pd: send soft reset on boot if VBUS is present

On boot, if VBUS is present, then when PD protocol gets to
SNK_DISCOVERY state, if it times out waiting for source cap,
then send attempt to send a soft reset first instead of
directly sending a hard reset. This allows us to not lose
VBUS in the case that we were in a stable contract as a sink
before this boot (for example a sysjump or EC reboot).

BUG=chrome-os-partner:44085, chrome-os-partner:44952
BRANCH=none
TEST=test on glados and samus. test by sysjumping between
RO and RW with zinger plugged in and no battery, and verify
that we don't lose power. also test rebooting with a battery
and verify we don't lose power. also tested with a third
party PD charger.

Change-Id: Ib7ce46d8b9843db66805ba3237d8919d611324e0
Signed-off-by: Alec Berg <alecaberg@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/308201
Reviewed-by: Rong Chang <rongchang@chromium.org>

3 files changed, 33 insertions, 48 deletions

diff --git a/common/system.c b/common/system.c
index 851836effb..fa3a557d8b 100644
--- a/common/system.c
+++ b/common/system.c
@@ -439,11 +439,6 @@ static void jump_to_image(uintptr_t init_addr)
 	usleep(MSEC);
 	gpio_set_level(GPIO_ENTERING_RW, 0);
 
-#ifdef CONFIG_USB_POWER_DELIVERY
-	/* Notify USB PD module that we are about to reset */
-	pd_prepare_reset();
-#endif
-
 #if defined(CONFIG_I2C) && !defined(CONFIG_I2C_SLAVE_ONLY)
 	/* Prepare I2C module for sysjump */
 	i2c_prepare_sysjump();
@@ -735,10 +730,6 @@ static int handle_pending_reboot(enum ec_reboot_cmd cmd)
 	case EC_REBOOT_JUMP_RW:
 		return system_run_image_copy(SYSTEM_IMAGE_RW);
 	case EC_REBOOT_COLD:
-#ifdef CONFIG_USB_POWER_DELIVERY
-		/* Notify USB PD module that we are about to reset */
-		pd_prepare_reset();
-#endif
 #ifdef HAS_TASK_PDCMD
 		/* Reboot the PD chip as well */
 		board_reset_pd_mcu();
@@ -934,11 +925,6 @@ static int command_reboot(int argc, char **argv)
 	ccputs("Rebooting!\n\n\n");
 	cflush();
 
-#ifdef CONFIG_USB_POWER_DELIVERY
-	/* Notify USB PD module that we are about to reset */
-	pd_prepare_reset();
-#endif
-
 	system_reset(flags);
 	return EC_SUCCESS;
 }
diff --git a/common/usb_charger.c b/common/usb_charger.c
index 0474bc18b8..b22e8dc99d 100644
--- a/common/usb_charger.c
+++ b/common/usb_charger.c
@@ -82,6 +82,8 @@ void usb_charger_set_switches(int port, enum usb_switch setting)
 
 void usb_charger_vbus_change(int port, int vbus_level)
 {
+	/* If VBUS has transitioned low, notify PD module directly */
+	pd_vbus_low(port);
 	/* Update VBUS supplier and signal VBUS change to USB_CHG task */
 	update_vbus_supplier(port, vbus_level);
 #if CONFIG_USB_PD_PORT_COUNT == 2
diff --git a/common/usb_pd_protocol.c b/common/usb_pd_protocol.c
index 8154d9ecee..4cc0e0259a 100644
--- a/common/usb_pd_protocol.c
+++ b/common/usb_pd_protocol.c
@@ -212,6 +212,11 @@ int pd_is_connected(int port)
 }
 
 #ifdef CONFIG_USB_PD_DUAL_ROLE
+void pd_vbus_low(int port)
+{
+	pd[port].flags &= ~PD_FLAGS_VBUS_NEVER_LOW;
+}
+
 static inline int pd_is_vbus_present(int port)
 {
 #ifdef CONFIG_USB_PD_TCPM_VBUS
@@ -542,12 +547,6 @@ static void execute_soft_reset(int port)
 	pd[port].msg_id = 0;
 	set_state(port, DUAL_ROLE_IF_ELSE(port, PD_STATE_SNK_DISCOVERY,
 						PD_STATE_SRC_DISCOVERY));
-#ifdef CONFIG_COMMON_RUNTIME
-	/* if flag to disable PD comms after soft reset, then disable comms */
-	if (pd[port].flags & PD_FLAGS_SFT_RST_DIS_COMM)
-		pd_comm_enable(0);
-#endif
-
 	CPRINTF("C%d Soft Rst\n", port);
 }
 
