CVS commit: src/sys/arch/x86/isa

[Chuck Cranor <chuck%netbsd.org@localhost>]

Module Name:    src
Committed By:   chuck
Date:           Wed Jan 16 18:38:24 UTC 2008

Modified Files:
        src/sys/arch/x86/isa: clock.c

Log Message:
fix clock accounting problem in i8254_get_timecount that caused
the auich auich_calibrate() function to get the wrong ac97 freq
(may cause audio to play at wrong speed on some systems).  this
error was inadvertently introduced in rev 1.98 of the old
src/sys/arch/i386/isa/clock.c (2006/09/03) and manifests itself
on systems that do not use an alternate timecounter (e.g. ACPI-Fast).

the basic problem is that the code that handled when the i8254
counter wrapped was firing in cases when it shouldn't have,
causing the counter to run fast.   a more detailed discussion
can be found here:
  http://mail-index.netbsd.org/tech-kern/2008/01/15/0001.html
  http://mail-index.netbsd.org/tech-kern/2008/01/16/0000.html


To generate a diff of this commit:
cvs rdiff -r1.22 -r1.23 src/sys/arch/x86/isa/clock.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.