[src/trunk]: src/sys/arch/alpha/alpha New delay() function that uses the RPCC...

[thorpej <thorpej%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/08f23ab1c89b
branches:  trunk
changeset: 493965:08f23ab1c89b
user:      thorpej <thorpej%NetBSD.org@localhost>
date:      Wed Jun 28 02:02:26 2000 +0000

description:
New delay() function that uses the RPCC instruction.  From
Matthew Jacob <mjacob%feral.com@localhost>.

diffstat:

 sys/arch/alpha/alpha/machdep.c |  45 ++++++++++++++++++++++++++++++-----------
 1 files changed, 33 insertions(+), 12 deletions(-)

diffs (68 lines):

diff -r 137079a5edab -r 08f23ab1c89b sys/arch/alpha/alpha/machdep.c
--- a/sys/arch/alpha/alpha/machdep.c    Wed Jun 28 01:30:56 2000 +0000
+++ b/sys/arch/alpha/alpha/machdep.c    Wed Jun 28 02:02:26 2000 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: machdep.c,v 1.215 2000/06/26 14:20:27 mrg Exp $ */
+/* $NetBSD: machdep.c,v 1.216 2000/06/28 02:02:26 thorpej Exp $ */
 
 /*-
  * Copyright (c) 1998, 1999, 2000 The NetBSD Foundation, Inc.
@@ -73,7 +73,7 @@
 
 #include <sys/cdefs.h>                 /* RCS ID & Copyright macro defns */
 
-__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.215 2000/06/26 14:20:27 mrg Exp $");
+__KERNEL_RCSID(0, "$NetBSD: machdep.c,v 1.216 2000/06/28 02:02:26 thorpej Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -1866,18 +1866,39 @@
 delay(n)
        unsigned long n;
 {
-       long N = cycles_per_usec * (n);
+       unsigned long pcc0, pcc1, curcycle, cycles, usec;
 
-       /*
-        * XXX Should be written to use RPCC?
-        */
+       if (n == 0)
+               return;
+
+       pcc0 = alpha_rpcc() & 0xffffffffUL;
+       cycles = 0;
+       usec = 0;
 
-       __asm __volatile(
-               "# The 2 corresponds to the insn count\n"
-               "1:     subq    %2, %1, %0      \n"
-               "       bgt     %0, 1b"
-               : "=r" (N)
-               : "i" (2), "0" (N));
+       while (usec <= n) {
+               /*
+                * Get the next CPU cycle count- assumes that we cannot
+                * have had more than one 32 bit overflow.
+                */
+               pcc1 = alpha_rpcc() & 0xffffffffUL;
+               if (pcc1 < pcc0)
+                       curcycle = (pcc1 + 0x100000000UL) - pcc0;
+               else
+                       curcycle = pcc1 - pcc0;
+
+               /*
+                * We now have the number of processor cycles since we
+                * last checked. Add the current cycle count to the
+                * running total. If it's over cycles_per_usec, increment
+                * the usec counter.
+                */
+               cycles += curcycle;
+               while (cycles > cycles_per_usec) {
+                       usec++;
+                       cycles -= cycles_per_usec;
+               }
+               pcc0 = pcc1;
+       }
 }
 
 #if defined(COMPAT_OSF1) || 1          /* XXX */