b43: LP-PHY: Fix and simplify Qdiv roundup

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>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

diff --git a/drivers/net/wireless/b43/phy_lp.c b/drivers/net/wireless/b43/phy_lp.c
index 7e70c078475b0c34a41cc32ee69c7206191ccaef..5306f2c66b34001717d2b085b5aaef3c50b29a27 100644 (file)
--- a/drivers/net/wireless/b43/phy_lp.c
+++ b/drivers/net/wireless/b43/phy_lp.c
@@ -1032,9 +1032,10 @@ static int lpphy_loopback(struct b43_wldev *dev)
        return index;
 }
 
+/* Fixed-point division algorithm using only integer math. */
 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 +1043,16 @@ 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;
+       while (precision > 0) {
                quotient <<= 1;
-               if (remainder >= roundup)
-                       remainder = (tmp << 1) + rbit;
-               else
-                       remainder <<= 1;
+               if (remainder << 1 >= divisor) {
+                       quotient++;
+                       remainder = (remainder << 1) - divisor;
+               }
                precision--;
        }
 
-       if (remainder >= roundup)
+       if (remainder << 1 >= divisor)
                quotient++;
 
        return quotient;