Revert "ACPI: EC: Use a spin lock without disabing interrupts"

Commit eb9299be ("ACPI: EC: Use a spin lock without disabing
interrupts") introduced an unexpected user-visible change in
behavior, which is a significant CPU load increase when the EC
is in use.

This most likely happens due to increased spinlock contention
and so reducing this effect would require a major rework of the
EC driver locking.  There is no time for this in the current
cycle, so revert commit eb9299be.

Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218511Reported-by: Dieter Mummenschanz <dmummenschanz@web.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/ec.c

@@ -525,10 +525,12 @@ static void acpi_ec_clear(struct acpi_ec *ec)
 
 static void acpi_ec_enable_event(struct acpi_ec *ec)
 {
-	spin_lock(&ec->lock);
+	unsigned long flags;
+
+	spin_lock_irqsave(&ec->lock, flags);
 	if (acpi_ec_started(ec))
 		__acpi_ec_enable_event(ec);
-	spin_unlock(&ec->lock);
+	spin_unlock_irqrestore(&ec->lock, flags);
 
 	/* Drain additional events if hardware requires that */
 	if (EC_FLAGS_CLEAR_ON_RESUME)
@@ -544,9 +546,11 @@ static void __acpi_ec_flush_work(void)
 
 static void acpi_ec_disable_event(struct acpi_ec *ec)
 {
-	spin_lock(&ec->lock);
+	unsigned long flags;
+
+	spin_lock_irqsave(&ec->lock, flags);
 	__acpi_ec_disable_event(ec);
-	spin_unlock(&ec->lock);
+	spin_unlock_irqrestore(&ec->lock, flags);
 
 	/*
 	 * When ec_freeze_events is true, we need to flush events in
@@ -567,9 +571,10 @@ void acpi_ec_flush_work(void)
 
 static bool acpi_ec_guard_event(struct acpi_ec *ec)
 {
+	unsigned long flags;
 	bool guarded;
 
-	spin_lock(&ec->lock);
+	spin_lock_irqsave(&ec->lock, flags);
 	/*
 	 * If firmware SCI_EVT clearing timing is "event", we actually
 	 * don't know when the SCI_EVT will be cleared by firmware after
@@ -585,29 +590,31 @@ static bool acpi_ec_guard_event(struct acpi_ec *ec)
 	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(&ec->lock);
+	spin_unlock_irqrestore(&ec->lock, flags);
 	return guarded;
 }
 
 static int ec_transaction_polled(struct acpi_ec *ec)
 {
+	unsigned long flags;
 	int ret = 0;
 
-	spin_lock(&ec->lock);
+	spin_lock_irqsave(&ec->lock, flags);
 	if (ec->curr && (ec->curr->flags & ACPI_EC_COMMAND_POLL))
 		ret = 1;
-	spin_unlock(&ec->lock);
+	spin_unlock_irqrestore(&ec->lock, flags);
 	return ret;
 }
 
 static int ec_transaction_completed(struct acpi_ec *ec)
 {
+	unsigned long flags;
 	int ret = 0;
 
-	spin_lock(&ec->lock);
+	spin_lock_irqsave(&ec->lock, flags);
 	if (ec->curr && (ec->curr->flags & ACPI_EC_COMMAND_COMPLETE))
 		ret = 1;
-	spin_unlock(&ec->lock);
+	spin_unlock_irqrestore(&ec->lock, flags);
 	return ret;
 }
 
@@ -749,6 +756,7 @@ static int ec_guard(struct acpi_ec *ec)
 
 static int ec_poll(struct acpi_ec *ec)
 {
+	unsigned long flags;
 	int repeat = 5; /* number of command restarts */
 
 	while (repeat--) {
@@ -757,14 +765,14 @@ static int ec_poll(struct acpi_ec *ec)
 		do {
 			if (!ec_guard(ec))
 				return 0;
-			spin_lock(&ec->lock);
+			spin_lock_irqsave(&ec->lock, flags);
 			advance_transaction(ec, false);
-			spin_unlock(&ec->lock);
+			spin_unlock_irqrestore(&ec->lock, flags);
 		} while (time_before(jiffies, delay));
 		pr_debug("controller reset, restart transaction\n");
-		spin_lock(&ec->lock);
+		spin_lock_irqsave(&ec->lock, flags);
 		start_transaction(ec);
-		spin_unlock(&ec->lock);
+		spin_unlock_irqrestore(&ec->lock, flags);
 	}
 	return -ETIME;
 }
@@ -772,10 +780,11 @@ static int ec_poll(struct acpi_ec *ec)
 static int acpi_ec_transaction_unlocked(struct acpi_ec *ec,
 					struct transaction *t)
 {
+	unsigned long tmp;
 	int ret = 0;
 
