Make USB_PD_POWER_INFO detect inactive supplier

Currently, CMD_USB_PD_POWER_INFO does not report a supplier if the
available current is 0. This causes a dedicated charger (a barrel
jack adapter) to be ignored by the command if it's not the active
supplier.

This change allows a supplier which has 0 current to be reported
by the command as long as there is no other supplier with positive
current on the same port. With this change, the host can detect
a BJ adapter's physical presence regardless of its charging status.

In other words, a supplier with positive current always supersedes
whatever supplier with zero current.

Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>

BUG=chromium:841944,b:111667665,b:111777351
BRANCH=none
TEST=Verify ectool usbpdpower 1 return 'Port 1: Disconnected' and
'Port 1: SNK (not charging)' without and with a BJ adapter connected
respectively on Fizz.

Change-Id: I22ba5f147209177c0c9cac87a123d4c3d0f2ec68
Reviewed-on: https://chromium-review.googlesource.com/1236850
Reviewed-by: Daisuke Nojiri <dnojiri@chromium.org>
Tested-by: Daisuke Nojiri <dnojiri@chromium.org>
Commit-Queue: Daisuke Nojiri <dnojiri@chromium.org>

1 files changed, 37 insertions, 15 deletions

diff --git a/common/charge_manager.c b/common/charge_manager.c
index afe1fc21ed..76c9d4e436 100644
--- a/common/charge_manager.c
+++ b/common/charge_manager.c
@@ -231,6 +231,35 @@ static int charge_manager_get_source_current(int port)
 	}
 }
 
+/*
+ * Find a supplier considering available current, voltage, power, and priority.
+ */
+static enum charge_supplier find_supplier(int port, enum charge_supplier sup,
+					  int min_cur)
+{
+	int i;
+	for (i = 0; i < CHARGE_SUPPLIER_COUNT; ++i) {
+		if (available_charge[i][port].current <= min_cur ||
+		    available_charge[i][port].voltage <= 0)
+			/* Doesn't meet volt or current requirement. Skip it. */
+			continue;
+		if (sup == CHARGE_SUPPLIER_NONE)
+			/* Haven't found any yet. Take it unconditionally. */
+			sup = i;
+		else if (supplier_priority[sup] < supplier_priority[i])
+			/* There is already a higher priority supplier. */
+			continue;
+		else if (supplier_priority[i] < supplier_priority[sup])
+			/* This has a higher priority. Take it. */
+			sup = i;
+		else if (POWER(available_charge[i][port]) >
+			 POWER(available_charge[sup][port]))
+			/* Priority is tie. Take it if power is higher. */
+			sup = i;
+	}
+	return sup;
+}
+
 /**
  * Fills passed power_info structure with current info about the passed port.
  *
@@ -241,24 +270,17 @@ static void charge_manager_fill_power_info(int port,
 	struct ec_response_usb_pd_power_info *r)
 {
 	int sup = CHARGE_SUPPLIER_NONE;
-	int i;
 
 	/* Determine supplier information to show. */
-	if (port == charge_port)
+	if (port == charge_port) {
 		sup = charge_supplier;
-	else
-		/* Find highest priority supplier */
-		for (i = 0; i < CHARGE_SUPPLIER_COUNT; ++i)
-			if (available_charge[i][port].current > 0 &&
-			    available_charge[i][port].voltage > 0 &&
-			    (sup == CHARGE_SUPPLIER_NONE ||
-			     supplier_priority[i] <
-			     supplier_priority[sup] ||
-			    (supplier_priority[i] ==
-			     supplier_priority[sup] &&
-			     POWER(available_charge[i][port]) >
-			     POWER(available_charge[sup][port]))))
-				sup = i;
+	} else {
+		/* Consider available current */
+		sup = find_supplier(port, sup, 0);
+		if (sup == CHARGE_SUPPLIER_NONE)
+			/* Ignore available current */
+			sup = find_supplier(port, sup, -1);
+	}
 
 	/* Fill in power role */
 	if (charge_port == port)