charge_state_v2: Throttle AP in high battery discharge current

When EC sees discharge current hit BAT_MAX_DISCHG_CURRENT,
we kick off a timer and ask AP to throttle.

Then EC keeps monitoring discharge current. If the current doesn't
drop below BAT_MAX_DISCHG_CURRENT - BAT_OCP_HYSTERESIS, we restart
the timer and notify AP again, which shouldn't happen unless
AP misses or ignores the first notification.

When the timer expires, which means EC hasn't seen over-current
for BAT_OCP_TIMEOUT_US, we ask AP to stop throttling.

BUG=b:74321682, chromium:838754
BRANCH=scarlet
TEST=manually test on scarlet, confirm EC sends
EC_HOST_EVENT_THROTTLE_START and EC_HOST_EVENT_THROTTLE_STOP
host events when entering/exiting OCP.

Change-Id: I1e55fc23249596d8afec52a3885655ca9c1f2151
Signed-off-by: Philip Chen <philipchen@google.com>
Reviewed-on: https://chromium-review.googlesource.com/994188
Commit-Ready: Philip Chen <philipchen@chromium.org>
Tested-by: Philip Chen <philipchen@chromium.org>
Reviewed-by: Daisuke Nojiri <dnojiri@chromium.org>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>

1 files changed, 44 insertions, 0 deletions

diff --git a/common/charge_state_v2.c b/common/charge_state_v2.c
index 514e3add92..958257ea71 100644
--- a/common/charge_state_v2.c
+++ b/common/charge_state_v2.c
@@ -25,6 +25,7 @@
 #include "printf.h"
 #include "system.h"
 #include "task.h"
+#include "throttle_ap.h"
 #include "timer.h"
 #include "util.h"
 
@@ -41,6 +42,20 @@
 #define PRECHARGE_TIMEOUT_US (PRECHARGE_TIMEOUT * SECOND)
 #define LFCC_EVENT_THRESH 5 /* Full-capacity change reqd for host event */
 
+#ifdef CONFIG_THROTTLE_AP_ON_BAT_DISCHG_CURRENT
+#ifndef CONFIG_HOSTCMD_EVENTS
+#error "CONFIG_THROTTLE_AP_ON_BAT_DISCHG_CURRENT needs CONFIG_HOSTCMD_EVENTS"
+#endif /* CONFIG_HOSTCMD_EVENTS */
+#define BAT_OCP_TIMEOUT_US (60 * SECOND)
+/* BAT_OCP_HYSTERESIS_PCT can be optionally overridden in board.h. */
+#ifndef BAT_OCP_HYSTERESIS_PCT
+#define BAT_OCP_HYSTERESIS_PCT	10
+#endif /* BAT_OCP_HYSTERESIS_PCT */
+#define BAT_OCP_HYSTERESIS \
+	(BAT_MAX_DISCHG_CURRENT * BAT_OCP_HYSTERESIS_PCT / 100) /* mA */
+static timestamp_t ocp_throttle_start_time;
+#endif /* CONFIG_THROTTLE_AP_ON_BAT_DISCHG_CURRENT */
+
 static int charge_request(int voltage, int current);
 
 /*
@@ -1326,6 +1341,33 @@ static void set_charge_state(enum charge_state_v2 state)
 	curr.state = state;
 }
 
+static void notify_host_of_over_current(struct batt_params *batt)
+{
+#ifdef CONFIG_THROTTLE_AP_ON_BAT_DISCHG_CURRENT
+	if (batt->flags & BATT_FLAG_BAD_CURRENT)
+		return;
+
+	if ((!ocp_throttle_start_time.val &&
+	     (batt->current < -BAT_MAX_DISCHG_CURRENT)) ||
+	    (ocp_throttle_start_time.val &&
+	     (batt->current < -BAT_MAX_DISCHG_CURRENT + BAT_OCP_HYSTERESIS))) {
+		ocp_throttle_start_time = get_time();
+		throttle_ap(THROTTLE_ON, THROTTLE_SOFT,
+			    THROTTLE_SRC_BAT_DISCHG_CURRENT);
+	} else if (ocp_throttle_start_time.val &&
+		   (get_time().val > ocp_throttle_start_time.val +
+		    BAT_OCP_TIMEOUT_US)) {
+		/*
+		 * Clear the timer and notify AP to stop throttling if
+		 * we haven't seen over current for BAT_OCP_TIMEOUT_US.
+		 */
+		ocp_throttle_start_time.val = 0;
+		throttle_ap(THROTTLE_OFF, THROTTLE_SOFT,
+			    THROTTLE_SRC_BAT_DISCHG_CURRENT);
+	}
+#endif
+}
+
 const struct batt_params *charger_current_battery_params(void)
 {
 	return &curr.batt;
@@ -1500,6 +1542,8 @@ void charger_task(void *u)
 			curr.batt.flags |= BATT_FLAG_BAD_STATE_OF_CHARGE;
 		}
 
+		notify_host_of_over_current(&curr.batt);
+
 		/*
 		 * Now decide what we want to do about it. We'll normally just
 		 * pass along whatever the battery wants to the charger. Note