charger: Add LIMIT_POWER charger param for low bat + weak charger

Add support for two new configs to specify critical energy battery
percentage and critical external charger power. When we are under both
thresholds, set the LIMIT_POWER charger parameter to inform the AP that it
should conserve power to avoid brownout, and consider jumping to EC RW
to negotiate PD.

In addition, modify the existing CONFIG_CHARGER_MIN_BAT_PCT_FOR_POWER_ON
to allow power-up regardless of power level if a 15W+ charger is
attached, since there is a reasonable chance it may speak PD and provide
sufficient power to boot the AP.

BUG=chromium:537269
TEST=Manual on Glados. Set CHG_MW thresh to 20000, BAT_PCT to 50. Verify
that LIMIT_POWER charger param is set until Zinger negotiates to 20V. Also
veify that system can boot with Donette.
BRANCH=None

Signed-off-by: Shawn Nematbakhsh <shawnn@chromium.org>
Change-Id: Ic963c82fea4ad10e8a5d7e476c5ce3e5ae525dad
Reviewed-on: https://chromium-review.googlesource.com/306774
Commit-Ready: Shawn N <shawnn@chromium.org>
Tested-by: Shawn N <shawnn@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Reviewed-by: Alec Berg <alecaberg@chromium.org>

7 files changed, 74 insertions, 3 deletions

diff --git a/common/charge_manager.c b/common/charge_manager.c
index d88cc0cab8..2dec5210b6 100644
--- a/common/charge_manager.c
+++ b/common/charge_manager.c
@@ -804,6 +804,21 @@ int charge_manager_get_active_charge_port(void)
 	return charge_port;
 }
 
+/**
+ * Return the power limit (uW) set by charge manager.
+ */
+int charge_manager_get_power_limit_uw(void)
+{
+	int current_ma = charge_current;
+	int voltage_mv = charge_voltage;
+
+	if (current_ma == CHARGE_CURRENT_UNINITIALIZED ||
+	    voltage_mv == CHARGE_VOLTAGE_UNINITIALIZED)
+		return 0;
+	else
+		return current_ma * voltage_mv;
+}
+
 #ifndef TEST_BUILD
 static int hc_pd_power_info(struct host_cmd_handler_args *args)
 {
diff --git a/common/charge_state_v2.c b/common/charge_state_v2.c
index b01f537b20..b4ffd06aa5 100644
--- a/common/charge_state_v2.c
+++ b/common/charge_state_v2.c
@@ -7,6 +7,7 @@
 
 #include "battery.h"
 #include "battery_smart.h"
+#include "charge_manager.h"
 #include "charge_state.h"
 #include "charger.h"
 #include "chipset.h"
@@ -33,6 +34,9 @@
 #define PRECHARGE_TIMEOUT_US (PRECHARGE_TIMEOUT * SECOND)
 #define LFCC_EVENT_THRESH 5 /* Full-capacity change reqd for host event */
 
+/* Prior to negotiating PD, most PD chargers advertise 15W */
+#define LIKELY_PD_USBC_POWER_MW 15000
+
 /*
  * State for charger_task(). Here so we can reset it on a HOOK_INIT, and
  * because stack space is more limited than .bss
@@ -907,6 +911,19 @@ int charge_prevent_power_on(void)
 	    CONFIG_CHARGER_MIN_BAT_PCT_FOR_POWER_ON)
 		prevent_power_on = 1;
 
+#ifdef CONFIG_CHARGER_LIMIT_POWER_THRESH_BAT_PCT
+	/*
+	 * Allow power-on if our charger advertises more than
+	 * LIKELY_PD_USBC_POWER_MW since it may speak PD and provide
+	 * sufficient power once we enable PD communication.
+	 */
+	if (prevent_power_on)
+		if (charge_manager_get_power_limit_uw() >=
+		    MIN(LIKELY_PD_USBC_POWER_MW * 1000,
+			CONFIG_CHARGER_LIMIT_POWER_THRESH_CHG_MW * 1000));
+			prevent_power_on = 0;
+#endif
+
 	/*
 	 * Factory override: Always allow power on if WP is disabled,
 	 * except when EC is starting up, due to brown out potential.
@@ -1144,6 +1161,23 @@ static int charge_command_charge_state(struct host_cmd_handler_args *args)
 			case CS_PARAM_CHG_OPTION:
 				val = curr.chg.option;
 				break;
+			case CS_PARAM_LIMIT_POWER:
+#ifdef CONFIG_CHARGER_LIMIT_POWER_THRESH_BAT_PCT
+				/*
+				 * LIMIT_POWER status is based on battery level
+				 * and external charger power.
+				 */
+				if ((curr.batt.is_present != BP_YES ||
+				     curr.batt.state_of_charge <
+				     CONFIG_CHARGER_LIMIT_POWER_THRESH_BAT_PCT)
+				     && charge_manager_get_power_limit_uw() <
+				     CONFIG_CHARGER_LIMIT_POWER_THRESH_CHG_MW
+				     * 1000 && system_is_locked())
+					val = 1;
+				else
+#endif
+					val = 0;
+				break;
 			default:
 				rv = EC_RES_INVALID_PARAM;
 			}
@@ -1181,6 +1215,7 @@ static int charge_command_charge_state(struct host_cmd_handler_args *args)
 					rv = EC_RES_ERROR;
 				break;
 			case CS_PARAM_CHG_STATUS:
+			case CS_PARAM_LIMIT_POWER:
 				/* Can't set this */
 				rv = EC_RES_ACCESS_DENIED;
 				break;
diff --git a/include/charge_manager.h b/include/charge_manager.h
index 6cfd6cc7ce..d3f14117b5 100644
--- a/include/charge_manager.h
+++ b/include/charge_manager.h
@@ -74,6 +74,9 @@ int charge_manager_get_override(void);
 /* Returns the current active charge port, as determined by charge manager */
 int charge_manager_get_active_charge_port(void);
 
