1 files changed, 63 insertions, 0 deletions
diff --git a/src/soc/intel/skylake/monotonic_timer.c b/src/soc/intel/skylake/monotonic_timer.c
new file mode 100644
index 0000000000..39134ef20a
--- /dev/null
+++ b/src/soc/intel/skylake/monotonic_timer.c
@@ -0,0 +1,63 @@
+/*
+ * This file is part of the coreboot project.
+ *
+ * Copyright (C) 2014 Google Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; version 2 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <stdint.h>
+#include <cpu/x86/msr.h>
+#include <timer.h>
+#include <soc/msr.h>
+
+static struct monotonic_counter {
+	int initialized;
+	struct mono_time time;
+	uint32_t last_value;
+} mono_counter;
+
+static inline uint32_t read_counter_msr(void)
+{
+	/* Even though the MSR is 64-bit it is assumed that the hardware
+	 * is polled frequently enough to only use the lower 32-bits. */
+	msr_t counter_msr;
+
+	counter_msr = rdmsr(MSR_COUNTER_24_MHZ);
+
+	return counter_msr.lo;
+}
+
+void timer_monotonic_get(struct mono_time *mt)
+{
+	uint32_t current_tick;
+	uint32_t usecs_elapsed;
+
+	if (!mono_counter.initialized) {
+		mono_counter.last_value = read_counter_msr();
+		mono_counter.initialized = 1;
+	}
+
+	current_tick = read_counter_msr();
+	usecs_elapsed = (current_tick - mono_counter.last_value) / 24;
+
+	/* 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;
+}