[patch 3/5] ACPI: EC: Don't degrade to poll mode at storm automatically

[akpm@linux-foundation.org]

From: Alexey Starikovskiy <astarikovskiy@suse.de>

Not all users of semi-broken EC devices want to degrade to poll mode, so
give them right to choose.

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: Alexey Starikovskiy <astarikovskiy@suse.de>
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>
---

 Documentation/kernel-parameters.txt |    5 +++
 drivers/acpi/ec.c                   |   36 ++++++++++++++++++--------
 2 files changed, 31 insertions(+), 10 deletions(-)

diff -puN Documentation/kernel-parameters.txt~acpi-ec-dont-degrade-to-poll-mode-at-storm-automatically Documentation/kernel-parameters.txt
--- a/Documentation/kernel-parameters.txt~acpi-ec-dont-degrade-to-poll-mode-at-storm-automatically
+++ a/Documentation/kernel-parameters.txt
@@ -736,6 +736,11 @@ and is between 256 and 4096 characters. 
 
 	eata=		[HW,SCSI]
 
+	ec_intr=	[HW,ACPI] ACPI Embedded Controller interrupt mode
+			Format: <int>
+			0: polling mode
+			non-0: interrupt mode (default)
+
 	edd=		[EDD]
 			Format: {"off" | "on" | "skip[mbr]"}
 
diff -puN drivers/acpi/ec.c~acpi-ec-dont-degrade-to-poll-mode-at-storm-automatically drivers/acpi/ec.c
--- a/drivers/acpi/ec.c~acpi-ec-dont-degrade-to-poll-mode-at-storm-automatically
+++ a/drivers/acpi/ec.c
@@ -110,6 +110,8 @@ static struct acpi_ec {
 	u8 handlers_installed;
 } *boot_ec, *first_ec;
 
+int acpi_ec_intr = 1; /* Default is interrupt mode */
+
 /* 
  * Some Asus system have exchanged ECDT data/command IO addresses.
  */
@@ -516,12 +518,14 @@ static u32 acpi_ec_gpe_handler(void *dat
 	acpi_status status = AE_OK;
 	struct acpi_ec *ec = data;
 	u8 state = acpi_ec_read_status(ec);
+	static bool warn_done = false;
 
 	pr_debug(PREFIX "~~~> interrupt\n");
 	atomic_inc(&ec->irq_count);
-	if (atomic_read(&ec->irq_count) > 5) {
-		pr_err(PREFIX "GPE storm detected, disabling EC GPE\n");
-		ec_switch_to_poll_mode(ec);
+	if (!warn_done && atomic_read(&ec->irq_count) > 5) {
+		pr_warning(PREFIX "GPE storm detected, try to use ec_intr=0 "
+			"kernel option, if you see problems with keyboard.\n");
+		warn_done = 1;
 		goto end;
 	}
 	clear_bit(EC_FLAGS_WAIT_GPE, &ec->flags);
@@ -848,20 +852,21 @@ static int ec_install_handlers(struct ac
 	acpi_status status;
 	if (ec->handlers_installed)
 		return 0;
-	status = acpi_install_gpe_handler(NULL, ec->gpe,
+	if (acpi_ec_intr) {
+		status = acpi_install_gpe_handler(NULL, ec->gpe,
 					  ACPI_GPE_EDGE_TRIGGERED,
 					  &acpi_ec_gpe_handler, ec);
-	if (ACPI_FAILURE(status))
-		return -ENODEV;
-
-	acpi_set_gpe_type(NULL, ec->gpe, ACPI_GPE_TYPE_RUNTIME);
-	acpi_enable_gpe(NULL, ec->gpe, ACPI_NOT_ISR);
+		if (ACPI_FAILURE(status))
+			return -ENODEV;
 
+		acpi_set_gpe_type(NULL, ec->gpe, ACPI_GPE_TYPE_RUNTIME);
+		acpi_enable_gpe(NULL, ec->gpe, ACPI_NOT_ISR);
+	}
 	status = acpi_install_address_space_handler(ec->handle,
 						    ACPI_ADR_SPACE_EC,
 						    &acpi_ec_space_handler,
 						    NULL, ec);
-	if (ACPI_FAILURE(status)) {
+	if (ACPI_FAILURE(status) && acpi_ec_intr) {
 		acpi_remove_gpe_handler(NULL, ec->gpe, &acpi_ec_gpe_handler);
 		return -ENODEV;
 	}
@@ -1047,3 +1052,14 @@ static void __exit acpi_ec_exit(void)
 	return;
 }
 #endif	/* 0 */
+
+static int __init acpi_ec_set_intr_mode(char *str)
+{
+	if (!get_option(&str, &acpi_ec_intr)) {
+		acpi_ec_intr = 0;
+		return 0;
+	}
+	return 1;
+}
+
+__setup("ec_intr=", acpi_ec_set_intr_mode);
_