Hi,
On Wed, Feb 23, 2022 at 10:05 AM Kieran Bingham kieran.bingham@ideasonboard.com 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