drm/exynos: add generic check for plane state

This patch adds generic check for plane state - display area dimensions,
so drivers can always assume that they get valid plane state to set.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
diff --git a/drivers/gpu/drm/exynos/exynos_drm_plane.c b/drivers/gpu/drm/exynos/exynos_drm_plane.c
index b620d7a7..9eaa862 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_plane.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_plane.c
@@ -173,6 +173,36 @@
 	.atomic_destroy_state = exynos_drm_plane_destroy_state,
 };
 
+static int
+exynos_drm_plane_check_size(const struct exynos_drm_plane_config *config,
+			    struct exynos_drm_plane_state *state)
+{
+	bool width_ok = false, height_ok = false;
+
+	if (config->capabilities & EXYNOS_DRM_PLANE_CAP_SCALE)
+		return 0;
+
+	if (state->src.w == state->crtc.w)
+		width_ok = true;
+
+	if (state->src.h == state->crtc.h)
+		height_ok = true;
+
+	if ((config->capabilities & EXYNOS_DRM_PLANE_CAP_DOUBLE) &&
+	    state->h_ratio == (1 << 15))
+		width_ok = true;
+
+	if ((config->capabilities & EXYNOS_DRM_PLANE_CAP_DOUBLE) &&
+	    state->v_ratio == (1 << 15))
+		height_ok = true;
+
+	if (width_ok & height_ok)
+		return 0;
+
+	DRM_DEBUG_KMS("scaling mode is not supported");
+	return -ENOTSUPP;
+}
+
 static int exynos_plane_atomic_check(struct drm_plane *plane,
 				     struct drm_plane_state *state)
 {
@@ -187,6 +217,7 @@
 	/* translate state into exynos_state */
 	exynos_plane_mode_set(exynos_state);
 
+	ret = exynos_drm_plane_check_size(exynos_plane->config, exynos_state);
 	return ret;
 }