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authorMaarten Lankhorst <maarten.lankhorst@linux.intel.com>2018-05-03 13:22:14 +0200
committerMaarten Lankhorst <maarten.lankhorst@linux.intel.com>2018-05-04 11:09:54 +0200
commitf96bdf564f3e7511aecdd4c35cc18ac5e0750a2f (patch)
treee0b610aaad29b30bf9af55abbb72821b43c0307f /drivers/gpu/drm/drm_rect.c
parent6f96f2000ac27b0f5f769b0bc2f0440ebfa1c3a3 (diff)
downloadlinux-f96bdf564f3e7511aecdd4c35cc18ac5e0750a2f.tar.bz2
drm/rect: Handle rounding errors in drm_rect_clip_scaled, v3.
Instead of relying on a scale which may increase rounding errors, clip src by doing: src * (dst - clip) / dst and rounding the result away from 1, so the new coordinates get closer to 1. We won't need to fix up with a magic macro afterwards, because our scaling factor will never go to the other side of 1. Changes since v1: - Adjust dst immediately, else drm_rect_width/height on dst gives bogus results. Change since v2: - Get rid of macros and use 64-bits math. Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com> [mlankhorst: Add Villes comment, and rename newsrc to tmp. (Ville)] Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20180503112217.37292-3-maarten.lankhorst@linux.intel.com
Diffstat (limited to 'drivers/gpu/drm/drm_rect.c')
-rw-r--r--drivers/gpu/drm/drm_rect.c49
1 files changed, 36 insertions, 13 deletions
diff --git a/drivers/gpu/drm/drm_rect.c b/drivers/gpu/drm/drm_rect.c
index a8e934795c7d..8c057829b804 100644
--- a/drivers/gpu/drm/drm_rect.c
+++ b/drivers/gpu/drm/drm_rect.c
@@ -50,13 +50,25 @@ bool drm_rect_intersect(struct drm_rect *r1, const struct drm_rect *r2)
}
EXPORT_SYMBOL(drm_rect_intersect);
+static u32 clip_scaled(u32 src, u32 dst, u32 clip)
+{
+ u64 tmp = mul_u32_u32(src, dst - clip);
+
+ /*
+ * Round toward 1.0 when clipping so that we don't accidentally
+ * change upscaling to downscaling or vice versa.
+ */
+ if (src < (dst << 16))
+ return DIV_ROUND_UP_ULL(tmp, dst);
+ else
+ return DIV_ROUND_DOWN_ULL(tmp, dst);
+}
+
/**
* drm_rect_clip_scaled - perform a scaled clip operation
* @src: source window rectangle
* @dst: destination window rectangle
* @clip: clip rectangle
- * @hscale: horizontal scaling factor
- * @vscale: vertical scaling factor
*
* Clip rectangle @dst by rectangle @clip. Clip rectangle @src by the
* same amounts multiplied by @hscale and @vscale.
@@ -66,33 +78,44 @@ EXPORT_SYMBOL(drm_rect_intersect);
* %false otherwise
*/
bool drm_rect_clip_scaled(struct drm_rect *src, struct drm_rect *dst,
- const struct drm_rect *clip,
- int hscale, int vscale)
+ const struct drm_rect *clip)
{
int diff;
diff = clip->x1 - dst->x1;
if (diff > 0) {
- int64_t tmp = src->x1 + (int64_t) diff * hscale;
- src->x1 = clamp_t(int64_t, tmp, INT_MIN, INT_MAX);
+ u32 new_src_w = clip_scaled(drm_rect_width(src),
+ drm_rect_width(dst), diff);
+
+ src->x1 = clamp_t(int64_t, src->x2 - new_src_w, INT_MIN, INT_MAX);
+ dst->x1 = clip->x1;
}
diff = clip->y1 - dst->y1;
if (diff > 0) {
- int64_t tmp = src->y1 + (int64_t) diff * vscale;
- src->y1 = clamp_t(int64_t, tmp, INT_MIN, INT_MAX);
+ u32 new_src_h = clip_scaled(drm_rect_height(src),
+ drm_rect_height(dst), diff);
+
+ src->y1 = clamp_t(int64_t, src->y2 - new_src_h, INT_MIN, INT_MAX);
+ dst->y1 = clip->y1;
}
diff = dst->x2 - clip->x2;
if (diff > 0) {
- int64_t tmp = src->x2 - (int64_t) diff * hscale;
- src->x2 = clamp_t(int64_t, tmp, INT_MIN, INT_MAX);
+ u32 new_src_w = clip_scaled(drm_rect_width(src),
+ drm_rect_width(dst), diff);
+
+ src->x2 = clamp_t(int64_t, src->x1 + new_src_w, INT_MIN, INT_MAX);
+ dst->x2 = clip->x2;
}
diff = dst->y2 - clip->y2;
if (diff > 0) {
- int64_t tmp = src->y2 - (int64_t) diff * vscale;
- src->y2 = clamp_t(int64_t, tmp, INT_MIN, INT_MAX);
+ u32 new_src_h = clip_scaled(drm_rect_height(src),
+ drm_rect_height(dst), diff);
+
+ src->y2 = clamp_t(int64_t, src->y1 + new_src_h, INT_MIN, INT_MAX);
+ dst->y2 = clip->y2;
}
- return drm_rect_intersect(dst, clip);
+ return drm_rect_visible(dst);
}
EXPORT_SYMBOL(drm_rect_clip_scaled);