On 23 Jun 2002 12:57:02 -0400,
In could this get cleaned up...,
"Perry E. Metzger" <perry@piermont.com> wrote:
> 
> sys/arch/x68k/x68k/clock.c uses
> #define CLOCKS_PER_SEC 100
> instead of the usual HZ mechanisms to set up the port clock
> rate. At the very least, the name of the #define is ill advised -- it
> is also used by a standard #define in userland that is about to be
> changed to be more standards conformant.

I rewrote it.
The kernel with default HZ(100) seems to work. Also the
kernel with 'options HZ=200' seems to work. Can I commit?
Please review.

By the way, clkread() has returned unusable value.
1) clkread() should return the time in microseconds unit.
But it returns something else (clock unit ?).
2) clkread() should return the time since last tick. It
however does not, because mfp_get_tcdr() is decremented by
each clock.

Index: clock.c
===================================================================
RCS file: /cvsroot/syssrc/sys/arch/x68k/x68k/clock.c,v
retrieving revision 1.11
diff -u -r1.11 clock.c
--- clock.c	2001/03/15 06:10:53	1.11
+++ clock.c	2002/07/07 02:06:48
@@ -98,10 +98,14 @@
 }
 
 
-/* We're using a 100 Hz clock. */
+/*
+ * MFP of X68k uses 4MHz clock always and we use 1/200 prescaler here.
+ * Therefore, clock interval is 50 usec.
+ */
+#define CLK_RESOLUTION	(50)
+#define CLOCKS_PER_SEC	(1000000 / CLK_RESOLUTION)
 
-#define CLK_INTERVAL 200
-#define CLOCKS_PER_SEC 100
+static int clkint;		/* clock interval */
 
 static int clkread __P((void));
 
@@ -130,10 +134,17 @@
 void
 cpu_initclocks()
 {
-	mfp_set_tcdcr(mfp_get_tcdcr() & 0x0f); /* stop timer C */
-	mfp_set_tcdr(CLK_INTERVAL);
+	if (CLOCKS_PER_SEC % hz ||
+	    hz <= (CLOCKS_PER_SEC / 256) || hz > CLOCKS_PER_SEC) {
+		printf("cannot set %d Hz clock. using 100 Hz\n", hz);
+		hz = 100;
+	}
+	clkint = CLOCKS_PER_SEC / hz;
 
+	mfp_set_tcdcr(mfp_get_tcdcr() & 0x0f); /* stop timer C */
 	mfp_set_tcdcr(mfp_get_tcdcr() | 0x70); /* 1/200 delay mode */
+
+	mfp_set_tcdr(clkint);
 	mfp_bit_set_ierb(MFP_INTR_TIMER_C);
 }
 
@@ -155,7 +166,7 @@
 int
 clkread()
 {
-	return (mfp_get_tcdr() * CLOCKS_PER_SEC) / CLK_INTERVAL;
+	return (clkint - mfp_get_tcdr()) * CLK_RESOLUTION;
 }
 
 
---
Tetsuya Isaki <isaki@par.odn.ne.jp / isaki@NetBSD.org>