Re: [Xenomai] problem gpio interrupts xenomai3 on the raspberry pi 2 (or 3)

[Harco Kuppens <h.kuppens@cs.ru.nl>]

On 30/05/17 19:30, Philippe Gerum wrote:
> On 05/30/2017 06:38 PM, Harco Kuppens wrote:
>> So I decided to also  test these wiringpi test programs on mine build
>> xenomai 3 image for the rpi2. Unfortunately the isr.c wiringpi program
>> didn't work anymore on mine build image. So even without using xenomai3,
>> but just using linux the pi2 just hangs and a hard reset was needed.
>>
>> Thus I guess there is still something wrong with mine image?
>> Does anybody know what I'm doing wrong?
>> Or is this still a bug in the gpio library or in the patches applied?
>>
> It looks obvious that you tried hard and got your feet wet with Xenomai
> already, so let's go straight to the point: the lockup issue when using
> GPIO interrupts is most likely due to the I-pipe patch not properly
> adapting the GPIO chip driver for dealing with IRQ virtualization.
>
> In short, each IRQ controller which may be active on a SoC must be
> driven by I-pipe aware code. For instance, the bcm2835 family has common
> GPIOs controlled by the driver at drivers/pinctrl/pinctrl-bcm2835.c. If
> that driver has not been patched specifically for supporting the IRQ
> pipeline, then this won't work with Xenomai, and may well end up with
> painful IRQ storms causing a machine hang. The same goes for any other
> chip serving as an IRQ controller you might need on your platform.
>
> So, first and foremost, I would recommend to make sure the I-pipe code
> is right for your kernel, then build on top of that. A good way to
> figure out which IRQ controllers are active is look at the output of
> /proc/interrupts on a kernel that disables the interrupt pipeline.
yes, I already checked  /proc/interrupts and when the xeno_gpio module
was loaded I could see the IRQ used.
> Each IRQ information mentions the label of the controller which deals
> with it. With that information, you need to cross-check whether the
> corresponding IRQ chip driver (the one that bears this label in the
> irq_chip descriptor structure) was made I-pipe aware.
I thought the label said "gpio", I have to look that up again.

In the installations instructions I put on the github page, there was 
next to
the ipipe patch an extra patch specific for the bcm2836 chip. I guess
that something is wrong in that patch. But I'm not an expert in the linux
kernel and ipipe code so I find it difficult  to find out what is wrong 
with it.
>
> Some time ago, I ported Xenomai 3 to the PI Zero (kernel 4.1.18), which
> is based on the bcm2835 SoC like the PI 1 series. That code is available
> from the vendors/raspberry/ipipe-4.1 branch at
> git://git.xenomai.org/ipipe.git. This may be a good starting point, at
> least for testing with a PI 1, before working on the required fixups for
> supporting other Broadcom SoCs.
Ok I'll try to first get the xenomai 4 working on mine pi 1,
then I will try the same code on the pi zero which should be ok.
Maybe we can use the pi zero instead in the course.

But when I get this working, I will try to take a deeper look into how
for this chip the  patch works. If I then understand it better then
I can take a look at the chip for the pi2 or pi3 to fix the ipipe or bcm 
patch.

>
> IIRC, RPI 2B and RPI 3 are based on the bcm2836, bcm2837 SoCs resp.,
> which are not covered by the port just mentioned. You may find some
> preliminary I-pipe related changes in the bcm2836 core interrupt support
> code, but those have never been tested. By preliminary, I mean that
> there is likely a few more IRQ controllers to make I-pipe aware on these
> SoCs, aside of testing the initial changes.
>
> Bottom line: using a stock I-pipe patch is unlikely to work out of the
> box. The fact that such patch does support several SoCs equipped with
> Cortex A7/A9 CPUs is by no mean a guarantee that all Cortex-based SoCs
> are supported by the same code.

Message is clear, unfortunately there is no quick fix, but with your 
tips, I now have at least an approach via the rpi1
to see if I can fix it.  If I find a  solution I will report it.

Thank you for the quick response ,

Harco

>