 	/* start transaction */
-	spin_lock(&ec->lock);
+	spin_lock_irqsave(&ec->lock, tmp);
 	/* Enable GPE for command processing (IBF=0/OBF=1) */
 	if (!acpi_ec_submit_flushable_request(ec)) {
 		ret = -EINVAL;
@@ -786,11 +795,11 @@ static int acpi_ec_transaction_unlocked(struct acpi_ec *ec,
 	ec->curr = t;
 	ec_dbg_req("Command(%s) started", acpi_ec_cmd_string(t->command));
 	start_transaction(ec);
-	spin_unlock(&ec->lock);
+	spin_unlock_irqrestore(&ec->lock, tmp);
 
 	ret = ec_poll(ec);
 
-	spin_lock(&ec->lock);
+	spin_lock_irqsave(&ec->lock, tmp);
 	if (t->irq_count == ec_storm_threshold)
 		acpi_ec_unmask_events(ec);
 	ec_dbg_req("Command(%s) stopped", acpi_ec_cmd_string(t->command));
@@ -799,7 +808,7 @@ static int acpi_ec_transaction_unlocked(struct acpi_ec *ec,
 	acpi_ec_complete_request(ec);
 	ec_dbg_ref(ec, "Decrease command");
 unlock:
-	spin_unlock(&ec->lock);
+	spin_unlock_irqrestore(&ec->lock, tmp);
 	return ret;
 }
 
@@ -927,7 +936,9 @@ EXPORT_SYMBOL(ec_get_handle);
 
 static void acpi_ec_start(struct acpi_ec *ec, bool resuming)
 {
-	spin_lock(&ec->lock);
+	unsigned long flags;
+
+	spin_lock_irqsave(&ec->lock, flags);
 	if (!test_and_set_bit(EC_FLAGS_STARTED, &ec->flags)) {
 		ec_dbg_drv("Starting EC");
 		/* Enable GPE for event processing (SCI_EVT=1) */
@@ -937,28 +948,31 @@ static void acpi_ec_start(struct acpi_ec *ec, bool resuming)
 		}
 		ec_log_drv("EC started");
 	}
-	spin_unlock(&ec->lock);
+	spin_unlock_irqrestore(&ec->lock, flags);
 }
 
 static bool acpi_ec_stopped(struct acpi_ec *ec)
 {
+	unsigned long flags;
 	bool flushed;
 
-	spin_lock(&ec->lock);
+	spin_lock_irqsave(&ec->lock, flags);
 	flushed = acpi_ec_flushed(ec);
-	spin_unlock(&ec->lock);
+	spin_unlock_irqrestore(&ec->lock, flags);
 	return flushed;
 }
 
 static void acpi_ec_stop(struct acpi_ec *ec, bool suspending)
 {
-	spin_lock(&ec->lock);
+	unsigned long flags;
+
+	spin_lock_irqsave(&ec->lock, flags);
 	if (acpi_ec_started(ec)) {
 		ec_dbg_drv("Stopping EC");
 		set_bit(EC_FLAGS_STOPPED, &ec->flags);
-		spin_unlock(&ec->lock);
+		spin_unlock_irqrestore(&ec->lock, flags);
 		wait_event(ec->wait, acpi_ec_stopped(ec));
-		spin_lock(&ec->lock);
+		spin_lock_irqsave(&ec->lock, flags);
 		/* Disable GPE for event processing (SCI_EVT=1) */
 		if (!suspending) {
 			acpi_ec_complete_request(ec);
@@ -969,25 +983,29 @@ static void acpi_ec_stop(struct acpi_ec *ec, bool suspending)
 		clear_bit(EC_FLAGS_STOPPED, &ec->flags);
 		ec_log_drv("EC stopped");
 	}
-	spin_unlock(&ec->lock);
+	spin_unlock_irqrestore(&ec->lock, flags);
 }
 
 static void acpi_ec_enter_noirq(struct acpi_ec *ec)
 {
-	spin_lock(&ec->lock);
+	unsigned long flags;
+
+	spin_lock_irqsave(&ec->lock, flags);
 	ec->busy_polling = true;
 	ec->polling_guard = 0;
 	ec_log_drv("interrupt blocked");
-	spin_unlock(&ec->lock);
+	spin_unlock_irqrestore(&ec->lock, flags);
 }
 
 static void acpi_ec_leave_noirq(struct acpi_ec *ec)
 {
-	spin_lock(&ec->lock);
+	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(&ec->lock);
+	spin_unlock_irqrestore(&ec->lock, flags);
 }
 
 void acpi_ec_block_transactions(void)
@@ -1119,9 +1137,9 @@ static void acpi_ec_event_processor(struct work_struct *work)
 
 	ec_dbg_evt("Query(0x%02x) stopped", handler->query_bit);
 
