[patch 2/2] acpi: Avoid dropping rapid hotkey events (or other GPEs) on Asus EeePC

[akpm@linux-foundation.org]

From: Alan Jenkins <alan-jenkins@tuffmail.co.uk>

It looks like this EC clears the SMI_EVT bit after every query, even if
there are more events pending.  The workaround is to repeatedly query the
EC until it reports that no events remain.

This fixes a regression in 2.6.26 (from 2.6.25.3).  Initially reported as
"Asus Eee PC hotkeys stop working if pressed quickly" in bugzilla
<http://bugzilla.kernel.org/show_bug.cgi?id=11089>.

The regression was caused by a recently added check for interrupt storms. 
The Eee PC triggers this check and switches to polling.  When multiple
events arrive between polling intervals, only one is fetched from the EC. 
This causes erroneous behaviour; ultimately events stop being delivered
altogether when the EC buffer overflows.

Signed-off-by: Alan Jenkins <alan-jenkins@tuffmail.co.uk>
Cc: Alexey Starikovskiy <astarikovskiy@suse.de>
Cc: Maximilian Engelhardt <maxi@daemonizer.de>
Cc: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/acpi/ec.c |   18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff -puN drivers/acpi/ec.c~acpi-avoid-dropping-rapid-hotkey-events-or-other-gpes-on-asus-eeepc drivers/acpi/ec.c
--- a/drivers/acpi/ec.c~acpi-avoid-dropping-rapid-hotkey-events-or-other-gpes-on-asus-eeepc
+++ a/drivers/acpi/ec.c
@@ -486,14 +486,10 @@ void acpi_ec_remove_query_handler(struct
 
 EXPORT_SYMBOL_GPL(acpi_ec_remove_query_handler);
 
-static void acpi_ec_gpe_query(void *ec_cxt)
+static void acpi_ec_gpe_run_handler(struct acpi_ec *ec, u8 value)
 {
-	struct acpi_ec *ec = ec_cxt;
-	u8 value = 0;
 	struct acpi_ec_query_handler *handler, copy;
 
-	if (!ec || acpi_ec_query(ec, &value))
-		return;
 	mutex_lock(&ec->lock);
 	list_for_each_entry(handler, &ec->list, node) {
 		if (value == handler->query_bit) {
@@ -511,6 +507,18 @@ static void acpi_ec_gpe_query(void *ec_c
 	mutex_unlock(&ec->lock);
 }
 
+static void acpi_ec_gpe_query(void *ec_cxt)
+{
+	struct acpi_ec *ec = ec_cxt;
+	u8 value = 0;
+
+	if (!ec)
+		return;
+
+	while (!acpi_ec_query(ec, &value))
+		acpi_ec_gpe_run_handler(ec, value);
+}
+
 static u32 acpi_ec_gpe_handler(void *data)
 {
 	acpi_status status = AE_OK;
_