mkbp: handle multiple writes of interrupt

We need to handle the case of multiple tasks trying to set the mkbp
interrupt while the host command task is trying to clear it. The setting
of the interrupt may also take a while and we need to ensure that we
synchronize correct after a longer delay.

BRANCH=none
BUG=b:129159505
TEST=passing CTS sensor run (except test 133 nullptr) with this change
TEST=pass CTS sensor run on eSPI-based system
TEST=pass CTS sensor run on GPIO-based system

Change-Id: I056b72c1210d7525c29a8555f97e6f09d773d12f
Signed-off-by: Jett Rink <jettrink@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1560229
Tested-by: Alexandru M Stan <amstan@chromium.org>
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>

2 files changed, 283 insertions, 76 deletions

diff --git a/common/mkbp_event.c b/common/mkbp_event.c
index 5807d6ba80..5e64183e43 100644
--- a/common/mkbp_event.c
+++ b/common/mkbp_event.c
@@ -11,49 +11,110 @@
 #include "host_command.h"
 #include "host_command_heci.h"
 #include "hwtimer.h"
+#include "timer.h"
 #include "link_defs.h"
 #include "mkbp_event.h"
 #include "power.h"
 #include "util.h"
 
-static uint32_t events;
-uint32_t mkbp_last_event_time;
-
-static void set_event(uint8_t event_type)
-{
-	atomic_or(&events, 1 << event_type);
-}
+#define CPUTS(outstr) cputs(CC_COMMAND, outstr)
+#define CPRINTS(format, args...) cprints(CC_COMMAND, format, ## args)
+#define CPRINTF(format, args...) cprintf(CC_COMMAND, format, ## args)
 
-static void clear_event(uint8_t event_type)
-{
-	atomic_clear(&events, 1 << event_type);
-}
+/*
+ * Tracks the current state of the MKBP interrupt send from the EC to the AP.
+ *
+ * The inactive state is only valid when there are no events to set to the AP.
+ * If the AP is asleep, then some events are not worth waking the AP up, so the
+ * interrupt could remain in an inactive in that case.
+ *
+ * The transition state (INTERRUPT_INACTIVE_TO_ACTIVE) is used to track the
+ * sometimes lock transition for a "rising edge" for platforms that send the
+ * rising edge interrupt through a host communication layer
+ *
+ * The active state represents that a rising edge interrupt has already been
+ * sent to the AP, and the EC is waiting for the AP to call get next event
+ * host command to consume all of the events (at which point the state will
+ * move to inactive).
+ *
+ * The transition from ACTIVE -> INACTIVE is considerer to be simple meaning
+ * the operation can be performed within a blocking mutex (e.g. no-op or setting
+ * a gpio).
+ */
+enum interrupt_state {
+	INTERRUPT_INACTIVE,
+	INTERRUPT_INACTIVE_TO_ACTIVE, /* Transitioning */
+	INTERRUPT_ACTIVE,
+};
+
+struct mkbp_state {
+	struct mutex lock;
+	uint32_t events;
+	enum interrupt_state interrupt;
+	/*
+	 * Tracks unique transitions to INTERRUPT_INACTIVE_TO_ACTIVE allowing
+	 * only the most recent transition to finish the transition to a final
+	 * state -- either active or inactive depending on the result of the
+	 * operation.
+	 */
+	uint8_t interrupt_id;
+	/*
+	 * Tracks the number of consecutive failed attempts for the AP to poll
+	 * get_next_events in order to limit the retry logic.
+	 */
+	uint8_t failed_attempts;
+};
 
-static int event_is_set(uint8_t event_type)
-{
-	return events & BIT(event_type);
-}
+static struct mkbp_state state;
+uint32_t mkbp_last_event_time;
 
 #ifdef CONFIG_MKBP_USE_GPIO
-static void mkbp_set_host_active_via_gpio(int active)
+static int mkbp_set_host_active_via_gpio(int active, uint32_t *timestamp)
 {
+	/*
+	 * If we want to take a timestamp, then disable interrupts temporarily
+	 * to ensure that the timestamp is as close as possible to the setting
+	 * of the GPIO pin in hardware (i.e. we aren't interrupted between
+	 * taking the timestamp and setting the gpio)
+	 */
+	if (timestamp) {
+		interrupt_disable();
+		*timestamp = __hw_clock_source_read();
+	}
+
 	gpio_set_level(GPIO_EC_INT_L, !active);
+
+	if (timestamp)
+		interrupt_enable();
+
+	return EC_SUCCESS;
 }
 #endif
 
