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Commit 3f275ea3 authored by Krzysztof Helt's avatar Krzysztof Helt Committed by Linus Torvalds
Browse files

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: default avatarKrzysztof Helt <krzysztof.h1@wp.pl>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 6fb48823

drivers/video/tridentfb.c

+12 −12
Original line number Diff line number Diff line
@@ -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 */