| Message ID | 20200313000638.10548-1-rasmus.villemoes@prevas.dk |
|---|---|
| State | Accepted |
| Commit | 7ddea756540b5adddfde3b890fa46a40c649e68f |
| Headers | show |
| Series | spi: use is_power_of_2 instead of hweight32 in spi_nor_write() | expand |
Hi, On 13/03/20 5:36 am, Rasmus Villemoes wrote: > hweight32 is a somewhat expensive way to check for power-of-2. Use the > is_power_of_2 helper, which does the standard and cheap idiom > foo&(foo-1)==0. > > add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-96 (-96) > Function old new delta > spi_nor_write 388 292 -96 > > Signed-off-by: Rasmus Villemoes <rasmus.villemoes at prevas.dk> Acked-by: Vignesh Raghavendra <vigneshr at ti.com> > --- > drivers/mtd/spi/spi-nor-core.c | 5 +---- > 1 file changed, 1 insertion(+), 4 deletions(-) > > diff --git a/drivers/mtd/spi/spi-nor-core.c b/drivers/mtd/spi/spi-nor-core.c > index eb49a6c11c..4076646225 100644 > --- a/drivers/mtd/spi/spi-nor-core.c > +++ b/drivers/mtd/spi/spi-nor-core.c > @@ -1240,11 +1240,8 @@ static int spi_nor_write(struct mtd_info *mtd, loff_t to, size_t len, > * If page_size is a power of two, the offset can be quickly > * calculated with an AND operation. On the other cases we > * need to do a modulus operation (more expensive). > - * Power of two numbers have only one bit set and we can use > - * the instruction hweight32 to detect if we need to do a > - * modulus (do_div()) or not. > */ > - if (hweight32(nor->page_size) == 1) { > + if (is_power_of_2(nor->page_size)) { > page_offset = addr & (nor->page_size - 1); > } else { > u64 aux = addr; >
diff --git a/drivers/mtd/spi/spi-nor-core.c b/drivers/mtd/spi/spi-nor-core.c index eb49a6c11c..4076646225 100644 --- a/drivers/mtd/spi/spi-nor-core.c +++ b/drivers/mtd/spi/spi-nor-core.c @@ -1240,11 +1240,8 @@ static int spi_nor_write(struct mtd_info *mtd, loff_t to, size_t len, * If page_size is a power of two, the offset can be quickly * calculated with an AND operation. On the other cases we * need to do a modulus operation (more expensive). - * Power of two numbers have only one bit set and we can use - * the instruction hweight32 to detect if we need to do a - * modulus (do_div()) or not. */ - if (hweight32(nor->page_size) == 1) { + if (is_power_of_2(nor->page_size)) { page_offset = addr & (nor->page_size - 1); } else { u64 aux = addr;
hweight32 is a somewhat expensive way to check for power-of-2. Use the is_power_of_2 helper, which does the standard and cheap idiom foo&(foo-1)==0. add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-96 (-96) Function old new delta spi_nor_write 388 292 -96 Signed-off-by: Rasmus Villemoes <rasmus.villemoes at prevas.dk> --- drivers/mtd/spi/spi-nor-core.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-)