tridentfb: various pixclock and timing improvements

This patch fixes few issues related to timings and pixclock generation:

 - disallow the pixclocks with numerator lower than
   double denominator. This fixes display instability
   for some modes.
 - choose the pixelclock with the highest
   numerator and denominator values. This improve
   image quality and fixes display instability
   for some modes.
 - make interlaced modes work.
 - set synchronization pulses polarization
   correctly.
 - horizontal synchronization timing are now
   the same as generated by X.

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>

1 files changed, 28 insertions, 7 deletions

diff --git a/drivers/video/tridentfb.c b/drivers/video/tridentfb.c
index d896dee7b487..ff82ec1e5e4d 100644
--- a/drivers/video/tridentfb.c
+++ b/drivers/video/tridentfb.c
@@ -680,10 +680,12 @@ static void set_vclk(struct tridentfb_par *par, unsigned long freq)
 
         d = 20000;
         for (k = 1; k >= 0; k--)
-                for (m = 0; m < 32; m++)
-                        for (n = 0; n < 122; n++) {
+                for (m = 0; m < 32; m++) {
+                        n = 2 * (m + 2) - 8;
+                        for (n = (n < 0 ? 0 : n); n < 122; n++) {
                                 fi = ((14318l * (n + 8)) / (m + 2)) >> k;
-                                if ((di = abs(fi - freq)) < d) {
+                                di = abs(fi - freq);
+                                if (di <= d) {
                                         d = di;
                                         best_n = n;
                                         best_m = m;
@@ -692,6 +694,7 @@ static void set_vclk(struct tridentfb_par *par, unsigned long freq)
                                 if (fi > freq)
                                         break;
                         }
+                }
 
         if (is_oldclock(par->chip_id)) {
                 lo = best_n | (best_m << 7);
@@ -977,8 +980,8 @@ static int tridentfb_set_par(struct fb_info *info)
 
         debug("enter\n");
         hdispend = var->xres / 8 - 1;
-        hsyncstart = (var->xres + var->right_margin) / 8 - 1;
-        hsyncend = (var->xres + var->right_margin + var->hsync_len) / 8 - 1;
+        hsyncstart = (var->xres + var->right_margin) / 8;
+        hsyncend = (var->xres + var->right_margin + var->hsync_len) / 8;
         htotal = (var->xres + var->left_margin + var->right_margin +
                   var->hsync_len) / 8 - 5;
         hblankstart = hdispend + 1;
@@ -991,8 +994,22 @@ static int tridentfb_set_par(struct fb_info *info)
         vblankstart = vdispend + 1;
         vblankend = vtotal;
 
+        if (info->var.vmode & FB_VMODE_INTERLACED) {
+                vtotal /= 2;
+                vdispend /= 2;
+                vsyncstart /= 2;
+                vsyncend /= 2;
+                vblankstart /= 2;
+                vblankend /= 2;
+        }
+
         crtc_unlock(par);
         write3CE(par, CyberControl, 8);
+        tmp = 0xEB;
+        if (var->sync & FB_SYNC_HOR_HIGH_ACT)
+                tmp &= ~0x40;
+        if (var->sync & FB_SYNC_VERT_HIGH_ACT)
+                tmp &= ~0x80;
 
         if (par->flatpanel && var->xres < nativex) {
                 /*
@@ -1000,7 +1017,7 @@ static int tridentfb_set_par(struct fb_info *info)
                  * than requested resolution decide whether
                  * we stretch or center
                  */
-                t_outb(par, 0xEB, VGA_MIS_W);
+                t_outb(par, tmp | 0xC0, VGA_MIS_W);
 
                 shadowmode_on(par);
 
@@ -1010,7 +1027,7 @@ static int tridentfb_set_par(struct fb_info *info)
                         screen_stretch(par);
 
         } else {
-                t_outb(par, 0x2B, VGA_MIS_W);
+                t_outb(par, tmp, VGA_MIS_W);
                 write3CE(par, CyberControl, 8);
         }
 
@@ -1071,6 +1088,10 @@ static int tridentfb_set_par(struct fb_info *info)
         tmp = (info->var.vmode & FB_VMODE_INTERLACED) ? 0x84 : 0x80;
         /* enable access extended memory */
         write3X4(par, CRTCModuleTest, tmp);
+        tmp = read3CE(par, MiscIntContReg) & ~0x4;
+        if (info->var.vmode & FB_VMODE_INTERLACED)
+                tmp |= 0x4;
+        write3CE(par, MiscIntContReg, tmp);
 
         /* enable GE for text acceleration */
         write3X4(par, GraphEngReg, 0x80);