Commit 02096a0c authored by Arnd Bergmann's avatar Arnd Bergmann Committed by Richard Weinberger
Browse files

mtd: ubi: avoid expensive do_div() on 32-bit machines 



The use of do_div() in ubi_nvmem_reg_read() makes calling it on
32-bit machines rather expensive. Since the 'from' variable is
known to be a 32-bit quantity, it is clearly never needed and
can be optimized into a regular division operation.

Fixes: b8a77b9a ("mtd: ubi: fix NVMEM over UBI volumes on 32-bit systems")
Fixes: 3ce48580 ("mtd: ubi: provide NVMEM layer over UBI volumes")
Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
Reviewed-by: default avatarZhihao Cheng <chengzhihao1@huawei.com>
Signed-off-by: default avatarRichard Weinberger <richard@nod.at>
parent 299af26e

drivers/mtd/ubi/nvmem.c

+3 −3
Original line number Diff line number Diff line
@@ -6,7 +6,6 @@ 
/* UBI NVMEM provider */

#include "ubi.h"

#include <linux/nvmem-provider.h>

#include <asm/div64.h>



/* List of all NVMEM devices */

static LIST_HEAD(nvmem_devices);
@@ -27,14 +26,15 @@ static int ubi_nvmem_reg_read(void *priv, unsigned int from, 
	struct ubi_nvmem *unv = priv;

	struct ubi_volume_desc *desc;

	uint32_t offs;

	uint64_t lnum = from;

	uint32_t lnum;

	int err = 0;



	desc = ubi_open_volume(unv->ubi_num, unv->vol_id, UBI_READONLY);

	if (IS_ERR(desc))

		return PTR_ERR(desc);



	offs = do_div(lnum, unv->usable_leb_size);

	offs = from % unv->usable_leb_size;

	lnum = from / unv->usable_leb_size;

	while (bytes_left) {

		to_read = unv->usable_leb_size - offs;