add a function to fast forward system timer

When we wake up from a deep sleep mode, the system timer clock might
have been stopped. We need to be able to set using another time source
(e.g. the RTC).

Signed-off-by: Vincent Palatin <vpalatin@chromium.org>

BUG=chrome-os-partner:8866
TEST=make BOARD=snow && make BOARD=link
on Snow, on a software implementing STOP mode, check the system time is
still accurate by comparing it to the wall clock.

Change-Id: Ieddbb423d052c7aceb398470866b25b25a74c0a0
Reviewed-on: https://gerrit.chromium.org/gerrit/29314
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Commit-Ready: Vincent Palatin <vpalatin@chromium.org>
Tested-by: Vincent Palatin <vpalatin@chromium.org>

5 files changed, 33 insertions, 3 deletions

diff --git a/chip/lm4/hwtimer.c b/chip/lm4/hwtimer.c
index b3c8498294..9c23cbf961 100644
--- a/chip/lm4/hwtimer.c
+++ b/chip/lm4/hwtimer.c
@@ -42,6 +42,12 @@ uint32_t __hw_clock_source_read(void)
 }
 
 
+void __hw_clock_source_set(uint32_t ts)
+{
+	LM4_TIMER_TAV(6) = 0xffffffff - ts;
+}
+
+
 static void __hw_clock_source_irq(void)
 {
 	uint32_t status = LM4_TIMER_RIS(6);
@@ -99,7 +105,7 @@ int __hw_clock_source_init(uint32_t start_t)
 	LM4_TIMER_CTL(6) |= 0x1;
 	/* Override the count with the start value now that counting has
 	 * started. */
-	LM4_TIMER_TAV(6) = 0xffffffff - start_t;
+	__hw_clock_source_set(start_t);
 
 	/* Enable interrupt */
 	task_enable_irq(LM4_IRQ_TIMERW0A);
diff --git a/chip/stm32/hwtimer.c b/chip/stm32/hwtimer.c
index f43a444088..1dbf2b5606 100644
--- a/chip/stm32/hwtimer.c
+++ b/chip/stm32/hwtimer.c
@@ -84,6 +84,12 @@ uint32_t __hw_clock_source_read(void)
 	return (hi << 16) | lo;
 }
 
+void __hw_clock_source_set(uint32_t ts)
+{
+	STM32_TIM_CNT(3) = ts >> 16;
+	STM32_TIM_CNT(4) = ts & 0xffff;
+}
+
 static void __hw_clock_source_irq(void)
 {
 	uint32_t stat_tim3 = STM32_TIM_SR(3);
@@ -147,8 +153,7 @@ int __hw_clock_source_init(uint32_t start_t)
 
 	/* Override the count with the start value now that counting has
 	 * started. */
-	STM32_TIM_CNT(3) = start_t >> 16;
-	STM32_TIM_CNT(4) = start_t & 0xffff;
+	__hw_clock_source_set(start_t);
 
 	/* Enable timer interrupts */
 	task_enable_irq(STM32_IRQ_TIM3);
diff --git a/core/cortex-m/timer.c b/core/cortex-m/timer.c
index 994f9c1245..10370aeeb6 100644
--- a/core/cortex-m/timer.c
+++ b/core/cortex-m/timer.c
@@ -169,6 +169,14 @@ timestamp_t get_time(void)
 }
 
 
+void force_time(timestamp_t ts)
+{
+	clksrc_high = ts.le.hi;
+	__hw_clock_source_set(ts.le.lo);
+	/* some timers might be already expired : process them */
+	task_trigger_irq(timer_irq);
+}
+
 void timer_print_info(void)
 {
 	uint64_t t = get_time().val;
diff --git a/include/hwtimer.h b/include/hwtimer.h
index fdf1d94852..b9b2270fd6 100644
--- a/include/hwtimer.h
+++ b/include/hwtimer.h
@@ -52,6 +52,9 @@ void __hw_clock_event_clear(void);
 /* Returns the value of the free-running counter used as clock. */
 uint32_t __hw_clock_source_read(void);
 
+/* Override the current value of the hardware counter */
+void __hw_clock_source_set(uint32_t ts);
+
 /**
  * Initializes the hardware timer used to provide clock services, using the
  * specified start timer value.
diff --git a/include/timer.h b/include/timer.h
index d3a4989e05..0a4273ff25 100644
--- a/include/timer.h
+++ b/include/timer.h
@@ -53,6 +53,14 @@ void usleep(unsigned us);
 /* Get the current timestamp from the system timer. */
 timestamp_t get_time(void);
 
+/* Force the current value of the system timer.
+ *
+ * This function is for the power management implementation which wants to fix
+ * the system time when waking up from a mode with clocks turned off.
+ * Note: must be called with interrupts disabled.
+ */
+void force_time(timestamp_t ts);
+
 /* Print the current timer information using the command output channel.  This
  * may be called from interrupt level. */
 void timer_print_info(void);