svn commit: r219046 - head/sys/x86/cpufreq

[Jung-uk Kim]

Author: jkim
Date: Fri Feb 25 23:14:24 2011
New Revision: 219046
URL: http://svn.freebsd.org/changeset/base/219046

Log:
  Set C1 "I/O then Halt" capability bit for Intel EIST.  Some broken BIOSes
  refuse to load external SSDTs if this bit is unset for _PDC.  It seems Linux
  and OpenSolaris did the same long ago.
  
  MFC after:	1 week

Modified:
  head/sys/x86/cpufreq/est.c

Modified: head/sys/x86/cpufreq/est.c
==============================================================================
--- head/sys/x86/cpufreq/est.c	Fri Feb 25 23:05:35 2011	(r219045)
+++ head/sys/x86/cpufreq/est.c	Fri Feb 25 23:14:24 2011	(r219046)
@@ -947,8 +947,11 @@ static int
 est_features(driver_t *driver, u_int *features)
 {
 
-	/* Notify the ACPI CPU that we support direct access to MSRs */
-	*features = ACPI_CAP_PERF_MSRS;
+	/*
+	 * Notify the ACPI CPU that we support direct access to MSRs.
+	 * XXX C1 "I/O then Halt" seems necessary for some broken BIOS.
+	 */
+	*features = ACPI_CAP_PERF_MSRS | ACPI_CAP_C1_IO_HALT;
 	return (0);
 }