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/*
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 * IC Designs ICD2061A Dual Programmable Graphics Clock Generator.
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 */
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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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enum {
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	Prescale	= 2,			/* P counter prescale (default) */
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	NIndex		= 14,			/* number of index field values */
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};
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/*
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 * For an index value of x, the appropriate VCO range
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 * is >= index[x] && <= index[x+1]. The higher index is
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 * prefered if VCO is on a boundary.
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 */
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static ulong index[NIndex] = {
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	 50000000,
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	 51000000,
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	 53200000,
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	 58500000,
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	 60700000,
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	 64400000,
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	 66800000,
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	 73500000,
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	 75600000,
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	 80900000,
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	 83200000,
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	 91500000,
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	100000000,
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	120000000,
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};
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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, n;
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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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	if(vga->mode->z > 8)
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		error("depth %d not supported\n", vga->mode->z);
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	/*
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	 * Post-VCO divisor. Constraint:
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	 * 	50MHz <= vga->f <= 120MHz
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	 */
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	for(vga->p[0] = 0; vga->f[0] <= 50000000; vga->p[0]++)
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		vga->f[0] <<= 1;
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	/*
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	 * Determine index.
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	 */
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	for(vga->i[0] = NIndex-1; vga->f[0] < index[vga->i[0]] && vga->i[0]; vga->i[0]--)
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		;
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	/*
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	 * Denominator. Constraints:
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	 *	200KHz <= RefFreq/d <= 1MHz
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	 * and
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	 *	3 <= d <= 129
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	 *
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	 * Numerator. Constraint:
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	 *	4 <= n <= 130
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	 */
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	d = RefFreq/1000000 > 3 ? RefFreq/1000000: 3;
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	dmax = RefFreq/200000 < 129 ? RefFreq/200000: 129;
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	/*
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	 * Now look for values of p and q that give
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	 * the least error for
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	 *	vga->f = (Prescale*RefFreq*n/d);
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	 */
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	vga->d[0] = d;
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	vga->n[0] = 4;
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	for(fmin = vga->f[0]; d <= dmax; d++){
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		for(n = 4; n <= 130; n++){
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			f = vga->f[0] - (Prescale*RefFreq*n/d);
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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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			}
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		}
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	}
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	/*
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	 * The serial word to be loaded into the icd2061a is
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	 *	(2<<21)|(vga->i<<17)|((vga->n)<<10)|(vga->p<<7)|vga->d
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	 * Always select ICD2061A REG2.
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	 */
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	vga->f[0] = (Prescale*RefFreq*vga->n[0]/vga->d[0]);
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	vga->d[0] -= 2;
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	vga->n[0] -= 3;
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	ctlr->flag |= Finit;
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}
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Ctlr icd2061a = {
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	"icd2061a",
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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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};