[PATCH] ACPI: EC: add support for hardware-reduced systems

[Daniel Drake <drake@endlessm.com>]

As defined in the ACPI spec section 12.11, ACPI hardware-reduced
platforms define the EC SCI interrupt as a GpioInt in the _CRS object.

This replaces the previous way of using a GPE for this interrupt;
GPE blocks are not available on reduced hardware platforms.

Add support for handling this interrupt as an EC event source, and
avoid GPE usage on reduced hardware platforms.

This enables the use of several media keys (e.g. screen brightness
up/down) on Asus UX434DA.

Signed-off-by: Daniel Drake <drake@endlessm.com>
---
 drivers/acpi/ec.c       | 81 +++++++++++++++++++++++++++++++----------
 drivers/acpi/internal.h |  1 +
 2 files changed, 63 insertions(+), 19 deletions(-)

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index c33756ed3304..37bbec89be82 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -99,7 +99,7 @@ enum {
 	EC_FLAGS_EVT_HANDLER_INSTALLED, /* _Qxx handlers installed */
 	EC_FLAGS_STARTED,		/* Driver is started */
 	EC_FLAGS_STOPPED,		/* Driver is stopped */
-	EC_FLAGS_GPE_MASKED,		/* GPE masked */
+	EC_FLAGS_EVENTS_MASKED,		/* GPE or IRQ masked */
 };
 
 #define ACPI_EC_COMMAND_POLL		0x01 /* Available for command byte */
@@ -414,20 +414,26 @@ static void acpi_ec_complete_request(struct acpi_ec *ec)
 		wake_up(&ec->wait);
 }
 
-static void acpi_ec_mask_gpe(struct acpi_ec *ec)
+static void acpi_ec_mask_events(struct acpi_ec *ec)
 {
-	if (!test_bit(EC_FLAGS_GPE_MASKED, &ec->flags)) {
-		acpi_ec_disable_gpe(ec, false);
+	if (!test_bit(EC_FLAGS_EVENTS_MASKED, &ec->flags)) {
+		if (ec->irq >= 0)
+			disable_irq_nosync(ec->irq);
+		else
+			acpi_ec_disable_gpe(ec, false);
 		ec_dbg_drv("Polling enabled");
-		set_bit(EC_FLAGS_GPE_MASKED, &ec->flags);
+		set_bit(EC_FLAGS_EVENTS_MASKED, &ec->flags);
 	}
 }
 
-static void acpi_ec_unmask_gpe(struct acpi_ec *ec)
+static void acpi_ec_unmask_events(struct acpi_ec *ec)
 {
-	if (test_bit(EC_FLAGS_GPE_MASKED, &ec->flags)) {
-		clear_bit(EC_FLAGS_GPE_MASKED, &ec->flags);
-		acpi_ec_enable_gpe(ec, false);
+	if (test_bit(EC_FLAGS_EVENTS_MASKED, &ec->flags)) {
+		clear_bit(EC_FLAGS_EVENTS_MASKED, &ec->flags);
+		if (ec->irq >= 0)
+			enable_irq(ec->irq);
+		else
+			acpi_ec_enable_gpe(ec, false);
 		ec_dbg_drv("Polling disabled");
 	}
 }
@@ -453,7 +459,7 @@ static bool acpi_ec_submit_flushable_request(struct acpi_ec *ec)
 
 static void acpi_ec_submit_query(struct acpi_ec *ec)
 {
-	acpi_ec_mask_gpe(ec);
+	acpi_ec_mask_events(ec);
 	if (!acpi_ec_event_enabled(ec))
 		return;
 	if (!test_and_set_bit(EC_FLAGS_QUERY_PENDING, &ec->flags)) {
@@ -469,7 +475,7 @@ static void acpi_ec_complete_query(struct acpi_ec *ec)
 	if (test_and_clear_bit(EC_FLAGS_QUERY_PENDING, &ec->flags))
 		ec_dbg_evt("Command(%s) unblocked",
 			   acpi_ec_cmd_string(ACPI_EC_COMMAND_QUERY));
-	acpi_ec_unmask_gpe(ec);
+	acpi_ec_unmask_events(ec);
 }
 
 static inline void __acpi_ec_enable_event(struct acpi_ec *ec)
@@ -647,7 +653,8 @@ static void advance_transaction(struct acpi_ec *ec)
 	 * ensure a hardware STS 0->1 change after this clearing can always
 	 * trigger a GPE interrupt.
 	 */
-	acpi_ec_clear_gpe(ec);
+	if (ec->irq < 0)
+		acpi_ec_clear_gpe(ec);
 	status = acpi_ec_read_status(ec);
 	t = ec->curr;
 	/*
@@ -716,7 +723,7 @@ static void advance_transaction(struct acpi_ec *ec)
 				++t->irq_count;
 			/* Allow triggering on 0 threshold */
 			if (t->irq_count == ec_storm_threshold)
-				acpi_ec_mask_gpe(ec);
+				acpi_ec_mask_events(ec);
 		}
 	}
 out:
@@ -814,7 +821,7 @@ static int acpi_ec_transaction_unlocked(struct acpi_ec *ec,
 
 	spin_lock_irqsave(&ec->lock, tmp);
 	if (t->irq_count == ec_storm_threshold)
-		acpi_ec_unmask_gpe(ec);
+		acpi_ec_unmask_events(ec);
 	ec_dbg_req("Command(%s) stopped", acpi_ec_cmd_string(t->command));
 	ec->curr = NULL;
 	/* Disable GPE for command processing (IBF=0/OBF=1) */
@@ -1292,18 +1299,32 @@ static void acpi_ec_event_handler(struct work_struct *work)
 	acpi_ec_check_event(ec);
 }
 
