While studying the reason why kernel copy from NOR was so slow on our platform,
I realized U-Boot is pulling it from 32-bit NOR in 8-bit chunks needlessly.
bootm uses memmove() and that just takes the approach by default to move u8s
around.
This optimization prefers memcpy() implementation (done mostly in 32-bit reads
and writes) if there's no overlap in source and dest, resulting in a huge
speedup on our platform (480ms copy from 32-bit NOR ---> 140ms)
Signed-off-by: Andy Green <andy.gr...@linaro.org>
---
lib/string.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/lib/string.c b/lib/string.c
index c3ad055..96d66e0 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -542,13 +542,21 @@ void * memmove(void * dest,const void *src,size_t count)
if (src == dest)
return dest;
- if (dest <= src) {
+ if (dest < src) {
+
+ if ((unsigned long)dest + count <= (unsigned long)src)
+ return memcpy(dest, src, count);
+
tmp = (char *) dest;
s = (char *) src;
while (count--)
*tmp++ = *s++;
}
else {
+
+ if ((unsigned long)src + count <= (unsigned long)dest)
+ return memcpy(dest, src, count);
+
tmp = (char *) dest + count;
s = (char *) src + count;
while (count--)
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