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#include <u.h>
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#include <libc.h>
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#include <bio.h>
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#include "pci.h"
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#include "vga.h"
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#define SCALE(f)	((f)/1)		/* could be /10 */
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static void
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init(Vga* vga, Ctlr* ctlr)
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{
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	int f;
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	ulong d, dmax, fmin, fvco, n, nmax, p;
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	if(ctlr->flag & Finit)
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		return;
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	if(vga->f[0] == 0)
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		vga->f[0] = vga->mode->frequency;
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	/*
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	 * Look for values of n, d and p that give
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	 * the least error for
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	 *	Fvco = RefFreq*((n+2)*8)/(d+2)
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	 *	Fpll = Fvco/2**p
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	 * N and d are 7-bits, p is 2-bits. Constraints:
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	 *	RefFreq/(n+2) > 1MHz
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	 *	110MHz <= Fvco <= 220MHz
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	 *	n, d >= 1
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	 * Should try to minimise n, d.
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	 *
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	 * There's nothing like brute force and ignorance.
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	 */
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	fmin = vga->f[0];
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	vga->d[0] = 6;
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	vga->n[0] = 5;
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	vga->p[0] = 2;
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	dmax = (RefFreq/1000000)-2;
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	for(d = 1; d < dmax; d++){
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		/*
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		 * Calculate an upper bound on n
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		 * to satisfy the condition
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		 *	Fvco <= 220MHz
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		 * This will hopefully prevent arithmetic
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		 * overflow.
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		 */
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		nmax = ((220000000+RefFreq)*(d+2))/(RefFreq*8) - 2;
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		for(n = 1; n < nmax; n++){
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			fvco = SCALE(RefFreq)*((n+2)*8)/(d+2);
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			if(fvco < SCALE(110000000) || fvco > SCALE(220000000))
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				continue;
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			for(p = 1; p < 4; p++){
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				f = SCALE(vga->f[0]) - (fvco>>p);
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				if(f < 0)
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					f = -f;
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				if(f < fmin){
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					fmin = f;
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					vga->d[0] = d;
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					vga->n[0] = n;
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					vga->p[0] = p;
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				}
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			}
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		}
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	}
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	ctlr->flag |= Finit;
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}
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Ctlr tvp3025clock = {
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	"tvp3025clock",			/* name */
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	0,				/* snarf */
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	0,				/* options */
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	init,				/* init */
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	0,				/* load */
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	0,				/* dump */
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};