chgstv2/sustainer: Stop AC current when discharging

Currently, the battery sustainer discharges the battery using
CHARGE_CONTROL_IDLE, which uses the AC current and stops the
current from the battery.

With this change, when lower < upper, the sustainer discharges using
DISCHARGE. When lower == upper, the sustainer discharges using IDLE.

BUG=b:188457962
BRANCH=None
TEST=run-sbs_charging_v2

Change-Id: I4af31eff488bc9cfa627f84994b685488c3c9061
Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3049290
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>
Reviewed-by: Derek Basehore <dbasehore@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3105743

2 files changed, 79 insertions, 7 deletions

diff --git a/common/charge_state_v2.c b/common/charge_state_v2.c
index 104539e780..b8ad1fc425 100644
--- a/common/charge_state_v2.c
+++ b/common/charge_state_v2.c
@@ -1531,22 +1531,28 @@ static void sustain_battery_soc(void)
 
 	soc = charge_get_display_charge() / 10;
 
+	/*
+	 * When lower < upper, the sustainer discharges using DISCHARGE. When
+	 * lower == upper, the sustainer discharges using IDLE. The following
+	 * switch statement handle both cases but in reality either DISCHARGE
+	 * or IDLE is used but not both.
+	 */
 	switch (mode) {
 	case CHARGE_CONTROL_NORMAL:
 		/* Going up */
 		if (sustain_soc.upper < soc)
-			mode = CHARGE_CONTROL_DISCHARGE;
+			mode = sustain_soc.upper == sustain_soc.lower ?
+				CHARGE_CONTROL_IDLE : CHARGE_CONTROL_DISCHARGE;
 		break;
 	case CHARGE_CONTROL_IDLE:
-		/* discharging naturally */
+		/* Discharging naturally */
 		if (soc < sustain_soc.lower)
-			/* TODO: Charge slowly */
 			mode = CHARGE_CONTROL_NORMAL;
 		break;
 	case CHARGE_CONTROL_DISCHARGE:
-		/* discharging rapidly (discharge_on_ac) */
-		if (soc < sustain_soc.upper)
-			mode = CHARGE_CONTROL_IDLE;
+		/* Discharging actively. */
+		if (soc < sustain_soc.lower)
+			mode = CHARGE_CONTROL_NORMAL;
 		break;
 	default:
 		return;
diff --git a/test/sbs_charging_v2.c b/test/sbs_charging_v2.c
index 6b7bf04ca4..addd438d7e 100644
--- a/test/sbs_charging_v2.c
+++ b/test/sbs_charging_v2.c
@@ -748,7 +748,7 @@ static int test_battery_sustainer(void)
 	ccprintf("Test lower < SoC < upper.\n");
 	display_soc = 799;
 	wait_charging_state();
-	TEST_ASSERT(get_chg_ctrl_mode() == CHARGE_CONTROL_IDLE);
+	TEST_ASSERT(get_chg_ctrl_mode() == CHARGE_CONTROL_DISCHARGE);
 	ccprintf("Pass.\n");
 
 	ccprintf("Test SoC < lower < upper.\n");
@@ -805,6 +805,71 @@ static int test_battery_sustainer(void)
 	return EC_SUCCESS;
 }
 
+static int test_battery_sustainer_discharge_idle(void)
+{
+	struct ec_params_charge_control p;
+	int rv;
+
+	test_setup(1);
+
+	/* Enable sustainer */
+	p.cmd = EC_CHARGE_CONTROL_CMD_SET;
+	p.mode = CHARGE_CONTROL_NORMAL;
+	p.sustain_soc.lower = 80;
+	p.sustain_soc.upper = 80;
+	rv = test_send_host_command(EC_CMD_CHARGE_CONTROL, 2,
+				    &p, sizeof(p), NULL, 0);
+	TEST_ASSERT(rv == EC_RES_SUCCESS);
+
+	/* Check mode transition as the SoC changes. */
+
+	/* SoC < lower (= upper) */
+	display_soc = 780;
+	wait_charging_state();
+	TEST_ASSERT(get_chg_ctrl_mode() == CHARGE_CONTROL_NORMAL);
+
+	/* (lower =) upper < SoC */
+	display_soc = 810;
+	wait_charging_state();
+	TEST_ASSERT(get_chg_ctrl_mode() == CHARGE_CONTROL_IDLE);
+
+	/* Unplug AC. Sustainer gets deactivated. */
+	gpio_set_level(GPIO_AC_PRESENT, 0);
+	wait_charging_state();
+	TEST_ASSERT(get_chg_ctrl_mode() == CHARGE_CONTROL_NORMAL);
+
+	/* Replug AC. Sustainer gets re-activated. */
+	gpio_set_level(GPIO_AC_PRESENT, 1);
+	wait_charging_state();
+	TEST_ASSERT(get_chg_ctrl_mode() == CHARGE_CONTROL_IDLE);
+
+	/* lower = SoC = upper */
+	display_soc = 800;
+	wait_charging_state();
+	TEST_ASSERT(get_chg_ctrl_mode() == CHARGE_CONTROL_IDLE);
+
+	/* SoC < lower (= upper) */
+	display_soc = 789;
+	wait_charging_state();
+	TEST_ASSERT(get_chg_ctrl_mode() == CHARGE_CONTROL_NORMAL);
+
+	/* Disable sustainer */
+	p.cmd = EC_CHARGE_CONTROL_CMD_SET;
+	p.mode = CHARGE_CONTROL_NORMAL;
+	p.sustain_soc.lower = -1;
+	p.sustain_soc.upper = -1;
+	rv = test_send_host_command(EC_CMD_CHARGE_CONTROL, 2,
+				    &p, sizeof(p), NULL, 0);
+	TEST_ASSERT(rv == EC_RES_SUCCESS);
+
+	/* This time, mode will stay in NORMAL even when upper < SoC. */
+	display_soc = 810;
+	wait_charging_state();
+	TEST_ASSERT(get_chg_ctrl_mode() == CHARGE_CONTROL_NORMAL);
+
+	return EC_SUCCESS;
+}
+
 void run_test(void)
 {
 	RUN_TEST(test_charge_state);
@@ -815,6 +880,7 @@ void run_test(void)
 	RUN_TEST(test_hc_current_limit);
 	RUN_TEST(test_low_battery_hostevents);
 	RUN_TEST(test_battery_sustainer);
+	RUN_TEST(test_battery_sustainer_discharge_idle);
 
 	test_print_result();
 }