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>

1 files changed, 8 insertions, 11 deletions

diff --git a/drivers/net/wireless/b43/phy_lp.c b/drivers/net/wireless/b43/phy_lp.c
index 7e70c078475b..5306f2c66b34 100644
--- 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;