-static u32 acpi_ec_gpe_handler(acpi_handle gpe_device,
-	u32 gpe_number, void *data)
+static void acpi_ec_handle_interrupt(struct acpi_ec *ec)
 {
 	unsigned long flags;
-	struct acpi_ec *ec = data;
 
 	spin_lock_irqsave(&ec->lock, flags);
 	advance_transaction(ec);
 	spin_unlock_irqrestore(&ec->lock, flags);
+}
+
+static u32 acpi_ec_gpe_handler(acpi_handle gpe_device,
+	u32 gpe_number, void *data)
+{
+	struct acpi_ec *ec = data;
+
+	acpi_ec_handle_interrupt(ec);
 	return ACPI_INTERRUPT_HANDLED;
 }
 
+static irqreturn_t acpi_ec_irq_handler(int irq, void *data)
+{
+	struct acpi_ec *ec = data;
+
+	acpi_ec_handle_interrupt(ec);
+	return IRQ_HANDLED;
+}
+
 /* --------------------------------------------------------------------------
  *                           Address Space Management
  * -------------------------------------------------------------------------- */
@@ -1376,6 +1397,7 @@ static struct acpi_ec *acpi_ec_alloc(void)
 	ec->timestamp = jiffies;
 	ec->busy_polling = true;
 	ec->polling_guard = 0;
+	ec->irq = -1;
 	return ec;
 }
 
@@ -1419,7 +1441,7 @@ ec_parse_device(acpi_handle handle, u32 Level, void *context, void **retval)
 		 * EC.
 		 */
 		ec->gpe = boot_ec->gpe;
-	} else {
+	} else if (!acpi_gbl_reduced_hardware) {
 		/* Get GPE bit assignment (EC events). */
 		/* TODO: Add support for _GPE returning a package */
 		status = acpi_evaluate_integer(handle, "_GPE", NULL, &tmp);
@@ -1480,7 +1502,8 @@ static int ec_install_handlers(struct acpi_ec *ec, bool handle_events)
 				    NULL, ec, NULL);
 		set_bit(EC_FLAGS_EVT_HANDLER_INSTALLED, &ec->flags);
 	}
-	if (!test_bit(EC_FLAGS_GPE_HANDLER_INSTALLED, &ec->flags)) {
+	if (!acpi_gbl_reduced_hardware &&
+	    !test_bit(EC_FLAGS_GPE_HANDLER_INSTALLED, &ec->flags)) {
 		status = acpi_install_gpe_raw_handler(NULL, ec->gpe,
 					  ACPI_GPE_EDGE_TRIGGERED,
 					  &acpi_ec_gpe_handler, ec);
@@ -1493,6 +1516,12 @@ static int ec_install_handlers(struct acpi_ec *ec, bool handle_events)
 				acpi_ec_enable_gpe(ec, true);
 		}
 	}
+	if (ec->irq >= 0) {
+		int ret = request_irq(ec->irq, acpi_ec_irq_handler,
+				      IRQF_SHARED, "ACPI EC", ec);
+		if (ret)
+			return ret;
+	}
 	/* EC is fully operational, allow queries */
 	acpi_ec_enable_event(ec);
 
@@ -1521,6 +1550,8 @@ static void ec_remove_handlers(struct acpi_ec *ec)
 	 */
 	acpi_ec_stop(ec, false);
 
+	if (ec->irq >= 0)
+		free_irq(ec->irq, ec);
 	if (test_bit(EC_FLAGS_GPE_HANDLER_INSTALLED, &ec->flags)) {
 		if (ACPI_FAILURE(acpi_remove_gpe_handler(NULL, ec->gpe,
 					&acpi_ec_gpe_handler)))
@@ -1611,6 +1642,18 @@ static int acpi_ec_add(struct acpi_device *device)
 			acpi_ec_free(ec);
 			ec = boot_ec;
 		}
+
+		/*
+		 * Reduced hartware platforms use a GpioInt specified in
+		 * _CRS.
+		 */
+		if (acpi_gbl_reduced_hardware) {
+			ret = acpi_dev_gpio_irq_get(device, 0);
+			if (ret == -EPROBE_DEFER)
+				goto err_alloc;
+
+			ec->irq = ret;
+		}
 	}
 
 	ret = acpi_ec_setup(ec, true);
diff --git a/drivers/acpi/internal.h b/drivers/acpi/internal.h
index f4c2fe6be4f2..34c2c85e667e 100644
--- a/drivers/acpi/internal.h
+++ b/drivers/acpi/internal.h
@@ -166,6 +166,7 @@ static inline void acpi_early_processor_osc(void) {}
 struct acpi_ec {
 	acpi_handle handle;
 	u32 gpe;
+	int irq;
 	unsigned long command_addr;
 	unsigned long data_addr;
 	bool global_lock;
-- 
2.20.1