[PATCH] gpiolib: acpi: Do not set the IRQ type if the IRQ is already in use

[Hans de Goede <hdegoede@redhat.com>]

If the IRQ is already in use, then acpi_dev_gpio_irq_get_by() really
should not change the type underneath the current owner.

I specifically hit an issue with this an a Chuwi Hi8 Super (CWI509) Bay
Trail tablet, when the Boot OS selection in the BIOS is set to Android.
In this case _STA for a MAX17047 ACPI I2C device wrongly returns 0xf and
the _CRS resources for this device include a GpioInt pointing to a GPIO
already in use by an _AEI handler, with a different type then specified
in the _CRS for the MAX17047 device. Leading to the acpi_dev_gpio_irq_get()
call done by the i2c-core-acpi.c code changing the type breaking the
_AEI handler.

Now this clearly is a bug in the DSDT of this tablet (in Android mode),
but in general calling irq_set_irq_type() on an IRQ which already is
in use seems like a bad idea.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
---
Changes in v2:
- Emit a dev_dbg when the IRQ is already in use. Note while making this
  change I realized that i2c-multi-instantiate.c actually uses
  acpi_dev_gpio_irq_get_by() with shared interrupts, so I decided to
  go with a dev_dbg instead of a dev_warn after all
---
 drivers/gpio/gpiolib-acpi.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/gpio/gpiolib-acpi.c b/drivers/gpio/gpiolib-acpi.c
index 985e8589c58b..feb8157d2d67 100644
--- a/drivers/gpio/gpiolib-acpi.c
+++ b/drivers/gpio/gpiolib-acpi.c
@@ -1056,10 +1056,17 @@ int acpi_dev_gpio_irq_get_by(struct acpi_device *adev, const char *name, int ind
 			irq_flags = acpi_dev_get_irq_type(info.triggering,
 							  info.polarity);
 
-			/* Set type if specified and different than the current one */
-			if (irq_flags != IRQ_TYPE_NONE &&
-			    irq_flags != irq_get_trigger_type(irq))
-				irq_set_irq_type(irq, irq_flags);
+			/*
+			 * If the IRQ is not already in use then set type
+			 * if specified and different than the current one.
+			 */
+			if (can_request_irq(irq, irq_flags)) {
+				if (irq_flags != IRQ_TYPE_NONE &&
+				    irq_flags != irq_get_trigger_type(irq))
+					irq_set_irq_type(irq, irq_flags);
+			} else {
+				dev_dbg(&adev->dev, "IRQ %d already in use\n", irq);
+			}
 
 			return irq;
 		}
-- 
2.33.1