[src/trunk]: src/sys/dev/acpi Clarify a comment.

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

details:   https://anonhg.NetBSD.org/src/rev/19fc1d91aab9
branches:  trunk
changeset: 762657:19fc1d91aab9
user:      jruoho <jruoho%NetBSD.org@localhost>
date:      Fri Feb 25 05:07:43 2011 +0000

description:
Clarify a comment.

diffstat:

 sys/dev/acpi/acpi_cpu_tstate.c |  14 ++++++++++----
 1 files changed, 10 insertions(+), 4 deletions(-)

diffs (35 lines):

diff -r 76942c213de9 -r 19fc1d91aab9 sys/dev/acpi/acpi_cpu_tstate.c
--- a/sys/dev/acpi/acpi_cpu_tstate.c    Fri Feb 25 01:36:37 2011 +0000
+++ b/sys/dev/acpi/acpi_cpu_tstate.c    Fri Feb 25 05:07:43 2011 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: acpi_cpu_tstate.c,v 1.21 2011/02/23 06:17:55 jruoho Exp $ */
+/* $NetBSD: acpi_cpu_tstate.c,v 1.22 2011/02/25 05:07:43 jruoho Exp $ */
 
 /*-
  * Copyright (c) 2010 Jukka Ruohonen <jruohonen%iki.fi@localhost>
@@ -27,7 +27,7 @@
  * SUCH DAMAGE.
  */
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: acpi_cpu_tstate.c,v 1.21 2011/02/23 06:17:55 jruoho Exp $");
+__KERNEL_RCSID(0, "$NetBSD: acpi_cpu_tstate.c,v 1.22 2011/02/25 05:07:43 jruoho Exp $");
 
 #include <sys/param.h>
 #include <sys/evcnt.h>
@@ -518,8 +518,14 @@
                return AE_AML_ILLEGAL_ADDRESS;
 
        /*
-        * A zero DUTY_WIDTH is used announce that
-        * T-states are not available via FADT.
+        * A zero DUTY_WIDTH may be used announce
+        * that T-states are not available via FADT
+        * (ACPI 4.0, p. 121). See also (section 9.3):
+        *
+        *      Advanced Micro Devices: BIOS and Kernel
+        *      Developer's Guide for AMD Athlon 64 and
+        *      AMD Opteron Processors. Revision 3.30,
+        *      February 2006.
         */
        if (width == 0 || width + offset > 4)
                return AE_AML_BAD_RESOURCE_VALUE;