Commit c33676aa authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
Browse files

ACPI: EC: Make the event work state machine visible 



The EC driver uses a relatively simple state machine for the event
work handling, but it is not really straightforward to figure out.

The states are as follows:

 "Ready": The event handling work can be submitted.

  In this state, the EC_FLAGS_QUERY_PENDING flag is clear.

 "In progress": The event handling work is pending or is being
                processed.  It cannot be submitted again.

  In ths state, the EC_FLAGS_QUERY_PENDING flag is set and both the
  events_to_process count is nonzero and the EC_FLAGS_QUERY_GUARDING
  flag is clear.

 "Complete": The event handling work has been completed, but it still
             cannot be submitted again.

  In ths state, the EC_FLAGS_QUERY_PENDING flag is set and the
  events_to_process count is zero or the EC_FLAGS_QUERY_GUARDING
  flag is set.

The state changes from "Ready" to "In progress" when new event is
detected by advance_transaction() and acpi_ec_submit_event() is
called by it.

Next, the state can change from "In progress" directly to "Ready" in
the following situations:

 * ec_event_clearing is ACPI_EC_EVT_TIMING_STATUS and the state of
   an ACPI_EC_COMMAND_QUERY transaction becomes ACPI_EC_COMMAND_POLL.

 * ec_event_clearing is ACPI_EC_EVT_TIMING_QUERY and the state of
   an ACPI_EC_COMMAND_QUERY transaction becomes
   ACPI_EC_COMMAND_COMPLETE.

 * ec_event_clearing is either ACPI_EC_EVT_TIMING_STATUS or
   ACPI_EC_EVT_TIMING_QUERY and there are no more events to
   process (ie. ec->events_to_process becomes 0).

If ec_event_clearing is ACPI_EC_EVT_TIMING_EVENT, however, the
state must change from "In progress" to "Complete" before it
can change to "Ready".  The changes from "In progress" to
"Complete" in that case occur in the following situations:

 * The state of an ACPI_EC_COMMAND_QUERY transaction becomes
   ACPI_EC_COMMAND_COMPLETE.

 * There are no more events to process (ie. ec->events_to_process
   becomes 0).

Finally, the state changes from "Complete" to "Ready" when
advance_transaction() is invoked when the state is "Complete" and
the state of the current transaction is not ACPI_EC_COMMAND_POLL.

To make this state machine visible in the code, add a new
event_state field to struct acpi_ec and modify the code to use
it istead the EC_FLAGS_QUERY_PENDING and EC_FLAGS_QUERY_GUARDING
flags.

Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent c793570d

drivers/acpi/ec.c

+44 −31
Original line number Diff line number Diff line
@@ -92,8 +92,6 @@ enum ec_command { 


enum {

	EC_FLAGS_QUERY_ENABLED,		/* Query is enabled */

	EC_FLAGS_QUERY_PENDING,		/* Query is pending */

	EC_FLAGS_QUERY_GUARDING,	/* Guard for SCI_EVT check */

	EC_FLAGS_EVENT_HANDLER_INSTALLED,	/* Event handler installed */

	EC_FLAGS_EC_HANDLER_INSTALLED,	/* OpReg handler installed */

	EC_FLAGS_QUERY_METHODS_INSTALLED, /* _Qxx handlers installed */
@@ -450,9 +448,11 @@ static bool acpi_ec_submit_event(struct acpi_ec *ec) 
	if (!acpi_ec_event_enabled(ec))

		return false;



	if (!test_and_set_bit(EC_FLAGS_QUERY_PENDING, &ec->flags)) {

	if (ec->event_state == EC_EVENT_READY) {

		ec_dbg_evt("Command(%s) submitted/blocked",

			   acpi_ec_cmd_string(ACPI_EC_COMMAND_QUERY));



		ec->event_state = EC_EVENT_IN_PROGRESS;

		/*

		 * If events_to_process is greqter than 0 at this point, the

		 * while () loop in acpi_ec_event_handler() is still running
@@ -474,11 +474,19 @@ static bool acpi_ec_submit_event(struct acpi_ec *ec) 
	return true;

}



static void acpi_ec_complete_event(struct acpi_ec *ec)

{

	if (ec->event_state == EC_EVENT_IN_PROGRESS)

		ec->event_state = EC_EVENT_COMPLETE;

}



static void acpi_ec_close_event(struct acpi_ec *ec)

{

	if (test_and_clear_bit(EC_FLAGS_QUERY_PENDING, &ec->flags))

	if (ec->event_state != EC_EVENT_READY)

		ec_dbg_evt("Command(%s) unblocked",

			   acpi_ec_cmd_string(ACPI_EC_COMMAND_QUERY));



	ec->event_state = EC_EVENT_READY;

	acpi_ec_unmask_events(ec);

}
@@ -565,8 +573,8 @@ void acpi_ec_flush_work(void) 


static bool acpi_ec_guard_event(struct acpi_ec *ec)

{

	bool guarded = true;

	unsigned long flags;

	bool guarded;



	spin_lock_irqsave(&ec->lock, flags);

	/*
@@ -575,19 +583,15 @@ static bool acpi_ec_guard_event(struct acpi_ec *ec) 
	 * evaluating _Qxx, so we need to re-check SCI_EVT after waiting an

	 * acceptable period.

