Re: [Xenomai-core] Xenomai on Freescale i.MX21 (ARM926J)

[Philippe Gerum <rpm@xenomai.org>]

ROSSIER Daniel wrote:
> Hi Philippe,
> 
> Any chance to see our work integrated within an official distribution?
> 
> Are you still reviewing the code?
> 

It's reviewed and mostly ok, except the "poll mode" boot parameter which 
is not there (i.e. adding a static compilation option is not the way to 
go). The main issue that remains is to merge it properly with the latest 
Adeos codebase (i.e. w/ pipeline head optimizations and wired IRQ 
support), and optionally, with the existing ARM port for the ARM1136, 
but since the i.MX21 support needs to be provided by an additional 
patch, the latter seems unlikely, unfortunately.

> Thanks for your feedback
> 
> Daniel
> 
> 
>>-----Message d'origine-----
>>De : xenomai-core-bounces@domain.hid [mailto:xenomai-core-bounces@domain.hid] De
>>la part de ROSSIER Daniel
>>Envoyé : mardi, 25. avril 2006 15:17
>>À : Philippe Gerum
>>Cc : xenomai@xenomai.org
>>Objet : RE: [Xenomai-core] Xenomai on Freescale i.MX21 (ARM926J)
>>
>>
>>
>>
>>>-----Message d'origine-----
>>>De : Philippe Gerum [mailto:rpm@xenomai.org]
>>>Envoyé : jeudi, 20. avril 2006 15:43
>>>À : ROSSIER Daniel
>>>Cc : xenomai@xenomai.org
>>>Objet : Re: [Xenomai-core] Xenomai on Freescale i.MX21 (ARM926J)
>>>
>>>ROSSIER Daniel wrote:
>>>
>>>>Dear all,
>>>>
>>>>We finally succeeded in the port of Xenomai on our Freescale i.MX21
>>>
>>>board (ARM-926J);
>>>
>>>>(The board used is the CSB535FS issued from Cogent with the BSP from
>>>
>>>Microcross)
>>>
>>>>To have further technical references, please see there:
>>>
>>http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=i.MX_LITEKI
>>
>>>T&parentCode=i.MX21&nodeId=0162468rH31143ZrDR
>>>
>>>>So, you will find two patches: the first one (patch-linux-
>>>
>>>2.6.14.imx21_1.0.0) is used to patch the Linux 2.6.14 for supporting the
>>>board. Then, the second one (adeos-ipipe-2.6.14-arm-imx21-0.1.00.patch)
>>>can be used against the imx21-enabled kernel for Xenomai, simply using
>>
>>the
>>
>>>prepare-kernel.sh script. The patch was originally inspired from the
>>>Integrator/ARM11 patch; thanks to its author :-)
>>>
>>>>We will publish soon some results regarding the different latencies,
>>
>>but
>>
>>>so far we measured about 2us between the IRQ and the timer reprogramming
>>>(at the ipipe level). The problem now is the jitter which is pretty
>>
>>high:
>>
>>>about 1-2us, with some occasional peaks up to 5us.
>>>
>>>>Having quite a few experience with this kind of board, we don't know
>>
>>if
>>
>>>it comes from the code itself, or purely from the hardware. Any
>>>idea/suggestions would be welcome. For periodic tasks around 20us,
>>>everything works perfecly.
>>>
>>>Those results are pretty impressive actually. Assuming that you compare
>>>those figures with those obtained from traditional standalone RTOS e.g.
>>>VxWorks on the same board, the critical difference with Xenomai is that
>>>Linux is competing for the hw resources, and for instance, happily
>>>trashes the cache under Xenomai's feet when scheduling its own tasks
>>>during Xeno's idle time. Additionally, Adeos adds a small overhead due
>>>to the interrupt virtualization, in exchange of real-time predictability
>>>for their delivery. Therefore, in this respect, 5 us does not look that
>>>bad already.
>>>
>>>Are 20 us a measure of the worst-case interrupt latency (i.e. running
>>>latency -t2), or scheduling latency in user-space (i.e. running latency
>>>-t0)?
>>>
>>
>>No, I think we can go lower; the measure we actually got between the IRQ
>>and the timer reprogramming is about 2 us with some jitters up to 5 us; we
>>could
>>normally guarantee not to exceed 5 us between the IRQ and timer
>>reprogramming. Now, considering the ISR itself, we could get some time
>>under 10us provided that the ISR remains short.
>>
>>So far, we measured the reaction time with the oscillo; we are now about
>>to check the latencies with the latency utility from Xenomai.
>>
>>
>>>>I don't know to what extent this (1 or 2) patch(es) can be integrated
>>
>>in
>>
>>>the official distribution;
>>>but of course we are willing to make any adaptations to fulfill the
>>>requirements for that.
>>>
>>>For the technical part, I guess that anyone interested in the ARM
>>>support for Adeos/Xenomai will review this code; I'll be one of these
>>>people, for sure. The usefulness of such contribution looks obvious to
>>
>>me.
>>
>>>For the non-technical part, a pre-requisite for adding code to the Adeos
>>>or Xenomai codebases is to properly identify it as coming from a
>>>legitimate source, so if you, as a submitter, can confirm that you may
>>>freely contribute it on behalf of the HEIG-VD (I guess?) or yourself,
>>>that's fine with us. Btw, at first glance, I did not find any additional
>>>GPL copyrights coming with your changes in the patches, it would be
>>>better to have them, so that we always know who contributed to what, as
>>>much as possible.
>>
>>Yes, it's ok. HEIG-VD is the University of Applied Sciences of Western
>>Switzerland in Yverdon (http://www.heig-vd.ch) and I'm working at
>>the REDS Institute (http://reds.eivd.ch, unfortunately in French only at
>>the moment). We are granted to publish our work, at least
>>all part which are not directly bound to some industrial projects (I'm
>>trying to keep the stuff as open and public as possible ;-).
>>
>>
>>>>It's a first step; I hope it will help some other ARM9 developers and
>>>
>>>look forward to reading some feedbacks.
>>>
>>>>I profit to thank a lot the Xenomai team (Philippe, Jan, Gilles and
>>
>>the
>>
>>>others) for their excellent work and support).
>>>
>>>Xenomai exists because people participate in the Sisyphean task of
>>>making it better, like you just did. In other words, welcome to the
>>>band. Let's roll the rock.
>>>
>>
>>Cool.
>>
>>
>>>>Kind regards
>>>>
>>>>Daniel
>>>>
>>>>
>>>>
>>>>----------------------------------------------------------------------
>>
>>--
>>
>>>>_______________________________________________
>>>>Xenomai-core mailing list
>>>>Xenomai-core@domain.hid
>>>>https://mail.gna.org/listinfo/xenomai-core
>>>
>>>
>>>--
>>>
>>>Philippe.
>>
>>Daniel
>>
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> 
> 


-- 

Philippe.