Re: [PATCH v2 1/2] drm/i915/fbc: keep FBC disabled if selective update is on in xe2lpd

["Hogander, Jouni" <jouni.hogander@intel.com>]

On Fri, 2025-03-21 at 11:45 +0200, Vinod Govindapillai wrote:
> FBC was disabled in case PSR2 selective update in display 12 to
> 14 as part of a wa. From xe2lpd onwards there is a logic to be
> implemented to decide between FBC and selective update. Until
> that logic is implemented keep FBC disabled in case selective
> update is enabled.
> 
> v1: updated patch description and some explanation and todo
> 
> Signed-off-by: Vinod Govindapillai <vinod.govindapillai@intel.com>

Reviewed-by: Jouni Högander <jouni.hogander@intel.com>

> ---
>  drivers/gpu/drm/i915/display/intel_fbc.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_fbc.c
> b/drivers/gpu/drm/i915/display/intel_fbc.c
> index b6978135e8ad..92b00da4c0ab 100644
> --- a/drivers/gpu/drm/i915/display/intel_fbc.c
> +++ b/drivers/gpu/drm/i915/display/intel_fbc.c
> @@ -1464,13 +1464,15 @@ static int intel_fbc_check_plane(struct
> intel_atomic_state *state,
>  	 * Recommendation is to keep this combination disabled
>  	 * Bspec: 50422 HSD: 14010260002
>  	 *
> -	 * In Xe3, PSR2 selective fetch and FBC dirty rect feature
> cannot
> -	 * coexist. So if PSR2 selective fetch is supported then
> mark that
> -	 * FBC is not supported.
> -	 * TODO: Need a logic to decide between PSR2 and FBC Dirty
> rect
> +	 * TODO: Implement a logic to select between PSR2 selective
> fetch and
> +	 * FBC based on Bspec: 68881 in xe2lpd onwards.
> +	 *
> +	 * As we still see some strange underruns in those platforms
> while
> +	 * disabling PSR2, keep FBC disabled in case of selective
> update is on
> +	 * until the selection logic is implemented.
>  	 */
> -	if ((IS_DISPLAY_VER(display, 12, 14) ||
> HAS_FBC_DIRTY_RECT(display)) &&
> -	    crtc_state->has_sel_update && !crtc_state-
> >has_panel_replay) {
> +	if (DISPLAY_VER(display) >= 12 && crtc_state->has_sel_update
> &&
> +	    !crtc_state->has_panel_replay) {
>  		plane_state->no_fbc_reason = "PSR2 enabled";
>  		return 0;
>  	}