[PATCH 1/5] ACPI: EC: Make the GPE storm threshold a module parameter

[Feng Tang <feng.tang@intel.com>]

This is to solve bug https://bugzilla.kernel.org/show_bug.cgi?id=45151

The ACPI_EC_STORM_THRESHOLD was initially 20 when it's created, and was
changed to 8 in commit 06cf7d3c7 "ACPI: EC: lower interrupt storm treshold"
to fix another 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 chose a number according to their specific EC HW.
It doesn't affect current EC behavior.

Signed-off-by: Feng Tang <feng.tang@intel.com>
---
 drivers/acpi/ec.c |   14 ++++++++++----
 1 files 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)
 		msleep(1);
 		/* 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);
-- 
1.7.1