From 7258064b16ab4f44db708670f63c88db8b3f2eea Mon Sep 17 00:00:00 2001
From: Thomas Zimmermann <tzimmermann@suse.de>
Date: Mon, 26 Aug 2019 09:53:38 +0200
Subject: prefetch shadow buffer two lines ahead of blit offset

---
 drivers/gpu/drm/drm_fb_helper.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index a7ba5b4902d6..61cf436840c7 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -33,6 +33,7 @@
 #include <linux/dma-buf.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
+#include <linux/prefetch.h>
 #include <linux/slab.h>
 #include <linux/sysrq.h>
 #include <linux/vmalloc.h>
@@ -390,6 +391,8 @@ static void drm_fb_helper_dirty_blit_real(struct drm_fb_helper *fb_helper,
 	unsigned int y;
 
 	for (y = clip->y1; y < clip->y2; y++) {
+		if (y < clip->y2 - 2)
+			prefetch_range(src + 2 * fb->pitches[0], len);
 		memcpy(dst, src, len);
 		src += fb->pitches[0];
 		dst += fb->pitches[0];
-- 
2.22.0