Hi, On Wed, Feb 23, 2022 at 10:05 AM Kieran Bingham <kieran.bingham@xxxxxxxxxxxxxxxx> wrote: > > > > > + /* For DisplayPort, disable scrambling mode. */ > > > > + if (pdata->bridge.type == DRM_MODE_CONNECTOR_DisplayPort) > > > > + regmap_update_bits(pdata->regmap, SN_TRAINING_SETTING_REG, > > > > + SCRAMBLE_DISABLE, SCRAMBLE_DISABLE); > > > > > > I'm assuming that this is the important part of your patch? Would be > > > sorta nice to include the "why" in your comment. Why do you want to > > > disable scrambling mode for DP but not for eDP? Maybe you care about > > > compatibility but not EMI if you're hooking up to random DP things? > > > > I'll investigate and include proper documentation in v2 (or drop the > > change altogether if it's not required). > > And indeed, this part is important. If I drop this hunk - then I get no > display output. > > I'm afraid I don't (yet) know the reasons 'why' to extend the comment, > beyond "Scrambling is not supported for DP". > > If anyone already does, please feel free to provide the text, and I'll > include it in the next revision, or I'll try to do some more digging > into this part. I don't know _tons_ about it, but I later learned that the "alternate" scrambler is used for eDP and the normal scrambler is used for DP. I don't have any background about why they are different other than what looks to be intentionally making the two things incompatible. ...so I guess that would make it pretty clear why you can't use the alternate scrambler for DP. I haven't personally done the research to know if you can be officially DP compliant with the scrambler disabled. I also don't know why the ti-sn65dsi86 makes it so difficult to switch to the standard scrambler or if it works at all... ;-) -Doug
