On 2019-02-01 5:55 p.m., sylvain.bertrand@xxxxxxxxx wrote: > On Fri, Feb 01, 2019 at 09:20:56PM +0000, Wentland, Harry wrote: >> DRM's AUX code uses usleep_range in drm_dp_dpcd_access. > > My bad, forgot about the usleep_range switch. That said AUX_RETRY_INTERVAL is > 500 us, with a usleep_range top bound of 600 us. > > Then, it would mean DC DP timeout retries would happen after ~1ms, and drm > ~600us. Additionaly, it seems that the number of retries are 3 in drm code and > 7 in DC code. > DRM actually bumped this to 32 due to an issue with a Dell 4k display. > I may be wrong, but it seems DC code is much more "insisting" on auxchannel > (edid retrieval) and much more forgiving on monitor ability to timeout in > time (~1ms). > > If I did read the code the right way, it may be more reasonable to have similar > behavior in drm code than in DC code, right? > It depends. I wouldn't call one or the other more correct. I seem to remember that the DP spec is quite vague on these retries but I could be mistaken. Since our driver hasn't show any problems with the DRM code and I believe others (such as i915) also pass DP compliance without issues I wouldn't proactively change this. Harry _______________________________________________ amd-gfx mailing list amd-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/amd-gfx
