Subversion Repositories planix.SVN

#include <u.h>
#include <libc.h>
#include <bio.h>

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

#define SCALE(f)        ((f)/10)                /* could be /10 */

static void
init(Vga* vga, Ctlr* ctlr)
{
        int f, k;
        ulong fmin, fvco, m, n, p, q;
        double z;

        if(ctlr->flag & Finit)
                return;

        if(vga->f[0] == 0)
                vga->f[0] = vga->mode->frequency;
        vga->misc &= ~0x0C;
        if(vga->f[0] == VgaFreq0){
                /* nothing to do */;
        }
        else if(vga->f[0] == VgaFreq1)
                vga->misc |= 0x04;
        else
                vga->misc |= 0x0C;

        /*
         * Look for values of n, d and p that give
         * the least error for
         *      Fvco = 8*RefFreq*(65-m)/(65-n)
         *      Fpll = Fvco/2**p
         * N and m are 6 bits, p is 2 bits. Constraints:
         *      110MHz <= Fvco <= 250MHz
         *      40 <= n <= 62
         *       1 <= m <= 62
         *       0 <= p <=  3
         * Should try to minimise n, m.
         *
         * There's nothing like brute force and ignorance.
         */
        fmin = vga->f[0];
        vga->m[0] = 0x15;
        vga->n[0] = 0x18;
        vga->p[0] = 3;
        for(m = 62; m > 0; m--){
                for(n = 62; n >= 40; n--){
                        fvco = 8*SCALE(RefFreq)*(65-m)/(65-n);
                        if(fvco < SCALE(110000000) || fvco > SCALE(250000000))
                                continue;
                        for(p = 0; p < 4; p++){
                                f = SCALE(vga->f[0]) - (fvco>>p);
                                if(f < 0)
                                        f = -f;
                                if(f < fmin){
                                        fmin = f;
                                        vga->m[0] = m;
                                        vga->n[0] = n;
                                        vga->p[0] = p;
                                }
                        }
                }
        }

        /*
         * Now the loop clock:
         *      m is fixed;
         *      calculate n;
         *      set z to the lower bound (110MHz) and calculate p and q.
         */
        vga->m[1] = 61;
        if(ctlr->flag & Uenhanced)
                k = 64/8;
        else
                k = 8/8;
        n = 65 - 4*k;
        fvco = (8*RefFreq*(65-vga->m[0]))/(65-vga->n[0]);
        vga->f[1] = fvco;
        z = 110.0*(65-n)/(4*(fvco/1000000.0)*k);
        if(z <= 16){
                for(p = 0; p < 4; p++){
                        if(1<<(p+1) > z)
                                break;
                }
                q = 0;
        }
        else{
                p = 3;
                q = (z - 16)/16 + 1;
        }
        vga->n[1] = n;
        vga->p[1] = p;
        vga->q[1] = q;

        ctlr->flag |= Finit;
}

Ctlr tvp3026clock = {
        "tvp3026clock",                 /* name */
        0,                              /* snarf */
        0,                              /* options */
        init,                           /* init */
        0,                              /* load */
        0,                              /* dump */
};