Variable Refresh Rate & flickering screens

[Harry Wentland]

On 2020-03-17 5:08 a.m., Simon Ser wrote:
> On Thursday, March 12, 2020 3:43 PM, Harry Wentland <hwentlan at amd.com> wrote:
> 
>> Not the main VRR expert and we're still discussing this internally but I
>> think it'll very much depend on the display whether you'll see flicker
>> in this case.
>>
>> The other complication is that for gaming we don't want to use the
>> cursor as a VRR trigger and only look at page flips in order to allow
>> for smooth gameplay. For a desktop use-case that's probably not the
>> right policy.
> 
> I think user-space can handle this and correctly synchronize cursor
> updates with game updates via the KMS atomic API.
> 
> However I still think flickering should be avoided by the hardware.
> Flickering is a completely separate issue and user-space shouldn't add
> workarounds for screen issues like this.
> 
> Do you think that would be acceptable? Do you have any "slew rate
> register" in AMD hardware?
> 

There are no slew rate registers in current AMD HW but I also think
slewing would best be done in kernel space, either directly in HW by HW
that supports it or in SW for HW that doesn't support it.

Harry

> Thanks,
> 
> Simon
>