Variable Refresh Rate & flickering screens

[Simon Ser]

On Wednesday, March 25, 2020 7:53 PM, Manasi Navare <manasi.d.navare at intel.com> wrote:

> But I am still figuring out how the panel indicates this restriction that we need to program
> in the HW registers.
>
> Harry/SImon, do you know of any such panels that have these restrictions and if they
> indicate this limitation or the maxshift through EDID or DPCD?

As far as I've understood, there is no such information exposed by the
connector. This is the main annoying thing with this slew rate: it
seems like we can only guess what slew rate to pick.

Hence Martin's proposal to add some properties to allow user-space to
tune this (with sane default values that work on most screens).

Another idea is to have a hwdb of "bad VRR screens", and only apply
a slew rate to these screens.

Not sure what the best would be yet. Having a lot of VRR screens to
test with could help getting a better understanding. I think AMD has a
certification program for FreeSync, maybe they have a flickering
requirement? (Something like "screen must not flicker if rate increases
or decreases by XXX Hz each vblank"?)

Simon