neofb: simplify clock calculation
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>
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5798712d60
Коммит
7fc80b7bd6
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@ -201,7 +201,6 @@ static int neoFindMode(int xres, int yres, int depth)
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*
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* Determine the closest clock frequency to the one requested.
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*/
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#define REF_FREQ 0xe517 /* 14.31818 in 20.12 fixed point */
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#define MAX_N 127
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#define MAX_D 31
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#define MAX_F 1
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@ -211,27 +210,24 @@ static void neoCalcVCLK(const struct fb_info *info,
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{
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int n, d, f;
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int n_best = 0, d_best = 0, f_best = 0;
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long f_best_diff = (0x7ffff << 12); /* 20.12 */
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long f_target = (freq << 12) / 1000; /* 20.12 */
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long f_best_diff = 0x7ffff;
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for (f = 0; f <= MAX_F; f++)
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for (n = 0; n <= MAX_N; n++)
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for (d = 0; d <= MAX_D; d++) {
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long f_out; /* 20.12 */
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long f_diff; /* 20.12 */
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for (d = 0; d <= MAX_D; d++)
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for (n = 0; n <= MAX_N; n++) {
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long f_out;
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long f_diff;
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f_out =
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((((n + 1) << 12) / ((d +
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1) *
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(1 << f))) >> 12)
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* REF_FREQ;
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f_diff = abs(f_out - f_target);
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if (f_diff < f_best_diff) {
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f_out = ((14318 * (n + 1)) / (d + 1)) >> f;
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f_diff = abs(f_out - freq);
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if (f_diff <= f_best_diff) {
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f_best_diff = f_diff;
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n_best = n;
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d_best = d;
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f_best = f;
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}
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if (f_out > freq)
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break;
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}
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if (info->fix.accel == FB_ACCEL_NEOMAGIC_NM2200 ||
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@ -248,11 +244,11 @@ static void neoCalcVCLK(const struct fb_info *info,
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par->VCLK3Denominator = d_best;
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#ifdef NEOFB_DEBUG
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printk("neoVCLK: f:%d NumLow=%d NumHi=%d Den=%d Df=%d\n",
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f_target >> 12,
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printk(KERN_DEBUG "neoVCLK: f:%ld NumLow=%d NumHi=%d Den=%d Df=%ld\n",
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freq,
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par->VCLK3NumeratorLow,
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par->VCLK3NumeratorHigh,
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par->VCLK3Denominator, f_best_diff >> 12);
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par->VCLK3Denominator, f_best_diff);
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#endif
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}
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