[ 3.5.yuz extended stable ] Patch "ACPI: EC: Make the GPE storm threshold a module parameter" has been added to staging queue

Herton Ronaldo Krzesinski herton.krzesinski at canonical.com
Thu Nov 15 05:49:06 UTC 2012

This is a note to let you know that I have just added a patch titled

    ACPI: EC: Make the GPE storm threshold a module parameter

to the linux-3.5.y-queue branch of the 3.5.yuz extended stable tree 
which can be found at:


If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.yuz tree, see



>From 0b506089c0287884f72c2f72c72d5186c77fb744 Mon Sep 17 00:00:00 2001
From: Feng Tang <feng.tang at intel.com>
Date: Fri, 28 Sep 2012 15:22:00 +0800
Subject: [PATCH] ACPI: EC: Make the GPE storm threshold a module parameter

commit a520d52e99b14ba7db135e916348f12f2a6e09be upstream.

The Linux EC driver includes a mechanism to detect GPE storms,
and switch from interrupt-mode to polling mode.  However, polling
mode sometimes doesn't work, so the workaround is problematic.
Also, different systems seem to need the threshold for detecting
the GPE storm at different levels.

ACPI_EC_STORM_THRESHOLD was initially 20 when it's created, and
was changed to 8 in 2.6.28 commit 06cf7d3c7 "ACPI: EC: lower interrupt storm
threshold" to fix kernel bug 11892 by forcing the laptop in that bug to
work in polling mode. However in bug 45151, it works fine in interrupt
mode if we lift the threshold back to 20.

This patch makes the threshold a module parameter so that user has a
flexible option to debug/workaround this issue.

The default is unchanged.

This is also a preparation patch to fix specific systems:

Signed-off-by: Feng Tang <feng.tang at intel.com>
Signed-off-by: Len Brown <len.brown at intel.com>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
 drivers/acpi/ec.c |   14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index 7edaccc..615264c 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -71,9 +71,6 @@ enum ec_command {
 #define ACPI_EC_UDELAY_GLK	1000	/* Wait 1ms max. to get global lock */
 #define ACPI_EC_MSI_UDELAY	550	/* Wait 550us for MSI EC */

-#define ACPI_EC_STORM_THRESHOLD 8	/* number of false interrupts
-					   per one transaction */
 enum {
 	EC_FLAGS_QUERY_PENDING,		/* Query is pending */
 	EC_FLAGS_GPE_STORM,		/* GPE storm detected */
@@ -87,6 +84,15 @@ static unsigned int ec_delay __read_mostly = ACPI_EC_DELAY;
 module_param(ec_delay, uint, 0644);
 MODULE_PARM_DESC(ec_delay, "Timeout(ms) waited until an EC command completes");

+ * If the number of false interrupts per one transaction exceeds
+ * this threshold, will think there is a GPE storm happened and
+ * will disable the GPE for normal transaction.
+ */
+static unsigned int ec_storm_threshold  __read_mostly = 8;
+module_param(ec_storm_threshold, uint, 0644);
+MODULE_PARM_DESC(ec_storm_threshold, "Maxim false GPE numbers not considered as GPE storm");
 /* If we find an EC via the ECDT, we need to keep a ptr to its context */
 /* External interfaces use first EC only, so remember */
 typedef int (*acpi_ec_query_func) (void *data);
@@ -319,7 +325,7 @@ static int acpi_ec_transaction(struct acpi_ec *ec, struct transaction *t)
 		/* It is safe to enable the GPE outside of the transaction. */
 		acpi_enable_gpe(NULL, ec->gpe);
-	} else if (t->irq_count > ACPI_EC_STORM_THRESHOLD) {
+	} else if (t->irq_count > ec_storm_threshold) {
 		pr_info(PREFIX "GPE storm detected, "
 			"transactions will use polling mode\n");
 		set_bit(EC_FLAGS_GPE_STORM, &ec->flags);

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