gpio: Add support for hierarchical IRQ domains

Hierarchical IRQ domains can be used to stack different IRQ
controllers on top of each other.

Bring hierarchical IRQ domains into the GPIOLIB core with the
following basic idea:

Drivers that need their interrupts handled hierarchically
specify a callback to translate the child hardware IRQ and
IRQ type for each GPIO offset to a parent hardware IRQ and
parent hardware IRQ type.

Users have to pass the callback, fwnode, and parent irqdomain
before calling gpiochip_irqchip_add().

We use the new method of just filling in the struct
gpio_irq_chip before adding the gpiochip for all hierarchical
irqchips of this type.

The code path for device tree is pretty straight-forward,
while the code path for old boardfiles or anything else will
be more convoluted requireing upfront allocation of the
interrupts when adding the chip.

One specific use-case where this can be useful is if a power
management controller has top-level controls for wakeup
interrupts. In such cases, the power management controller can
be a parent to other interrupt controllers and program
additional registers when an IRQ has its wake capability
enabled or disabled.

The hierarchical irqchip helper code will only be available
when IRQ_DOMAIN_HIERARCHY is selected to GPIO chips using
this should select or depend on that symbol. When using
hierarchical IRQs, the parent interrupt controller must
also be hierarchical all the way up to the top interrupt
controller wireing directly into the CPU, so on systems
that do not have this we can get rid of all the extra
code for supporting hierarchical irqs.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Lina Iyer <ilina@codeaurora.org>
Cc: Jon Hunter <jonathanh@nvidia.com>
Cc: Sowjanya Komatineni <skomatineni@nvidia.com>
Cc: Bitan Biswas <bbiswas@nvidia.com>
Cc: linux-tegra@vger.kernel.org
Cc: David Daney <david.daney@cavium.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Brian Masney <masneyb@onstation.org>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Brian Masney <masneyb@onstation.org>
Co-developed-by: Brian Masney <masneyb@onstation.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20190808123242.5359-1-linus.walleij@linaro.org

1 files changed, 111 insertions, 0 deletions

diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index 6a0e420915a3..0e6d3b0c0211 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -23,6 +23,9 @@ enum gpio_lookup_flags;
 #ifdef CONFIG_GPIOLIB
 
 #ifdef CONFIG_GPIOLIB_IRQCHIP
+
+struct gpio_chip;
+
 /**
  * struct gpio_irq_chip - GPIO interrupt controller
  */
@@ -49,6 +52,84 @@ struct gpio_irq_chip {
 	 */
 	const struct irq_domain_ops *domain_ops;
 
+#ifdef CONFIG_IRQ_DOMAIN_HIERARCHY
+	/**
+	 * @fwnode:
+	 *
+	 * Firmware node corresponding to this gpiochip/irqchip, necessary
+	 * for hierarchical irqdomain support.
+	 */
+	struct fwnode_handle *fwnode;
+
+	/**
+	 * @parent_domain:
+	 *
+	 * If non-NULL, will be set as the parent of this GPIO interrupt
+	 * controller's IRQ domain to establish a hierarchical interrupt
+	 * domain. The presence of this will activate the hierarchical
+	 * interrupt support.
+	 */
+	struct irq_domain *parent_domain;
+
+	/**
+	 * @child_to_parent_hwirq:
+	 *
+	 * This callback translates a child hardware IRQ offset to a parent
+	 * hardware IRQ offset on a hierarchical interrupt chip. The child
+	 * hardware IRQs correspond to the GPIO index 0..ngpio-1 (see the
+	 * ngpio field of struct gpio_chip) and the corresponding parent
+	 * hardware IRQ and type (such as IRQ_TYPE_*) shall be returned by
+	 * the driver. The driver can calculate this from an offset or using
+	 * a lookup table or whatever method is best for this chip. Return
+	 * 0 on successful translation in the driver.
+	 *
+	 * If some ranges of hardware IRQs do not have a corresponding parent
+	 * HWIRQ, return -EINVAL, but also make sure to fill in @valid_mask and
+	 * @need_valid_mask to make these GPIO lines unavailable for
+	 * translation.
+	 */
+	int (*child_to_parent_hwirq)(struct gpio_chip *chip,
+				     unsigned int child_hwirq,
+				     unsigned int child_type,
+				     unsigned int *parent_hwirq,
+				     unsigned int *parent_type);
+
+	/**
+	 * @populate_parent_fwspec:
+	 *
+	 * This optional callback populates the &struct irq_fwspec for the
+	 * parent's IRQ domain. If this is not specified, then
+	 * &gpiochip_populate_parent_fwspec_twocell will be used. A four-cell
+	 * variant named &gpiochip_populate_parent_fwspec_fourcell is also
+	 * available.
+	 */
+	void (*populate_parent_fwspec)(struct gpio_chip *chip,
+				       struct irq_fwspec *fwspec,
+				       unsigned int parent_hwirq,
+				       unsigned int parent_type);
+
+	/**
+	 * @child_offset_to_irq:
+	 *
+	 * This optional callback is used to translate the child's GPIO line
+	 * offset on the GPIO chip to an IRQ number for the GPIO to_irq()
+	 * callback. If this is not specified, then a default callback will be
+	 * provided that returns the line offset.
+	 */
+	unsigned int (*child_offset_to_irq)(struct gpio_chip *chip,
+					    unsigned int pin);
+
+	/**
+	 * @child_irq_domain_ops:
+	 *
+	 * The IRQ domain operations that will be used for this GPIO IRQ
+	 * chip. If no operations are provided, then default callbacks will
+	 * be populated to setup the IRQ hierarchy. Some drivers need to
+	 * supply their own translate function.
+	 */
+	struct irq_domain_ops child_irq_domain_ops;
+#endif
+
 	/**
 	 * @handler:
 	 *
@@ -449,6 +530,36 @@ struct bgpio_pdata {
 	int ngpio;
 };
 
+#ifdef CONFIG_IRQ_DOMAIN_HIERARCHY
+
+void gpiochip_populate_parent_fwspec_twocell(struct gpio_chip *chip,
+					     struct irq_fwspec *fwspec,
+					     unsigned int parent_hwirq,
+					     unsigned int parent_type);
+void gpiochip_populate_parent_fwspec_fourcell(struct gpio_chip *chip,
+					      struct irq_fwspec *fwspec,
+					      unsigned int parent_hwirq,
+					      unsigned int parent_type);
+
+#else
+
+static void gpiochip_populate_parent_fwspec_twocell(struct gpio_chip *chip,
+						    struct irq_fwspec *fwspec,
+						    unsigned int parent_hwirq,
+						    unsigned int parent_type)
+{
+}
+
+static void gpiochip_populate_parent_fwspec_fourcell(struct gpio_chip *chip,
+						     struct irq_fwspec *fwspec,
+						     unsigned int parent_hwirq,
+						     unsigned int parent_type)
+{
+}
+
+#endif /* CONFIG_IRQ_DOMAIN_HIERARCHY */
+
+
 #if IS_ENABLED(CONFIG_GPIO_GENERIC)
 
 int bgpio_init(struct gpio_chip *gc, struct device *dev,