drm/vc4: plane: Remove subpixel positioning check

There is little harm in ignoring fractional coordinates
(they just get truncated).

Without this:
modetest -M vc4 -F tiles,gradient -s 32:1920x1080-60 -P89@74:1920x1080*.1.1@XR24

is rejected. We have the same issue in Kodi when trying to
use zoom options on video.

Note: even if all coordinates are fully integer. e.g.
src:[0,0,1920,1080] dest:[-10,-10,1940,1100]

it will still get rejected as drm_atomic_helper_check_plane_state
uses drm_rect_clip_scaled which transforms this to fractional src coords

Fixes: 21af94cf ("drm/vc4: Add support for scaling of display planes.")
Signed-off-by: Dom Cobley <popcornmix@gmail.com>
Link: https://lore.kernel.org/r/20220613144800.326124-5-maxime@cerno.techSigned-off-by: Maxime Ripard <maxime@cerno.tech>

drivers/gpu/drm/vc4/vc4_plane.c

@@ -341,7 +341,6 @@ static int vc4_plane_setup_clipping_and_scaling(struct drm_plane_state *state)
 	struct vc4_plane_state *vc4_state = to_vc4_plane_state(state);
 	struct drm_framebuffer *fb = state->fb;
 	struct drm_gem_cma_object *bo = drm_fb_cma_get_gem_obj(fb, 0);
-	u32 subpixel_src_mask = (1 << 16) - 1;
 	int num_planes = fb->format->num_planes;
 	struct drm_crtc_state *crtc_state;
 	u32 h_subsample = fb->format->hsub;
@@ -363,18 +362,15 @@ static int vc4_plane_setup_clipping_and_scaling(struct drm_plane_state *state)
 	for (i = 0; i < num_planes; i++)
 		vc4_state->offsets[i] = bo->paddr + fb->offsets[i];
 
-	/* We don't support subpixel source positioning for scaling. */
-	if ((state->src.x1 & subpixel_src_mask) ||
-	    (state->src.x2 & subpixel_src_mask) ||
-	    (state->src.y1 & subpixel_src_mask) ||
-	    (state->src.y2 & subpixel_src_mask)) {
-		return -EINVAL;
-	}
-
-	vc4_state->src_x = state->src.x1 >> 16;
-	vc4_state->src_y = state->src.y1 >> 16;
-	vc4_state->src_w[0] = (state->src.x2 - state->src.x1) >> 16;
-	vc4_state->src_h[0] = (state->src.y2 - state->src.y1) >> 16;
+	/*
+	 * We don't support subpixel source positioning for scaling,
+	 * but fractional coordinates can be generated by clipping
+	 * so just round for now
+	 */
+	vc4_state->src_x = DIV_ROUND_CLOSEST(state->src.x1, 1 << 16);
+	vc4_state->src_y = DIV_ROUND_CLOSEST(state->src.y1, 1 << 16);
+	vc4_state->src_w[0] = DIV_ROUND_CLOSEST(state->src.x2, 1 << 16) - vc4_state->src_x;
+	vc4_state->src_h[0] = DIV_ROUND_CLOSEST(state->src.y2, 1 << 16) - vc4_state->src_y;
 
 	vc4_state->crtc_x = state->dst.x1;
 	vc4_state->crtc_y = state->dst.y1;