[Xenomai] xenomai , irq and pci

Johann Obermayr johann.obermayr at sigmatek.at
Thu Mar 6 20:53:21 CET 2014


Am 06.03.2014 20:46, schrieb Gilles Chanteperdrix:
> On 03/06/2014 08:44 PM, Johann Obermayr wrote:
>> Am 06.03.2014 20:20, schrieb Gilles Chanteperdrix:
>>> On 03/06/2014 09:25 AM, Johann Obermayr wrote:
>>>> Am 05.03.2014 17:41, schrieb Gilles Chanteperdrix:
>>>>> On 03/05/2014 05:22 PM, Johann Obermayr wrote:
>>>>>> Hello,
>>>>>>
>>>>>> celeron dual core with PCIe - PCI bridge
>>>>>> we use kernel 3.10.xx smp with  (isolcpus=0)
>>>>>> smi is disabled.
>>>>>> xenomai 2.6.3
>>>>>>
>>>>>> we have a pci card with a fpga (with irq) and sram.
>>>>>>
>>>>>> we have 2 task running.
>>>>>>
>>>>>> task0 is one high prior in primary domain on core0.
>>>>>> this task wait for event, that is fired by fpga irq.
>>>>>> than this task will make some pci accesses to the fpga.
>>>>>>
>>>>>> the other task (task1) is a shadow task, but running in secondary domain
>>>>>> on core 1.
>>>>>> This task make many big memcpy to sram.
>>>>>>
>>>>>> in the ipipe_handler_irq we have a function callback.
>>>>>> a small driver hooks to this callback add make some tracepoint into
>>>>>> a shared memory.
>>>>>>
>>>>>> with the trace we see some time a very high jitter in the ipipe_handler_irq
>>>>>> function (around 250 us).
>>>>>> has anyone an explanation for this?
>>>>>>
>>>>>> and a 4 byte access from task0 to fpga need more than 300us,
>>>>>>      while task1 is writing to sram.
>>>>> Maybe the problem is the size of the PCI burst when writing to the SRAM?
>>>>> How large is it? If the sram is mapped with "write-combine", it will be
>>>>> buffered and written in large bursts. Maybe you could try mapping the
>>>>> sram area uncached?
>>>>>
>>>> Hi,
>>>>
>>>> we use 2 real cores, no HT.
>>>> task1 do a memcpy with 10000 bytes.
>>> have you tried splitting the copy in smaller chunks, and use a mutex for
>>> exclusion between the two threads?
>> That can we do.
>> Only in our testsystem, but in customer application, we have no way to
>> change this.
> Ok, I suppose you can change the FPGA then? Have you tried to make the
> BAR with the SRAM appear as register intead of memory?
>
i'll talk to the fpga department.





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