Patch "ACPI / EC: Use busy polling mode when GPE is not enabled" has been added to the 4.9-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

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

to the 4.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     acpi-ec-use-busy-polling-mode-when-gpe-is-not-enabled.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From c3a696b6e8f8f75f9f75e556a9f9f6472eae2655 Mon Sep 17 00:00:00 2001
From: Lv Zheng <lv.zheng@intel.com>
Date: Fri, 20 Jan 2017 16:42:48 +0800
Subject: ACPI / EC: Use busy polling mode when GPE is not enabled

From: Lv Zheng <lv.zheng@intel.com>

commit c3a696b6e8f8f75f9f75e556a9f9f6472eae2655 upstream.

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>
Cc: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/acpi/ec.c       |   62 +++++++++++++++++++++++-------------------------
 drivers/acpi/internal.h |    4 +--
 2 files changed, 32 insertions(+), 34 deletions(-)

--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -729,12 +729,12 @@ static void start_transaction(struct acp
 
 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;
@@ -998,6 +998,28 @@ static void acpi_ec_stop(struct acpi_ec
 	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;
@@ -1278,7 +1300,7 @@ acpi_ec_space_handler(u32 function, acpi
 	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)
@@ -1286,7 +1308,7 @@ acpi_ec_space_handler(u32 function, acpi
 			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) {
@@ -1329,6 +1351,8 @@ static struct acpi_ec *acpi_ec_alloc(voi
 	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;
 }
 
@@ -1390,6 +1414,7 @@ static int ec_install_handlers(struct ac
 	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,
@@ -1429,6 +1454,7 @@ static int ec_install_handlers(struct ac
 		/* 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);
@@ -1839,34 +1865,6 @@ 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 =
--- a/drivers/acpi/internal.h
+++ b/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;


Patches currently in stable-queue which might be from lv.zheng@intel.com are

queue-4.9/acpi-ec-use-busy-polling-mode-when-gpe-is-not-enabled.patch