Re: [PATCH v3 03/12] drm/i915/display: Use async flip when available for initial plane config

[Jani Nikula <jani.nikula@linux.intel.com>]

On Thu, 03 Oct 2024, Maarten Lankhorst <maarten.lankhorst@linux.intel.com> wrote:
> I'm planning to reorder readout in the Xe sequence in such a way that
> interrupts will not be available, so just use an async flip.
>
> Since the new FB points to the same pages, it will not tear. It also
> has the benefit of perhaps being slightly faster.
>
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/display/skl_universal_plane.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/skl_universal_plane.c b/drivers/gpu/drm/i915/display/skl_universal_plane.c
> index fdb141cfa4274..73a3624e34098 100644
> --- a/drivers/gpu/drm/i915/display/skl_universal_plane.c
> +++ b/drivers/gpu/drm/i915/display/skl_universal_plane.c
> @@ -2800,7 +2800,7 @@ bool skl_fixup_initial_plane_config(struct intel_crtc *crtc,
>  		to_intel_plane_state(plane->base.state);
>  	enum plane_id plane_id = plane->id;
>  	enum pipe pipe = crtc->pipe;
> -	u32 base;
> +	u32 base, plane_ctl;
>  
>  	if (!plane_state->uapi.visible)
>  		return false;
> @@ -2814,7 +2814,16 @@ bool skl_fixup_initial_plane_config(struct intel_crtc *crtc,
>  	if (plane_config->base == base)
>  		return false;
>  
> +	/* Perform an async flip to the new surface. */
> +	plane_ctl = intel_read(i915, PLANE_CTL(pipe, plane_id));
> +	plane_ctl |= PLANE_CTL_ASYNC_FLIP;
> +
> +	intel_de_write(i915, PLANE_CTL(pipe, plane_id), plane_ctl);
>  	intel_de_write(i915, PLANE_SURF(pipe, plane_id), base);
>  
> -	return true;
> +	if (intel_de_wait_custom(i915, PLANE_SURFLIVE(pipe, plane_id), ~0U, base, 0, 40, NULL) < 0)

Why not just intel_de_wait()?

BR,
Jani.

> +		drm_warn(&i915->drm, "async flip timed out\n");
> +
> +	/* No need to vblank wait either */
> +	return false;
>  }

-- 
Jani Nikula, Intel