[Intel-gfx] [PATCH 4/4] drm/i915/dp: Limit max_requested_bpc based on src DSC bpc limits

[Ville Syrjälä]

On Thu, Oct 26, 2023 at 11:24:38AM +0530, Nautiyal, Ankit K wrote:
> 
> On 10/25/2023 6:20 PM, Ville Syrjälä wrote:
> > On Wed, Oct 25, 2023 at 05:43:18PM +0530, Ankit Nautiyal wrote:
> >> At the moment the max requested bpc is limited to 6 to 10/12.
> >> For platforms that support DSC, min and max src bpc with DSC are
> >> different.
> >>
> >> Account for DSC bpc limitations, when setting min and max value for
> >> max_requested_bpc property.
> > NAK. DSC capabiliies change dynamically, the property does not.
> 
> Hmm, perhaps I should remove the check for sink DSC support and have 
> only Platform check HAS_DSC.
> 
> The problem I am trying to fix is that our HW does not support DSC with 
> 6bpc, but we are allowing the max_requested_bpc to be 6 bpc.
> 
> This can be a problem with some eDP panels that support modes like 
> 4k at 120 which will always need DSC and when max requested bpc property is 
> set to 6.
> 
> I am wondering how to avoid this. Does it make sense to have the min 
> value for the max_requested_bpc to be 8, for platforms that support DSC?

I think the easy fix is to just use 'min_bpc = max(dsc_min_bpc, max_bpc*3)'
with DSC. And likely we should do something like that for YCbCr output
as well.

-- 
Ville Syrjälä
Intel