drm/i915: Implement proper clipping for video sprites

Properly clip the source when the destination gets clipped
by the pipe dimensions.

Sadly the video sprite hardware is rather limited so it can't do proper
sub-pixel postitioning. Resort to truncating the source coordinates to
(macro)pixel boundary.

The scaling checks are done using the strict drm_region functions.
Which means that an error is returned when the min/max scaling
ratios are exceeded.

Also do some additional checking against various hardware limits.

v2: Truncate src coords instead of rounding to avoid increasing src
    viewport size, and adapt to changes in drm_calc_{h,v}scale().
v3: Adapt to drm_region->drm_rect rename. Fix misaligned crtc_w for
    packed YUV formats when scaling isn't supported.
v4: Use stricter scaling checks, use drm_rect_equals()
v5: If sprite is below min size, make it invisible instead returning
    an error.
    Use WARN_ON() instead if BUG_ON(), and add one to sanity check the
    src viewport size.
v6: Add comments to remind about src and dst coordinate types
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_sprite.c

@@ -32,6 +32,7 @@
 #include <drm/drmP.h>
 #include <drm/drm_crtc.h>
 #include <drm/drm_fourcc.h>
+#include <drm/drm_rect.h>
 #include "intel_drv.h"
 #include <drm/i915_drm.h>
 #include "i915_drv.h"
@@ -583,6 +584,20 @@ ilk_get_colorkey(struct drm_plane *plane, struct drm_intel_sprite_colorkey *key)
 		key->flags = I915_SET_COLORKEY_NONE;
 }
 
+static bool
+format_is_yuv(uint32_t format)
+{
+	switch (format) {
+	case DRM_FORMAT_YUYV:
+	case DRM_FORMAT_UYVY:
+	case DRM_FORMAT_VYUY:
+	case DRM_FORMAT_YVYU:
+		return true;
+	default:
+		return false;
+	}
+}
+
 static int
 intel_update_plane(struct drm_plane *plane, struct drm_crtc *crtc,
 		   struct drm_framebuffer *fb, int crtc_x, int crtc_y,
@@ -600,9 +615,29 @@ intel_update_plane(struct drm_plane *plane, struct drm_crtc *crtc,
 	enum transcoder cpu_transcoder = intel_pipe_to_cpu_transcoder(dev_priv,
 								      pipe);
 	int ret = 0;
-	int x = src_x >> 16, y = src_y >> 16;
-	int primary_w = crtc->mode.hdisplay, primary_h = crtc->mode.vdisplay;
 	bool disable_primary = false;
+	bool visible;
+	int hscale, vscale;
+	int max_scale, min_scale;
+	int pixel_size = drm_format_plane_cpp(fb->pixel_format, 0);
+	struct drm_rect src = {
+		/* sample coordinates in 16.16 fixed point */
+		.x1 = src_x,
+		.x2 = src_x + src_w,
+		.y1 = src_y,
+		.y2 = src_y + src_h,
+	};
+	struct drm_rect dst = {
+		/* integer pixels */
+		.x1 = crtc_x,
+		.x2 = crtc_x + crtc_w,
+		.y1 = crtc_y,
+		.y2 = crtc_y + crtc_h,
+	};
+	const struct drm_rect clip = {
+		.x2 = crtc->mode.hdisplay,
+		.y2 = crtc->mode.vdisplay,
+	};
 
 	intel_fb = to_intel_framebuffer(fb);
 	obj = intel_fb->obj;
@@ -618,19 +653,23 @@ intel_update_plane(struct drm_plane *plane, struct drm_crtc *crtc,
 	intel_plane->src_w = src_w;
 	intel_plane->src_h = src_h;
 
-	src_w = src_w >> 16;
-	src_h = src_h >> 16;
-
 	/* Pipe must be running... */
-	if (!(I915_READ(PIPECONF(cpu_transcoder)) & PIPECONF_ENABLE))
+	if (!(I915_READ(PIPECONF(cpu_transcoder)) & PIPECONF_ENABLE)) {
+		DRM_DEBUG_KMS("Pipe disabled\n");
 		return -EINVAL;
+	}
 
