samus: Allow samus to charge w/o battery or with dead batterystabilize-5942.B

Use a EC to PD host command to notify the PD MCU when a battery
is present and charged enough that it is ok to negotiate for a
higher power. The PD MCU will not negotiate until the host command
is received, which allows the system to be powered without a
battery or with a dead battery with 5V.

BUG=chrome-os-partner:28611
BRANCH=none
TEST=Tested on a samus:

1) Tested the normal case of battery charged and plugged in. When
charger is plugged in, the device immediately starts negotiating
for 20V and starts charging.
2) Tested with no battery. Plug in a charger, samus boots and stays
alive. VBUS measured at 5V. When a battery is plugged in, device
negotiates for 20V and starts charging.
3) Tested dead battery by taking a battery with no charge, and
plugging in zinger. Everything boots, but PD does not negotiate
for power. Then when battery reaches 1%, PD negotiates and zinger
switches to 20V without causing a reboot.

Change-Id: Iaa451403674e86cddbd3fe80e9503584910be576
Signed-off-by: Alec Berg <alecaberg@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/201958
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>

1 files changed, 52 insertions, 0 deletions

diff --git a/common/host_command_pd.c b/common/host_command_pd.c
new file mode 100644
index 0000000000..5d9a3adf6d
--- /dev/null
+++ b/common/host_command_pd.c
@@ -0,0 +1,52 @@
+/* Copyright (c) 2014 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+/* Host command module for PD MCU */
+
+#include "charge_state.h"
+#include "common.h"
+#include "host_command.h"
+#include "task.h"
+#include "timer.h"
+#include "util.h"
+
+#define TASK_EVENT_EXCHANGE_PD_STATUS  TASK_EVENT_CUSTOM(1)
+
+void host_command_pd_send_status(void)
+{
+	task_set_event(TASK_ID_PDCMD, TASK_EVENT_EXCHANGE_PD_STATUS, 0);
+}
+
+static void pd_exchange_status(void)
+{
+	struct ec_params_pd_status ec_status;
+
+	/*
+	 * TODO(crosbug.com/p/29499): Change sending state of charge to
+	 * remaining capacity for finer grained control.
+	 */
+	/* Send battery state of charge */
+	if (charge_get_flags() & CHARGE_FLAG_BATT_RESPONSIVE)
+		ec_status.batt_soc = charge_get_percent();
+	else
+		ec_status.batt_soc = -1;
+
+	pd_host_command(EC_CMD_PD_EXCHANGE_STATUS, 0, &ec_status,
+			sizeof(struct ec_params_pd_status), NULL, 0);
+}
+
+void pd_command_task(void)
+{
+
+	while (1) {
+		/* Wait for the next command event */
+		int evt = task_wait_event(-1);
+
+		/* Process event to send status to PD */
+		if (evt & TASK_EVENT_EXCHANGE_PD_STATUS)
+			pd_exchange_status();
+	}
+}
+