 #ifdef CONFIG_MKBP_USE_HOST_EVENT
-static void mkbp_set_host_active_via_event(int active)
+static int mkbp_set_host_active_via_event(int active, uint32_t *timestamp)
 {
+	/* This should be moved into host_set_single_event for more accuracy */
+	if (timestamp)
+		*timestamp = __hw_clock_source_read();
 	if (active)
 		host_set_single_event(EC_HOST_EVENT_MKBP);
+	return EC_SUCCESS;
 }
 #endif
 
 #ifdef CONFIG_MKBP_USE_HECI
-static void mkbp_set_host_active_via_heci(int active)
+static int mkbp_set_host_active_via_heci(int active, uint32_t *timestamp)
 {
+	/*
+	 * TODO change heci_send_mkbp_event declaration. Done in
+	 * child CL to decouple changes.
+	 */
+	if (timestamp)
+		*timestamp = __hw_clock_source_read();
 	if (active)
 		heci_send_mkbp_event();
+	return EC_SUCCESS;
 }
 #endif
 
@@ -61,49 +122,30 @@ static void mkbp_set_host_active_via_heci(int active)
  * This communicates to the AP whether an MKBP event is currently available
  * for processing.
  *
+ * NOTE: When active is 0 this function CANNOT de-schedule. It must be very
+ * simple like toggling a GPIO or no-op
+ *
  * @param active  1 if there is an event, 0 otherwise
+ * @param timestamp, if non-null this variable will be written as close to the
+ *			hardware interrupt from EC->AP as possible.
  */
-static void mkbp_set_host_active(int active)
+static int mkbp_set_host_active(int active, uint32_t *timestamp)
 {
 #if defined(CONFIG_MKBP_USE_CUSTOM)
+	/*
+	 * TODO change mkbp_set_host_active_via_custom declaration. Done in
+	 * child CL to decouple changes
+	 */
+	if (timestamp)
+		*timestamp = __hw_clock_source_read();
 	mkbp_set_host_active_via_custom(active);
+	return EC_SUCCESS;
 #elif defined(CONFIG_MKBP_USE_HOST_EVENT)
-	mkbp_set_host_active_via_event(active);
+	return mkbp_set_host_active_via_event(active, timestamp);
 #elif defined(CONFIG_MKBP_USE_GPIO)
-	mkbp_set_host_active_via_gpio(active);
+	return mkbp_set_host_active_via_gpio(active, timestamp);
 #elif defined(CONFIG_MKBP_USE_HECI)
-	mkbp_set_host_active_via_heci(active);
-#endif
-}
-
-/**
- * Assert host keyboard interrupt line.
- */
-static void set_host_interrupt(int active)
-{
-	static int old_active;
-	/*
-	 * If we are going to perform a simple GPIO toggle, then pause
-	 * interrupts to let last_event_time marker have the best chance of
-	 * matching the time we toggle the GPIO pin.
-	 *
-	 * If we are passing mkbp events through host communication, then
-	 * pausing interrupts can have unintended consequences (say if that code
-	 * waits for a mutex and then de-schedules its tasks).
-	 */
-#ifdef CONFIG_MKBP_USE_GPIO
-	interrupt_disable();
-#endif
-
-	if (old_active == 0 && active == 1)
-		mkbp_last_event_time = __hw_clock_source_read();
-
-	mkbp_set_host_active(active);
-
-	old_active = active;
-
-#ifdef CONFIG_MKBP_USE_GPIO
-	interrupt_enable();
+	return mkbp_set_host_active_via_heci(active, timestamp);
 #endif
 }
 
@@ -126,24 +168,130 @@ static inline int host_is_sleeping(void)
 }
 #endif /* CONFIG_MKBP_WAKEUP_MASK */
 
-int mkbp_send_event(uint8_t event_type)
+/*
+ * This is the deferred function that ensures that we attempt to set the MKBP
+ * interrupt again if there was a failure in the system (EC or AP) and the AP
+ * never called get_next_event.
+ */
+static void force_mkbp_if_events(void);
+DECLARE_DEFERRED(force_mkbp_if_events);
+
+static void activate_mkbp_with_events(uint32_t events_to_add)
 {
-	set_event(event_type);
+	int interrupt_id = -1;
+	int skip_interrupt = 0;
+	int rv, schedule_deferred = 0;
 
 #ifdef CONFIG_MKBP_WAKEUP_MASK
 	/* Only assert interrupt for wake events if host is sleeping */
-	if (host_is_sleeping()) {
-		/* Skip host wake if this isn't a wake event */
-		if (!(host_get_events() & CONFIG_MKBP_WAKEUP_MASK) &&
-		      event_type != EC_MKBP_EVENT_KEY_MATRIX)
-			return 0;
-	}
+	skip_interrupt = host_is_sleeping() &&
+			 !(host_get_events() & CONFIG_MKBP_WAKEUP_MASK);
 #endif
 
