New patch to review for coreboot: abfee58 lapic: monotonic time implementation

[Aaron Durbin]

Aaron Durbin ([e-mail]) just uploaded a new patch set to gerrit, which you can find at http://review.coreboot.org/3154

-gerrit

commit abfee587b43baf76c9c1deb319f5a5bc53bd64eb
Author: Aaron Durbin 
Date:   Mon Apr 29 17:18:49 2013 -0500

lapic: monotonic time implementation

Implement the time_monotonic_get() functionality based off of
    the local apic timer.

Change-Id: I1aa1ff64d15a3056d6abd1372be13da682c5ee2e
    Signed-off-by: Aaron Durbin 
---
 src/cpu/x86/Kconfig            |  7 +++++++
 src/cpu/x86/lapic/apic_timer.c | 43 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/src/cpu/x86/Kconfig b/src/cpu/x86/Kconfig
index 4c5176b..6b70ae7 100644
--- a/src/cpu/x86/Kconfig
+++ b/src/cpu/x86/Kconfig
@@ -11,6 +11,13 @@ config UDELAY_LAPIC
    bool
    default n

+config LAPIC_MONOTONIC_TIMER
+	def_bool n
+	depends on UDELAY_LAPIC
+	select HAVE_MONOTONIC_TIMER
+	help
+	  Expose monotonic time using the local apic.
+
 config UDELAY_LAPIC_FIXED_FSB
    int

diff --git a/src/cpu/x86/lapic/apic_timer.c b/src/cpu/x86/lapic/apic_timer.c
index b60da27..749fef0 100644
--- a/src/cpu/x86/lapic/apic_timer.c
+++ b/src/cpu/x86/lapic/apic_timer.c
@@ -19,6 +19,7 @@
  */

#include <stdint.h>
+#include <console/console.h>
 #include <delay.h>
 #include <arch/io.h>
 #include <arch/cpu.h>
@@ -106,3 +107,45 @@ void udelay(u32 usecs)
    	value = lapic_read(LAPIC_TMCCT);
    } while((start - value) < ticks);
 }
+
+#if CONFIG_LAPIC_MONOTONIC_TIMER && !defined(__PRE_RAM__)
+#include <timer.h>
+
+static struct monotonic_counter {
+	int initialized;
+	struct mono_time time;
+	uint32_t last_value;
+} mono_counter;
+
+void timer_monotonic_get(struct mono_time *mt)
+{
+	uint32_t current_tick;
+	uint32_t usecs_elapsed;
+
+	if (!mono_counter.initialized) {
+		init_timer();
+		/* An FSB frequency of 200Mhz provides a 20 second polling
+		 * interval between timer_monotonic_get() calls before wrap
+		 * around occurs. */
+		if (timer_fsb > 200)
+			printk(BIOS_WARNING,
+			       "apic timer freq (%d) may be too fast.\n",
+			       timer_fsb);
+		mono_counter.last_value = lapic_read(LAPIC_TMCCT);
+		mono_counter.initialized = 1;
+	}
+
+	current_tick = lapic_read(LAPIC_TMCCT);
+	/* Note that the APIC timer counts down. */
+	usecs_elapsed = (mono_counter.last_value - current_tick) / timer_fsb;
+
+	/* Update current time and tick values only if a full tick occurred. */
+	if (usecs_elapsed) {
+		mono_time_add_usecs(&mono_counter.time, usecs_elapsed);
+		mono_counter.last_value = current_tick;
+	}
+
+	/* Save result. */
+	*mt = mono_counter.time;
+}
+#endif