drm/amd/display: Add basic downscale and upscale valdiation

[Why]
Planes have downscaling limits and upscaling limits per format and DM
is expected to validate these using DC caps. We should fail atomic
check validation if we aren't capable of doing the scaling.

[How]
We don't currently create store which DC plane maps to which DRM plane
so we can't easily check the caps directly. For now add basic
constraints that cover the absolute min and max downscale / upscale
limits for most RGB and YUV formats across ASICs.

Leave a TODO indicating that these should really be done with DC caps.
We'll probably need to subclass DRM planes again in order to correctly
identify which DC plane maps to it.
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Acked-by: Bhawanpreet Lakha <Bhawanpreet Lakha@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -2389,6 +2389,8 @@ static const struct drm_encoder_funcs amdgpu_dm_encoder_funcs = {
 static int fill_dc_scaling_info(const struct drm_plane_state *state,
 				struct dc_scaling_info *scaling_info)
 {
+	int scale_w, scale_h;
+
 	memset(scaling_info, 0, sizeof(*scaling_info));
 
 	/* Source is fixed 16.16 but we ignore mantissa for now... */
@@ -2419,6 +2421,19 @@ static int fill_dc_scaling_info(const struct drm_plane_state *state,
 	/* DRM doesn't specify clipping on destination output. */
 	scaling_info->clip_rect = scaling_info->dst_rect;
 
+	/* TODO: Validate scaling per-format with DC plane caps */
+	scale_w = scaling_info->dst_rect.width * 1000 /
+		  scaling_info->src_rect.width;
+
+	if (scale_w < 250 || scale_w > 16000)
+		return -EINVAL;
+
+	scale_h = scaling_info->dst_rect.height * 1000 /
+		  scaling_info->src_rect.height;
+
+	if (scale_h < 250 || scale_h > 16000)
+		return -EINVAL;
+
 	/*
 	 * The "scaling_quality" can be ignored for now, quality = 0 has DC
 	 * assume reasonable defaults based on the format.