power: introducing pwr_avg console command

pwr_avg provides an average voltage, current, and power over the last
1 minute. It's up to the battery drivers to implement this
functionality.
This change allows us to have better power tracking while minimizing
the power impact on the EC, because
- the pwr_avg command only needs to be called once every minute, and is
short, thus less expensive to parse on ECs without a UART buffer
- the work done to keep the avg is partially done by the batteries
already and it's just a question of retrieving it.

undefined on wheatley since no power debugging planned on that board.

usage:
> pwr_avg
mv = 7153
ma = -605
mw = -4327

BUG=chromium:752320
BRANCH=None
TEST=make buildall -j

Change-Id: Id1a3479d277aedf90dfa965afb4ee9136654b1cf
Signed-off-by: Ruben Rodriguez Buchillon <coconutruben@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/823884
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>

2 files changed, 38 insertions, 0 deletions

diff --git a/driver/battery/max17055.c b/driver/battery/max17055.c
index cd0a379e8e..1a38c2748f 100644
--- a/driver/battery/max17055.c
+++ b/driver/battery/max17055.c
@@ -263,6 +263,20 @@ void battery_get_params(struct batt_params *batt)
 		batt->flags |= BATT_FLAG_WANT_CHARGE;
 }
 
+#ifdef CONFIG_CMD_PWR_AVG
+int battery_get_avg_current(void)
+{
+	/* TODO(crbug.com/752320) implement this */
+	return EC_ERROR_UNIMPLEMENTED;
+}
+
+int battery_get_avg_voltage(void)
+{
+	/* TODO(crbug.com/752320) implement this */
+	return -EC_ERROR_UNIMPLEMENTED;
+}
+#endif /* CONFIG_CMD_PWR_AVG */
+
 /* Wait until battery is totally stable. */
 int battery_wait_for_stable(void)
 {
diff --git a/driver/battery/smart.c b/driver/battery/smart.c
index bbbec8f21e..743ebc1ee1 100644
--- a/driver/battery/smart.c
+++ b/driver/battery/smart.c
@@ -283,6 +283,30 @@ test_mockable int battery_device_chemistry(char *dest, int size)
 	return sb_read_string(SB_DEVICE_CHEMISTRY, dest, size);
 }
 
+#ifdef CONFIG_CMD_PWR_AVG
+int battery_get_avg_current(void)
+{
+	int current;
+
+	/* This is a signed 16-bit value. */
+	sb_read(SB_AVERAGE_CURRENT, &current);
+	return (int16_t)current;
+}
+
+/*
+ * Technically returns only the instantaneous reading, but tests showed that
+ * for the majority of charge states above 3% this varies by less than 40mV
+ * every minute, so we accept the inaccuracy here.
+ */
+int battery_get_avg_voltage(void)
+{
+	int voltage = -EC_ERROR_UNKNOWN;
+
+	sb_read(SB_VOLTAGE, &voltage);
+	return voltage;
+}
+#endif /* CONFIG_CMD_PWR_AVG */
+
 void battery_get_params(struct batt_params *batt)
 {
 	struct batt_params batt_new = {0};