[[RFC PATCH]] gpio: gpio-mxc: make sure gpio is input when request IRQ

[Linus Walleij]

On Wed, Jul 16, 2014 at 3:51 PM, Markus Niebel
<list-09_linux_arm at tqsc.de> wrote:

> From: Markus Niebel <Markus.Niebel at tq-group.com>
>
> When requesting an GPIO irq for imx Soc two things are missing:
> - there is no check, if the GPIO is already requested
> - there is no check, if the GPIO is configured as input
>
> The first case can lead to reconfiguring the GPIO pin from third
> party while it is used as IRQ pin, second case will (eventually)
> prevent IRQ from being seen by SOC becaus the pin is driven by
> Soc
>
> This patch tries to implement (logic taken roughly from gpio-omap)
> - basic check if gpio already requested
> - if needed requests the gpio and configures as IN.
> - if gpio is already requested it is only verified if pin is IN
> - gpio is locked as irq
>
> Tested on a not mainlined i.MX6 based hardware with pin configured
> by bootloader as OUT HIGH and expecting a low active IRQ.
>
> Signed-off-by: Markus Niebel <Markus.Niebel at tq-group.com>
> ---
>  drivers/gpio/gpio-mxc.c |   35 +++++++++++++++++++++++++++++++++++
>  1 file changed, 35 insertions(+)
>
> diff --git a/drivers/gpio/gpio-mxc.c b/drivers/gpio/gpio-mxc.c
> index db83b3c..4316a38 100644
> --- a/drivers/gpio/gpio-mxc.c
> +++ b/drivers/gpio/gpio-mxc.c
> @@ -175,6 +175,31 @@ static int gpio_set_irq_type(struct irq_data *d, u32 type)
>         u32 gpio = port->bgc.gc.base + gpio_idx;
>         int edge;
>         void __iomem *reg = port->base;
> +       int ret = 0;
> +
> +       if (!gpiochip_is_requested(&port->bgc.gc, gpio_idx)) {
> +               char label[32];
> +
> +               snprintf(label, 32, "gpio%u-irq", gpio);
> +               ret = gpio_request_one(gpio, GPIOF_DIR_IN, label);

Wut? Auto-request here? This can not be right.

> +       } else {
> +               val = readl(port->base + GPIO_GDIR);
> +               if (val & BIT(gpio_idx))
> +                       ret = -EINVAL;
> +       }
> +
> +       if (ret) {
> +               dev_err(port->bgc.gc.dev, "unable to set gpio_idx %u as IN\n",
> +                       gpio_idx);
> +               return ret;
> +       }
> +
> +       ret = gpio_lock_as_irq(&port->bgc.gc, gpio_idx);

This call should be done in the new
.irq_request_resources callback in struct irq_chip.

> +       if (ret) {
> +               dev_err(port->bgc.gc.dev, "unable to lock gpio_idx %u for IRQ\n",
> +                       gpio_idx);
> +               return ret;
> +       }
>
>         port->both_edges &= ~(1 << gpio_idx);
>         switch (type) {
> @@ -231,6 +256,15 @@ static int gpio_set_irq_type(struct irq_data *d, u32 type)
>         return 0;
>  }
>
> +static void gpio_irq_shutdown(struct irq_data *d)
> +{
> +       struct irq_chip_generic *gc = irq_data_get_irq_chip_data(d);
> +       struct mxc_gpio_port *port = gc->private;
> +       u32 gpio_idx = d->hwirq;
> +
> +       gpio_unlock_as_irq(&port->bgc.gc, gpio_idx);
> +}

This call should be done in the new
.irq_release_resources callback in struct irq_chip.

Looking at the driver, it should be switched to using the new
irqchip helpers inside gpiolib, see e.g.
commit 7bcbce55f20e41c014df4d5d9c8448f7b5e49d79
"gpio: pca953x: use gpiolib irqchip helpers"

Yours,
Linus Walleij