[PATCH] Allow early access to the power management timer

Allow early access to the power management timer by exposing the verified read
function and providing a helper function which checks the pmtmr_ioport
variable and returns either the pm timer readout or 0 in case the pm timer is
not available.

Create a new header file and replace also the ifdef'ed extern definition in
arch/i386/kernel/acpi/boot.c

This is a preperatory patch for the rework of the local apic timer
calibration.

No functional changes.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 38 insertions, 0 deletions

diff --git a/include/linux/acpi_pmtmr.h b/include/linux/acpi_pmtmr.h
new file mode 100644
index 000000000000..1d0ef1ae8036
--- /dev/null
+++ b/include/linux/acpi_pmtmr.h
@@ -0,0 +1,38 @@
+#ifndef _ACPI_PMTMR_H_
+#define _ACPI_PMTMR_H_
+
+#include <linux/clocksource.h>
+
+/* Number of PMTMR ticks expected during calibration run */
+#define PMTMR_TICKS_PER_SEC 3579545
+
+/* limit it to 24 bits */
+#define ACPI_PM_MASK CLOCKSOURCE_MASK(24)
+
+/* Overrun value */
+#define ACPI_PM_OVRRUN	(1<<24)
+
+#ifdef CONFIG_X86_PM_TIMER
+
+extern u32 acpi_pm_read_verified(void);
+extern u32 pmtmr_ioport;
+
+static inline u32 acpi_pm_read_early(void)
+{
+	if (!pmtmr_ioport)
+		return 0;
+	/* mask the output to 24 bits */
+	return acpi_pm_read_verified() & ACPI_PM_MASK;
+}
+
+#else
+
+static inline u32 acpi_pm_read_early(void)
+{
+	return 0;
+}
+
+#endif
+
+#endif
+