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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)/10)		/* 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, k;
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	ulong fmin, fvco, m, n, p, q;
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	double z;
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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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	vga->misc &= ~0x0C;
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	if(vga->f[0] == VgaFreq0){
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		/* nothing to do */;
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	}
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	else if(vga->f[0] == VgaFreq1)
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		vga->misc |= 0x04;
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	else
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		vga->misc |= 0x0C;
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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 = 8*RefFreq*(65-m)/(65-n)
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	 *	Fpll = Fvco/2**p
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	 * N and m are 6 bits, p is 2 bits. Constraints:
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	 *	110MHz <= Fvco <= 250MHz
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	 *	40 <= n <= 62
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	 *	 1 <= m <= 62
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	 *	 0 <= p <=  3
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	 * Should try to minimise n, m.
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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->m[0] = 0x15;
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	vga->n[0] = 0x18;
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	vga->p[0] = 3;
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	for(m = 62; m > 0; m--){
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		for(n = 62; n >= 40; n--){
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			fvco = 8*SCALE(RefFreq)*(65-m)/(65-n);
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			if(fvco < SCALE(110000000) || fvco > SCALE(250000000))
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				continue;
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			for(p = 0; 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->m[0] = m;
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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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	/*
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	 * Now the loop clock:
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	 * 	m is fixed;
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	 *	calculate n;
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	 *	set z to the lower bound (110MHz) and calculate p and q.
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	 */
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	vga->m[1] = 61;
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	if(ctlr->flag & Uenhanced)
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		k = 64/8;
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	else
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		k = 8/8;
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	n = 65 - 4*k;
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	fvco = (8*RefFreq*(65-vga->m[0]))/(65-vga->n[0]);
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	vga->f[1] = fvco;
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	z = 110.0*(65-n)/(4*(fvco/1000000.0)*k);
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	if(z <= 16){
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		for(p = 0; p < 4; p++){
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			if(1<<(p+1) > z)
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				break;
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		}
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		q = 0;
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	}
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	else{
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		p = 3;
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		q = (z - 16)/16 + 1;
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	}
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	vga->n[1] = n;
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	vga->p[1] = p;
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	vga->q[1] = q;
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	ctlr->flag |= Finit;
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}
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Ctlr tvp3026clock = {
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	"tvp3026clock",			/* 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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};