power_button_x86: Inhibit AP power-on if battery level is too low

Allow CONFIG_CHARGER_MIN_BAT_PCT_FOR_POWER_ON to be defined at the board
level to be the minimum battery percentage required for power-on. If the
battery level is below the threshold, or if the battery is missing,
power button presses will be ignored.

BUG=chrome-os-partner:31127
TEST=Manual on Samus with subsequent commit. Verify that AP continues
to boot normally when charge level exceeds
CONFIG_CHARGER_MIN_BAT_PCT_FOR_POWER_ON. Verify that power button
presses are ignored when the charge level is below the threshold, and
we return to G3.
BRANCH=Samus

Change-Id: I0ff3f7ddabf38080332470e172c8b2e307bf1655
Signed-off-by: Shawn Nematbakhsh <shawnn@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/236021
Reviewed-by: Alec Berg <alecaberg@chromium.org>

4 files changed, 36 insertions, 2 deletions

diff --git a/common/charge_state_v1.c b/common/charge_state_v1.c
index b4ecb74c5b..9be0d47c15 100644
--- a/common/charge_state_v1.c
+++ b/common/charge_state_v1.c
@@ -681,6 +681,19 @@ int charge_want_shutdown(void)
 		charge_get_percent() < BATTERY_LEVEL_SHUTDOWN;
 }
 
+int charge_prevent_power_on(void)
+{
+	int prevent_power_on = 0;
+#ifdef CONFIG_CHARGER_MIN_BAT_PCT_FOR_POWER_ON
+	/* Require a minimum battery level to power on */
+	if (battery_is_present() == BP_NO ||
+	    charge_get_percent() < CONFIG_CHARGER_MIN_BAT_PCT_FOR_POWER_ON)
+		prevent_power_on = 1;
+#endif
+	/* Factory override: Always allow power on if WP is disabled */
+	return prevent_power_on && system_is_locked();
+}
+
 static int charge_force_idle(int enable)
 {
 	if (enable) {
diff --git a/common/charge_state_v2.c b/common/charge_state_v2.c
index 531cc8bf83..5dd30856d7 100644
--- a/common/charge_state_v2.c
+++ b/common/charge_state_v2.c
@@ -812,6 +812,19 @@ int charge_want_shutdown(void)
 		(curr.batt.state_of_charge < BATTERY_LEVEL_SHUTDOWN);
 }
 
+int charge_prevent_power_on(void)
+{
+	int prevent_power_on = 0;
+#ifdef CONFIG_CHARGER_MIN_BAT_PCT_FOR_POWER_ON
+	/* Require a minimum battery level to power on */
+	if (curr.batt.is_present == BP_NO ||
+	    curr.batt.state_of_charge < CONFIG_CHARGER_MIN_BAT_PCT_FOR_POWER_ON)
+		prevent_power_on = 1;
+#endif
+	/* Factory override: Always allow power on if WP is disabled */
+	return prevent_power_on && system_is_locked();
+}
+
 enum charge_state charge_get_state(void)
 {
 	switch (curr.state) {
diff --git a/common/power_button_x86.c b/common/power_button_x86.c
index 8b221b8e30..9570d9c3b3 100644
--- a/common/power_button_x86.c
+++ b/common/power_button_x86.c
@@ -116,10 +116,12 @@ static void set_pwrbtn_to_pch(int high)
 {
 	/*
 	 * If the battery is discharging and low enough we'd shut down the
-	 * system, don't press the power button.
+	 * system, don't press the power button. Also, don't press the
+	 * power button if the battery is charging but the battery level
+	 * is too low.
 	 */
 #ifdef CONFIG_CHARGER
-	if (!high && charge_want_shutdown()) {
+	if (!high && (charge_want_shutdown() || charge_prevent_power_on())) {
 		CPRINTS("PB PCH pwrbtn ignored due to battery level");
 		high = 1;
 	}
diff --git a/include/charge_state.h b/include/charge_state.h
index 5c81decf10..fea4231def 100644
--- a/include/charge_state.h
+++ b/include/charge_state.h
@@ -98,6 +98,12 @@ int charge_get_percent(void);
 int charge_want_shutdown(void);
 
 /**
+ * Return non-zero if the battery level is too low to allow power on, even if
+ * a charger is attached.
+ */
+int charge_prevent_power_on(void);
+
+/**
  * Get the last polled battery/charger temperature.
  *
  * @param idx		Sensor index to read.