Further patch to support HDMI VRR over PCOM

[elise-ng]

A follow up to #128

Below patch will further support HDMI VRR (in addition to FreeSync) for devices that do not have FreeSync support but only HDMI VRR.

Tested 4K 240Hz VRR working on top of cachyos kernel 6.18.2, with the ugreen adapter and Alienware AW3225QF (this particular monitor only have gsync and hdmi vrr certification but not freesync, so #128 alone does not work)

https://gitlab.freedesktop.org/drm/amd/-/issues?sort=created_date&state=opened&search=vrr&first_page_size=20&show=eyJpaWQiOiI0ODA1IiwiZnVsbF9wYXRoIjoiZHJtL2FtZCIsImlkIjoxNDUxMzh9

(I'm not the original author of the patch, just reposting here for visibility; thanks!)

[1Naim]

Is the previous patch still needed with this recent patchset?

[Lawstorant]

Yes and no. Yes, it's till needed to support VRR for Chrontel CH7218 BUT it's a standalone work not depended on that other patch.

[elise-ng]

From my understanding:

#128 adds the ugreen adapter to the FreeSync over PCON allowlist

This patch adds support for displays with HDMI VRR over PCON

In practice, for a setup to work:

• the HDMI to DP adapter will have to be on the allowlist (which Add UGreen DP to HDMI adapter to amdgpu VRR whitelist #128 expands), and
• the display will have to support FreeSync (the status quo before this patch) or HDMI VRR (expanded with this patch)

[1Naim]

Alright, thanks for the comments!

As this new patchset touches a lot more common code I'd like to wait until it gets some comments from the mailing list. Sorry for tthe inconvenience.