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mtd: nand: Optimize checking of erased buffers 

If we see ~0UL in flash, there's no need for hweight, and no need to
check number of bitflips. So this should be net win.

Signed-off-by: Pavel Machek <pavel@denx.de>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
This commit is contained in:
Pavel Machek 2017-04-21 12:51:07 +02:00 committed by Boris Brezillon
parent 838ff7b333
commit 086567f12e
1 changed files with 4 additions and 1 deletions
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5
drivers/mtd/nand/nand_base.c
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@ -1421,7 +1421,10 @@ static int nand_check_erased_buf(void *buf, int len, int bitflips_threshold)
for (; len >= sizeof(long);
len -= sizeof(long), bitmap += sizeof(long)) {
weight = hweight_long(*((unsigned long *)bitmap));
unsigned long d = *((unsigned long *)bitmap);
if (d == ~0UL)
continue;
weight = hweight_long(d);
bitflips += BITS_PER_LONG - weight;
if (unlikely(bitflips > bitflips_threshold))
return -EBADMSG;