	 *

	 * The guarding period begins when EC_FLAGS_QUERY_PENDING is

	 * flagged, which means SCI_EVT check has just been performed.

	 * But if the current transaction is ACPI_EC_COMMAND_QUERY, the

	 * guarding should have already been performed (via

	 * EC_FLAGS_QUERY_GUARDING) and should not be applied so that the

	 * ACPI_EC_COMMAND_QUERY transaction can be transitioned into

	 * ACPI_EC_COMMAND_POLL state immediately.

	 * The guarding period is applicable if the event state is not

	 * EC_EVENT_READY, but otherwise if the current transaction is of the

	 * ACPI_EC_COMMAND_QUERY type, the guarding should have elapsed already

	 * and it should not be applied to let the transaction transition into

	 * the ACPI_EC_COMMAND_POLL state immediately.

	 */

	if (ec_event_clearing == ACPI_EC_EVT_TIMING_STATUS ||

	    ec_event_clearing == ACPI_EC_EVT_TIMING_QUERY ||

	    !test_bit(EC_FLAGS_QUERY_PENDING, &ec->flags) ||

	    (ec->curr && ec->curr->command == ACPI_EC_COMMAND_QUERY))

		guarded = false;

	guarded = ec_event_clearing == ACPI_EC_EVT_TIMING_EVENT &&

		ec->event_state != EC_EVENT_READY &&

		(!ec->curr || ec->curr->command != ACPI_EC_COMMAND_QUERY);

	spin_unlock_irqrestore(&ec->lock, flags);

	return guarded;

}
@@ -619,16 +623,26 @@ static int ec_transaction_completed(struct acpi_ec *ec) 
static inline void ec_transaction_transition(struct acpi_ec *ec, unsigned long flag)

{

	ec->curr->flags |= flag;

	if (ec->curr->command == ACPI_EC_COMMAND_QUERY) {

		if (ec_event_clearing == ACPI_EC_EVT_TIMING_STATUS &&

		    flag == ACPI_EC_COMMAND_POLL)



	if (ec->curr->command != ACPI_EC_COMMAND_QUERY)

		return;



	switch (ec_event_clearing) {

	case ACPI_EC_EVT_TIMING_STATUS:

		if (flag == ACPI_EC_COMMAND_POLL)

			acpi_ec_close_event(ec);

		if (ec_event_clearing == ACPI_EC_EVT_TIMING_QUERY &&

		    flag == ACPI_EC_COMMAND_COMPLETE)



		return;



	case ACPI_EC_EVT_TIMING_QUERY:

		if (flag == ACPI_EC_COMMAND_COMPLETE)

			acpi_ec_close_event(ec);

		if (ec_event_clearing == ACPI_EC_EVT_TIMING_EVENT &&

		    flag == ACPI_EC_COMMAND_COMPLETE)

			set_bit(EC_FLAGS_QUERY_GUARDING, &ec->flags);



		return;



	case ACPI_EC_EVT_TIMING_EVENT:

		if (flag == ACPI_EC_COMMAND_COMPLETE)

			acpi_ec_complete_event(ec);

	}

}
@@ -674,11 +688,9 @@ static bool advance_transaction(struct acpi_ec *ec, bool interrupt) 
	 */

	if (!t || !(t->flags & ACPI_EC_COMMAND_POLL)) {

		if (ec_event_clearing == ACPI_EC_EVT_TIMING_EVENT &&

		    (!ec->events_to_process ||

		     test_bit(EC_FLAGS_QUERY_GUARDING, &ec->flags))) {

			clear_bit(EC_FLAGS_QUERY_GUARDING, &ec->flags);

		    ec->event_state == EC_EVENT_COMPLETE)

			acpi_ec_close_event(ec);

		}



		if (!t)

			goto out;

	}
@@ -1246,8 +1258,9 @@ static void acpi_ec_event_handler(struct work_struct *work) 
	 * event handling work again regardless of whether or not the query

	 * queued up above is processed successfully.

	 */

	if (ec_event_clearing == ACPI_EC_EVT_TIMING_STATUS ||

	    ec_event_clearing == ACPI_EC_EVT_TIMING_QUERY)

	if (ec_event_clearing == ACPI_EC_EVT_TIMING_EVENT)

		acpi_ec_complete_event(ec);

	else

		acpi_ec_close_event(ec);



	spin_unlock_irq(&ec->lock);

drivers/acpi/internal.h

+8 −0
Original line number Diff line number Diff line
@@ -166,6 +166,13 @@ static inline void acpi_early_processor_osc(void) {} 
/* --------------------------------------------------------------------------

                                  Embedded Controller

   -------------------------------------------------------------------------- */



enum acpi_ec_event_state {

	EC_EVENT_READY = 0,	/* Event work can be submitted */

	EC_EVENT_IN_PROGRESS,	/* Event work is pending or being processed */

	EC_EVENT_COMPLETE,	/* Event work processing has completed */

};



struct acpi_ec {

	acpi_handle handle;

	int gpe;
@@ -182,6 +189,7 @@ struct acpi_ec { 
	spinlock_t lock;

	struct work_struct work;

	unsigned long timestamp;

	enum acpi_ec_event_state event_state;

	unsigned int events_to_process;

	unsigned int events_in_progress;

	unsigned int queries_in_progress;