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Date: Thu, 24 Jan 2013 18:38:37 +0100
From: Christophe Blaess <mailist@logilin.fr>
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Subject: Re: [Xenomai] GPIO Interrupts problem with RTDM
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On 24/01/2013 18:12, Paul wrote:
> On Thursday 24 January 2013, Christophe Blaess wrote:
>> On 22/01/2013 04:06, Paul wrote:
>>> On Sunday 20 January 2013, Gilles Chanteperdrix wrote:
>>>> Yes, this patch is based on 3.5.7 and is used with and without
>>>> GENERIC_CLOCKEVENTS.
>>> Short version: Updated my kernel to 3.5.7 and backported the
>>> Raspberry Pi changes from 3.6.11 and added in the ipipe support.
>>> Interrupts are not being recognised unless irq_set_irq_type() is
>>> called. Digging through the rtdm, nucleus, and ipipe code, at no
>>> point is
>>> irq_chip->irq_set_type() called - Also have a problem that none of
>>> the ipipe_pic_muter fields are set, so __ipipe_enable_irqdesc() &
>>> friends do nothing.
>> I'm trying to follow the same steps as you but I still have some
>> compilation errors while porting
>> R-Pi modifications to 3.5.7. (especially arm timer code).
>>
>> Do you have any available patch against 3.5.7 vanilla kernel ?
> Funny that you should ask - I am in the middle of generating a patch set
> against 3.5.7 with the Raspberry Pi additions. This will include the
> ipipe modifications along with a fix to the gpio interrupt handler.

Great.

>
>> I have a working GPIO interrupt rtdm driver with 3.2.21 kernel
>> (Xenomai 2.6.2) but the interrupt latencies seems terrible (about
>> 20us and jiterring up to 150us without any load). To compare with the
>> 7us latency I see on a vanilla Linux GPIO interrupt handler.
> Should be better than that - Did you make any changes to the interrupt
> handler in bcm207_gpio.c ?

I replaced generic_handle_irq() by ipipe_handle_demuxed_irq().


My interrupt handler toggle an ouput GPIO pin :

static int handler_irq(rtdm_irq_t * irq)
{
         static int value = 0;
         gpio_set_value(GPIO_OUT, value);
         value = 1 - value;
         return RTDM_IRQ_HANDLED;
}

I think that gpio_set_value() doesn't call any Linux services, but I may 
be wrong.