> https://patchwork.kernel.org/patch/9271401/ > >> > >> But later reverted: > >> https://patchwork.kernel.org/patch/9410765/ > >> > >> We're finding that since aspect ratio information isn't supported, modes > >> conflict, and the userspace isn't able to see the full list of modes. > >> > >> Similarly, there's a case where two modes differ only by aspect_ratio > >> and vrefresh. In drm_edid.c, within drm_display_mode_from_vic_index, > >> newmode->vrefresh is forcibly being cleared to 0. Since refresh rate is > >> forced to 0, and aspect ratio isn’t considered in general, the modes > >> collide and we can’t advertise one of the modes. > >> > >> https://github.com/torvalds/linux/blob/v4.14-rc4/drivers/gpu/drm/drm_edid.c#L3153 > >> > >> Have there been any follow-up discussions on this topic? > >> > >> What is the reason to clear the vrefresh within > >> drm_display_mode_from_vic_index? > > > > +Ville who might remember the history.. > > > > I don't remember if we found a userspace app that was broken, or if > > reverting was an "abundance of caution" thing (which is equally valid, > > it is basically impossible to track down and test "all of > > userspace"..) > > > > Wasn't there an issue with SNA? Exposing the aspect ratio flags broke sna, at least. -- Ville Syrjälä Intel OTC _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
