[PATCH v5 10/13] video: Only dcache flush damaged lines

[Alper Nebi Yasak]

From: Alexander Graf <agraf at csgraf.de>

Now that we have a damage area tells us which parts of the frame buffer
actually need updating, let's only dcache flush those on video_sync()
calls. With this optimization in place, frame buffer updates - especially
on large screen such as 4k displays - speed up significantly.

Signed-off-by: Alexander Graf <agraf at csgraf.de>
Reported-by: Da Xue <da at libre.computer>
[Alper: Use damage.xstart/yend, IS_ENABLED()]
Co-developed-by: Alper Nebi Yasak <alpernebiyasak at gmail.com>
Signed-off-by: Alper Nebi Yasak <alpernebiyasak at gmail.com>
---

Changes in v5:
- Use xstart, ystart, xend, yend as names for damage region
- Use IS_ENABLED() instead of CONFIG_IS_ENABLED()

Changes in v2:
- Fix dcache range; we were flushing too much before
- Remove ifdefs

 drivers/video/video-uclass.c | 41 +++++++++++++++++++++++++++++++-----
 1 file changed, 36 insertions(+), 5 deletions(-)

diff --git a/drivers/video/video-uclass.c b/drivers/video/video-uclass.c
index 8bfcbc88dda7..a50220bcc684 100644
--- a/drivers/video/video-uclass.c
+++ b/drivers/video/video-uclass.c
@@ -385,6 +385,41 @@ void video_damage(struct udevice *vid, int x, int y, int width, int height)
 	priv->damage.yend = max(yend, priv->damage.yend);
 }
 
+#if defined(CONFIG_ARM) && !CONFIG_IS_ENABLED(SYS_DCACHE_OFF)
+static void video_flush_dcache(struct udevice *vid)
+{
+	struct video_priv *priv = dev_get_uclass_priv(vid);
+
+	if (!priv->flush_dcache)
+		return;
+
+	if (!IS_ENABLED(CONFIG_VIDEO_DAMAGE)) {
+		flush_dcache_range((ulong)priv->fb,
+				   ALIGN((ulong)priv->fb + priv->fb_size,
+					 CONFIG_SYS_CACHELINE_SIZE));
+
+		return;
+	}
+
+	if (priv->damage.xend && priv->damage.yend) {
+		int lstart = priv->damage.xstart * VNBYTES(priv->bpix);
+		int lend = priv->damage.xend * VNBYTES(priv->bpix);
+		int y;
+
+		for (y = priv->damage.ystart; y < priv->damage.yend; y++) {
+			ulong fb = (ulong)priv->fb;
+			ulong start = fb + (y * priv->line_length) + lstart;
+			ulong end = start + lend - lstart;
+
+			start = ALIGN_DOWN(start, CONFIG_SYS_CACHELINE_SIZE);
+			end = ALIGN(end, CONFIG_SYS_CACHELINE_SIZE);
+
+			flush_dcache_range(start, end);
+		}
+	}
+}
+#endif
+
 /* Flush video activity to the caches */
 int video_sync(struct udevice *vid, bool force)
 {
@@ -404,11 +439,7 @@ int video_sync(struct udevice *vid, bool force)
 	 * out whether it exists? For now, ARM is safe.
 	 */
 #if defined(CONFIG_ARM) && !CONFIG_IS_ENABLED(SYS_DCACHE_OFF)
-	if (priv->flush_dcache) {
-		flush_dcache_range((ulong)priv->fb,
-				   ALIGN((ulong)priv->fb + priv->fb_size,
-					 CONFIG_SYS_CACHELINE_SIZE));
-	}
+	video_flush_dcache(vid);
 #elif defined(CONFIG_VIDEO_SANDBOX_SDL)
 	static ulong last_sync;
 
-- 
2.40.1