gpiolib: add irq_not_threaded flag to gpio_chip

Some GPIO chips (e.g. the DLN2 USB adapter) have blocking get/set
operation but do not need a threaded irq handler.
Signed-off-by: Octavian Purdila <octavian.purdila@intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpiolib.c

@@ -437,7 +437,7 @@ static int gpiochip_irq_map(struct irq_domain *d, unsigned int irq,
 	irq_set_lockdep_class(irq, &gpiochip_irq_lock_class);
 	irq_set_chip_and_handler(irq, chip->irqchip, chip->irq_handler);
 	/* Chips that can sleep need nested thread handlers */
-	if (chip->can_sleep)
+	if (chip->can_sleep && !chip->irq_not_threaded)
 		irq_set_nested_thread(irq, 1);
 #ifdef CONFIG_ARM
 	set_irq_flags(irq, IRQF_VALID);

include/linux/gpio/driver.h

@@ -56,6 +56,8 @@ struct seq_file;
  *	as the chip access may sleep when e.g. reading out the IRQ status
  *	registers.
  * @exported: flags if the gpiochip is exported for use from sysfs. Private.
+ * @irq_not_threaded: flag must be set if @can_sleep is set but the
+ *	IRQs don't need to be threaded
  *
  * A gpio_chip can help platforms abstract various sources of GPIOs so
  * they can all be accessed through a common programing interface.
@@ -101,6 +103,7 @@ struct gpio_chip {
 	struct gpio_desc	*desc;
 	const char		*const *names;
 	bool			can_sleep;
+	bool			irq_not_threaded;
 	bool			exported;
 
 #ifdef CONFIG_GPIOLIB_IRQCHIP