Re: [PATCH 2/2] drm/i915/display: Don't wait for vblank for LUT DSB programming

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Tue, Feb 25, 2025 at 11:39:05PM +0530, Chaitanya Kumar Borah wrote:
> >From PTL, LUT registers are made double buffered. With this change,
> we don't need to wait for vblank to program them. Start DSB1 for
> programming them without waiting for vblank.
> 
> Signed-off-by: Chaitanya Kumar Borah <chaitanya.kumar.borah@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_display.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
> index 919e236a9650..9c3fdfcd6759 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -7352,6 +7352,7 @@ static void intel_atomic_dsb_finish(struct intel_atomic_state *state,
>  {
>  	struct intel_crtc_state *new_crtc_state =
>  		intel_atomic_get_new_crtc_state(state, crtc);
> +	struct intel_display *display = to_intel_display(state);
>  
>  	if (!new_crtc_state->use_dsb && !new_crtc_state->dsb_color_vblank)
>  		return;
> @@ -7408,7 +7409,8 @@ static void intel_atomic_dsb_finish(struct intel_atomic_state *state,
>  
>  	if (new_crtc_state->dsb_color_vblank)
>  		intel_dsb_chain(state, new_crtc_state->dsb_commit,
> -				new_crtc_state->dsb_color_vblank, true);
> +				new_crtc_state->dsb_color_vblank,
> +				HAS_DOUBLE_BUFFERED_LUT(display) ? false : true);

Using chaining for this is a bit ugly. GOSUB would seem more
appropriate. Here's a quick 1h effort to implement the basics
for that (completely untested):
https://github.com/vsyrjala/linux.git dsb_gosub

>  
>  	intel_dsb_finish(new_crtc_state->dsb_commit);
>  }
> -- 
> 2.25.1

-- 
Ville Syrjälä
Intel