charge_ramp: initial commit of charge ramp module

Add new charge_ramp module which works with charge_manager to
slowly increase input current limit in order to find the optimal
charging current. To do this it looks for either VBUS drooping
too low or for the charger to over-current.

BUG=chrome-os-partner:34946
BRANCH=samus
TEST=tested with a variety of BC1.2 chargers, type-C only chargers,
and PD chargers to make sure we always stabilize charging at an
appropriate current limit.

Change-Id: Icc95aa2738ddb221f163f91c14a342a0674f9e0f
Signed-off-by: Alec Berg <alecaberg@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/247304
Reviewed-by: Vic Yang <victoryang@chromium.org>
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>

1 files changed, 323 insertions, 0 deletions

diff --git a/common/charge_ramp.c b/common/charge_ramp.c
new file mode 100644
index 0000000000..37bc45942d
--- /dev/null
+++ b/common/charge_ramp.c
@@ -0,0 +1,323 @@
+/* Copyright 2015 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.
+ */
+
+/* Charge input current limit ramp module for Chrome EC */
+
+#include "charge_manager.h"
+#include "charge_ramp.h"
+#include "common.h"
+#include "console.h"
+#include "task.h"
+#include "timer.h"
+#include "usb_pd_config.h"
+#include "util.h"
+
+#define CPRINTS(format, args...) cprints(CC_USBCHARGE, format, ## args)
+
+/* Number of times to ramp current searching for limit before stable charging */
+#define RAMP_COUNT          3
+
+/*
+ * Time to delay for detecting the charger type (must be long enough for BC1.2
+ * driver to get supplier information and notify charge manager).
+ */
+#define CHARGE_DETECT_DELAY (2*SECOND)
+
+/* Maximum allowable time charger can be unplugged to be considered an OCP */
+#define OC_RECOVER_MAX_TIME (SECOND)
+
+/* Delay for running state machine when board is not consuming full current */
+#define CURRENT_DRAW_DELAY  (5*SECOND)
+
+/* Current ramp increment */
+#define RAMP_CURR_INCR_MA   64
+#define RAMP_CURR_DELAY     (500*MSEC)
+
+/* How much to backoff the input current limit when limit has been found */
+#define RAMP_ICL_BACKOFF    (2*RAMP_CURR_INCR_MA)
+
+/* Interval at which VBUS voltage is monitored in stable state */
+#define STABLE_VBUS_MONITOR_INTERVAL (SECOND)
+
+/* Time to delay for stablizing the charging current */
+#define STABLIZE_DELAY (5*SECOND)
+
+enum chg_ramp_state {
+	CHG_RAMP_DISCONNECTED,
+	CHG_RAMP_CHARGE_DETECT,
+	CHG_RAMP_OVERCURRENT_DETECT,
+	CHG_RAMP_RAMP,
+	CHG_RAMP_STABILIZE,
+	CHG_RAMP_STABLE,
+};
+static enum chg_ramp_state ramp_st;
+
+struct oc_info {
+	timestamp_t ts;
+	uint64_t recover;
+	int sup;
+	int icl;
+};
+
+/* OCP info for each over-current */
+static struct oc_info oc_info[PD_PORT_COUNT][RAMP_COUNT];
+static int oc_info_idx[PD_PORT_COUNT];
+#define ACTIVE_OC_INFO (oc_info[active_port][oc_info_idx[active_port]])
+
+/* Active charging information */
+static int active_port = CHARGE_PORT_NONE;
+static int active_sup;
+static int active_icl;
+static timestamp_t reg_time;
+
+static int stablize_port;
+static int stablize_sup;
+
+/* Maximum/minimum input current limit for active charger */
+static int max_icl;
+static int min_icl;
+
+
+void chg_ramp_charge_supplier_change(int port, int supplier, int current,
+				     timestamp_t registration_time)
+{
+	/*
