Re: [Xenomai] GPIO irq handler on powerpc.

[Philippe Gerum <rpm@xenomai.org>]

On 06/07/2012 11:16 PM, Chris Stone wrote:
> I am using Xenomai 2.6.0 on kernel 3.0.13, with adeos-ipipe-3.0.13-powerpc-2.13-06 applied. My target CPU
> is Freescale MPC8378.
>
> On a powerpc, GPIO's are mapped to virtual irqs. Thus, in order to install an irq handler for a gpio
> interrupt, one must do the following in the kernel:
>
> 	err = gpio_request(HYPHY_IRQ_GPIO, NULL);
> 	if (err<0) {
> 		printk(KERN_ERR "%s: could not request gpio %d, rc %d\n", __func__, HYPHY_IRQ_GPIO, err);
> 		return err;
> 	}
> 	err = gpio_direction_input(HYPHY_IRQ_GPIO);
> 	if (err<0) {
> 		printk(KERN_ERR "%s: could not set gpio %d to input, rc %d\n", __func__, HYPHY_IRQ_GPIO, err);
> 		return err;
> 	}
>
> 	virq = __gpio_to_irq(HYPHY_IRQ_GPIO);
> 	if (virq<  0) {
> 		printk(KERN_ERR "%s: could not map gpio %d to virq \n", __func__, HYPHY_IRQ_GPIO);
> 		return virq;
> 	}
>        err = request_irq(virq, hyphy20G_irq, 0, hyphy20G_dev.name,&hyphy20G_dev);
>
> In other words, you install the irq handler on the virtual irq number returned from __gpio_to_irq. The above
> code works in my system, i.e., the hyphy20G_irq handler is called on an interrupt.
>
> However, if I use:
>
> err = rt_intr_create(intrObj, "HyPhyIRQ", virq, hyphy20G_irq, NULL, 0);
> rt_intr_enable(intrObj);
>
> then the hyphy20G_irq handler is not called on an interrupt. I realize that interrupt handlers are
> recommended to be implemented in user space, but a user space implementation does not work either,

I believe this is a typo, but just for the record: the rt_intr* API is 
deprecated, and interrupt handlers in user-space over Xenomai are NOT 
recommended.

> so I moved into the kernel to see if I could get something to work.
>
> Is it possible to install an Xenomai ISR on a powerpc virtual irq?

Xenomai, and more specifically the I-pipe does interface with irq 
numbers defined in the kernel namespace, so yes, virqs is what we always 
use internally for powerpc.

You may want to check whether that GPIO is actually chained from a 
multiplex parent IRQ.

-- 
Philippe.