+/* Return the power limit (uW) set by charge manager. */
+int charge_manager_get_power_limit_uw(void);
+
 #ifdef CONFIG_USB_PD_LOGGING
 /* Save power state log entry for the given port */
 void charge_manager_save_log(int port);
diff --git a/include/config.h b/include/config.h
index 26fced9a46..8f8469f3da 100644
--- a/include/config.h
+++ b/include/config.h
@@ -400,6 +400,14 @@
 #undef CONFIG_CHARGER_MIN_BAT_PCT_FOR_POWER_ON
 
 /*
+ * Low energy thresholds - when battery level is below BAT_PCT and an external
+ * charger provides less than CHG_MW of power, inform the AP of the situation
+ * through the LIMIT_POWER host event.
+ */
+#undef CONFIG_CHARGER_LIMIT_POWER_THRESH_BAT_PCT
+#undef CONFIG_CHARGER_LIMIT_POWER_THRESH_CHG_MW
+
+/*
  * Equivalent of CONFIG_BATTERY_OVERRIDE_PARAMS for use with
  * CONFIG_CHARGER_V2
  */
diff --git a/include/ec_commands.h b/include/ec_commands.h
index b959db783e..54f91e3054 100644
--- a/include/ec_commands.h
+++ b/include/ec_commands.h
@@ -2839,6 +2839,11 @@ enum charge_state_params {
 	CS_PARAM_CHG_INPUT_CURRENT,   /* charger input current limit */
 	CS_PARAM_CHG_STATUS,	      /* charger-specific status */
 	CS_PARAM_CHG_OPTION,	      /* charger-specific options */
+	CS_PARAM_LIMIT_POWER,	      /*
+				       * Check if power is limited due to
+				       * low battery and / or a weak external
+				       * charger. READ ONLY.
+				       */
 	/* How many so far? */
 	CS_NUM_BASE_PARAMS,
 
diff --git a/test/sbs_charging_v2.c b/test/sbs_charging_v2.c
index 7bf467d2be..5e11c722fe 100644
--- a/test/sbs_charging_v2.c
+++ b/test/sbs_charging_v2.c
@@ -454,7 +454,10 @@ static int test_hc_charge_state(void)
 					    &params, sizeof(params),
 					    &resp, sizeof(resp));
 		TEST_ASSERT(rv == EC_RES_SUCCESS);
-		TEST_ASSERT(resp.get_param.value);
+		if (i != CS_PARAM_LIMIT_POWER)
+			TEST_ASSERT(resp.get_param.value);
+		else
+			TEST_ASSERT(!resp.get_param.value);
 
 		/* Bump it up a bit */
 		tmp = resp.get_param.value;
@@ -465,7 +468,8 @@ static int test_hc_charge_state(void)
 			tmp -= 128;		/* Should be valid delta */
 			break;
 		case CS_PARAM_CHG_STATUS:
-			/* This one can't be set */
+		case CS_PARAM_LIMIT_POWER:
+			/* These ones can't be set */
 			break;
 		case CS_PARAM_CHG_OPTION:
 			tmp = CHG_OPT2;
@@ -477,7 +481,7 @@ static int test_hc_charge_state(void)
 		rv = test_send_host_command(EC_CMD_CHARGE_STATE, 0,
 					    &params, sizeof(params),
 					    &resp, sizeof(resp));
-		if (i == CS_PARAM_CHG_STATUS)
+		if (i == CS_PARAM_CHG_STATUS || i == CS_PARAM_LIMIT_POWER)
 			TEST_ASSERT(rv == EC_RES_ACCESS_DENIED);
 		else
 			TEST_ASSERT(rv == EC_RES_SUCCESS);
diff --git a/util/ectool.c b/util/ectool.c
index 1c409846e0..0b2f561211 100644
--- a/util/ectool.c
+++ b/util/ectool.c
@@ -5136,6 +5136,7 @@ static const char * const base_params[] = {
 	"chg_input_current",
 	"chg_status",
 	"chg_option",
+	"limit_power",
 };
 BUILD_ASSERT(ARRAY_SIZE(base_params) == CS_NUM_BASE_PARAMS);