ACPI / EC: Use busy polling mode when GPE is not enabled

When GPE is not enabled, it is not efficient to use the wait polling mode
as it introduces an unexpected scheduler delay.
So before the GPE handler is installed, this patch uses busy polling mode
for all EC(s) and the logic can be applied to non boot EC(s) during the
suspend/resume process.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=191561
Tested-by: Jakobus Schurz <jakobus.schurz@gmail.com>
Tested-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/ec.c

@@ -704,12 +704,12 @@ static void start_transaction(struct acpi_ec *ec)
 
 static int ec_guard(struct acpi_ec *ec)
 {
-	unsigned long guard = usecs_to_jiffies(ec_polling_guard);
+	unsigned long guard = usecs_to_jiffies(ec->polling_guard);
 	unsigned long timeout = ec->timestamp + guard;
 
 	/* Ensure guarding period before polling EC status */
 	do {
-		if (ec_busy_polling) {
+		if (ec->busy_polling) {
 			/* Perform busy polling */
 			if (ec_transaction_completed(ec))
 				return 0;
@@ -973,6 +973,28 @@ static void acpi_ec_stop(struct acpi_ec *ec, bool suspending)
 	spin_unlock_irqrestore(&ec->lock, flags);
 }
 
+static void acpi_ec_enter_noirq(struct acpi_ec *ec)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&ec->lock, flags);
+	ec->busy_polling = true;
+	ec->polling_guard = 0;
+	ec_log_drv("interrupt blocked");
+	spin_unlock_irqrestore(&ec->lock, flags);
+}
+
+static void acpi_ec_leave_noirq(struct acpi_ec *ec)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&ec->lock, flags);
+	ec->busy_polling = ec_busy_polling;
+	ec->polling_guard = ec_polling_guard;
+	ec_log_drv("interrupt unblocked");
+	spin_unlock_irqrestore(&ec->lock, flags);
+}
+
 void acpi_ec_block_transactions(void)
 {
 	struct acpi_ec *ec = first_ec;
@@ -1253,7 +1275,7 @@ acpi_ec_space_handler(u32 function, acpi_physical_address address,
 	if (function != ACPI_READ && function != ACPI_WRITE)
 		return AE_BAD_PARAMETER;
 
-	if (ec_busy_polling || bits > 8)
+	if (ec->busy_polling || bits > 8)
 		acpi_ec_burst_enable(ec);
 
 	for (i = 0; i < bytes; ++i, ++address, ++value)
@@ -1261,7 +1283,7 @@ acpi_ec_space_handler(u32 function, acpi_physical_address address,
 			acpi_ec_read(ec, address, value) :
 			acpi_ec_write(ec, address, *value);
 
-	if (ec_busy_polling || bits > 8)
+	if (ec->busy_polling || bits > 8)
 		acpi_ec_burst_disable(ec);
 
 	switch (result) {
@@ -1304,6 +1326,8 @@ static struct acpi_ec *acpi_ec_alloc(void)
 	spin_lock_init(&ec->lock);
 	INIT_WORK(&ec->work, acpi_ec_event_handler);
 	ec->timestamp = jiffies;
+	ec->busy_polling = true;
+	ec->polling_guard = 0;
 	return ec;
 }
 
@@ -1365,6 +1389,7 @@ static int ec_install_handlers(struct acpi_ec *ec, bool handle_events)
 	acpi_ec_start(ec, false);
 
 	if (!test_bit(EC_FLAGS_EC_HANDLER_INSTALLED, &ec->flags)) {
+		acpi_ec_enter_noirq(ec);
 		status = acpi_install_address_space_handler(ec->handle,
 							    ACPI_ADR_SPACE_EC,
 							    &acpi_ec_space_handler,
@@ -1404,6 +1429,7 @@ static int ec_install_handlers(struct acpi_ec *ec, bool handle_events)
 		/* This is not fatal as we can poll EC events */
 		if (ACPI_SUCCESS(status)) {
 			set_bit(EC_FLAGS_GPE_HANDLER_INSTALLED, &ec->flags);
+			acpi_ec_leave_noirq(ec);
 			if (test_bit(EC_FLAGS_STARTED, &ec->flags) &&
 			    ec->reference_count >= 1)
 				acpi_ec_enable_gpe(ec, true);
@@ -1786,34 +1812,6 @@ error:
 }
 
 #ifdef CONFIG_PM_SLEEP
-static void acpi_ec_enter_noirq(struct acpi_ec *ec)
-{
-	unsigned long flags;
-
-	if (ec == first_ec) {
-		spin_lock_irqsave(&ec->lock, flags);
-		ec->saved_busy_polling = ec_busy_polling;
-		ec->saved_polling_guard = ec_polling_guard;
-		ec_busy_polling = true;
-		ec_polling_guard = 0;
-		ec_log_drv("interrupt blocked");
-		spin_unlock_irqrestore(&ec->lock, flags);
-	}
-}
-
-static void acpi_ec_leave_noirq(struct acpi_ec *ec)
-{
-	unsigned long flags;
-
-	if (ec == first_ec) {
-		spin_lock_irqsave(&ec->lock, flags);
-		ec_busy_polling = ec->saved_busy_polling;
-		ec_polling_guard = ec->saved_polling_guard;
-		ec_log_drv("interrupt unblocked");
-		spin_unlock_irqrestore(&ec->lock, flags);
-	}
-}
-
 static int acpi_ec_suspend_noirq(struct device *dev)
 {
 	struct acpi_ec *ec =

drivers/acpi/internal.h

@@ -172,8 +172,8 @@ struct acpi_ec {
 	struct work_struct work;
 	unsigned long timestamp;
 	unsigned long nr_pending_queries;
-	bool saved_busy_polling;
-	unsigned int saved_polling_guard;
+	bool busy_polling;
+	unsigned int polling_guard;
 };
 
 extern struct acpi_ec *first_ec;