> -----Original Message-----
> From: Intel-gfx <intel-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx> On Behalf Of Ville
> Syrjala
> Sent: Wednesday, March 20, 2024 9:34 PM
> To: intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> Subject: [PATCH 2/6] drm/i915: Reject async flips if we need to change
> DDB/watermarks
>
> From: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
>
> DDB/watermarks are always double buffered on the vblank, so we can't safely
> change them during async flips. Currently this never happens, but we'll be
> making changing between sync and async flips a bit more flexible, in which case
> we can actually end up here.
Rather on getting wm/DDB changes should we switch from async to sync flip to honour the wm/DDB changes else might end up in underrun or flicker/corruption.
Spec is also aligned to this approach.
Thanks and Regards,
Arun R Murthy
--------------------
>
> Signed-off-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/display/skl_watermark.c | 12 ++++++++++++
> 1 file changed, 12 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/display/skl_watermark.c
> b/drivers/gpu/drm/i915/display/skl_watermark.c
> index bc341abcab2f..1fa416a70d51 100644
> --- a/drivers/gpu/drm/i915/display/skl_watermark.c
> +++ b/drivers/gpu/drm/i915/display/skl_watermark.c
> @@ -2540,6 +2540,12 @@ skl_ddb_add_affected_planes(const struct
> intel_crtc_state *old_crtc_state,
> &new_crtc_state-
> >wm.skl.plane_ddb_y[plane_id]))
> continue;
>
> + if (new_crtc_state->do_async_flip) {
> + drm_dbg_kms(&i915->drm, "[PLANE:%d:%s] Can't
> change DDB during async flip\n",
> + plane->base.base.id, plane->base.name);
> + return -EINVAL;
> + }
> +
> plane_state = intel_atomic_get_plane_state(state, plane);
> if (IS_ERR(plane_state))
> return PTR_ERR(plane_state);
> @@ -2906,6 +2912,12 @@ static int skl_wm_add_affected_planes(struct
> intel_atomic_state *state,
> &new_crtc_state-
> >wm.skl.optimal))
> continue;
>
> + if (new_crtc_state->do_async_flip) {
> + drm_dbg_kms(&i915->drm, "[PLANE:%d:%s] Can't
> change watermarks during async flip\n",
> + plane->base.base.id, plane->base.name);
> + return -EINVAL;
> + }
> +
> plane_state = intel_atomic_get_plane_state(state, plane);
> if (IS_ERR(plane_state))
> return PTR_ERR(plane_state);
> --
> 2.43.2
