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)
 
 static u32 do_calc_pll(int freq, int* freq_out) 
 {
-        int m, n, k, best_m, best_n, best_k, f_cur, best_error;
+        int m, n, k, best_m, best_n, best_k, best_error;
         int fref = 14318;
   
-        /* this really could be done with more intelligence --
-           255*63*4 = 64260 iterations is silly */
         best_error = freq;
         best_n = best_m = best_k = 0;
-        for (n = 1; n < 256; n++) {
-                for (m = 1; m < 64; m++) {
-                        for (k = 0; k < 4; k++) {
-                                f_cur = fref*(n + 2)/(m + 2)/(1 << k);
-                                if (abs(f_cur - freq) < best_error) {
-                                        best_error = abs(f_cur-freq);
-                                        best_n = n;
-                                        best_m = m;
-                                        best_k = k;
+
+        for (k = 3; k >= 0; k--) {
+                for (m = 63; m >= 0; m--) {
+                        /*
+                         * Estimate value of n that produces target frequency
+                         * with current m and k
+                         */
+                        int n_estimated = (freq * (m + 2) * (1 << k) / fref) - 2;
+
+                        /* Search neighborhood of estimated n */
+                        for (n = max(0, n_estimated - 1);
+                                        n <= min(255, n_estimated + 1); n++) {
+                                /*
+                                 * Calculate PLL freqency with current m, k and
+                                 * estimated n
+                                 */
+                                int f = fref * (n + 2) / (m + 2) / (1 << k);
+                                int error = abs (f - freq);
+
+                                /*
+                                 *  If this is the closest we've come to the
+                                 * target frequency then remember n, m and k
+                                 */
+                                if (error  < best_error) {
+                                        best_error = error;
+                                        best_n     = n;
+                                        best_m     = m;
+                                        best_k     = k;
                                 }
                         }
                 }
         }
+
         n = best_n;
         m = best_m;
         k = best_k;
         *freq_out = fref*(n + 2)/(m + 2)/(1 << k);
+
         return (n << 8) | (m << 2) | k;
 }