pd: support gotoMin and giveBack

In Sink mode, on the receipt of a GotoMin message,
reduce the current consumption to some minimum level.

BUG=chrome-os-partner:33688
TEST=Manual testing
	Used a Kevin, with test routine, to test GotoMin feature
	on another Kevin unit.

	Test routine:
		 if (!strcasecmp(argv[2], "gm")) {
		    ccprintf("send goto min\n");
		    send_control(port, PD_CTRL_GOTO_MIN);
		    send_control(port, PD_CTRL_PS_RDY);
		}

	Kevin with GotoMin feature:
		# ectool usbpdpower 0
		Port 0: SNK DRP PD 4277mV / 3000mA, max 5000mV / 3000mA / 15000mW
		Port 1: Disconnected

		After Test routine is executed:

		# ectool usbpdpower 0
		Port 0: SNK DRP PD 4906mV / 500mA, max 5000mV / 500mA / 2500mW
		Port 1: Disconnected
BRANCH=none

Change-Id: Iaac6e19706ceb10ccaff4d602d63fc086c808c8f
Reviewed-on: https://chromium-review.googlesource.com/425728
Commit-Ready: Sam Hurst <shurst@google.com>
Tested-by: Sam Hurst <shurst@google.com>
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/740001
Reviewed-by: Shawn N <shawnn@chromium.org>
Reviewed-by: Sam Hurst <shurst@google.com>
Tested-by: Shawn N <shawnn@chromium.org>
Commit-Queue: Shawn N <shawnn@chromium.org>

11 files changed, 111 insertions, 3 deletions

diff --git a/board/host/board.h b/board/host/board.h
index a5b6a5dc20..aa82d600d4 100644
--- a/board/host/board.h
+++ b/board/host/board.h
@@ -69,4 +69,7 @@ extern const int supplier_priority[];
 #define PD_MAX_CURRENT_MA     3000
 #define PD_MAX_VOLTAGE_MV     20000
 
+#define PD_MIN_CURRENT_MA     500
+#define PD_MIN_POWER_MW       7500
+
 #endif /* __CROS_EC_BOARD_H */
diff --git a/board/kevin/board.h b/board/kevin/board.h
index a0a2498945..7186e0fc45 100644
--- a/board/kevin/board.h
+++ b/board/kevin/board.h
@@ -135,6 +135,7 @@
 
 #ifdef BOARD_KEVIN
 #define CONFIG_BATTERY_REQUESTS_NIL_WHEN_DEAD
+#define CONFIG_USB_PD_GIVE_BACK
 #endif
 
 #define PD_OPERATING_POWER_MW 15000
@@ -142,6 +143,9 @@
 #define PD_MAX_CURRENT_MA     3000
 #define PD_MAX_VOLTAGE_MV     20000
 
+#define PD_MIN_CURRENT_MA     500
+#define PD_MIN_POWER_MW       2500
+
 #define PD_POWER_SUPPLY_TURN_ON_DELAY  30000  /* us */
 #define PD_POWER_SUPPLY_TURN_OFF_DELAY 50000  /* us */
 #define PD_VCONN_SWAP_DELAY 5000 /* us */
diff --git a/board/kevin/usb_pd_policy.c b/board/kevin/usb_pd_policy.c
index bc1910df55..d8cf201a94 100644
--- a/board/kevin/usb_pd_policy.c
+++ b/board/kevin/usb_pd_policy.c
@@ -60,6 +60,16 @@ int board_vbus_source_enabled(int port)
 	return vbus_en[port];
 }
 
+void pd_snk_give_back(int port, uint32_t * const ma, uint32_t * const mv)
+{
+	/* Just reduce the current */
+	*ma = PD_MIN_CURRENT_MA;
+	pd_set_input_current_limit(port, *ma, *mv);
+#ifdef CONFIG_CHARGE_MANAGER
+	charge_manager_set_ceil(port, CEIL_REQUESTOR_PD, *ma);
+#endif
+}
+
 static void board_vbus_update_source_current(int port)
 {
 	enum gpio_signal gpio = port ? GPIO_USB_C1_5V_EN : GPIO_USB_C0_5V_EN;
diff --git a/common/usb_pd_policy.c b/common/usb_pd_policy.c
index 6a3d8b3ee8..808b7e4bd1 100644
--- a/common/usb_pd_policy.c
+++ b/common/usb_pd_policy.c
@@ -179,6 +179,8 @@ int pd_build_request(int cnt, uint32_t *src_caps, uint32_t *rdo,
 {
 	int pdo_index, flags = 0;
 	int uw;
+	int max_or_min_ma;
+	int max_or_min_mw;
 
 	if (req_type == PD_REQUEST_VSAFE5V)
 		/* src cap 0 should be vSafe5V */
@@ -197,11 +199,35 @@ int pd_build_request(int cnt, uint32_t *src_caps, uint32_t *rdo,
 	if (uw < (1000 * PD_OPERATING_POWER_MW))
 		flags |= RDO_CAP_MISMATCH;
 
