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Subject[PATCH v3 1/2] gpio: Add support for hierarchical IRQ domains
Date
From: Thierry Reding <treding@nvidia.com>

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

Signed-off-by: Thierry Reding <treding@nvidia.com>
---
Changes in v3:
- use irq_create_fwspec_mapping() instead of irq_domain_alloc_irqs()
- add missing kerneldoc for new parent_domain field
- keep IRQ_DOMAIN dependency for clarity

Changes in v2:
- select IRQ_DOMAIN_HIERARCHY to avoid build failure
- move more code into the gpiolib core

drivers/gpio/Kconfig | 1 +
drivers/gpio/gpiolib.c | 33 +++++++++++++++++++++++++++++----
include/linux/gpio/driver.h | 8 ++++++++
3 files changed, 38 insertions(+), 4 deletions(-)

diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index 62f3fe06cd2f..b87cc36005d8 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -45,6 +45,7 @@ config GPIO_ACPI

config GPIOLIB_IRQCHIP
select IRQ_DOMAIN
+ select IRQ_DOMAIN_HIERARCHY
bool

config DEBUG_GPIO
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index e013d417a936..6b64bfa90089 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1825,9 +1825,22 @@ EXPORT_SYMBOL_GPL(gpiochip_irq_domain_deactivate);

static int gpiochip_to_irq(struct gpio_chip *chip, unsigned offset)
{
+ struct irq_domain *domain = chip->irq.domain;
+
if (!gpiochip_irqchip_irq_valid(chip, offset))
return -ENXIO;

+ if (irq_domain_is_hierarchy(domain)) {
+ struct irq_fwspec spec;
+
+ spec.fwnode = domain->fwnode;
+ spec.param_count = 2;
+ spec.param[0] = offset;
+ spec.param[1] = IRQ_TYPE_NONE;
+
+ return irq_create_fwspec_mapping(&spec);
+ }
+
return irq_create_mapping(chip->irq.domain, offset);
}

@@ -1936,7 +1949,14 @@ static int gpiochip_add_irqchip(struct gpio_chip *gpiochip,
type = IRQ_TYPE_NONE;
}

- gpiochip->to_irq = gpiochip_to_irq;
+ /*
+ * Allow GPIO chips to override the ->to_irq() if they really need to.
+ * This should only be very rarely needed, the majority should be fine
+ * with gpiochip_to_irq().
+ */
+ if (!gpiochip->to_irq)
+ gpiochip->to_irq = gpiochip_to_irq;
+
gpiochip->irq.default_type = type;
gpiochip->irq.lock_key = lock_key;
gpiochip->irq.request_key = request_key;
@@ -1946,9 +1966,14 @@ static int gpiochip_add_irqchip(struct gpio_chip *gpiochip,
else
ops = &gpiochip_domain_ops;

- gpiochip->irq.domain = irq_domain_add_simple(np, gpiochip->ngpio,
- gpiochip->irq.first,
- ops, gpiochip);
+ if (gpiochip->irq.parent_domain)
+ gpiochip->irq.domain = irq_domain_add_hierarchy(gpiochip->irq.parent_domain,
+ 0, gpiochip->ngpio,
+ np, ops, gpiochip);
+ else
+ gpiochip->irq.domain = irq_domain_add_simple(np, gpiochip->ngpio,
+ gpiochip->irq.first,
+ ops, gpiochip);
if (!gpiochip->irq.domain)
return -EINVAL;

diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index a1d273c96016..472f2c127bf6 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -48,6 +48,14 @@ struct gpio_irq_chip {
*/
const struct irq_domain_ops *domain_ops;

+ /**
+ * @parent_domain:
+ *
+ * If non-NULL, will be set as the parent of this GPIO interrupt
+ * controller's IRQ domain to establish a hierarchy.
+ */
+ struct irq_domain *parent_domain;
+
/**
* @handler:
*
--
2.21.0
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