samus: limit input current when batt near full and 5V charger

Limit input current to 2A when battery is near full and we are using
a charger below the boost bypass threshold in order to prevent
charging noise from the charge circuit.

This also changes the threshold at which 5V ramping is allowed to
90% because this is roughly the threshold at which the battery stops
drawing full current.

BUG=chrome-os-partner:36534
BRANCH=samus
TEST=load onto samus. use battfake EC console command to test
various battery states of charge:

- With zinger, verify that at 20V we never limit input current based
on battery SOC.
- With zinger at 5V, verify that >= 90% we limit input current to
2A, and < 90% it's still 3A.
- With 5V BC1.2 DCP, verify that >= 90% we don't ramp, <90% we do.

Change-Id: I868828b5807572736ea58f62bf3596f6416533d2
Signed-off-by: Alec Berg <alecaberg@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/256072
Reviewed-by: Shawn N <shawnn@chromium.org>

2 files changed, 51 insertions, 23 deletions

diff --git a/board/samus_pd/board.c b/board/samus_pd/board.c
index 0c996d5b6d..5e6100c85d 100644
--- a/board/samus_pd/board.c
+++ b/board/samus_pd/board.c
@@ -36,6 +36,15 @@
 /* Default input current limit when VBUS is present */
 #define DEFAULT_CURR_LIMIT            500  /* mA */
 
+/*
+ * When battery is high, system may not be pulling full current. Also, when
+ * high AND input voltage is below boost bypass, then limit input current
+ * limit to HIGH_BATT_LIMIT_CURR_MA to reduce audible ringing.
+ */
+#define HIGH_BATT_THRESHOLD 90
+#define HIGH_BATT_LIMIT_BOOST_BYPASS_MV 11000
+#define HIGH_BATT_LIMIT_CURR_MA 2000
+
 /* Chipset power state */
 static enum power_state ps;
 
@@ -43,11 +52,18 @@ static enum power_state ps;
 static int batt_soc;
 
 /* Default to 5V charging allowed for dead battery case */
-enum pd_charge_state charge_state = PD_CHARGE_5V;
+static enum pd_charge_state charge_state = PD_CHARGE_5V;
 
-/* PD MCU status and host event status for host command */
-static struct ec_response_pd_status pd_status;
-static struct ec_response_host_event_status host_event_status;
+/*
+ * PD MCU status and host event status for host command
+ * Note: these vars must be aligned on 4-byte boundary because we pass the
+ * address to atomic_ functions which use assembly to access them.
+ */
+static struct ec_response_pd_status pd_status __aligned(4);
+static struct ec_response_host_event_status host_event_status __aligned(4);
+
+/* Desired input current limit */
+static int desired_charge_rate_ma = -1;
 
 /*
  * Store the state of our USB data switches so that they can be restored
@@ -621,10 +637,6 @@ void board_flip_usb_mux(int port)
 	gpio_set_level(usb_mux->ss2_dp_mode, usb_polarity);
 }
 
-void board_update_battery_soc(int soc)
-{
-	batt_soc = soc;
-}
 
 int board_get_battery_soc(void)
 {
@@ -742,7 +754,7 @@ int board_get_ramp_current_limit(int supplier)
  */
 int board_is_consuming_full_charge(void)
 {
-	return batt_soc >= 1 && batt_soc < 95;
+	return batt_soc >= 1 && batt_soc < HIGH_BATT_THRESHOLD;
 }
 
 /*
@@ -796,20 +808,21 @@ int board_is_vbus_too_low(enum chg_ramp_vbus_state ramp_state)
 	return vbus_sum < (VBUS_STABLE_SAMPLE_COUNT * VBUS_LOW_THRESHOLD_MV);
 }
 
-/**
- * Set the charge limit based upon desired maximum.
- *
- * @param charge_ma     Desired charge limit (mA).
- */
-void board_set_charge_limit(int charge_ma)
+static int board_update_charge_limit(int charge_ma)
 {
-	static int last_charge_ma = -1;
+	static int actual_charge_rate_ma = -1;
+
+	desired_charge_rate_ma = charge_ma;
+
+	if (batt_soc >= HIGH_BATT_THRESHOLD &&
+	    adc_read_channel(ADC_VBUS) < HIGH_BATT_LIMIT_BOOST_BYPASS_MV)
+		charge_ma = MIN(charge_ma, HIGH_BATT_LIMIT_CURR_MA);
 
 	/* if current hasn't changed, don't do anything */
-	if (charge_ma == last_charge_ma)
-		return;
+	if (charge_ma == actual_charge_rate_ma)
+		return 0;
 
-	last_charge_ma = charge_ma;
+	actual_charge_rate_ma = charge_ma;
 
 #ifdef CONFIG_PWM
 	int pwm_duty = MA_TO_PWM(charge_ma);
@@ -823,9 +836,27 @@ void board_set_charge_limit(int charge_ma)
 
 	pd_status.curr_lim_ma = MAX(0, charge_ma -
 					INPUT_CURRENT_LIMIT_OFFSET_MA);
-	pd_send_ec_int();
 
 	CPRINTS("New ilim %d", charge_ma);
+	return 1;
+}
+
+/**
+ * Set the charge limit based upon desired maximum.
+ *
+ * @param charge_ma     Desired charge limit (mA).
+ */
+void board_set_charge_limit(int charge_ma)
+{
+	/* Update current limit and notify EC if it changed */
+	if (board_update_charge_limit(charge_ma))
+		pd_send_ec_int();
+}
+
+static void board_update_battery_soc(int soc)
+{
+	batt_soc = soc;
+	board_update_charge_limit(desired_charge_rate_ma);
 }
 
 /* Send host event up to AP */
diff --git a/board/samus_pd/board.h b/board/samus_pd/board.h
index 97a20b302c..cb9d0f991e 100644
--- a/board/samus_pd/board.h
+++ b/board/samus_pd/board.h
@@ -124,9 +124,6 @@ extern const int supplier_priority[];
 /* Map current in milli-amps to PWM duty cycle percentage */
 #define MA_TO_PWM(curr) (((curr) - PWM_0_MA) * 100 / (PWM_100_MA - PWM_0_MA))
 
-/* Called when we receive battery level info from the EC. */
-void board_update_battery_soc(int soc);
-
 /* Get the last received battery level. */
 int board_get_battery_soc(void);