From 086567f12e1188c57e061a53825a5eff5a7923a0 Mon Sep 17 00:00:00 2001 From: Pavel Machek Date: Fri, 21 Apr 2017 12:51:07 +0200 Subject: [PATCH] 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 Signed-off-by: Boris Brezillon --- drivers/mtd/nand/nand_base.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c index ed08e3946727..79d98c9fa8a7 100644 --- a/drivers/mtd/nand/nand_base.c +++ b/drivers/mtd/nand/nand_base.c @@ -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; -- 2.20.1