+	 * If the last active port was a valid port and the port
+	 * has changed, then this may have been an over-current.
+	 */
+	if (active_port != CHARGE_PORT_NONE &&
+	    port != active_port) {
+		if (oc_info_idx[active_port] == RAMP_COUNT - 1)
+			oc_info_idx[active_port] = 0;
+		else
+			oc_info_idx[active_port]++;
+		ACTIVE_OC_INFO.ts = get_time();
+		ACTIVE_OC_INFO.sup = active_sup;
+		ACTIVE_OC_INFO.icl = active_icl;
+	}
+
+	/* Set new active port, set ramp state, and wake ramp task */
+	active_port = port;
+	active_sup = supplier;
+	min_icl = current;
+	max_icl = board_get_ramp_current_limit(active_sup);
+	reg_time = registration_time;
+	if (ramp_st != CHG_RAMP_STABILIZE) {
+		ramp_st = (active_port == CHARGE_PORT_NONE) ?
+			  CHG_RAMP_DISCONNECTED : CHG_RAMP_CHARGE_DETECT;
+		CPRINTS("Ramp reset: st%d\n", ramp_st);
+		task_wake(TASK_ID_CHG_RAMP);
+	}
+}
+
+int chg_ramp_get_current_limit(void)
+{
+	/*
+	 * If we are ramping or stable, then use the active input
+	 * current limit. Otherwise, use the minimum input current
+	 * limit.
+	 */
+	switch (ramp_st) {
+	case CHG_RAMP_RAMP:
+	case CHG_RAMP_STABILIZE:
+	case CHG_RAMP_STABLE:
+		return active_icl;
+	default:
+		return min_icl;
+	}
+}
+
+void chg_ramp_task(void)
+{
+	int task_wait_time = -1;
+	int i;
+	/*
+	 * Static initializer so that we don't clobber early calls to this
+	 * module.
+	 */
+	static enum chg_ramp_state ramp_st_prev = CHG_RAMP_DISCONNECTED,
+				   ramp_st_new = CHG_RAMP_DISCONNECTED;
+	int active_icl_new;
+
+	/* Clear last OCP supplier to guarantee we ramp on first connect */
+	for (i = 0; i < PD_PORT_COUNT; i++)
+		oc_info[i][0].sup = CHARGE_SUPPLIER_NONE;
+
+	while (1) {
+		ramp_st_new = ramp_st;
+		active_icl_new = active_icl;
+		switch (ramp_st) {
+		case CHG_RAMP_DISCONNECTED:
+			/* Do nothing */
+			task_wait_time = -1;
+			break;
+		case CHG_RAMP_CHARGE_DETECT:
+			/* Delay for charge_manager to determine supplier */
+			/* On entry to state, store the OC recovery time */
+			if (ramp_st_prev != ramp_st)
+				ACTIVE_OC_INFO.recover =
+					reg_time.val - ACTIVE_OC_INFO.ts.val;
+
+			/*
+			 * If we are not drawing full charge, then don't ramp,
+			 * just wait in this state, until we are.
+			 */
+			if (!board_is_consuming_full_charge()) {
+				task_wait_time = CURRENT_DRAW_DELAY;
+				break;
+			}
+
+			ramp_st_new = CHG_RAMP_OVERCURRENT_DETECT;
+			task_wait_time = CHARGE_DETECT_DELAY;
+			break;
+		case CHG_RAMP_OVERCURRENT_DETECT:
+			/* Check if we should ramp or go straight to stable */
+			task_wait_time = SECOND;
+
+			/* Skip ramp for specific suppliers */
+			if (!board_is_ramp_allowed(active_sup)) {
+				active_icl_new = min_icl;
+				ramp_st_new = CHG_RAMP_STABLE;
+				break;
+			}
+
+			/*
+			 * Compare recent OCP events, if all info matches,
+			 * then we don't need to ramp anymore.
+			 */
+			for (i = 0; i < RAMP_COUNT; i++) {
+				if (oc_info[active_port][i].sup != active_sup ||
+				    oc_info[active_port][i].recover >
+				    OC_RECOVER_MAX_TIME)
+					break;
+			}
+
+			if (i == RAMP_COUNT) {
+				/* Found OC threshold! */
+				active_icl_new = ACTIVE_OC_INFO.icl -
+						 RAMP_ICL_BACKOFF;
+				ramp_st_new = CHG_RAMP_STABLE;
+			} else {
+				/*
+				 * Need to ramp to find OC threshold, start
+				 * at the minimum input current limit.
