spring: a more aggressive current control approach

Currently we stop raising current input when a predefined limit is
reached. To take advantage of high power charger, we now push the limit
and detect over current shut off if any. This allows us to detect the
actual current limit of the charger.

BUG=chrome-os-partner:14319
TEST=Manual on Spring
BRANCH=none

Change-Id: I5aefd8c0ac02bd0ca9920e861a4fa62fc6e588e5
Signed-off-by: Vic Yang <victoryang@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/43863
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>

1 files changed, 89 insertions, 3 deletions

diff --git a/board/spring/usb_charging.c b/board/spring/usb_charging.c
index 7efc698062..a7f3e45728 100644
--- a/board/spring/usb_charging.c
+++ b/board/spring/usb_charging.c
@@ -40,7 +40,10 @@
 
 /* PWM control loop parameters */
 #define PWM_CTRL_BEGIN_OFFSET	30
-#define PWM_CTRL_STEP_DOWN	1
+#define PWM_CTRL_OC_MARGIN	15
+#define PWM_CTRL_OC_DETECT_TIME	(800 * MSEC)
+#define PWM_CTRL_OC_BACK_OFF	3
+#define PWM_CTRL_STEP_DOWN	2
 #define PWM_CTRL_STEP_UP	5
 #define PWM_CTRL_VBUS_LOW	4500
 #define PWM_CTRL_VBUS_HIGH	4700 /* Must be higher than 4.5V */
@@ -49,6 +52,24 @@ static int current_dev_type = TSU6721_TYPE_NONE;
 static int nominal_pwm_duty;
 static int current_pwm_duty;
 
+static enum {
+	LIMIT_NORMAL,
+	LIMIT_AGGRESSIVE,
+} current_limit_mode;
+
+/*
+ * Last time we see a power source removed. Also records the power source
+ * type and PWM duty cycle at that moment.
+ * Index: 0 = Unknown power source.
+ *        1 = Recognized power source.
+ */
+static timestamp_t power_removed_time[2];
+static uint32_t power_removed_type[2];
+static int power_removed_pwm_duty[2];
+
+/* PWM duty cycle limit based on over current event */
+static int over_current_pwm_duty;
+
 static enum ilim_config current_ilim_config = ILIM_CONFIG_MANUAL_OFF;
 
 static const int apple_charger_type[4] = {I_LIMIT_500MA,
@@ -180,6 +201,18 @@ void board_pwm_init_limit(void)
 		board_ilim_config(ILIM_CONFIG_MANUAL_ON);
 }
 
+static int board_pwm_check_lower_bound(void)
+{
+	if (current_limit_mode == LIMIT_AGGRESSIVE)
+		return (current_pwm_duty > nominal_pwm_duty -
+					   PWM_CTRL_OC_MARGIN &&
+			current_pwm_duty > over_current_pwm_duty &&
+			current_pwm_duty > 0);
+	else
+		return (current_pwm_duty > nominal_pwm_duty &&
+			current_pwm_duty > 0);
+}
+
 static void board_pwm_tweak(void)
 {
 	int vbus, current;
@@ -203,8 +236,7 @@ static void board_pwm_tweak(void)
 	    current >= 0) {
 		board_pwm_duty_cycle(current_pwm_duty + PWM_CTRL_STEP_UP);
 		CPRINTF("[%T PWM duty up %d%%]\n", current_pwm_duty);
-	} else if (vbus > PWM_CTRL_VBUS_HIGH &&
-		   current_pwm_duty > nominal_pwm_duty) {
+	} else if (vbus > PWM_CTRL_VBUS_HIGH && board_pwm_check_lower_bound()) {
 		board_pwm_duty_cycle(current_pwm_duty - PWM_CTRL_STEP_DOWN);
 		CPRINTF("[%T PWM duty down %d%%]\n", current_pwm_duty);
 	}
@@ -235,6 +267,36 @@ static void usb_device_change(int dev_type)
 	if (current_dev_type == dev_type)
 		return;
 
+	over_current_pwm_duty = 0;
+
+	/*
+	 * When a power source is removed, record time, power source type,
+	 * and PWM duty cycle. Then when we see a power source, compare type
+	 * and calculate time difference to determine if we have just
+	 * encountered an over current event.
+	 */
+	if ((current_dev_type & TSU6721_TYPE_VBUS_DEBOUNCED) &&
+	    (dev_type == TSU6721_TYPE_NONE)) {
+		int idx = !(current_dev_type == TSU6721_TYPE_VBUS_DEBOUNCED);
+		power_removed_time[idx] = get_time();
+		power_removed_type[idx] = current_dev_type;
+		/*
+		 * Considering user may plug/unplug the charger too fast, we
+		 * don't limit current to lower than nominal current limit.
+		 */
+		power_removed_pwm_duty[idx] = MIN(current_pwm_duty,
+						  nominal_pwm_duty);
+	} else if (dev_type & TSU6721_TYPE_VBUS_DEBOUNCED) {
+		int idx = !(dev_type == TSU6721_TYPE_VBUS_DEBOUNCED);
+		timestamp_t now = get_time();
+		now.val -= power_removed_time[idx].val;
+		if (power_removed_type[idx] == dev_type &&
+		    now.val < PWM_CTRL_OC_DETECT_TIME) {
+			over_current_pwm_duty = power_removed_pwm_duty[idx] +
+						PWM_CTRL_OC_BACK_OFF;
+		}
+	}
+
 	/*
 	 * Supply VBUS if needed. If we toggle power output, wait for a moment,
 	 * and then update device type. To avoid race condition, check if power
@@ -377,3 +439,27 @@ static int command_batdebug(int argc, char **argv)
 }
 DECLARE_CONSOLE_COMMAND(batdebug, command_batdebug,
 			NULL, NULL, NULL);
+
+static int command_current_limit_mode(int argc, char **argv)
+{
+	if (1 == argc) {
+		if (current_limit_mode == LIMIT_NORMAL)
+			ccprintf("Normal mode\n");
+		else
+			ccprintf("Aggressive mode\n");
+		return EC_SUCCESS;
+	} else if (2 == argc) {
+		if (!strcasecmp(argv[1], "normal"))
+			current_limit_mode = LIMIT_NORMAL;
+		else if (!strcasecmp(argv[1], "aggressive"))
+			current_limit_mode = LIMIT_AGGRESSIVE;
+		else
+			return EC_ERROR_INVAL;
+		return EC_SUCCESS;
+	}
+	return EC_ERROR_INVAL;
+}
+DECLARE_CONSOLE_COMMAND(limitmode, command_current_limit_mode,
+			"[normal | aggressive]",
+			"Set current limit mode",
+			NULL);