Re: [Xenomai-help] Handling a interrupt from user space on PPC405

[Wolfgang Grandegger <wg@domain.hid>]

Heikki Lindholm wrote:
> Wolfgang Grandegger kirjoitti:
>> Heikki Lindholm wrote:
>>
>>> Niklaus Giger kirjoitti:
>>>
>>>> Hi
>>>>
>>>> I tried to use the FIT (Fixed Interrupt Timer) on my PPC405GPr 
>>>> board, which uses 0x1010 as its interrupt vector in a user space 
>>>> (vxworks-skin) application.
>>>> <..>
>>>>   RT_INTR FITnterrupt;
>>>>   res = rt_intr_create(&FITnterrupt, 0, 0x1010, I_NOAUTOENA);
>>>> <..>
>>>> But I got -22 EINVAL as error.
>>>> Could somebody please tell me, what is wrong with my example.
>>>
>>>
>>> The 0x1010 is the HW interrupt vector, but the argument should be the 
>>> interrupt _line_. Besides, last time I checked, the ppc405 FIT isn't 
>>> even 'wired' in the kernel; actually, there's no space for the 
>>> interrupt prologue code, which basically results that no handler is 
>>> called when the FIT interrupt occurs.
>>
>>
>> Yes, in head_4xx.c there is the following note:
>>
>>   /* NOTE:
>>    * FIT and WDT handlers are not implemented yet.
>>    */
>>
>> But the relevant code could be copied from the PIT interrupt.
>>
>>   /* 0x1000 - Programmable Interval Timer (PIT) Exception */
>>         START_EXCEPTION(0x1000, Decrementer)
>>         NORMAL_EXCEPTION_PROLOG
>>         lis     r0,TSR_PIS@h
>>         mtspr   SPRN_TSR,r0             /* Clear the PIT exception */
>>         addi    r3,r1,STACK_FRAME_OVERHEAD
>>   #ifdef CONFIG_IPIPE
>>         EXC_XFER_IPIPE(0x1000, __ipipe_grab_timer)
>>   #else /* !CONFIG_IPIPE */
>>         EXC_XFER_LITE(0x1000, timer_interrupt)
>>   #endif /* CONFIG_IPIPE */
>>
>> and modified accordingly.
> 
> But one should note that the decrementer vector is at 0x1000 and the FIT 
> vector at 0x1010. The decrementer exception prologue is obviously bigger 
> than 0x10 (16) bytes and thus needs to be moved elsewhere (and branched 
> to from the decr vector.) It might be feasible to unite the handlers, 
> though, by passing some variable to the C-language handler, telling 
> which happened.

The above code snippet has to be modified for the FIT exception, of 
course, which calls _ipipe_grap_fit(). Here is what is basically needed:

   __ipipe_init_platform()
     calls fit_virq = ipipe_alloc_virq();

   __ipipe_grap_fit(regs)
     calls __ipipe_handle_irq(IPIPE_FIT_VIRQ, regs);

And the FIT timer has to be programed properly elsewhere.

Wolfgang.