[PATCH] tridentfb: Blade3D clock fixes

From: Krzysztof Helt <redacted>

This patch fixes following problems:
- does not allow the m parameter to reach 0 as
  it locks the graphics core (power cycle needed)
- for the newer chips (with new clock registers)
  does not allow of n / m ratio below 4 as it gives
  unstable image on the Blade3D core
- extend shift parameter (k) range  to 2 for the newer 
  chips to cope with the n /m >= 4 limit at low resolution
  (bandwidth) modes
- prefer modes with higher n / m ratio (higher k values)

Signed-off-by: Krzysztof Helt <redacted>

---
Another test, another patch...

diff -urp linux-old/drivers/video/tridentfb.c linux-new/drivers/video/tridentfb.c

--- linux-old/drivers/video/tridentfb.c	2008-05-30 20:43:03.416124771 +0200
+++ linux-new/drivers/video/tridentfb.c	2008-05-30 21:12:37.887397930 +0200

@@ -672,15 +672,16 @@ static void set_vclk(struct tridentfb_pa
 	unsigned long fi, d, di;
 	unsigned char best_m = 0, best_n = 0, best_k = 0;
 	unsigned char hi, lo;
+	unsigned char shift = !is_oldclock(par->chip_id) ? 2 : 1;
 
 	d = 20000;
-	for (k = 1; k >= 0; k--)
-		for (m = 0; m < 32; m++) {
-			n = 2 * (m + 2) - 8;
+	for (k = shift; k >= 0; k--)
+		for (m = 1; m < 32; m++) {
+			n = ((m + 2) << shift) - 8;
 			for (n = (n < 0 ? 0 : n); n < 122; n++) {
 				fi = ((14318l * (n + 8)) / (m + 2)) >> k;
 				di = abs(fi - freq);
-				if (di <= d) {
+				if (di < d || (di == d && k == best_k)) {
 					d = di;
 					best_n = n;
 					best_m = m;


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