After shutting down AP, hibernate EC if battery is low

This preserves more battery for the real-time clock.  It also gets rid
of one battery level/state, since the EC will now shut down at the
same level (2%) as the AP.

Having the EC hibernate at the same level as the AP shuts down also
prevents the following weird scenario:

- EC powers on at 2% battery.
- EC won't power on the AP to do software sync because battery is low.
- But the charge state machine won't actually hibernate the EC until 1%.
- Between 2% and 1%, AC is inserted and system starts charging.
- But EC-RO is what's doing the charging; we should go through software sync
  before charging.

BUG=chrome-os-partner:17124
BRANCH=link
TEST=manual

On battery power,
1) With system on, battfake 2 -> system shuts down and EC hibernates
2) With system off, battfake 2 -> EC hibernates

Change-Id: I87d17f70d60673f3e3f1c6eb88f3f00a8c9ed4e7
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/44314

2 files changed, 33 insertions, 12 deletions

diff --git a/common/charge_state.c b/common/charge_state.c
index e13f8969ce..7612f91036 100644
--- a/common/charge_state.c
+++ b/common/charge_state.c
@@ -109,16 +109,17 @@ static void update_battery_info(void)
  */
 static void poweroff_wait_ac(int hibernate_ec)
 {
-	/* Shutdown the main processor */
 	if (chipset_in_state(CHIPSET_STATE_ON)) {
-		CPRINTF("[%T force shutdown to avoid damaging battery]\n");
+		/*
+		 * Shut down the AP.  The EC will hibernate after the AP shuts
+		 * down.
+		 */
+		CPRINTF("[%T charge force shutdown due to low battery]\n");
 		chipset_force_shutdown();
 		host_set_single_event(EC_HOST_EVENT_BATTERY_SHUTDOWN);
-	}
-
-	/* If battery level is critical, hibernate the EC too */
-	if (hibernate_ec) {
-		CPRINTF("[%T force EC hibernate to avoid damaging battery]\n");
+	} else if (hibernate_ec) {
+		/* If battery level is critical, hibernate the EC */
+		CPRINTF("[%T charge force EC hibernate due to low battery]\n");
 		system_hibernate(0, 0);
 	}
 }
@@ -244,8 +245,7 @@ static int state_common(struct power_state_context *ctx)
 		     !(curr->error & F_BATTERY_STATE_OF_CHARGE)) ||
 		    (batt->voltage <= ctx->battery->voltage_min &&
 		     !(curr->error & F_BATTERY_VOLTAGE)))
-			poweroff_wait_ac(batt->state_of_charge <
-					 BATTERY_LEVEL_HIBERNATE_EC ? 1 : 0);
+			poweroff_wait_ac(1);
 	}
 
 	/* Check battery presence */
@@ -837,6 +837,22 @@ static void charge_init(void)
 }
 DECLARE_HOOK(HOOK_INIT, charge_init, HOOK_PRIO_DEFAULT);
 
+
+static void charge_shutdown(void)
+{
+	/* Hibernate immediately if battery level is too low */
+	if (charge_want_shutdown()) {
+		CPRINTF("[%T charge force EC hibernate after"
+			" shutdown due to low battery]\n");
+		system_hibernate(0, 0);
+	}
+}
+/*
+ * Run the charge shutdown hook last, since when it hibernates no subsequent
+ * hooks would be run.
+ */
+DECLARE_HOOK(HOOK_CHIPSET_SHUTDOWN, charge_shutdown, HOOK_PRIO_LAST);
+
 /*****************************************************************************/
 /* Host commands */
 
@@ -916,6 +932,10 @@ static int command_battfake(int argc, char **argv)
 	else
 		ccprintf("Reporting fake battery level %d%%\n",
 			 fake_state_of_charge);
+
+	/* Wake charger task immediately to see new level */
+	task_wake(TASK_ID_CHARGER);
+
 	return EC_SUCCESS;
 }
 DECLARE_CONSOLE_COMMAND(battfake, command_battfake,
diff --git a/include/battery.h b/include/battery.h
index da4071e158..50b4e53f7c 100644
--- a/include/battery.h
+++ b/include/battery.h
@@ -23,10 +23,11 @@
  * level.
  */
 #define BATTERY_LEVEL_CRITICAL		  5
-/* Shut down main processor when discharging and battery level < this level */
+/*
+ * Shut down main processor and/or hibernate EC when discharging and battery
+ * level < this level.
+ */
 #define BATTERY_LEVEL_SHUTDOWN		  3
-/* Hibernate EC immediately when discharging and battery level < this level */
-#define BATTERY_LEVEL_HIBERNATE_EC	  2
 
 #endif /* __CROS_EC_BATTERY_H */