On 05/25/2013 12:28 PM, CF wrote:
> Le 23/05/2013 09:14, Gilles Chanteperdrix a écrit :
>> On 05/23/2013 12:10 AM, CF wrote:
>>
>>> Hello,
>>>
>>> Despite my munerous reading, i'm locked in how to perform a basic RTDM
>>> for a simple ppc board.
>>>
>>> This is a simple pin level setting. The linux kernel module i developped
>>> follow theses steps:
>>> -reading DTS for IOCTL et GPIOCTL base adress registers
>>> - out_be32(addr, value) at theses register to set line as an output and
>>> then set the logical level with setbits32(addr, bit) or clrbits32(addr,bit)
>>>
>>> Basically, it works but in NRT ops modes, so i'm unable (or at least i
>>> lack indication) to do this in RT ops mode (i don't think it is
>>> important, but i use ioctl to make my changes). I based my work on
>>> tut01/tut02 drivers, except i end up in using ioctl instead or
>>> read/write in the RTDM driver.
>>>
>>> I guess i still could read the DTS in nrt mode (because it is done at
>>> rtdm_dev_register() time and won't interfere with RT task), but how can
>>> i drive the hardware directly in RT op mode ?
>>
>> Hi,
>>
>> I am not sure I understand the problem you have. If the board you use
>> uses gpiolib (I do not know if gpiolib is customary on ppc), you simply
>> have to check that the gpiolib callbacks do not use any Linux services
>> which can not be called from RT mode (if it uses a spinlock, the usual
>> method is to turn the spinlock into an I-pipe spinlock, see:
>> http://www.xenomai.org/index.php/I-pipe-core:ArmPorting#GPIOs_in_real-time_drivers)
>>
>> If you are accessing directly the GPIO controller registers, and need a
>> "read-modify-write" operation, which what you posted seem to suggest,
>> you probably want to put a spinlock around these operations, but apart
>> from that, you can do this from an RT driver ioctl callback.
>>
>> Regards.
>>
>
> Thank you Gilles, very much.
>
> Precisely, my main concern is how to know if i use linux services (in
> others words, how can i say a function - in my case in_beX() or
> out_beX() - is RT compatible ?). If you have some documentations about
> this, thank you :)
Anything which relies on a Linux critical section (spinlocks, mutex,
local_irq_save) to ensure some software data coherency can not work when
in xenomai domain, because the Xenomai domain can interrupt Linux at any
point including in the middle of a critical section.
--
Gilles.
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