20060303

1 files changed, 68 insertions, 0 deletions

diff --git a/os/mpc/pit.c b/os/mpc/pit.c
new file mode 100644
index 00000000..bfc8bc8d
--- /dev/null
+++ b/os/mpc/pit.c
@@ -0,0 +1,68 @@
+/*
+ * programmable interrupt timer
+ */
+
+#include	"u.h"
+#include	"../port/lib.h"
+#include	"mem.h"
+#include	"dat.h"
+#include	"fns.h"
+#include	"io.h"
+#include	"ureg.h"
+
+enum {
+	/* piscr */
+	PTE =	1<<0,
+	PITF =	1<<1,
+	PIE =	1<<2,
+	PS =	1<<7,
+};
+
+static void
+pitinterrupt(Ureg*, void*)
+{
+	IMM *io;
+
+	io = m->iomem;
+	if(io->piscr & PS){
+		io->piscr |= PS;	/* clear by writing 1 */
+		/* do whatever is required */
+	}
+}
+
+static void
+pitreset(void)
+{
+	IMM *io;
+
+	io = ioplock();
+	io->piscrk = KEEP_ALIVE_KEY;
+	io->piscr = (PITlevel<<8) | PS | PITF;
+	if(0)
+		io->piscrk = ~KEEP_ALIVE_KEY;
+	/* piscrk is left unlocked for interrupt routine */
+	iopunlock();
+	intrenable(PITlevel, pitinterrupt, nil, BUSUNKNOWN, "pit");
+}
+
+static ulong
+pitload(ulong usec)
+{
+	IMM *io;
+	ulong v;
+
+	v = ((usec*m->oscclk)/512);
+	if(v == 0 || v >= (1<<16))
+		return 0;	/* can't do */
+	io = ioplock();
+	io->pitck = KEEP_ALIVE_KEY;
+	io->pitc = (v-1)<<16;
+	io->pitck = ~KEEP_ALIVE_KEY;
+	io->piscrk = KEEP_ALIVE_KEY;
+	io->piscr = (PITlevel<<8) | PS | PIE | PITF | PTE;
+	if(0)
+		io->piscrk = ~KEEP_ALIVE_KEY;
+	/* piscrk is left unlocked for interrupt routine */
+	iopunlock();
+	return (v*512)/m->oscclk;
+}