[PATCH 1/4] drm/i915/dsb: Allow DSB based updates without planes

[Shankar, Uma]

> -----Original Message-----
> From: Intel-xe <intel-xe-bounces at lists.freedesktop.org> On Behalf Of Ville Syrjala
> Sent: Wednesday, February 19, 2025 2:29 AM
> To: intel-gfx at lists.freedesktop.org
> Cc: intel-xe at lists.freedesktop.org
> Subject: [PATCH 1/4] drm/i915/dsb: Allow DSB based updates without planes
> 
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> We don't actually need any planes to get updated in order to perform the commit
> on the DSB. Allow DSB based updates even when we don't touch planes. The
> main benefit here is that pure LUT updates will now go through the DSB path and
> therefore we don't have to do vblank evasion/etc. on the CPU.
> 
> I think the reason I had this excluded was that I was originally contemplating using
> frame/flip timestamps as a way to complete the commits. But I had to scrap that
> idea when it turned out that those timestamp get corrupted when DSB is poking
> at random registers.

Looks Good to me.
Reviewed-by: Uma Shankar <uma.shankar at intel.com>

> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_display.c | 1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c
> b/drivers/gpu/drm/i915/display/intel_display.c
> index 065fdf6dbb88..8d46c092fa4d 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -7332,7 +7332,6 @@ static void intel_atomic_dsb_prepare(struct
> intel_atomic_state *state,
> 
>  	/* FIXME deal with everything */
>  	new_crtc_state->use_dsb =
> -		new_crtc_state->update_planes &&
>  		!new_crtc_state->do_async_flip &&
>  		(DISPLAY_VER(display) >= 20 || !new_crtc_state->has_psr) &&
>  		!new_crtc_state->scaler_state.scaler_users &&
> --
> 2.45.3