spring: keep AP off when battery level is too low

When battery level is too low, we want to keep the AP off even when a
power on event is received. Current threshold is set to 1 mAh.

Note that after this change, a board without a battery will need to wait
for 15 seconds before it can boot up.

BUG=chrome-os-partner:18318
TEST=Press power button and see power on event ignored. Charge battery
to over AP off threshold and check we can power on the system.
BRANCH=spring

Change-Id: If32a1935a69be102778bde7ad8976eea0921f87e
Signed-off-by: Vic Yang <victoryang@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/45825
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>

4 files changed, 48 insertions, 3 deletions

diff --git a/board/spring/board.h b/board/spring/board.h
index 67f16e9b44..ea4ce7db89 100644
--- a/board/spring/board.h
+++ b/board/spring/board.h
@@ -59,6 +59,9 @@
 /* Battery */
 #define CONFIG_BATTERY_BQ20Z453
 
+/* Low battery threshold. In mAh. */
+#define BATTERY_AP_OFF_LEVEL 1
+
 /* Charger/accessories detection */
 #define CONFIG_TSU6721
 
diff --git a/common/gaia_power.c b/common/gaia_power.c
index f197890f88..7f53dd800e 100644
--- a/common/gaia_power.c
+++ b/common/gaia_power.c
@@ -506,6 +506,28 @@ static int next_pwr_event(void)
 
 /*****************************************************************************/
 
+static int wait_for_power_on(void)
+{
+	int value;
+	while (1) {
+		value = check_for_power_on_event();
+		if (!value) {
+			task_wait_event(-1);
+			continue;
+		}
+
+		if (charge_keep_power_off()) {
+			CPRINTF("%T battery low. ignoring power on event.\n");
+			if (value == 1) /* System already on */
+				power_off();
+			continue;
+		}
+
+		CPRINTF("%T power on %d\n", value);
+		return value;
+	}
+}
+
 void chipset_task(void)
 {
 	int value;
@@ -515,9 +537,7 @@ void chipset_task(void)
 
 	while (1) {
 		/* Wait until we need to power on, then power on */
-		while (value = check_for_power_on_event(), !value)
-			task_wait_event(-1);
-		CPRINTF("%T power on %d\n", value);
+		wait_for_power_on();
 
 		if (!power_on()) {
 			int continue_power = 0;
diff --git a/common/pmu_tps65090_charger.c b/common/pmu_tps65090_charger.c
index 732a5b6d98..c07d643e97 100644
--- a/common/pmu_tps65090_charger.c
+++ b/common/pmu_tps65090_charger.c
@@ -42,6 +42,10 @@
 #define T2_USEC         (10 * SECOND)
 #define T3_USEC         (10 * SECOND)
 
+#ifndef BATTERY_AP_OFF_LEVEL
+#define BATTERY_AP_OFF_LEVEL 0
+#endif
+
 static const char * const state_list[] = {
 	"idle",
 	"pre-charging",
@@ -373,6 +377,19 @@ enum charging_state charge_get_state(void)
 	return current_state;
 }
 
+int charge_keep_power_off(void)
+{
+	int charge;
+
+	if (BATTERY_AP_OFF_LEVEL == 0)
+		return 0;
+
+	if (battery_remaining_capacity(&charge))
+		return current_state != ST_CHARGING_ERROR;
+
+	return charge <= BATTERY_AP_OFF_LEVEL;
+}
+
 void pmu_charger_task(void)
 {
 	int next_state;
diff --git a/include/pmu_tpschrome.h b/include/pmu_tpschrome.h
index 0af241682f..57ba4c0a7e 100644
--- a/include/pmu_tpschrome.h
+++ b/include/pmu_tpschrome.h
@@ -269,5 +269,10 @@ void pmu_task_throttled_wake(void);
  */
 enum charging_state charge_get_state(void);
 
+/**
+ * Return non-zero if battery is so low we want to keep AP off.
+ */
+int charge_keep_power_off(void);
+
 #endif /* __CROS_EC_TPSCHROME_H */