+#ifdef CONFIG_USB_PD_GIVE_BACK
+	/* Tell source we are give back capable. */
+	flags |= RDO_GIVE_BACK;
+
+	/*
+	 * BATTERY PDO: Inform the source that the sink will reduce
+	 * power to this minimum level on receipt of a GotoMin Request.
+	 */
+	max_or_min_mw = PD_MIN_POWER_MW;
+
+	/*
+	 * FIXED or VARIABLE PDO: Inform the source that the sink will reduce
+	 * current to this minimum level on receipt of a GotoMin Request.
+	 */
+	max_or_min_ma = PD_MIN_CURRENT_MA;
+#else
+	/*
+	 * Can't give back, so set maximum current and power to operating
+	 * level.
+	 */
+	max_or_min_ma = *ma;
+	max_or_min_mw = uw / 1000;
+#endif
+
 	if ((src_caps[pdo_index] & PDO_TYPE_MASK) == PDO_TYPE_BATTERY) {
 		int mw = uw / 1000;
-		*rdo = RDO_BATT(pdo_index + 1, mw, mw, flags);
+		*rdo = RDO_BATT(pdo_index + 1, mw, max_or_min_mw, flags);
 	} else {
-		*rdo = RDO_FIXED(pdo_index + 1, *ma, *ma, flags);
+		*rdo = RDO_FIXED(pdo_index + 1, *ma, max_or_min_ma, flags);
 	}
 	return EC_SUCCESS;
 }
diff --git a/common/usb_pd_protocol.c b/common/usb_pd_protocol.c
index d057fc54e6..0485f6316e 100644
--- a/common/usb_pd_protocol.c
+++ b/common/usb_pd_protocol.c
@@ -881,6 +881,21 @@ static void handle_ctrl_request(int port, uint16_t head,
 		break;
 #ifdef CONFIG_USB_PD_DUAL_ROLE
 	case PD_CTRL_GOTO_MIN:
+#ifdef CONFIG_USB_PD_GIVE_BACK
+		if (pd[port].task_state == PD_STATE_SNK_READY) {
+			/*
+			 * Reduce power consumption now!
+			 *
+			 * The source will restore power to this sink
+			 * by sending a new source cap message at a
+			 * later time.
+			 */
+			pd_snk_give_back(port, &pd[port].curr_limit,
+				&pd[port].supply_voltage);
+			set_state(port, PD_STATE_SNK_TRANSITION);
+		}
+#endif
+
 		break;
 	case PD_CTRL_PS_RDY:
 		if (pd[port].task_state == PD_STATE_SNK_SWAP_SRC_DISABLE) {
diff --git a/include/config.h b/include/config.h
index 56c9b3bde3..d1595d4247 100644
--- a/include/config.h
+++ b/include/config.h
@@ -2069,6 +2069,9 @@
 /* Check whether PD is the sole power source before flash erase operation */
 #undef CONFIG_USB_PD_FLASH_ERASE_CHECK
 
+/* Define if this board, operating as a sink, can give power back to a source */
+#undef CONFIG_USB_PD_GIVE_BACK
+
 /* Major and Minor ChromeOS specific PD device Hardware IDs. */
 #undef CONFIG_USB_PD_HW_DEV_ID_BOARD_MAJOR
 #undef CONFIG_USB_PD_HW_DEV_ID_BOARD_MINOR
diff --git a/include/usb_pd.h b/include/usb_pd.h
index 069125c432..c5feaf3699 100644
--- a/include/usb_pd.h
+++ b/include/usb_pd.h
@@ -911,6 +911,15 @@ int pd_is_max_request_allowed(void);
 void pd_process_source_cap(int port, int cnt, uint32_t *src_caps);
 
