Re: [PATCH 1/3] irq: If an IRQ is a GPIO, request and configure it

Rob Herring
2011-08-05T01:54:59Z

On 08/04/2011 06:00 PM, Stephen Warren wrote:
> Many IRQs are associated with GPIO pins. When the pin is used as an IRQ,
> it can't be used as anything else; it should be requested. Enhance the
> core interrupt code to call gpio_request() and gpio_direction_input() for
> any IRQ that is also a GPIO. This prevents duplication of these calls in
> each driver that uses an IRQ.
>
> Signed-off-by: Stephen Warren <swarren@nvidia.com>
> ---
> kernel/irq/manage.c | 23 +++++++++++++++++++++--
> 1 files changed, 21 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
> index 0a7840a..6e2db72 100644
> --- a/kernel/irq/manage.c
> +++ b/kernel/irq/manage.c
> @@ -7,6 +7,7 @@
> * This file contains driver APIs to the irq subsystem.
> */
>
> +#include <linux/gpio.h>
> #include <linux/irq.h>
> #include <linux/kthread.h>
> #include <linux/module.h>
> @@ -875,7 +876,7 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
> struct irqaction *old, **old_ptr;
> const char *old_name = NULL;
> unsigned long flags, thread_mask = 0;
> - int ret, nested, shared = 0;
> + int ret, nested, shared = 0, gpio = -1;
> cpumask_var_t mask;
>
> if (!desc)
> @@ -978,6 +979,16 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
> old = *old_ptr;
> } while (old);
> shared = 1;
> + } else {
> + gpio = irq_to_gpio(irq);

If you read the documentation for gpio, it is not recommended to use
irq_to_gpio. There's only a handful of users. Part of the problem is it
is platform specific and the gpio core cannot convert irq to gpio
number. Here is the relevant section:

Non-error values returned from irq_to_gpio() would most commonly be used
with gpio_get_value(), for example to initialize or update driver state
when the IRQ is edge-triggered. Note that some platforms don't support
this reverse mapping, so you should avoid using it.

Rob

> + if (gpio_is_valid(gpio)) {
> + ret = gpio_request(gpio, new->name);
> + if (ret < 0)
> + goto out_mask;
> + ret = gpio_direction_input(gpio);
> + if (ret < 0)
> + goto out_mask;
> + }
> }
>
> /*
> @@ -1083,6 +1094,8 @@ mismatch:
> ret = -EBUSY;
>
> out_mask:
> + if (gpio_is_valid(gpio))
> + gpio_free(gpio);
> raw_spin_unlock_irqrestore(&desc->lock, flags);
> free_cpumask_var(mask);
>
> @@ -1127,6 +1140,7 @@ static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
> struct irq_desc *desc = irq_to_desc(irq);
> struct irqaction *action, **action_ptr;
> unsigned long flags;
> + int gpio;
>
> WARN(in_interrupt(), "Trying to free IRQ %d from IRQ context!\n", irq);
>
> @@ -1165,8 +1179,13 @@ static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
> #endif
>
> /* If this was the last handler, shut down the IRQ line: */
> - if (!desc->action)
> + if (!desc->action) {
> irq_shutdown(desc);
> + /* If the IRQ line is a GPIO, it's no longer in use */
> + gpio = irq_to_gpio(irq);
> + if (gpio_is_valid(gpio))
> + gpio_free(gpio);
> + }
>
> #ifdef CONFIG_SMP
> /* make sure affinity_hint is cleaned up */