| Message ID | 1251211217-7816-1-git-send-email-netrolller.3d@gmail.com (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
2009/8/25 Gábor Stefanik <netrolller.3d@gmail.com>: > The Qdiv roundup routine is essentially a fixed-point > division algorithm, using only integer math. > However, the version in the specs had a major error > that has been recently fixed (a missing quotient++). > > Replace Qdiv roundup with a rewritten, simplified version. Hi! > @@ -1042,20 +1042,14 @@ static u32 lpphy_qdiv_roundup(u32 dividend, u32 divisor, u8 precision) >     quotient = dividend / divisor; >     remainder = dividend % divisor; > > -    rbit = divisor & 0x1; > -    roundup = (divisor >> 1) + rbit; > - >     while (precision != 0) { > -        tmp = remainder - roundup; >         quotient <<= 1; > -        if (remainder >= roundup) > -            remainder = (tmp << 1) + rbit; > -        else > -            remainder <<= 1; > +        quotient |= (remainder << 1) / divisor; > +        remainder = (remainder << 1) % divisor; >         precision--; >     } Unless precision is 0, this just added a bunch of divides into the inner loop, which might be a big surprise to anyone expecting this to be fast...
On Tuesday 25 August 2009 16:40:17 Gábor Stefanik wrote: > The Qdiv roundup routine is essentially a fixed-point > division algorithm, using only integer math. > However, the version in the specs had a major error > that has been recently fixed (a missing quotient++). > > Replace Qdiv roundup with a rewritten, simplified version. Don't we have some sort of standard library function somewhere in the kernel for this? If not, what about creating one? > > Signed-off-by: Gábor Stefanik <netrolller.3d@gmail.com> > --- > drivers/net/wireless/b43/phy_lp.c | 14 ++++---------- > 1 files changed, 4 insertions(+), 10 deletions(-) > > diff --git a/drivers/net/wireless/b43/phy_lp.c b/drivers/net/wireless/b43/phy_lp.c > index 7e70c07..d0280d5 100644 > --- a/drivers/net/wireless/b43/phy_lp.c > +++ b/drivers/net/wireless/b43/phy_lp.c > @@ -1034,7 +1034,7 @@ static int lpphy_loopback(struct b43_wldev *dev) > > static u32 lpphy_qdiv_roundup(u32 dividend, u32 divisor, u8 precision) > { > - u32 quotient, remainder, rbit, roundup, tmp; > + u32 quotient, remainder; > > if (divisor == 0) > return 0; > @@ -1042,20 +1042,14 @@ static u32 lpphy_qdiv_roundup(u32 dividend, u32 divisor, u8 precision) > quotient = dividend / divisor; > remainder = dividend % divisor; > > - rbit = divisor & 0x1; > - roundup = (divisor >> 1) + rbit; > - > while (precision != 0) { > - tmp = remainder - roundup; > quotient <<= 1; > - if (remainder >= roundup) > - remainder = (tmp << 1) + rbit; > - else > - remainder <<= 1; > + quotient |= (remainder << 1) / divisor; > + remainder = (remainder << 1) % divisor; > precision--; > } > > - if (remainder >= roundup) > + if (remainder << 1 >= divisor) > quotient++; > > return quotient;
diff --git a/drivers/net/wireless/b43/phy_lp.c b/drivers/net/wireless/b43/phy_lp.c index 7e70c07..d0280d5 100644 --- a/drivers/net/wireless/b43/phy_lp.c +++ b/drivers/net/wireless/b43/phy_lp.c @@ -1034,7 +1034,7 @@ static int lpphy_loopback(struct b43_wldev *dev) static u32 lpphy_qdiv_roundup(u32 dividend, u32 divisor, u8 precision) { - u32 quotient, remainder, rbit, roundup, tmp; + u32 quotient, remainder; if (divisor == 0) return 0; @@ -1042,20 +1042,14 @@ static u32 lpphy_qdiv_roundup(u32 dividend, u32 divisor, u8 precision) quotient = dividend / divisor; remainder = dividend % divisor; - rbit = divisor & 0x1; - roundup = (divisor >> 1) + rbit; - while (precision != 0) { - tmp = remainder - roundup; quotient <<= 1; - if (remainder >= roundup) - remainder = (tmp << 1) + rbit; - else - remainder <<= 1; + quotient |= (remainder << 1) / divisor; + remainder = (remainder << 1) % divisor; precision--; } - if (remainder >= roundup) + if (remainder << 1 >= divisor) quotient++; return quotient;
The Qdiv roundup routine is essentially a fixed-point division algorithm, using only integer math. However, the version in the specs had a major error that has been recently fixed (a missing quotient++). Replace Qdiv roundup with a rewritten, simplified version. Signed-off-by: Gábor Stefanik <netrolller.3d@gmail.com> --- drivers/net/wireless/b43/phy_lp.c | 14 ++++---------- 1 files changed, 4 insertions(+), 10 deletions(-)