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-rw-r--r--drivers/video/tdfxfb.c43
1 files changed, 31 insertions, 12 deletions
diff --git a/drivers/video/tdfxfb.c b/drivers/video/tdfxfb.c
index c34ba39b6f7e..c8b0be2d8715 100644
--- a/drivers/video/tdfxfb.c
+++ b/drivers/video/tdfxfb.c
@@ -317,30 +317,49 @@ static inline void do_setpalentry(struct tdfx_par *par, unsigned regno, u32 c)
317 317
318static u32 do_calc_pll(int freq, int* freq_out) 318static u32 do_calc_pll(int freq, int* freq_out)
319{ 319{
320 int m, n, k, best_m, best_n, best_k, f_cur, best_error; 320 int m, n, k, best_m, best_n, best_k, best_error;
321 int fref = 14318; 321 int fref = 14318;
322 322
323 /* this really could be done with more intelligence --
324 255*63*4 = 64260 iterations is silly */
325 best_error = freq; 323 best_error = freq;
326 best_n = best_m = best_k = 0; 324 best_n = best_m = best_k = 0;
327 for (n = 1; n < 256; n++) { 325
328 for (m = 1; m < 64; m++) { 326 for (k = 3; k >= 0; k--) {
329 for (k = 0; k < 4; k++) { 327 for (m = 63; m >= 0; m--) {
330 f_cur = fref*(n + 2)/(m + 2)/(1 << k); 328 /*
331 if (abs(f_cur - freq) < best_error) { 329 * Estimate value of n that produces target frequency
332 best_error = abs(f_cur-freq); 330 * with current m and k
333 best_n = n; 331 */
334 best_m = m; 332 int n_estimated = (freq * (m + 2) * (1 << k) / fref) - 2;
335 best_k = k; 333
334 /* Search neighborhood of estimated n */
335 for (n = max(0, n_estimated - 1);
336 n <= min(255, n_estimated + 1); n++) {
337 /*
338 * Calculate PLL freqency with current m, k and
339 * estimated n
340 */
341 int f = fref * (n + 2) / (m + 2) / (1 << k);
342 int error = abs (f - freq);
343
344 /*
345 * If this is the closest we've come to the
346 * target frequency then remember n, m and k
347 */
348 if (error < best_error) {
349 best_error = error;
350 best_n = n;
351 best_m = m;
352 best_k = k;
336 } 353 }
337 } 354 }
338 } 355 }
339 } 356 }
357
340 n = best_n; 358 n = best_n;
341 m = best_m; 359 m = best_m;
342 k = best_k; 360 k = best_k;
343 *freq_out = fref*(n + 2)/(m + 2)/(1 << k); 361 *freq_out = fref*(n + 2)/(m + 2)/(1 << k);
362
344 return (n << 8) | (m << 2) | k; 363 return (n << 8) | (m << 2) | k;
345} 364}
346 365