gpio: simplify adding threaded interrupts

This tries to simplify the use of CONFIG_GPIOLIB_IRQCHIP when
using threaded interrupts: add a new call
gpiochip_irqchip_add_nested() to indicate that we're dealing
with a nested rather than a chained irqchip, then create a
separate gpiochip_set_nested_irqchip() to mirror
the gpiochip_set_chained_irqchip() call to connect the
parent and child interrupts.

In the nested case gpiochip_set_nested_irqchip() does nothing
more than call irq_set_parent() on each valid child interrupt,
which has little semantic effect in the kernel, but this is
probably still formally correct.

Update all drivers using nested interrupts to use
gpiochip_irqchip_add_nested() so we can now see clearly
which these users are.

The DLN2 driver can drop its specific hack with
.irq_not_threaded as we now recognize whether a chip is
threaded or not from its use of gpiochip_irqchip_add_nested()
signature rather than from inspecting .can_sleep.

We rename the .irq_parent to .irq_chained_parent since this
parent IRQ is only really kept around for the chained
interrupt handlers.

Cc: Lars Poeschel <poeschel@lemonage.de>
Cc: Octavian Purdila <octavian.purdila@intel.com>
Cc: Daniel Baluta <daniel.baluta@intel.com>
Cc: Bin Gao <bin.gao@linux.intel.com>
Cc: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: Ajay Thomas <ajay.thomas.david.rajamanickam@intel.com>
Cc: Semen Protsenko <semen.protsenko@globallogic.com>
Cc: Alexander Stein <alexander.stein@systec-electronic.com>
Cc: Phil Reid <preid@electromag.com.au>
Cc: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Cc: Patrice Chotard <patrice.chotard@st.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

include/linux/gpio/driver.h

@@ -82,8 +82,6 @@ enum single_ended_mode {
  *	implies that if the chip supports IRQs, these IRQs need to be threaded
  *	as the chip access may sleep when e.g. reading out the IRQ status
  *	registers.
- * @irq_not_threaded: flag must be set if @can_sleep is set but the
- *	IRQs don't need to be threaded
  * @read_reg: reader function for generic GPIO
  * @write_reg: writer function for generic GPIO
  * @pin2mask: some generic GPIO controllers work with the big-endian bits
@@ -109,8 +107,10 @@ enum single_ended_mode {
  *	for GPIO IRQs, provided by GPIO driver
  * @irq_default_type: default IRQ triggering type applied during GPIO driver
  *	initialization, provided by GPIO driver
- * @irq_parent: GPIO IRQ chip parent/bank linux irq number,
- *	provided by GPIO driver
+ * @irq_chained_parent: GPIO IRQ chip parent/bank linux irq number,
+ *	provided by GPIO driver for chained interrupt (not for nested
+ *	interrupts).
+ * @irq_nested: True if set the interrupt handling is nested.
  * @irq_need_valid_mask: If set core allocates @irq_valid_mask with all
  *	bits set to one
  * @irq_valid_mask: If not %NULL holds bitmask of GPIOs which are valid to
@@ -166,7 +166,6 @@ struct gpio_chip {
 	u16			ngpio;
 	const char		*const *names;
 	bool			can_sleep;
-	bool			irq_not_threaded;
 
 #if IS_ENABLED(CONFIG_GPIO_GENERIC)
 	unsigned long (*read_reg)(void __iomem *reg);
@@ -192,7 +191,8 @@ struct gpio_chip {
 	unsigned int		irq_base;
 	irq_flow_handler_t	irq_handler;
 	unsigned int		irq_default_type;
-	int			irq_parent;
+	int			irq_chained_parent;
+	bool			irq_nested;
 	bool			irq_need_valid_mask;
 	unsigned long		*irq_valid_mask;
 	struct lock_class_key	*lock_key;
@@ -270,24 +270,40 @@ void gpiochip_set_chained_irqchip(struct gpio_chip *gpiochip,
 		int parent_irq,
 		irq_flow_handler_t parent_handler);
 
+void gpiochip_set_nested_irqchip(struct gpio_chip *gpiochip,
+		struct irq_chip *irqchip,
+		int parent_irq);
+
 int _gpiochip_irqchip_add(struct gpio_chip *gpiochip,
 			  struct irq_chip *irqchip,
 			  unsigned int first_irq,
 			  irq_flow_handler_t handler,
 			  unsigned int type,
+			  bool nested,
 			  struct lock_class_key *lock_key);
 
+/* FIXME: I assume threaded IRQchips do not have the lockdep problem */
+static inline int gpiochip_irqchip_add_nested(struct gpio_chip *gpiochip,
+			  struct irq_chip *irqchip,
+			  unsigned int first_irq,
+			  irq_flow_handler_t handler,
+			  unsigned int type)
+{
+	return _gpiochip_irqchip_add(gpiochip, irqchip, first_irq,
+				     handler, type, true, NULL);
+}
+
 #ifdef CONFIG_LOCKDEP
 #define gpiochip_irqchip_add(...)				\
 (								\
 	({							\
 		static struct lock_class_key _key;		\
-		_gpiochip_irqchip_add(__VA_ARGS__, &_key);	\
+		_gpiochip_irqchip_add(__VA_ARGS__, false, &_key); \
 	})							\
 )
 #else
 #define gpiochip_irqchip_add(...)				\
-	_gpiochip_irqchip_add(__VA_ARGS__, NULL)
+	_gpiochip_irqchip_add(__VA_ARGS__, false, NULL)
 #endif
 
 #endif /* CONFIG_GPIOLIB_IRQCHIP */