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ACPI: EC: Make the event work state machine visible

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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>
This commit is contained in:
Rafael J. Wysocki 2021-11-23 19:44:46 +01:00
parent c793570d87
commit c33676aa48
2 changed files with 52 additions and 31 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

75
drivers/acpi/ec.c
View file

@ -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);

8
drivers/acpi/internal.h
View file

@ -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;