[RFC] gpiolib-acpi: make sure we trigger edge events at least once on boot

[Hans de Goede <j.w.r.degoede@xxxxxxxxx>]

From: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>

On some systems using edge triggered ACPI Event Interrupts, the initial
state at boot is not setup by the firmware, instead relying on the edge
irq event handler running at least once to setup the initial state.

2 known examples of this are:

1) The Surface 3 has its _LID state controlled by an ACPI operation region
triggered by a GPIO event:

 OperationRegion (GPOR, GeneralPurposeIo, Zero, One)
 Field (GPOR, ByteAcc, NoLock, Preserve)
 {
     Connection (
         GpioIo (Shared, PullNone, 0x0000, 0x0000, IoRestrictionNone,
             "\\_SB.GPO0", 0x00, ResourceConsumer, ,
             )
             {   // Pin list
                 0x004C
             }
     ),
     HELD,   1
 }

 Method (_E4C, 0, Serialized)  // _Exx: Edge-Triggered GPE
 {
     If ((HELD == One))
     {
         ^^LID.LIDB = One
     }
     Else
     {
         ^^LID.LIDB = Zero
         Notify (LID, 0x80) // Status Change
     }

     Notify (^^PCI0.SPI1.NTRG, One) // Device Check
 }

Currently, the state of LIDB is wrong until the user actually closes or
open the cover. We need to trigger the GPIO event once to update the
internal ACPI state.

Coincidentally, this also enables the Surface 2 integrated HID sensor hub
which also requires an ACPI gpio operation region to start initialization.

2) Various Bay Trail based tablets come with an external USB mux and
TI T1210B USB phy to enable USB gadget mode. The mux is controlled by a
GPIO which is controlled by an edge triggered ACPI Event Interrupt which
monitors the micro-USB ID pin.

When the tablet is connected to a PC (or no cable is plugged in), the ID
pin is high and the tablet should be in gadget mode. But the GPIO
controlling the mux is initialized by the firmware so that the USB data
lines are muxed to the host controller.

This means that if the user wants to use gadget mode, the user needs to
first plug in a host-cable to force the ID pin low and then unplug it
and connect the tablet to a PC, to get the ACPI event handler to run and
switch the mux to device mode,

This commit fixes both by running the event-handler once on boot.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@xxxxxxxxxx>
[hdegoede: Document BYT USB mux reliance on initial trigger]
Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
---
 drivers/gpio/gpiolib-acpi.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/gpio/gpiolib-acpi.c b/drivers/gpio/gpiolib-acpi.c
index e2232cbcec8b..7749b2ff7367 100644
--- a/drivers/gpio/gpiolib-acpi.c
+++ b/drivers/gpio/gpiolib-acpi.c
@@ -136,7 +136,7 @@ static acpi_status acpi_gpiochip_request_interrupt(struct acpi_resource *ares,
 	irq_handler_t handler = NULL;
 	struct gpio_desc *desc;
 	unsigned long irqflags;
-	int ret, pin, irq;
+	int ret, pin, irq, value;
 
 	if (!acpi_gpio_get_irq_resource(ares, &agpio))
 		return AE_OK;
@@ -167,6 +167,8 @@ static acpi_status acpi_gpiochip_request_interrupt(struct acpi_resource *ares,
 
 	gpiod_direction_input(desc);
 
+	value = gpiod_get_value(desc);
+
 	ret = gpiochip_lock_as_irq(chip, pin);
 	if (ret) {
 		dev_err(chip->parent, "Failed to lock GPIO as interrupt\n");
@@ -222,6 +224,15 @@ static acpi_status acpi_gpiochip_request_interrupt(struct acpi_resource *ares,
 		enable_irq_wake(irq);
 
 	list_add_tail(&event->node, &acpi_gpio->events);
+
+	/*
+	 * Make sure we trigger the initial state of the IRQ when
+	 * using RISING or FALLING.
+	 */
+	if (((irqflags & IRQF_TRIGGER_RISING) && value == 1) ||
+	    ((irqflags & IRQF_TRIGGER_FALLING) && value == 0))
+		handler(-1, event);
+
 	return AE_OK;
 
 fail_free_event:
-- 
2.17.1

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