-	spin_lock(&ec->lock);
+	spin_lock_irq(&ec->lock);
 	ec->queries_in_progress--;
-	spin_unlock(&ec->lock);
+	spin_unlock_irq(&ec->lock);
 
 	acpi_ec_put_query_handler(handler);
 	kfree(q);
@@ -1184,12 +1202,12 @@ static int acpi_ec_submit_query(struct acpi_ec *ec)
 	 */
 	ec_dbg_evt("Query(0x%02x) scheduled", value);
 
-	spin_lock(&ec->lock);
+	spin_lock_irq(&ec->lock);
 
 	ec->queries_in_progress++;
 	queue_work(ec_query_wq, &q->work);
 
-	spin_unlock(&ec->lock);
+	spin_unlock_irq(&ec->lock);
 
 	return 0;
 
@@ -1205,14 +1223,14 @@ static void acpi_ec_event_handler(struct work_struct *work)
 
 	ec_dbg_evt("Event started");
 
-	spin_lock(&ec->lock);
+	spin_lock_irq(&ec->lock);
 
 	while (ec->events_to_process) {
-		spin_unlock(&ec->lock);
+		spin_unlock_irq(&ec->lock);
 
 		acpi_ec_submit_query(ec);
 
-		spin_lock(&ec->lock);
+		spin_lock_irq(&ec->lock);
 
 		ec->events_to_process--;
 	}
@@ -1229,11 +1247,11 @@ static void acpi_ec_event_handler(struct work_struct *work)
 
 		ec_dbg_evt("Event stopped");
 
-		spin_unlock(&ec->lock);
+		spin_unlock_irq(&ec->lock);
 
 		guard_timeout = !!ec_guard(ec);
 
-		spin_lock(&ec->lock);
+		spin_lock_irq(&ec->lock);
 
 		/* Take care of SCI_EVT unless someone else is doing that. */
 		if (guard_timeout && !ec->curr)
@@ -1246,7 +1264,7 @@ static void acpi_ec_event_handler(struct work_struct *work)
 
 	ec->events_in_progress--;
 
-	spin_unlock(&ec->lock);
+	spin_unlock_irq(&ec->lock);
 }
 
 static void clear_gpe_and_advance_transaction(struct acpi_ec *ec, bool interrupt)
@@ -1271,11 +1289,13 @@ static void clear_gpe_and_advance_transaction(struct acpi_ec *ec, bool interrupt
 
 static void acpi_ec_handle_interrupt(struct acpi_ec *ec)
 {
-	spin_lock(&ec->lock);
+	unsigned long flags;
+
+	spin_lock_irqsave(&ec->lock, flags);
 
 	clear_gpe_and_advance_transaction(ec, true);
 
-	spin_unlock(&ec->lock);
+	spin_unlock_irqrestore(&ec->lock, flags);
 }
 
 static u32 acpi_ec_gpe_handler(acpi_handle gpe_device,
@@ -2085,7 +2105,7 @@ bool acpi_ec_dispatch_gpe(void)
 	 * Dispatch the EC GPE in-band, but do not report wakeup in any case
 	 * to allow the caller to process events properly after that.
 	 */
-	spin_lock(&first_ec->lock);
+	spin_lock_irq(&first_ec->lock);
 
 	if (acpi_ec_gpe_status_set(first_ec)) {
 		pm_pr_dbg("ACPI EC GPE status set\n");
@@ -2094,7 +2114,7 @@ bool acpi_ec_dispatch_gpe(void)
 		work_in_progress = acpi_ec_work_in_progress(first_ec);
 	}
 
-	spin_unlock(&first_ec->lock);
+	spin_unlock_irq(&first_ec->lock);
 
 	if (!work_in_progress)
 		return false;
@@ -2107,11 +2127,11 @@ bool acpi_ec_dispatch_gpe(void)
 
 		pm_pr_dbg("ACPI EC work flushed\n");
 
-		spin_lock(&first_ec->lock);
+		spin_lock_irq(&first_ec->lock);
 
 		work_in_progress = acpi_ec_work_in_progress(first_ec);
 
-		spin_unlock(&first_ec->lock);
+		spin_unlock_irq(&first_ec->lock);
 	} while (work_in_progress && !pm_wakeup_pending());
 
 	return false;