amd/display: remove ChromeOS workaround

This reverts commits ddab8bd7 ("drm/amd/display: Fix two cursor duplication
when using overlay") and e7d9560a ("Revert "drm/amd/display: Fix overlay
validation by considering cursors"").

tl;dr ChromeOS uses the atomic interface for everything except the cursor. This
is incorrect and forces amdgpu to disable some hardware features. Let's revert
the ChromeOS-specific workaround in mainline and allow the Chrome team to keep
it internally in their own tree.

See [1] for more details. This patch is an alternative to [2], which added
ChromeOS detection.

[1]: https://lore.kernel.org/amd-gfx/JIQ_93_cHcshiIDsrMU1huBzx9P9LVQxucx8hQArpQu7Wk5DrCl_vTXj_Q20m_L-8C8A5dSpNcSJ8ehfcCrsQpfB5QG_Spn14EYkH9chtg0=@emersion.fr/
[2]: https://lore.kernel.org/amd-gfx/20211011151609.452132-1-contact@emersion.fr/Signed-off-by: Simon Ser <contact@emersion.fr>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Harry Wentland <hwentlan@amd.com>
Cc: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Cc: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>
Cc: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Cc: Sean Paul <seanpaul@chromium.org>
Fixes: ddab8bd7 ("drm/amd/display: Fix two cursor duplication when using overlay")
Fixes: e7d9560a ("Revert "drm/amd/display: Fix overlay validation by considering cursors"")
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c

@@ -10627,53 +10627,6 @@ static int add_affected_mst_dsc_crtcs(struct drm_atomic_state *state, struct drm
 }
 #endif
 
-static int validate_overlay(struct drm_atomic_state *state)
-{
-	int i;
-	struct drm_plane *plane;
-	struct drm_plane_state *new_plane_state;
-	struct drm_plane_state *primary_state, *overlay_state = NULL;
-
-	/* Check if primary plane is contained inside overlay */
-	for_each_new_plane_in_state_reverse(state, plane, new_plane_state, i) {
-		if (plane->type == DRM_PLANE_TYPE_OVERLAY) {
-			if (drm_atomic_plane_disabling(plane->state, new_plane_state))
-				return 0;
-
-			overlay_state = new_plane_state;
-			continue;
-		}
-	}
-
-	/* check if we're making changes to the overlay plane */
-	if (!overlay_state)
-		return 0;
-
-	/* check if overlay plane is enabled */
-	if (!overlay_state->crtc)
-		return 0;
-
-	/* find the primary plane for the CRTC that the overlay is enabled on */
-	primary_state = drm_atomic_get_plane_state(state, overlay_state->crtc->primary);
-	if (IS_ERR(primary_state))
-		return PTR_ERR(primary_state);
-
-	/* check if primary plane is enabled */
-	if (!primary_state->crtc)
-		return 0;
-
-	/* Perform the bounds check to ensure the overlay plane covers the primary */
-	if (primary_state->crtc_x < overlay_state->crtc_x ||
-	    primary_state->crtc_y < overlay_state->crtc_y ||
-	    primary_state->crtc_x + primary_state->crtc_w > overlay_state->crtc_x + overlay_state->crtc_w ||
-	    primary_state->crtc_y + primary_state->crtc_h > overlay_state->crtc_y + overlay_state->crtc_h) {
-		DRM_DEBUG_ATOMIC("Overlay plane is enabled with hardware cursor but does not fully cover primary plane\n");
-		return -EINVAL;
-	}
-
-	return 0;
-}
-
 /**
  * amdgpu_dm_atomic_check() - Atomic check implementation for AMDgpu DM.
  * @dev: The DRM device
@@ -10855,10 +10808,6 @@ static int amdgpu_dm_atomic_check(struct drm_device *dev,
 			goto fail;
 	}
 
-	ret = validate_overlay(state);
-	if (ret)
-		goto fail;
-
 	/* Add new/modified planes */
 	for_each_oldnew_plane_in_state_reverse(state, plane, old_plane_state, new_plane_state, i) {
 		ret = dm_update_plane_state(dc, state, plane,