Subversion Repositories planix.SVN

/*
 * IC Designs ICD2061A Dual Programmable Graphics Clock Generator.
 */
#include <u.h>
#include <libc.h>
#include <bio.h>

#include "pci.h"
#include "vga.h"

enum {
        Prescale        = 2,                    /* P counter prescale (default) */
        NIndex          = 14,                   /* number of index field values */
};

/*
 * For an index value of x, the appropriate VCO range
 * is >= index[x] && <= index[x+1]. The higher index is
 * prefered if VCO is on a boundary.
 */
static ulong index[NIndex] = {
         50000000,
         51000000,
         53200000,
         58500000,
         60700000,
         64400000,
         66800000,
         73500000,
         75600000,
         80900000,
         83200000,
         91500000,
        100000000,
        120000000,
};

static void
init(Vga* vga, Ctlr* ctlr)
{
        int f;
        ulong d, dmax, fmin, n;

        if(ctlr->flag & Finit)
                return;

        if(vga->f[0] == 0)
                vga->f[0] = vga->mode->frequency;

        if(vga->mode->z > 8)
                error("depth %d not supported\n", vga->mode->z);

        /*
         * Post-VCO divisor. Constraint:
         *      50MHz <= vga->f <= 120MHz
         */
        for(vga->p[0] = 0; vga->f[0] <= 50000000; vga->p[0]++)
                vga->f[0] <<= 1;

        /*
         * Determine index.
         */
        for(vga->i[0] = NIndex-1; vga->f[0] < index[vga->i[0]] && vga->i[0]; vga->i[0]--)
                ;

        /*
         * Denominator. Constraints:
         *      200KHz <= RefFreq/d <= 1MHz
         * and
         *      3 <= d <= 129
         *
         * Numerator. Constraint:
         *      4 <= n <= 130
         */
        d = RefFreq/1000000 > 3 ? RefFreq/1000000: 3;
        dmax = RefFreq/200000 < 129 ? RefFreq/200000: 129;

        /*
         * Now look for values of p and q that give
         * the least error for
         *      vga->f = (Prescale*RefFreq*n/d);
         */
        vga->d[0] = d;
        vga->n[0] = 4;
        for(fmin = vga->f[0]; d <= dmax; d++){
                for(n = 4; n <= 130; n++){
                        f = vga->f[0] - (Prescale*RefFreq*n/d);
                        if(f < 0)
                                f = -f;
                        if(f < fmin){
                                fmin = f;
                                vga->d[0] = d;
                                vga->n[0] = n;
                        }
                }
        }

        /*
         * The serial word to be loaded into the icd2061a is
         *      (2<<21)|(vga->i<<17)|((vga->n)<<10)|(vga->p<<7)|vga->d
         * Always select ICD2061A REG2.
         */
        vga->f[0] = (Prescale*RefFreq*vga->n[0]/vga->d[0]);
        vga->d[0] -= 2;
        vga->n[0] -= 3;

        ctlr->flag |= Finit;
}

Ctlr icd2061a = {
        "icd2061a",
        0,                              /* snarf */
        0,                              /* options */
        init,                           /* init */
        0,                              /* load */
        0,                              /* dump */
};