-	set_host_interrupt(1);
+	mutex_lock(&state.lock);
+	state.events |= events_to_add;
+
+	/* To skip the interrupt, we cannot have the EC_MKBP_EVENT_KEY_MATRIX */
+	skip_interrupt = skip_interrupt &&
+			 !(state.events & BIT(EC_MKBP_EVENT_KEY_MATRIX));
+
+	if (state.events && state.interrupt == INTERRUPT_INACTIVE &&
+	    !skip_interrupt) {
+		state.interrupt = INTERRUPT_INACTIVE_TO_ACTIVE;
+		interrupt_id = ++state.interrupt_id;
+	}
+	mutex_unlock(&state.lock);
+
+	/* If we don't need to send an interrupt we are done */
+	if (interrupt_id < 0)
+		return;
+
+	/* Send a rising edge MKBP interrupt */
+	rv = mkbp_set_host_active(1, &mkbp_last_event_time);
+
+	/*
+	 * If this was the last interrupt to the AP, update state;
+	 * otherwise the latest interrupt should update state.
+	 */
+	mutex_lock(&state.lock);
+	if (state.interrupt == INTERRUPT_INACTIVE_TO_ACTIVE &&
+	    interrupt_id == state.interrupt_id) {
+		schedule_deferred = 1;
+		state.interrupt = rv == EC_SUCCESS ? INTERRUPT_ACTIVE
+						   : INTERRUPT_INACTIVE;
+	}
+	mutex_unlock(&state.lock);
+
+	if (schedule_deferred) {
+		hook_call_deferred(&force_mkbp_if_events_data, SECOND);
+		if (rv != EC_SUCCESS)
+			CPRINTS("Could not activate MKBP (%d). Deferring", rv);
+	}
+}
+
+/*
+ * This is the deferred function that ensures that we attempt to set the MKBP
+ * interrupt again if there was a failure in the system (EC or AP) and the AP
+ * never called get_next_event.
+ */
+static void force_mkbp_if_events(void)
+{
+	int toggled = 0;
+
+	mutex_lock(&state.lock);
+	if (state.interrupt == INTERRUPT_ACTIVE) {
+		if (++state.failed_attempts < 3) {
+			state.interrupt = INTERRUPT_INACTIVE;
+			toggled = 1;
+		}
+	}
+	mutex_unlock(&state.lock);
+
+	if (toggled)
+		CPRINTS("MKBP not cleared within threshold, toggling.");
+
+	activate_mkbp_with_events(0);
+}
+
+int mkbp_send_event(uint8_t event_type)
+{
+	activate_mkbp_with_events(BIT(event_type));
+
 	return 1;
 }
 
+static int set_inactive_if_no_events(void)
+{
+	int interrupt_cleared;
+
+	mutex_lock(&state.lock);
+	interrupt_cleared = !state.events;
+	if (interrupt_cleared) {
+		state.interrupt = INTERRUPT_INACTIVE;
+		state.failed_attempts = 0;
+		/* Only simple tasks (i.e. gpio set or no-op) allowed here */
+		mkbp_set_host_active(0, NULL);
+	}
+	mutex_unlock(&state.lock);
+
+	/* Cancel our safety net since the events were cleared. */
+	if (interrupt_cleared)
+		hook_call_deferred(&force_mkbp_if_events_data, -1);
+
+	return interrupt_cleared;
+}
+
+/* This can only be called when the state.lock mutex is held */
+static int take_event_if_set(uint8_t event_type)
+{
+	int taken;
+
+	taken = state.events & BIT(event_type);
+	state.events &= ~BIT(event_type);
+
+	return taken;
+}
+
 static int mkbp_get_next_event(struct host_cmd_handler_args *args)
 {
 	static int last;
@@ -156,24 +304,22 @@ static int mkbp_get_next_event(struct host_cmd_handler_args *args)
 		 * Find the next event to service.  We do this in a round-robin
 		 * way to make sure no event gets starved.
 		 */
+		mutex_lock(&state.lock);
 		for (i = 0; i < EC_MKBP_EVENT_COUNT; ++i)
-			if (event_is_set((last + i) % EC_MKBP_EVENT_COUNT))
+			if (take_event_if_set((last + i) % EC_MKBP_EVENT_COUNT))
 				break;
+		mutex_unlock(&state.lock);
 
 		if (i == EC_MKBP_EVENT_COUNT) {
-			set_host_interrupt(0);
-			return EC_RES_UNAVAILABLE;
+			if (set_inactive_if_no_events())
+				return EC_RES_UNAVAILABLE;
+			/* An event was set just now, restart loop. */
+			continue;
 		}
 
 		evt = (i + last) % EC_MKBP_EVENT_COUNT;
 		last = evt + 1;
 
