Import sources from 2011-03-30 iso image

1 files changed, 77 insertions, 0 deletions

diff --git a/sys/src/cmd/aux/vga/tvp3025clock.c b/sys/src/cmd/aux/vga/tvp3025clock.c
new file mode 100755
index 000000000..8aebc5ffd
--- /dev/null
+++ b/sys/src/cmd/aux/vga/tvp3025clock.c
@@ -0,0 +1,77 @@
+#include <u.h>
+#include <libc.h>
+#include <bio.h>
+
+#include "pci.h"
+#include "vga.h"
+
+#define SCALE(f)	((f)/1)		/* could be /10 */
+
+static void
+init(Vga* vga, Ctlr* ctlr)
+{
+	int f;
+	ulong d, dmax, fmin, fvco, n, nmax, p;
+
+	if(ctlr->flag & Finit)
+		return;
+
+	if(vga->f[0] == 0)
+		vga->f[0] = vga->mode->frequency;
+
+	/*
+	 * Look for values of n, d and p that give
+	 * the least error for
+	 *	Fvco = RefFreq*((n+2)*8)/(d+2)
+	 *	Fpll = Fvco/2**p
+	 * N and d are 7-bits, p is 2-bits. Constraints:
+	 *	RefFreq/(n+2) > 1MHz
+	 *	110MHz <= Fvco <= 220MHz
+	 *	n, d >= 1
+	 * Should try to minimise n, d.
+	 *
+	 * There's nothing like brute force and ignorance.
+	 */
+	fmin = vga->f[0];
+	vga->d[0] = 6;
+	vga->n[0] = 5;
+	vga->p[0] = 2;
+	dmax = (RefFreq/1000000)-2;
+	for(d = 1; d < dmax; d++){
+		/*
+		 * Calculate an upper bound on n
+		 * to satisfy the condition
+		 *	Fvco <= 220MHz
+		 * This will hopefully prevent arithmetic
+		 * overflow.
+		 */
+		nmax = ((220000000+RefFreq)*(d+2))/(RefFreq*8) - 2;
+		for(n = 1; n < nmax; n++){
+			fvco = SCALE(RefFreq)*((n+2)*8)/(d+2);
+			if(fvco < SCALE(110000000) || fvco > SCALE(220000000))
+				continue;
+			for(p = 1; p < 4; p++){
+				f = SCALE(vga->f[0]) - (fvco>>p);
+				if(f < 0)
+					f = -f;
+				if(f < fmin){
+					fmin = f;
+					vga->d[0] = d;
+					vga->n[0] = n;
+					vga->p[0] = p;
+				}
+			}
+		}
+	}
+
+	ctlr->flag |= Finit;
+}
+
+Ctlr tvp3025clock = {
+	"tvp3025clock",			/* name */
+	0,				/* snarf */
+	0,				/* options */
+	init,				/* init */
+	0,				/* load */
+	0,				/* dump */
+};