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: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index d578f41410efc1fa7d52a26df80f7abba8a736bd..7d7bff4d2100cc2f99b19a1ea5cc88cd3b0d53fd 100644 (file)
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -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);

diff --git a/drivers/acpi/internal.h b/drivers/acpi/internal.h
index de546be3bc6a6b57ced2c85d39a5c30f2c90969d..1db3a2f81763fe845d963377120ca582d1c4cacb 100644 (file)
--- a/drivers/acpi/internal.h
+++ b/drivers/acpi/internal.h
@@ -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;