@@ -562,32 +561,6 @@ void pd_soft_reset(void)
 		}
 }
 
-void pd_prepare_reset(void)
-{
-	int i;
-
-	/*
-	 * On reset, we are most definitely going to drop pings (if any)
-	 * and lose all of our PD state. Instead of trying to remember all
-	 * the states and deal with on-going transmission, let's send soft
-	 * reset here and then disable PD communication until after sysjump
-	 * is complete so that the communication starts over without dropping
-	 * power.
-	 */
-	for (i = 0; i < CONFIG_USB_PD_PORT_COUNT; ++i)
-		if (pd_is_connected(i))
-			pd[i].flags |= PD_FLAGS_SFT_RST_DIS_COMM;
-
-	pd_soft_reset();
-
-	/*
-	 * Give time for soft reset to be sent
-	 * TODO (crosbug.com/p/45133): wait for soft reset to finish instead of
-	 * blind delay.
-	 */
-	usleep(8*MSEC);
-}
-
 #ifdef CONFIG_USB_PD_DUAL_ROLE
 static void pd_store_src_cap(int port, int cnt, uint32_t *src_caps)
 {
@@ -1410,6 +1383,15 @@ void pd_task(void)
 	/* Ensure the power supply is in the default state */
 	pd_power_supply_reset(port);
 
+#ifdef CONFIG_USB_PD_DUAL_ROLE
+	/*
+	 * If VBUS is high, then initialize flag for VBUS has always been
+	 * present. This flag is used to maintain a PD connection after a
+	 * reset by sending a soft reset.
+	 */
+	pd[port].flags = pd_is_vbus_present(port) ? PD_FLAGS_VBUS_NEVER_LOW : 0;
+#endif
+
 #ifdef CONFIG_USB_PD_TCPC
 	/* Initialize TCPM driver and wait for TCPC to be ready */
 	tcpm_init(port);
@@ -1427,7 +1409,6 @@ void pd_task(void)
 	/* Initialize PD protocol state variables for each port. */
 	pd[port].power_role = PD_ROLE_DEFAULT;
 	pd[port].vdm_state = VDM_STATE_DONE;
-	pd[port].flags = 0;
 	set_state(port, PD_DEFAULT_STATE);
 	tcpm_set_cc(port, PD_ROLE_DEFAULT == PD_ROLE_SOURCE ? TYPEC_CC_RP :
 							      TYPEC_CC_RD);
@@ -2142,11 +2123,25 @@ void pd_task(void)
 			if ((pd[port].last_state != pd[port].task_state)
 			    && pd_comm_enabled) {
 				/*
+				 * If VBUS has never been low, and we timeout
+				 * waiting for source cap, try a soft reset
+				 * first, in case we were already in a stable
+				 * contract before this boot.
+				 */
+				if (pd[port].flags & PD_FLAGS_VBUS_NEVER_LOW) {
+					pd[port].flags &=
+						~PD_FLAGS_VBUS_NEVER_LOW;
+					set_state_timeout(port,
+						  get_time().val +
+						  PD_T_SINK_WAIT_CAP,
+						  PD_STATE_SOFT_RESET);
+				}
+				/*
 				 * If we haven't passed hard reset counter,
 				 * start SinkWaitCapTimer, otherwise start
 				 * NoResponseTimer.
 				 */
-				if (hard_reset_count < PD_HARD_RESET_COUNT)
+				else if (hard_reset_count < PD_HARD_RESET_COUNT)
 					set_state_timeout(port,
 						  get_time().val +
 						  PD_T_SINK_WAIT_CAP,
@@ -2414,6 +2409,8 @@ void pd_task(void)
 #endif /* CONFIG_USB_PD_DUAL_ROLE */
 		case PD_STATE_SOFT_RESET:
 			if (pd[port].last_state != pd[port].task_state) {
+				/* Message ID of soft reset is always 0 */
+				pd[port].msg_id = 0;
 				res = send_control(port, PD_CTRL_SOFT_RESET);
 
 				/* if soft reset failed, try hard reset. */