 /**
+ * Reduce the sink power consumption to a minimum value.
+ *
+ * @param port USB-C port number
+ * @param ma reduce current to minimum value.
+ * @param mv reduce voltage to minimum value.
+ */
+void pd_snk_give_back(int port, uint32_t * const ma, uint32_t * const mv);
+
+/**
  * Put a cap on the max voltage requested as a sink.
  * @param mv maximum voltage in millivolts.
  */
diff --git a/test/build.mk b/test/build.mk
index 1e45061502..d6f1ac6cb8 100644
--- a/test/build.mk
+++ b/test/build.mk
@@ -39,6 +39,7 @@ test-list-host+=math_util motion_lid sbs_charging_v2 battery_get_params_smart
 test-list-host+=lightbar inductive_charging usb_pd fan charge_manager
 test-list-host+=charge_manager_drp_charging charge_ramp
 test-list-host+=rsa rsa3
+test-list-host+=usb_pd_giveback
 endif
 
 battery_get_params_smart-y=battery_get_params_smart.o
@@ -78,6 +79,7 @@ thermal-y=thermal.o
 timer_calib-y=timer_calib.o
 timer_dos-y=timer_dos.o
 usb_pd-y=usb_pd.o
+usb_pd_giveback-y=usb_pd.o
 utils-y=utils.o
 battery_get_params_smart-y=battery_get_params_smart.o
 lightbar-y=lightbar.o
diff --git a/test/test_config.h b/test/test_config.h
index 837dd8a5c0..9229c5cc8b 100644
--- a/test/test_config.h
+++ b/test/test_config.h
@@ -135,7 +135,7 @@ int ncp15wb_calculate_temp(uint16_t adc);
 #define CONFIG_ALS_LIGHTBAR_DIMMING 0
 #endif
 
-#ifdef TEST_USB_PD
+#if defined(TEST_USB_PD) || defined(TEST_USB_PD_GIVEBACK)
 #define CONFIG_USB_POWER_DELIVERY
 #define CONFIG_USB_PD_CUSTOM_VDM
 #define CONFIG_USB_PD_DUAL_ROLE
@@ -144,7 +144,10 @@ int ncp15wb_calculate_temp(uint16_t adc);
 #define CONFIG_USB_PD_TCPM_STUB
 #define CONFIG_SHA256
 #define CONFIG_SW_CRC
+#ifdef TEST_USB_PD_GIVEBACK
+#define CONFIG_USB_PD_GIVE_BACK
 #endif
+#endif /* TEST_USB_PD || TEST_USB_PD_GIVEBACK */
 
 #if defined(TEST_CHARGE_MANAGER) || defined(TEST_CHARGE_MANAGER_DRP_CHARGING)
 #define CONFIG_CHARGE_MANAGER
diff --git a/test/usb_pd.c b/test/usb_pd.c
index 3368484a24..f9a40aefa4 100644
--- a/test/usb_pd.c
+++ b/test/usb_pd.c
@@ -24,6 +24,8 @@ struct pd_port_t {
 	int partner_polarity;
 } pd_port[CONFIG_USB_PD_PORT_COUNT];
 
+static int give_back_called;
+
 /* Mock functions */
 
 int pd_adc_read(int port, int cc)
@@ -158,9 +160,39 @@ static void unplug(int port)
 	usleep(30 * MSEC);
 }
 
+void pd_snk_give_back(int port, uint32_t * const ma, uint32_t * const mv)
+{
+	if (*ma == 3000)
+		give_back_called = 1;
+}
+
+/*
+static void simulate_ps_rdy(int port)
+{
+	uint16_t header = PD_HEADER(PD_CTRL_PS_RDY, PD_ROLE_SOURCE,
+				PD_ROLE_DFP, pd_port[port].msg_rx_id,
+				0);
+
+	simulate_rx_msg(port, header, 0, NULL);
+}
+
+static void simulate_goto_min(int port)
+{
+	uint16_t header = PD_HEADER(PD_CTRL_GOTO_MIN, PD_ROLE_SOURCE,
+		PD_ROLE_DFP, pd_port[port].msg_rx_id, 0);
+
+	simulate_rx_msg(port, header, 0, NULL);
+}
+*/
+
 static int test_request(void)
 {
+#ifdef CONFIG_USB_PD_GIVE_BACK
+	uint32_t expected_rdo = RDO_FIXED(1, 900, PD_MIN_CURRENT_MA,
+					RDO_CAP_MISMATCH | RDO_GIVE_BACK);
+#else
 	uint32_t expected_rdo = RDO_FIXED(1, 900, 900, RDO_CAP_MISMATCH);
+#endif
 
 	plug_in_source(0, 0);
 	task_wake(PD_PORT_TO_TASK_ID(0));
diff --git a/test/usb_pd_giveback.tasklist b/test/usb_pd_giveback.tasklist
new file mode 120000
index 0000000000..45cc6c8aa2
--- /dev/null
+++ b/test/usb_pd_giveback.tasklist
@@ -0,0 +1 @@
+usb_pd.tasklist
\ No newline at end of file