[PATCH 3/6] drm/i915: Allow the initial async flip to change modifier

[Kulkarni, Vandita]

> -----Original Message-----
> From: Intel-gfx <intel-gfx-bounces at lists.freedesktop.org> On Behalf Of Ville
> Syrjala
> Sent: Wednesday, March 20, 2024 9:34 PM
> To: intel-gfx at lists.freedesktop.org
> Subject: [PATCH 3/6] drm/i915: Allow the initial async flip to change modifier
> 
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> With Xorg+modesetting on skl+ we see the following behaviour:
> 1. root pixmap is X-tiled
> 2. client submitted buffers can be Y-tiled (w/ 'Option "dmabuf_capable"') 3.
> we try to switch from the X-tiled buffer to the Y-tiled buffer
>    using an async flip (when vsync is disabled).
> 4. the async flip will be rejected by i915 due to the modifier change
> 
> Relax the rules a bit by turning the first async flip into a sync flip so that we
> can change the modifier if necessary. Note that we already convert the first
> async flip into a sync flip on adl+ in order to reprogram the watermarks.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---

LGTM.
Reviewed-by: Vandita Kulkarni <vandita.kulkarni at intel.com>

>  .../gpu/drm/i915/display/intel_atomic_plane.c    | 16 +++++++++++++---
>  drivers/gpu/drm/i915/display/intel_display.c     |  7 +++++++
>  2 files changed, 20 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_atomic_plane.c
> b/drivers/gpu/drm/i915/display/intel_atomic_plane.c
> index 76d77d5a0409..769010d0ebc4 100644
> --- a/drivers/gpu/drm/i915/display/intel_atomic_plane.c
> +++ b/drivers/gpu/drm/i915/display/intel_atomic_plane.c
> @@ -429,10 +429,20 @@ static bool intel_plane_do_async_flip(struct
> intel_plane *plane,
>  	 * In platforms after DISPLAY13, we might need to override
>  	 * first async flip in order to change watermark levels
>  	 * as part of optimization.
> -	 * So for those, we are checking if this is a first async flip.
> -	 * For platforms earlier than DISPLAY13 we always do async flip.
> +	 *
> +	 * And let's do this for all skl+ so that we can eg. change the
> +	 * modifier as well.
> +	 *
> +	 * TODO: For older platforms there is less reason to do this as
> +	 * only X-tile is supported with async flips, though we could
> +	 * extend this so other scanout parameters (stride/etc) could
> +	 * be changed as well...
> +	 *
> +	 * FIXME: Platforms with need_async_flip_disable_wa==true will
> +	 * now end up doing two sync flips initially. Would be nice to
> +	 * combine those into just the one sync flip...
>  	 */
> -	return DISPLAY_VER(i915) < 13 || old_crtc_state->uapi.async_flip;
> +	return DISPLAY_VER(i915) < 9 || old_crtc_state->uapi.async_flip;
>  }
> 
>  static bool i9xx_must_disable_cxsr(const struct intel_crtc_state
> *new_crtc_state, diff --git a/drivers/gpu/drm/i915/display/intel_display.c
> b/drivers/gpu/drm/i915/display/intel_display.c
> index d366a103a707..dbcda79cf53c 100644
> --- a/drivers/gpu/drm/i915/display/intel_display.c
> +++ b/drivers/gpu/drm/i915/display/intel_display.c
> @@ -6061,6 +6061,13 @@ static int intel_async_flip_check_hw(struct
> intel_atomic_state *state, struct in
>  			return -EINVAL;
>  		}
> 
> +		/*
> +		 * We turn the first async flip request into a sync flip
> +		 * so that we can reconfigure the plane (eg. change
> modifier).
> +		 */
> +		if (!new_crtc_state->do_async_flip)
> +			continue;
> +
>  		if (old_plane_state->view.color_plane[0].mapping_stride !=
>  		    new_plane_state->view.color_plane[0].mapping_stride) {
>  			drm_dbg_kms(&i915->drm,
> --
> 2.43.2