Re: [PATCH 16/16] drm/amd/display: Don't restrict bpc to 8 bpc

[Pekka Paalanen <ppaalanen@gmail.com>]

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On Mon, 12 Dec 2022 13:21:37 -0500
Harry Wentland <harry.wentland@amd.com> wrote:

> This will let us pass kms_hdr.bpc_switch.
> 
> I don't see any good reasons why we still need to
> limit bpc to 8 bpc and doing so is problematic when
> we enable HDR.
> 
> If I remember correctly there might have been some
> displays out there where the advertised link bandwidth
> was not large enough to drive the default timing at
> max bpc. This would leave to an atomic commit/check
> failure which should really be handled in compositors
> with some sort of fallback mechanism.
> 
> If this somehow turns out to still be an issue I
> suggest we add a module parameter to allow users to
> limit the max_bpc to a desired value.
> 
> Signed-off-by: Harry Wentland <harry.wentland@amd.com>
> Cc: Pekka Paalanen <ppaalanen@gmail.com>
> Cc: Sebastian Wick <sebastian.wick@redhat.com>
> Cc: Vitaly.Prosyak@amd.com
> Cc: Uma Shankar <uma.shankar@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Joshua Ashton <joshua@froggi.es>
> Cc: dri-devel@lists.freedesktop.org
> Cc: amd-gfx@lists.freedesktop.org
> ---
>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index d0c071000a5d..396e345f5d6b 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -7115,7 +7115,7 @@ void amdgpu_dm_connector_init_helper(struct amdgpu_display_manager *dm,
>  		drm_connector_attach_max_bpc_property(&aconnector->base, 8, 16);
>  
>  	/* This defaults to the max in the range, but we want 8bpc for non-edp. */
> -	aconnector->base.state->max_bpc = (connector_type == DRM_MODE_CONNECTOR_eDP) ? 16 : 8;
> +	aconnector->base.state->max_bpc = 16;

Hi,

missed to delete the comment. If it really defaults, then can't you
just drop the assignment?

Acked-by: Pekka Paalanen <pekka.paalanen@collabora.com>


Thanks,
pq


>  	aconnector->base.state->max_requested_bpc = aconnector->base.state->max_bpc;
>  
>  	if (connector_type == DRM_MODE_CONNECTOR_eDP &&


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