-	if (crtc_x >= primary_w || crtc_y >= primary_h)
+	/* Don't modify another pipe's plane */
+	if (intel_plane->pipe != intel_crtc->pipe) {
+		DRM_DEBUG_KMS("Wrong plane <-> crtc mapping\n");
 		return -EINVAL;
+	}
 
-	/* Don't modify another pipe's plane */
-	if (intel_plane->pipe != intel_crtc->pipe)
+	/* FIXME check all gen limits */
+	if (fb->width < 3 || fb->height < 3 || fb->pitches[0] > 16384) {
+		DRM_DEBUG_KMS("Unsuitable framebuffer for plane\n");
 		return -EINVAL;
+	}
 
 	/* Sprite planes can be linear or x-tiled surfaces */
 	switch (obj->tiling_mode) {
@@ -638,55 +677,115 @@ intel_update_plane(struct drm_plane *plane, struct drm_crtc *crtc,
 		case I915_TILING_X:
 			break;
 		default:
+			DRM_DEBUG_KMS("Unsupported tiling mode\n");
 			return -EINVAL;
 	}
 
-	/*
-	 * Clamp the width & height into the visible area.  Note we don't
-	 * try to scale the source if part of the visible region is offscreen.
-	 * The caller must handle that by adjusting source offset and size.
-	 */
-	if ((crtc_x < 0) && ((crtc_x + crtc_w) > 0)) {
-		crtc_w += crtc_x;
-		crtc_x = 0;
+	max_scale = intel_plane->max_downscale << 16;
+	min_scale = intel_plane->can_scale ? 1 : (1 << 16);
+
+	hscale = drm_rect_calc_hscale(&src, &dst, min_scale, max_scale);
+	if (hscale < 0) {
+		DRM_DEBUG_KMS("Horizontal scaling factor out of limits\n");
+		drm_rect_debug_print(&src, true);
+		drm_rect_debug_print(&dst, false);
+
+		return hscale;
 	}
-	if ((crtc_x + crtc_w) <= 0) /* Nothing to display */
-		goto out;
-	if ((crtc_x + crtc_w) > primary_w)
-		crtc_w = primary_w - crtc_x;
 
-	if ((crtc_y < 0) && ((crtc_y + crtc_h) > 0)) {
-		crtc_h += crtc_y;
-		crtc_y = 0;
+	vscale = drm_rect_calc_vscale(&src, &dst, min_scale, max_scale);
+	if (vscale < 0) {
+		DRM_DEBUG_KMS("Vertical scaling factor out of limits\n");
+		drm_rect_debug_print(&src, true);
+		drm_rect_debug_print(&dst, false);
+
+		return vscale;
 	}
-	if ((crtc_y + crtc_h) <= 0) /* Nothing to display */
-		goto out;
-	if (crtc_y + crtc_h > primary_h)
-		crtc_h = primary_h - crtc_y;
 
-	if (!crtc_w || !crtc_h) /* Again, nothing to display */
-		goto out;
+	visible = drm_rect_clip_scaled(&src, &dst, &clip, hscale, vscale);
 
-	/*
-	 * We may not have a scaler, eg. HSW does not have it any more
-	 */
-	if (!intel_plane->can_scale && (crtc_w != src_w || crtc_h != src_h))
-		return -EINVAL;
+	crtc_x = dst.x1;
+	crtc_y = dst.y1;
+	crtc_w = drm_rect_width(&dst);
+	crtc_h = drm_rect_height(&dst);
 