+				 */
+				active_icl_new = min_icl;
+				ramp_st_new = CHG_RAMP_RAMP;
+			}
+			break;
+		case CHG_RAMP_RAMP:
+			/* Keep ramping until we find the limit */
+			task_wait_time = RAMP_CURR_DELAY;
+
+			/* Pause ramping if we are not drawing full current */
+			if (!board_is_consuming_full_charge()) {
+				task_wait_time = CURRENT_DRAW_DELAY;
+				break;
+			}
+
+			/* If VBUS is sagging a lot, then stop ramping */
+			if (board_is_vbus_too_low(CHG_RAMP_VBUS_RAMPING)) {
+				CPRINTS("VBUS low");
+				active_icl_new = MAX(min_icl, active_icl -
+							      RAMP_ICL_BACKOFF);
+				ramp_st_new = CHG_RAMP_STABILIZE;
+				task_wait_time = STABLIZE_DELAY;
+				stablize_port = active_port;
+				stablize_sup = active_sup;
+				break;
+			}
+
+			/* Ramp the current limit if we haven't reached max */
+			if (active_icl == max_icl)
+				ramp_st_new = CHG_RAMP_STABLE;
+			else if (active_icl + RAMP_CURR_INCR_MA > max_icl)
+				active_icl_new = max_icl;
+			else
+				active_icl_new = active_icl + RAMP_CURR_INCR_MA;
+			break;
+		case CHG_RAMP_STABILIZE:
+			/* Wait for current to stabilize after ramp is done */
+			/* Use default delay for exiting this state */
+			task_wait_time = SECOND;
+			if (active_port == stablize_port &&
+			    active_sup == stablize_sup) {
+				ramp_st_new = CHG_RAMP_STABLE;
+				break;
+			}
+
+			ramp_st_new = active_port == CHARGE_PORT_NONE ?
+				      CHG_RAMP_DISCONNECTED :
+				      CHG_RAMP_CHARGE_DETECT;
+			break;
+		case CHG_RAMP_STABLE:
+			/* Maintain input current limit */
+			/* On entry log charging stats */
+#ifdef CONFIG_USB_PD_LOGGING
+			if (ramp_st_prev != ramp_st)
+				charge_manager_save_log(active_port);
+#endif
+
+			/* Keep an eye on VBUS and restart ramping if it dips */
+			if (board_is_ramp_allowed(active_sup) &&
+			    board_is_vbus_too_low(CHG_RAMP_VBUS_STABLE)) {
+				CPRINTS("VBUS low; Re-ramp");
+				active_icl_new = min_icl;
+				ramp_st_new = CHG_RAMP_RAMP;
+			}
+			task_wait_time = STABLE_VBUS_MONITOR_INTERVAL;
+			break;
+		}
+		if (ramp_st != ramp_st_new || active_icl != active_icl_new)
+			CPRINTS("Ramp p%d st%d %dmA %dmA",
+				active_port, ramp_st_new, min_icl,
+				active_icl_new);
+
+		ramp_st_prev = ramp_st;
+		ramp_st = ramp_st_new;
+		active_icl = active_icl_new;
+
+		/* Set the input current limit */
+		board_set_charge_limit(chg_ramp_get_current_limit());
+
+		if (ramp_st == CHG_RAMP_STABILIZE)
+			/*
+			 * When in stabilize state, supplier/port may change
+			 * and we don't want to wake up task until we have
+			 * slept this amount of time.
+			 */
+			usleep(task_wait_time);
+		else
+			task_wait_event(task_wait_time);
+	}
+}
+
+#ifdef CONFIG_CMD_CHGRAMP
+static int command_chgramp(int argc, char **argv)
+{
+	int i;
+	int port;
+
+	ccprintf("Chg Ramp:\nState: %d\nMin ICL: %d\nActive ICL: %d\n",
+		 ramp_st, min_icl, active_icl);
+
+	for (port = 0; port < PD_PORT_COUNT; port++) {
+		ccprintf("Port %d:\n", port);
+		ccprintf("  OC idx:%d\n", oc_info_idx[port]);
+		for (i = 0; i < RAMP_COUNT; i++) {
+			ccprintf("  OC %d: s%d recover%lu icl%d\n", i,
+				 oc_info[port][i].sup,
+				 oc_info[port][i].recover,
+				 oc_info[port][i].icl);
+		}
+	}
+
+	return EC_SUCCESS;
+}
+DECLARE_CONSOLE_COMMAND(chgramp, command_chgramp,
+	"",
+	"Dump charge ramp state info",
+	NULL);
+#endif