tridentfb: Blade3D clock fixes
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 <krzysztof.h1@wp.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/video/tridentfb.c b/drivers/video/tridentfb.c
index 138140b..854e2e5 100644
--- a/drivers/video/tridentfb.c
+++ b/drivers/video/tridentfb.c
@@ -672,15 +672,16 @@
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;