-	/*
-	 * We can take a larger source and scale it down, but
-	 * only so much...  16x is the max on SNB.
-	 */
-	if (((src_w * src_h) / (crtc_w * crtc_h)) > intel_plane->max_downscale)
-		return -EINVAL;
+	if (visible) {
+		/* Make the source viewport size an exact multiple of the scaling factors. */
+		drm_rect_adjust_size(&src,
+				     drm_rect_width(&dst) * hscale - drm_rect_width(&src),
+				     drm_rect_height(&dst) * vscale - drm_rect_height(&src));
+
+		/* sanity check to make sure the src viewport wasn't enlarged */
+		WARN_ON(src.x1 < (int) src_x ||
+			src.y1 < (int) src_y ||
+			src.x2 > (int) (src_x + src_w) ||
+			src.y2 > (int) (src_y + src_h));
+
+		/*
+		 * Hardware doesn't handle subpixel coordinates.
+		 * Adjust to (macro)pixel boundary, but be careful not to
+		 * increase the source viewport size, because that could
+		 * push the downscaling factor out of bounds.
+		 *
+		 * FIXME Should we be really strict and reject the
+		 * config if it results in non (macro)pixel aligned
+		 * coords?
+		 */
+		src_x = src.x1 >> 16;
+		src_w = drm_rect_width(&src) >> 16;
+		src_y = src.y1 >> 16;
+		src_h = drm_rect_height(&src) >> 16;
+
+		if (format_is_yuv(fb->pixel_format)) {
+			src_x &= ~1;
+			src_w &= ~1;
+
+			/*
+			 * Must keep src and dst the
+			 * same if we can't scale.
+			 */
+			if (!intel_plane->can_scale)
+				crtc_w &= ~1;
+
+			if (crtc_w == 0)
+				visible = false;
+		}
+	}
+
+	/* Check size restrictions when scaling */
+	if (visible && (src_w != crtc_w || src_h != crtc_h)) {
+		unsigned int width_bytes;
+
+		WARN_ON(!intel_plane->can_scale);
+
+		/* FIXME interlacing min height is 6 */
+
+		if (crtc_w < 3 || crtc_h < 3)
+			visible = false;
+
+		if (src_w < 3 || src_h < 3)
+			visible = false;
+
+		width_bytes = ((src_x * pixel_size) & 63) + src_w * pixel_size;
+
+		if (src_w > 2048 || src_h > 2048 ||
+		    width_bytes > 4096 || fb->pitches[0] > 4096) {
+			DRM_DEBUG_KMS("Source dimensions exceed hardware limits\n");
+			return -EINVAL;
+		}
+	}
+
+	dst.x1 = crtc_x;
+	dst.x2 = crtc_x + crtc_w;
+	dst.y1 = crtc_y;
+	dst.y2 = crtc_y + crtc_h;
 
 	/*
 	 * If the sprite is completely covering the primary plane,
 	 * we can disable the primary and save power.
 	 */
-	if ((crtc_x == 0) && (crtc_y == 0) &&
-	    (crtc_w == primary_w) && (crtc_h == primary_h))
-		disable_primary = true;
+	disable_primary = drm_rect_equals(&dst, &clip);
+	WARN_ON(disable_primary && !visible);
 
 	mutex_lock(&dev->struct_mutex);
 
@@ -708,8 +807,12 @@ intel_update_plane(struct drm_plane *plane, struct drm_crtc *crtc,
 	if (!disable_primary)
 		intel_enable_primary(crtc);
 
-	intel_plane->update_plane(plane, fb, obj, crtc_x, crtc_y,
-				  crtc_w, crtc_h, x, y, src_w, src_h);
+	if (visible)
+		intel_plane->update_plane(plane, fb, obj,
+					  crtc_x, crtc_y, crtc_w, crtc_h,
+					  src_x, src_y, src_w, src_h);
+	else
+		intel_plane->disable_plane(plane);
 
 	if (disable_primary)
 		intel_disable_primary(crtc);
@@ -732,7 +835,6 @@ intel_update_plane(struct drm_plane *plane, struct drm_crtc *crtc,
 
 out_unlock:
 	mutex_unlock(&dev->struct_mutex);
-out:
 	return ret;
 }