[CPUFREQ] Longhaul - Fix guess_fsb function

This is bug reported by John-Marc Chandonia:
> Detected 1002.292 MHz processor.
> longhaul: VIA C3 'Nehemiah B' [C5N] CPU detected.  Powersaver supported.
> longhaul: Using throttling support.
> longhaul: Invalid (reserved) FSB!
FSB is correcly guessed for 999.554 MHz CPU.
To fix this error:
- ROUNDING should be range, not mask - at it's current value it is +7 -8,
- more precise calculations inside guess_fsb - 7.5x133MHz is 1000MHz now.

Signed-off-by: Rafal Bilski <rafalbilski@interia.pl>
Signed-off-by: Dave Jones <davej@redhat.com>

1 files changed, 10 insertions, 22 deletions

diff --git a/arch/i386/kernel/cpu/cpufreq/longhaul.c b/arch/i386/kernel/cpu/cpufreq/longhaul.c
index 8ea34e951ea3..8b5ad308d656 100644
--- a/arch/i386/kernel/cpu/cpufreq/longhaul.c
+++ b/arch/i386/kernel/cpu/cpufreq/longhaul.c
@@ -318,31 +318,19 @@ static void longhaul_setstate(unsigned int clock_ratio_index)
 
 #define ROUNDING        0xf
 
-static int _guess(int guess, int mult)
-{
-        int target;
-
-        target = ((mult/10)*guess);
-        if (mult%10 != 0)
-                target += (guess/2);
-        target += ROUNDING/2;
-        target &= ~ROUNDING;
-        return target;
-}
-
-
 static int guess_fsb(int mult)
 {
-        int speed = (cpu_khz/1000);
+        int speed = cpu_khz / 1000;
         int i;
-        int speeds[] = { 66, 100, 133, 200 };
-
-        speed += ROUNDING/2;
-        speed &= ~ROUNDING;
-
-        for (i=0; i<4; i++) {
-                if (_guess(speeds[i], mult) == speed)
-                        return speeds[i];
+        int speeds[] = { 666, 1000, 1333, 2000 };
+        int f_max, f_min;
+
+        for (i = 0; i < 4; i++) {
+                f_max = ((speeds[i] * mult) + 50) / 100;
+                f_max += (ROUNDING / 2);
+                f_min = f_max - ROUNDING;
+                if ((speed <= f_max) && (speed >= f_min))
+                        return speeds[i] / 10;
         }
         return 0;
 }