samus: change backboosting workaround into a new task

Change backboosting workaround into a new extpower task. This
new task runs exactly what used to be run in a deferred function,
but at higher priority than charger task, which means that i2c
transactions from this new task will occur before charger task
i2c transactions.

This fixes the EC watchdog when writing PD device firmware
because the hooks task is no longer blocked on trying to grab
the i2c mutex for talking to BQ.

BUG=chrome-os-partner:33905
BRANCH=samus
TEST=loaded onto samus and tested remote update of zinger 10 times.

Change-Id: I01d259857aefc6bf456ab217bf46536237bc4008
Signed-off-by: Alec Berg <alecaberg@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/235862
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>

2 files changed, 59 insertions, 39 deletions

diff --git a/board/samus/ec.tasklist b/board/samus/ec.tasklist
index f59ca73403..815da6dbb9 100644
--- a/board/samus/ec.tasklist
+++ b/board/samus/ec.tasklist
@@ -21,6 +21,7 @@
 	TASK_NOTEST(ALS, als_task, NULL, TASK_STACK_SIZE) \
 	TASK_NOTEST(LIGHTBAR, lightbar_task, NULL, LARGER_TASK_STACK_SIZE) \
 	TASK_ALWAYS(CHARGER, charger_task, NULL, LARGER_TASK_STACK_SIZE) \
+	TASK_ALWAYS(EXTPOWER, extpower_task, NULL, SMALLER_TASK_STACK_SIZE) \
 	TASK_NOTEST(MOTIONSENSE, motion_sense_task, NULL, LARGER_TASK_STACK_SIZE) \
 	TASK_NOTEST(CHIPSET, chipset_task, NULL, TASK_STACK_SIZE) \
 	TASK_NOTEST(KEYPROTO, keyboard_protocol_task, NULL, TASK_STACK_SIZE) \
diff --git a/board/samus/extpower.c b/board/samus/extpower.c
index 9262c06d17..d8269efba2 100644
--- a/board/samus/extpower.c
+++ b/board/samus/extpower.c
@@ -15,47 +15,13 @@
 #include "gpio.h"
 #include "hooks.h"
 #include "host_command.h"
+#include "task.h"
 
 int extpower_is_present(void)
 {
 	return gpio_get_level(GPIO_AC_PRESENT);
 }
 
-/**
- * Deferred function to handle external power change
- */
-static void extpower_deferred(void)
-{
-	static int extpower_prev;
-	int extpower = extpower_is_present();
-
-	if (extpower && !extpower_prev) {
-		charger_discharge_on_ac(0);
-		/* If in G3, enable PP5000 for accurate sensing of CC */
-		if (chipset_in_state(CHIPSET_STATE_HARD_OFF))
-			gpio_set_level(GPIO_PP5000_EN, 1);
-	} else if (extpower && extpower_prev) {
-		/* glitch on AC_PRESENT, attempt to recover from backboost */
-		charger_discharge_on_ac(1);
-		charger_discharge_on_ac(0);
-	} else {
-		charger_discharge_on_ac(1);
-		/* If in G3, make sure PP5000 is off when no AC */
-		if (chipset_in_state(CHIPSET_STATE_HARD_OFF))
-			gpio_set_level(GPIO_PP5000_EN, 0);
-	}
-	extpower_prev = extpower;
-
-	hook_notify(HOOK_AC_CHANGE);
-
-	/* Forward notification to host */
-	if (extpower)
-		host_set_single_event(EC_HOST_EVENT_AC_CONNECTED);
-	else
-		host_set_single_event(EC_HOST_EVENT_AC_DISCONNECTED);
-}
-DECLARE_DEFERRED(extpower_deferred);
-
 static void extpower_buffer_to_pch(void)
 {
 	if (chipset_in_state(CHIPSET_STATE_HARD_OFF)) {
@@ -79,17 +45,70 @@ void extpower_interrupt(enum gpio_signal signal)
 {
 	extpower_buffer_to_pch();
 
-	/* Trigger deferred notification of external power change */
-	hook_call_deferred(extpower_deferred, 0);
+	/* Trigger notification of external power change */
+	task_wake(TASK_ID_EXTPOWER);
 }
 
 static void extpower_init(void)
 {
 	extpower_buffer_to_pch();
 
-	hook_call_deferred(extpower_deferred, 0);
-
 	/* Enable interrupts, now that we've initialized */
 	gpio_enable_interrupt(GPIO_AC_PRESENT);
 }
 DECLARE_HOOK(HOOK_INIT, extpower_init, HOOK_PRIO_DEFAULT);
+
+static void extpower_board_hacks(int extpower)
+{
+	static int extpower_prev;
+
+	/*
+	 * Use discharge_on_ac() to workaround hardware backboosting
+	 * charge circuit problems.
+	 *
+	 * When in G3, PP5000 needs to be enabled to accurately sense
+	 * CC voltage when AC is attached. When AC is disconnceted
+	 * it needs to be off to save power.
+	 */
+	if (extpower && !extpower_prev) {
+		charger_discharge_on_ac(0);
+		if (chipset_in_state(CHIPSET_STATE_HARD_OFF))
+			gpio_set_level(GPIO_PP5000_EN, 1);
+	} else if (extpower && extpower_prev) {
+		/* Glitch on AC_PRESENT, attempt to recover from backboost */
+		charger_discharge_on_ac(1);
+		charger_discharge_on_ac(0);
+	} else {
+		charger_discharge_on_ac(1);
+		if (chipset_in_state(CHIPSET_STATE_HARD_OFF))
+			gpio_set_level(GPIO_PP5000_EN, 0);
+	}
+	extpower_prev = extpower;
+}
+
+/**
+ * Task to handle external power change
+ */
+void extpower_task(void)
+{
+	int extpower = extpower_is_present();
+	extpower_board_hacks(extpower);
+
+	while (1) {
+		/* Wait until next extpower interrupt */
+		task_wait_event(-1);
+
+		extpower = extpower_is_present();
+
+		/* Various board hacks to run on extpower change */
+		extpower_board_hacks(extpower);
+
+		hook_notify(HOOK_AC_CHANGE);
+
+		/* Forward notification to host */
+		if (extpower)
+			host_set_single_event(EC_HOST_EVENT_AC_CONNECTED);
+		else
+			host_set_single_event(EC_HOST_EVENT_AC_DISCONNECTED);
+	}
+}