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
--- 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 @@
(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 @@
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 @@
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 */
