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authorAaron Durbin <adurbin@chromium.org>2013-04-29 22:22:55 -0500
committerRonald G. Minnich <rminnich@gmail.com>2013-05-01 07:15:55 +0200
commite850164bac08a5b3b4cd09f587775e68ad1b40c2 (patch)
tree2e9ab9f1b1a7e878cdcfea71ad8c69269d8dfe0e /src/cpu/x86
parentfd8291c9d438917e334f4211fb1142b6a7bb7e32 (diff)
tsc: provide monotonic timer
Implement the timer_monotonic_get() using the TSC. Change-Id: I5118da6fb9bccc75d2ce012317612e0ab20a2cac Signed-off-by: Aaron Durbin <adurbin@chromium.org> Reviewed-on: http://review.coreboot.org/3155 Tested-by: build bot (Jenkins) Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
Diffstat (limited to 'src/cpu/x86')
-rw-r--r--src/cpu/x86/Kconfig7
-rw-r--r--src/cpu/x86/tsc/delay_tsc.c37
2 files changed, 44 insertions, 0 deletions
diff --git a/src/cpu/x86/Kconfig b/src/cpu/x86/Kconfig
index 6b70ae7c6c..5cf40fa4a9 100644
--- a/src/cpu/x86/Kconfig
+++ b/src/cpu/x86/Kconfig
@@ -25,6 +25,13 @@ config UDELAY_TSC
bool
default n
+config TSC_MONOTONIC_TIMER
+ def_bool n
+ depends on UDELAY_TSC
+ select HAVE_MONOTONIC_TIMER
+ help
+ Expose monotonic time using the TSC.
+
config UDELAY_TIMER2
bool
default n
diff --git a/src/cpu/x86/tsc/delay_tsc.c b/src/cpu/x86/tsc/delay_tsc.c
index 1907a9cfec..e4993d0dd5 100644
--- a/src/cpu/x86/tsc/delay_tsc.c
+++ b/src/cpu/x86/tsc/delay_tsc.c
@@ -164,3 +164,40 @@ void udelay(unsigned us)
count = rdtscll();
}
}
+
+#if CONFIG_TSC_MONOTONIC_TIMER
+#include <timer.h>
+
+static struct monotonic_counter {
+ int initialized;
+ struct mono_time time;
+ uint64_t last_value;
+} mono_counter;
+
+void timer_monotonic_get(struct mono_time *mt)
+{
+ uint64_t current_tick;
+ uint64_t ticks_elapsed;
+
+ if (!mono_counter.initialized) {
+ init_timer();
+ mono_counter.last_value = rdtscll();
+ mono_counter.initialized = 1;
+ }
+
+ current_tick = rdtscll();
+ ticks_elapsed = current_tick - mono_counter.last_value;
+
+ /* Update current time and tick values only if a full tick occurred. */
+ if (ticks_elapsed >= clocks_per_usec) {
+ uint64_t usecs_elapsed;
+
+ usecs_elapsed = ticks_elapsed / clocks_per_usec;
+ mono_time_add_usecs(&mono_counter.time, (long)usecs_elapsed);
+ mono_counter.last_value = current_tick;
+ }
+
+ /* Save result. */
+ *mt = mono_counter.time;
+}
+#endif