tridentfb: improve clock setting accuracy

Improve clock calculation precision (to kHz from MHz) and removes parameter
field vclk from the tridentfb_par structure.

Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
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 982eeee..beefab2 100644 (file)
--- a/drivers/video/tridentfb.c
+++ b/drivers/video/tridentfb.c
@@ -27,7 +27,6 @@
 #define VERSION                "0.7.8-NEWAPI"
 
 struct tridentfb_par {
-       int vclk;               /* in MHz */
        void __iomem *io_virt;  /* iospace virtual memory address */
 };
 
@@ -669,27 +668,26 @@ static void set_screen_start(int base)
                 (read3X4(CRTHiOrd) & 0xF8) | ((base & 0xE0000) >> 17));
 }
 
-/* Use 20.12 fixed-point for NTSC value and frequency calculation */
-#define calc_freq(n, m, k)  ( ((unsigned long)0xE517 * (n + 8) / ((m + 2) * (1 << k))) >> 12 )
-
 /* Set dotclock frequency */
-static void set_vclk(int freq)
+static void set_vclk(unsigned long freq)
 {
        int m, n, k;
-       int f, fi, d, di;
+       unsigned long f, fi, d, di;
        unsigned char lo = 0, hi = 0;
 
-       d = 20;
+       d = 20000;
        for (k = 2; k >= 0; k--)
                for (m = 0; m < 63; m++)
                        for (n = 0; n < 128; n++) {
-                               fi = calc_freq(n, m, k);
+                               fi = ((14318l * (n + 8)) / (m + 2)) >> k;
                                if ((di = abs(fi - freq)) < d) {
                                        d = di;
                                        f = fi;
                                        lo = n;
                                        hi = (k << 6) | m;
                                }
+                               if (fi > freq)
+                                       break;
                        }
        if (chip3D) {
                write3C4(ClockHigh, hi);
@@ -888,6 +886,8 @@ static int tridentfb_set_par(struct fb_info *info)
        struct fb_var_screeninfo *var = &info->var;
        int bpp = var->bits_per_pixel;
        unsigned char tmp;
+       unsigned long vclk;
+
        debug("enter\n");
        hdispend = var->xres / 8 - 1;
        hsyncstart = (var->xres + var->right_margin) / 8;
@@ -1014,11 +1014,11 @@ static int tridentfb_set_par(struct fb_info *info)
        write3X4(Performance, 0x92);
        write3X4(PCIReg, 0x07);         /* MMIO & PCI read and write burst enable */
 
-       /* convert from picoseconds to MHz */
-       par->vclk = 1000000 / info->var.pixclock;
+       /* convert from picoseconds to kHz */
+       vclk = PICOS2KHZ(info->var.pixclock);
        if (bpp == 32)
-               par->vclk *= 2;
-       set_vclk(par->vclk);
+               vclk *= 2;
+       set_vclk(vclk);
 
        write3C4(0, 3);
        write3C4(1, 1);         /* set char clock 8 dots wide */