genirq: Setting trigger mode 8 for irq num failed (bcm2708_gpio_irq_set_type+0x0/0x68)

[msperl]

Hi!

Seems as if (low) level interrupts are not working with the RPI?

Is seems intentional from the code - the question is WHY?
What would be needed to make that work?

Martin

[notro]

BCM2708 doesn't support level interrupts as you say, just falling or rising:
https://github.com/raspberrypi/linux/blob/rpi-3.10.y/arch/arm/mach-bcm2708/bcm2708_gpio.c

static int bcm2708_gpio_irq_set_type(struct irq_data *d, unsigned type)
{
        unsigned irq = d->irq;
        struct bcm2708_gpio *gpio = irq_get_chip_data(irq);

        if (type & ~(IRQ_TYPE_EDGE_FALLING | IRQ_TYPE_EDGE_RISING))
                return -EINVAL;

        if (type & IRQ_TYPE_EDGE_RISING) {
                gpio->rising |= (1 << irq_to_gpio(irq));
        } else {
                gpio->rising &= ~(1 << irq_to_gpio(irq));
        }

        if (type & IRQ_TYPE_EDGE_FALLING) {
                gpio->falling |= (1 << irq_to_gpio(irq));
        } else {
                gpio->falling &= ~(1 << irq_to_gpio(irq));
        }
        return 0;
}

BCM2835 supports it:
http://lxr.free-electrons.com/source/drivers/pinctrl/pinctrl-bcm2835.c?v=3.10;a=arm#L578

static int __bcm2835_gpio_irq_set_type_disabled(struct bcm2835_pinctrl *pc,
        unsigned offset, unsigned int type)
{
        switch (type) {
        case IRQ_TYPE_NONE:
        case IRQ_TYPE_EDGE_RISING:
        case IRQ_TYPE_EDGE_FALLING:
        case IRQ_TYPE_EDGE_BOTH:
        case IRQ_TYPE_LEVEL_HIGH:
        case IRQ_TYPE_LEVEL_LOW:
                pc->irq_type[offset] = type;
                break;

        default:
                return -EINVAL;
        }
        return 0;
}

static int bcm2835_gpio_irq_set_type(struct irq_data *data, unsigned int type)
{
[...]
        if (test_bit(offset, &pc->enabled_irq_map[bank]))
                ret = __bcm2835_gpio_irq_set_type_enabled(pc, gpio, type);
        else
                ret = __bcm2835_gpio_irq_set_type_disabled(pc, gpio, type);
[...]
}

BCM2835 ARM Peripherals, Chapter 6 General Purpose I/O (GPIO), Figure 6-1 GPIO Block Diagram, shows that both level and edge triggering is supported by hardware.

Is seems intentional from the code - the question is WHY?

I guess that the one who wrote the driver was satisfied with having edge triggering?

What would be needed to make that work?

That I don't know. The two drivers have rather different approaches in handling this.