Re: [Xenomai] imx28 rtcan flexcan system freezes

[Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>]

On 01/26/2014 08:26 PM, Wolfgang Grandegger wrote:
> On 01/22/2014 03:12 PM, Gilles Chanteperdrix wrote:
>> On 01/22/2014 03:04 PM, Alexandre COFFIGNAL wrote:
>>>
>>> Le 22/01/2014 14:30, Gilles Chanteperdrix a écrit :
>>>> On 01/22/2014 02:27 PM, Alexandre COFFIGNAL wrote:
>>>>>
>>>>> Le 22/01/2014 13:00, Gilles Chanteperdrix a écrit :
>>>>>> On 01/22/2014 12:36 PM, Alexandre COFFIGNAL wrote:
>>>>>>>>> +        cf->data[3]=((data0 >> 0)  & 0xFF) ;
>>>>>>>>> +        cf->data[2]=((data0 >> 8)  & 0xFF) ;
>>>>>>>>> +        cf->data[1]=((data0 >> 16)  & 0xFF) ;
>>>>>>>>> +        cf->data[0]=((data0 >> 24)  & 0xFF) ;
>>>>>>>>> +        cf->data[7]=((data1 >> 0)  & 0xFF) ;
>>>>>>>>> +        cf->data[6]=((data1 >> 8)  & 0xFF) ;
>>>>>>>>> +        cf->data[5]=((data1 >> 16)  & 0xFF) ;
>>>>>>>>> +        cf->data[4]=((data1 >> 24)  & 0xFF) ;
>>>>>>>>>
>>>>>>>>> rtcan flexcan works perfectly.
>>>>>>>>> is  anyone know what is the problem with first instructions ?
>>>>>>>> Probably mb->data does not have the right alignment. Could you not
>>>>>>>> arrange to get it properly aligned? Failing that, you should use
>>>>>>>> put_unaligned instead of open coding it.
>>>>>>>>
>>>>>>>>
>>>>>>> here structures used in flexcan driver, it seem to be aligned
>>>>>>
>>>>>> I am talking about the alignment of cf->data, since obviously, that is
>>>>>> the one which is causing problems.
>>>>>>
>>>>>>
>>>>> Thank a lot, put_unaligned fix this issue if you want, i can send a
>>>>> path
>>>>>
>>>>
>>>> The other solution (getting cf->data to be properly aligned) would be
>>>> more efficient, why is not it possible to get cf->data properly aligned?
>>>>
>>> I think, i can't get cf->data to be properly aligned because "cf" is
>>> receive internal frame representation within the ring buffer
>>> of a struct rtcan_socket and struct rtcan_rb_frame is a generic
>>> structure used in all rtcan drivers .
>>
>> Well, if you fix rtcan_rb_frame to be aligned, it will be aligned for
>> all drivers, so that looks like a worthwile improvement...
> 
> I had a closer look. The CAN message (frame) queuing is optimized for
> size to get as much as possible messages into the queue. Therefore the
> CAN data are copied using memcpy, but only the real bytes. Directly
> behind the real data is the 64 bit timestamp, if requested, which is
> also not aligned. Therefore I suggest to use memcpy or byte accesses in
> the flexcan driver as well. If this was a good decision is another question.

Aligning the data begining costs 2 bytes by struct rtcan_rb_frame. How
many such structures are there for a typical driver?


-- 
                                                                Gilles.