Emulate clock={pmtmr,tsc,hpet,acpi_pm} options to be compatible to i386

No clock=pit though

Signed-off-by: Andi Kleen <ak@suse.de>

 Documentation/x86_64/boot-options.txt |    6 ++++++
 arch/x86_64/kernel/time.c             |   20 ++++++++++++++++++++
 2 files changed, 26 insertions(+)

Index: linux/Documentation/x86_64/boot-options.txt
===================================================================
--- linux.orig/Documentation/x86_64/boot-options.txt
+++ linux/Documentation/x86_64/boot-options.txt
@@ -86,6 +86,12 @@ Timing
   nohpet
   Don't use the HPET timer.
 
+  nopmtimer
+  Don't use the PM timer
+
+  clock={tsc,pmtmr,acpi_pm,hpet}   (for compatibility with i386)
+  Use TSC, PMtimer, HPET timers.
+
 Idle loop
 
   idle=poll
Index: linux/arch/x86_64/kernel/time.c
===================================================================
--- linux.orig/arch/x86_64/kernel/time.c
+++ linux/arch/x86_64/kernel/time.c
@@ -1329,3 +1329,23 @@ static int __init notsc_setup(char *s)
 }
 
 __setup("notsc", notsc_setup);
+
+/* Handle clock= for compatibility with i386 */
+static int __init parse_clock_opt(char *s)
+{
+	if (!strncmp(s, "pmtmr", 5) || !strncmp(s, "acpi_pm", 7)) {
+		notsc = 1;
+		nohpet = 1;
+	} else if (!strncmp(s, "hpet", 4)) {
+		notsc = 1;
+	} else if (!strncmp(s, "tsc", 3)) {
+		nohpet = 1;
+#ifdef CONFIG_X86_PM_TIMER
+		pmtmr_ioport = 0;
+#endif
+	}
+	/* pit not supported */
+	return 0;
+}
+__setup("clock=", parse_clock_opt);
+