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neofb: simplify clock calculation

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There is nothing to gain by converting value in kHz to fixed point MHz.
Just calculate everything in kHz.

A reorder of the loop allows reducing number of iterations (check if
frequency is not too high already).

Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Krzysztof Helt 2008-07-23 21:31:44 -07:00 committed by Linus Torvalds
parent 5798712d60
commit 7fc80b7bd6
1 changed files with 13 additions and 17 deletions
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30
drivers/video/neofb.c
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@ -201,7 +201,6 @@ static int neoFindMode(int xres, int yres, int depth)
*
* Determine the closest clock frequency to the one requested.
*/
#define REF_FREQ 0xe517 /* 14.31818 in 20.12 fixed point */
#define MAX_N 127
#define MAX_D 31
#define MAX_F 1
@ -211,27 +210,24 @@ static void neoCalcVCLK(const struct fb_info *info,
{
int n, d, f;
int n_best = 0, d_best = 0, f_best = 0;
long f_best_diff = (0x7ffff << 12); /* 20.12 */
long f_target = (freq << 12) / 1000; /* 20.12 */
long f_best_diff = 0x7ffff;
for (f = 0; f <= MAX_F; f++)
for (n = 0; n <= MAX_N; n++)
for (d = 0; d <= MAX_D; d++) {
long f_out; /* 20.12 */
long f_diff; /* 20.12 */
for (d = 0; d <= MAX_D; d++)
for (n = 0; n <= MAX_N; n++) {
long f_out;
long f_diff;
f_out =
((((n + 1) << 12) / ((d +
1) *
(1 << f))) >> 12)
* REF_FREQ;
f_diff = abs(f_out - f_target);
if (f_diff < f_best_diff) {
f_out = ((14318 * (n + 1)) / (d + 1)) >> f;
f_diff = abs(f_out - freq);
if (f_diff <= f_best_diff) {
f_best_diff = f_diff;
n_best = n;
d_best = d;
f_best = f;
}
if (f_out > freq)
break;
}
if (info->fix.accel == FB_ACCEL_NEOMAGIC_NM2200 ||
@ -248,11 +244,11 @@ static void neoCalcVCLK(const struct fb_info *info,
par->VCLK3Denominator = d_best;
#ifdef NEOFB_DEBUG
printk("neoVCLK: f:%d NumLow=%d NumHi=%d Den=%d Df=%d\n",
f_target >> 12,
printk(KERN_DEBUG "neoVCLK: f:%ld NumLow=%d NumHi=%d Den=%d Df=%ld\n",
freq,
par->VCLK3NumeratorLow,
par->VCLK3NumeratorHigh,
par->VCLK3Denominator, f_best_diff >> 12);
par->VCLK3Denominator, f_best_diff);
#endif
}