pm2fb: pixclock setting restriction

This patch adds restrictions to calculations of m, n and p factors
which sets the pixclock for the Permedia 2V. I found during tests
that synchronization is unstable if m (divisor) is bigger than
half of the n (numerator). The patch disallows such settings
combination.

Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Antonino Daplas <adaplas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/drivers/video/pm2fb.c b/drivers/video/pm2fb.c
index 6f634e3ae60da882067db71786f7932cee48adce..2a8ba6022d3db409555948e44d60497c68ee1698 100644 (file)
--- a/drivers/video/pm2fb.c
+++ b/drivers/video/pm2fb.c
@@ -302,10 +302,10 @@ static void pm2v_mnp(u32 clk, unsigned char* mm, unsigned char* nn,
        s32 delta = 1000;
 
        *mm = *nn = *pp = 0;
-       for (n = 1; n; n++) {
-               for ( m = 1; m; m++) {
+       for ( m = 1; m < 128; m++) {
+               for (n = 2 * m + 1; n; n++) {
                        for ( p = 0; p < 2; p++) {
-                               f = PM2_REFERENCE_CLOCK * n / (m * (1 << (p + 1)));
+                               f = ( PM2_REFERENCE_CLOCK >> ( p + 1 )) * n / m;
                                if ( clk > f - delta && clk < f + delta ) {
                                        delta = ( clk > f ) ? clk - f : f - clk;
                                        *mm=m;