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Subject[RFC/RFT PATCH 3/3] gpiolib: make gpio irqchip compatible with sparse_irq
Date
Now IRQ mappings are always created for all (allowed) GPIOs in gpio irqchip in
gpiochip_irqchip_add_key() which goes against the idea of SPARSE_IRQ and,
as result, leads to:
- increasing of memory consumption because of allocated IRQ descriptors most
of which will never ever be used (especially on platform with a
high number of GPIOs)
- imposibility to use GPIO irqchip APIs by gpio drivers when HW implements
GPIO IRQ functionality as IRQ crossbar/multiplexer which has only limited
number of IRQ outputs (example from [1], all GPIOs can be mapped on only 8
IRQs).

Hence, remove static IRQ mapping code from gpiochip_irqchip_add_key() and
instead replace irq_find_mapping() with irq_create_mapping() in
gpiochip_to_irq(). Also add additional gpiochip_irqchip_irq_valid() calls
in gpiochip_to_irq() and gpiochip_irq_map().

After this change gpio2irq mapping will happen the following way when GPIO
irqchip APIs are used by gpio driver:
- IRQ mappings will be created statically if driver passes first_irq>0
vlaue in gpiochip_irqchip_add_key().
- IRQ mappings will be created dynamically from gpio_to_irq() or
of_irq_get().

[1] https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1435847.html
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
---
drivers/gpio/gpiolib.c | 29 ++++++-----------------------
include/linux/gpio/driver.h | 1 -
2 files changed, 6 insertions(+), 24 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 9568708..ee6ba07 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1605,6 +1605,9 @@ static int gpiochip_irq_map(struct irq_domain *d, unsigned int irq,
{
struct gpio_chip *chip = d->host_data;

+ if (!gpiochip_irqchip_irq_valid(chip, hwirq))
+ return -ENXIO;
+
irq_set_chip_data(irq, chip);
/*
* This lock class tells lockdep that GPIO irqs are in a different
@@ -1671,7 +1674,9 @@ static void gpiochip_irq_relres(struct irq_data *d)

static int gpiochip_to_irq(struct gpio_chip *chip, unsigned offset)
{
- return irq_find_mapping(chip->irqdomain, offset);
+ if (!gpiochip_irqchip_irq_valid(chip, offset))
+ return -ENXIO;
+ return irq_create_mapping(chip->irqdomain, offset);
}

/**
@@ -1747,9 +1752,6 @@ int gpiochip_irqchip_add_key(struct gpio_chip *gpiochip,
struct lock_class_key *lock_key)
{
struct device_node *of_node;
- bool irq_base_set = false;
- unsigned int offset;
- unsigned irq_base = 0;

if (!gpiochip || !irqchip)
return -EINVAL;
@@ -1806,25 +1808,6 @@ int gpiochip_irqchip_add_key(struct gpio_chip *gpiochip,
irqchip->irq_release_resources = gpiochip_irq_relres;
}

- /*
- * Prepare the mapping since the irqchip shall be orthogonal to
- * any gpiochip calls. If the first_irq was zero, this is
- * necessary to allocate descriptors for all IRQs.
- */
- for (offset = 0; offset < gpiochip->ngpio; offset++) {
- if (!gpiochip_irqchip_irq_valid(gpiochip, offset))
- continue;
- irq_base = irq_create_mapping(gpiochip->irqdomain, offset);
- if (!irq_base_set) {
- /*
- * Store the base into the gpiochip to be used when
- * unmapping the irqs.
- */
- gpiochip->irq_base = irq_base;
- irq_base_set = true;
- }
- }
-
acpi_gpiochip_request_interrupts(gpiochip);

return 0;
diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index af20369..a3e2e3e 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -165,7 +165,6 @@ struct gpio_chip {
*/
struct irq_chip *irqchip;
struct irq_domain *irqdomain;
- unsigned int irq_base;
irq_flow_handler_t irq_handler;
unsigned int irq_default_type;
unsigned int irq_chained_parent;
--
2.10.1
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