On Thu, May 04, 2017 at 02:21:26PM -0600, Daniel Drake wrote: > Hi, > > Numerous Asus desktops and All-in-one computers (e.g. D520MT) have a > regression on Linux 4.9 where the VGA output is shown all-white. > > This is a regression caused by: > > commit 0ce140d45a8398b501934ac289aef0eb7f47c596 > Author: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx> > Date: Tue Oct 11 20:52:47 2016 +0300 > > drm/i915: Clean up DDI DDC/AUX CH sanitation > > > On these platforms, the VGA output is detected as DP (presumably > theres a DP-to-VGA converter on the motherboard). The sanitization > done by the code that was removed here was correctly realising that > port E's DP aux channel was DP_AUX_A, so it disabled DP output on port > A, also showing this message: > > [drm:intel_ddi_init] VBT says port A is not DVI/HDMI/DP compatible, > respect it > > But after this cleanup commit, both port A and port E are activated > and the screen shows all-white. Reverting the commit restores usable > VGA display output. > > The reason the new implementation doesn't catch the duplicate > configuration is because the new code only considers ports that are > present in the VBT where parse_ddi_port() has run on them (in order to > set that port's info->alternate_aux_channel). > > In this case, port A is not present in the VBT so it will not have > info->alternate_aux_channel set, and the new sanitize_aux_ch will run > on port E but will not consider any overlap with port A. > > debug logs from an affected kernel: > https://gist.github.com/dsd/7e56c9bca7b2345b678cfacdab30ec55 > > Should we modify sanitize_aux_ch to look at all aux channels, not only > for the ports specified in the VBT? Please check if commit bb1d132935c2 ("drm/i915/vbt: split out defaults that are set when there is no VBT") fixes things for you. -- Ville Syrjälä Intel OTC _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
