path: root/arch/arm/plat-omap/common.c
diff options
authorKevin Hilman <khilman@deeprootsystems.com>2009-09-24 16:35:48 -0700
committerKevin Hilman <khilman@deeprootsystems.com>2010-01-20 18:16:08 -0800
commitd92cfcbe39fdb2328a28b5505f31cb8be40fc339 (patch)
tree709d6537fae858fb700aa83884eec2080a11b0bf /arch/arm/plat-omap/common.c
parentdccaad895094a699c37c065bff3fa9bb997daeb9 (diff)
OMAP: timekeeping: time should not stop during suspend
During suspend, the kernel timekeeping subsystem is shut down. Before suspend and upon resume, it uses a weak function read_persistent_clock() to determine the amount of time that elapsed during suspend. This function was not implemented on OMAP, so from the timekeeping subsystem perspective (and thus userspace as well) it appeared that no time elapsed during suspend. This patch uses the 32k sync timer as a the persistent clock. NOTE: This does *NOT* fully handle wrapping of the 32k sync timer, so more than one wrapping of the 32k sync timer during suspend may cause problems. Also note there are not interrupts when the 32k sync timer wraps, so something else has to be done. Reported-by: Jon Hunter <jon-hunter@ti.com> Signed-off-by: Kevin Hilman <khilman@deeprootsystems.com>
Diffstat (limited to 'arch/arm/plat-omap/common.c')
1 files changed, 26 insertions, 0 deletions
diff --git a/arch/arm/plat-omap/common.c b/arch/arm/plat-omap/common.c
index bf1eaf3a27d4..dddc0273bc8b 100644
--- a/arch/arm/plat-omap/common.c
+++ b/arch/arm/plat-omap/common.c
@@ -172,6 +172,32 @@ unsigned long long sched_clock(void)
clocksource_32k.mult, clocksource_32k.shift);
+ * read_persistent_clock - Return time from a persistent clock.
+ *
+ * Reads the time from a source which isn't disabled during PM, the
+ * 32k sync timer. Convert the cycles elapsed since last read into
+ * nsecs and adds to a monotonically increasing timespec.
+ */
+static struct timespec persistent_ts;
+static cycles_t cycles, last_cycles;
+void read_persistent_clock(struct timespec *ts)
+ unsigned long long nsecs;
+ cycles_t delta;
+ struct timespec *tsp = &persistent_ts;
+ last_cycles = cycles;
+ cycles = clocksource_32k.read(&clocksource_32k);
+ delta = cycles - last_cycles;
+ nsecs = clocksource_cyc2ns(delta,
+ clocksource_32k.mult, clocksource_32k.shift);
+ timespec_add_ns(tsp, nsecs);
+ *ts = *tsp;
static int __init omap_init_clocksource_32k(void)
static char err[] __initdata = KERN_ERR