-		/*
-		 * Clear the event before retrieving the event data in case the
-		 * event source wants to send the same event.
-		 */
-		clear_event(evt);
-
 		for (src = __mkbp_evt_srcs; src < __mkbp_evt_srcs_end; ++src)
 			if (src->event_type == evt)
 				break;
@@ -192,13 +338,15 @@ static int mkbp_get_next_event(struct host_cmd_handler_args *args)
 		 * event first.
 		 */
 		data_size = src->get_data(resp + 1);
-		if (data_size == -EC_ERROR_BUSY)
-			set_event(evt);
+		if (data_size == -EC_ERROR_BUSY) {
+			mutex_lock(&state.lock);
+			state.events |= BIT(evt);
+			mutex_unlock(&state.lock);
+		}
 	} while (data_size == -EC_ERROR_BUSY);
 
-	if (!events)
-		set_host_interrupt(0);
-	else if (args->version >= 2)
+	/* If there are no more events and we support the "more" flag, set it */
+	if (!set_inactive_if_no_events() && args->version >= 2)
 		resp[0] |= EC_MKBP_HAS_MORE_EVENTS;
 
 	if (data_size < 0)
diff --git a/test/kb_mkbp.c b/test/kb_mkbp.c
index 15952e74bb..324b5b3e91 100644
--- a/test/kb_mkbp.c
+++ b/test/kb_mkbp.c
@@ -101,6 +101,46 @@ int verify_key(int c, int r, int pressed)
 	return 1;
 }
 
+int verify_key_v2(int c, int r, int pressed, int expect_more)
+{
+	struct host_cmd_handler_args args;
+	struct  ec_response_get_next_event_v1 event;
+	int i;
+
+	args.version = 2;
+	args.command = EC_CMD_GET_NEXT_EVENT;
+	args.params = NULL;
+	args.params_size = 0;
+	args.response = &event;
+	args.response_max = sizeof(event);
+	args.response_size = 0;
+
+	if (c >= 0 && r >= 0) {
+		ccprintf("Verify %s (%d, %d). Expect %smore.\n",
+			 action[pressed], c, r, expect_more ? "" : "no ");
+		set_state(c, r, pressed);
+
+		if (host_command_process(&args) != EC_RES_SUCCESS)
+			return 0;
+
+		if (!!(event.event_type & EC_MKBP_HAS_MORE_EVENTS) !=
+		    expect_more) {
+			ccprintf("Incorrect more events!\n");
+			return 0;
+		}
+
+		for (i = 0; i < KEYBOARD_COLS_MAX; ++i)
+			if (event.data.key_matrix[i] != state[i])
+				return 0;
+	} else {
+		ccprintf("Verify no events available\n");
+		if (host_command_process(&args) != EC_RES_UNAVAILABLE)
+			return 0;
+	}
+
+	return 1;
+}
+
 int mkbp_config(struct ec_params_mkbp_set_config params)
 {
 	struct host_cmd_handler_args args;
@@ -179,6 +219,24 @@ int single_key_press(void)
 	return EC_SUCCESS;
 }
 
+int single_key_press_v2(void)
+{
+	keyboard_clear_buffer();
+	clear_state();
+	TEST_ASSERT(press_key(0, 0, 1) == EC_SUCCESS);
+	TEST_ASSERT(FIFO_NOT_EMPTY());
+	TEST_ASSERT(press_key(0, 0, 0) == EC_SUCCESS);
+	TEST_ASSERT(FIFO_NOT_EMPTY());
+
+	clear_state();
+	TEST_ASSERT(verify_key_v2(0, 0, 1, 1));
+	TEST_ASSERT(FIFO_NOT_EMPTY());
+	TEST_ASSERT(verify_key_v2(0, 0, 0, 0));
+	TEST_ASSERT(FIFO_EMPTY());
+
+	return EC_SUCCESS;
+}
+
 int test_fifo_size(void)
 {
 	keyboard_clear_buffer();
@@ -236,6 +294,7 @@ void run_test(void)
 	/* Clear any pending events such as lid open. */
 	clear_mkbp_events();
 	RUN_TEST(single_key_press);
+	RUN_TEST(single_key_press_v2);
 	RUN_TEST(test_fifo_size);
 	RUN_TEST(test_enable);
 	RUN_TEST(fifo_underrun);