ACPI: Use GPE reference counting to support shared GPEs

To fix a bug and address the reviewers' comments regarding the ACPI
GPE refcounting patch, do the following additional changes:

o Remove the second argument of acpi_ev_enable_gpe(),
  'write_to_hardware', because it is not necessary any more.

o Add the "bad parameter" test against 'type' in
  acpi_enable_gpe() and acpi_disable_gpe().

o Make acpi_enable_gpe() only check 'status' for runtime GPEs if
  acpi_ev_enable_gpe() was actually called.

o Make acpi_disable_gpe() return 'status' returned by
  acpi_ev_disable_gpe() and fix a bug where ACPI_GPE_TYPE_WAKE
  and ACPI_GPE_TYPE_RUNTIME were exchanged by mistake.

o Add comments explaining why acpi_set_gpe() is used by the ACPI EC
  driver.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

1 files changed, 11 insertions, 3 deletions

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index 0fa65a8210da..27e0b92b2e39 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -307,6 +307,10 @@ static int acpi_ec_transaction(struct acpi_ec *ec, struct transaction *t)
         pr_debug(PREFIX "transaction start\n");
         /* disable GPE during transaction if storm is detected */
         if (test_bit(EC_FLAGS_GPE_STORM, &ec->flags)) {
+                /*
+                 * It has to be disabled at the hardware level regardless of the
+                 * GPE reference counting, so that it doesn't trigger.
+                 */
                 acpi_set_gpe(NULL, ec->gpe, ACPI_GPE_DISABLE);
         }
 
@@ -316,7 +320,11 @@ static int acpi_ec_transaction(struct acpi_ec *ec, struct transaction *t)
         ec_check_sci_sync(ec, acpi_ec_read_status(ec));
         if (test_bit(EC_FLAGS_GPE_STORM, &ec->flags)) {
                 msleep(1);
-                /* it is safe to enable GPE outside of transaction */
+                /*
+                 * It is safe to enable the GPE outside of the transaction.  Use
+                 * acpi_set_gpe() for that, since we used it to disable the GPE
+                 * above.
+                 */
                 acpi_set_gpe(NULL, ec->gpe, ACPI_GPE_ENABLE);
         } else if (t->irq_count > ACPI_EC_STORM_THRESHOLD) {
                 pr_info(PREFIX "GPE storm detected, "
@@ -1059,7 +1067,7 @@ error:
 static int acpi_ec_suspend(struct acpi_device *device, pm_message_t state)
 {
         struct acpi_ec *ec = acpi_driver_data(device);
-        /* Stop using GPE */
+        /* Stop using the GPE, but keep it reference counted. */
         acpi_set_gpe(NULL, ec->gpe, ACPI_GPE_DISABLE);
         return 0;
 }
@@ -1067,7 +1075,7 @@ static int acpi_ec_suspend(struct acpi_device *device, pm_message_t state)
 static int acpi_ec_resume(struct acpi_device *device)
 {
         struct acpi_ec *ec = acpi_driver_data(device);
-        /* Enable use of GPE back */
+        /* Enable the GPE again, but don't reference count it once more. */
         acpi_set_gpe(NULL, ec->gpe, ACPI_GPE_ENABLE);
         return 0;
 }