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ACPI / EC: Fix a code coverity issue when QR_EC transactions are failed. 

When the QR_EC transaction fails, the EC_FLAGS_QUERY_PENDING flag prevents
the event handling work queue from being scheduled again.

Though there shouldn't be failed QR_EC transactions, and this gap was
efficiently used for catching and learning the SCI_EVT clearing timing
compliance issues, we need to fix this as we are not fully compatible
with all platforms/Windows to handle SCI_EVT clearing timing correctly.
Fixing this gives the EC driver the chances to recover from a state machine
failure.

So this patch fixes this issue. When nr_pending_queries drops to 0, it
clears EC_FLAGS_QUERY_PENDING at the proper position for different modes in
order to ensure that the SCI_EVT handling can proceed.

In order to be clearer for future ec_event_clearing modes, all checks in
this patch are written in the inclusive style, not the exclusive style.

Cc: 3.16+ <stable@vger.kernel.org> # 3.16+
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Lv Zheng 2015-06-11 13:21:51 +08:00 committed by Rafael J. Wysocki
parent 3cb02aeb28
commit 66db383439
1 changed files with 13 additions and 1 deletions
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14
drivers/acpi/ec.c
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@ -512,7 +512,8 @@ static void advance_transaction(struct acpi_ec *ec)
*/
if (!t || !(t->flags & ACPI_EC_COMMAND_POLL)) {
if (ec_event_clearing == ACPI_EC_EVT_TIMING_EVENT &&
test_bit(EC_FLAGS_QUERY_GUARDING, &ec->flags)) {
(!ec->nr_pending_queries ||
test_bit(EC_FLAGS_QUERY_GUARDING, &ec->flags))) {
clear_bit(EC_FLAGS_QUERY_GUARDING, &ec->flags);
acpi_ec_complete_query(ec);
}
@ -1065,6 +1066,17 @@ static void acpi_ec_event_handler(struct work_struct *work)
(void)acpi_ec_query(ec, NULL);
spin_lock_irqsave(&ec->lock, flags);
ec->nr_pending_queries--;
/*
* Before exit, make sure that this work item can be
* scheduled again. There might be QR_EC failures, leaving
* EC_FLAGS_QUERY_PENDING uncleared and preventing this work
* item from being scheduled again.
*/
if (!ec->nr_pending_queries) {
if (ec_event_clearing == ACPI_EC_EVT_TIMING_STATUS ||
ec_event_clearing == ACPI_EC_EVT_TIMING_QUERY)
acpi_ec_complete_query(ec);
}
}
spin_unlock_irqrestore(&ec->lock, flags);