Having trouble with a BeagleBoard GPIO interrupt pin

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Re: [Xenomai-help] Having trouble with a BeagleBoard GPIO interrupt pin

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To: Bob Feretich <bob.feretich@xxxxxxxxxxxxxxx>
Date: Tue, 10 Aug 2010 08:43:41 +0200
Cc: xenomai-help@xxxxxxx, xenomai-core@xxxxxxx
Message-id: <1281422621.2986.39.camel@redshift.xenomai.org>
Organization: Xenomai
References: <307507.12667.qm@xxxxxxxxxxxxxxxxxxxxxxxxxxx> <1281350069.1706.139.camel@xxxxxxxxxxxxxxxxxxxx> <4C5FEB8C.200@xxxxxxxxxxx> <1281361025.1706.143.camel@xxxxxxxxxxxxxxxxxxxx> <4C603899.5050402@xxxxxxxxxxx> <1281418522.2986.21.camel@xxxxxxxxxxxxxxxxxxxx> <4C60F042.3000405@xxxxxxxxxxxxxxx>

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Posted by Philippe Gerum on August 10, 2010 - 08:44:

On Mon, 2010-08-09 at 23:22 -0700, Bob Feretich wrote:

The below sequence worked around the problem:
insmod linux_asuspidvr.ko   <-- this driver set the xxxDETET registers
via request_irq()
rmmod linux_asuspidvr.ko  <-- the driver exits, but the xxxDETECT
registers remain set
insmod rt_asuspidvr.ko      <-- interrupts now seem to occur properly

So I modified the rt driver probe routine to do the below:
    ret = request_irq(irq, adis_data_rdy_dummy_irq_handler, 
            IRQF_TRIGGER_FALLING | IRQF_DISABLED, "asuspidvr", 
            adis_data_rdy_dummy_irq_handler);
...
    disable_irq(GPIO133);
...
    ret = rtdm_irq_request(&adis_data_rdy_irq_handle, irq,
                   adis_data_rdy_irq_handler,
                   RTDM_IRQTYPE_EDGE,
                   "asuspidvr", ctx);
    ret = rtdm_irq_enable(&adis_data_rdy_irq_handle);
...
This seems to be working! I can now run the rt driver without first
running the Linux driver. :-) 

Do you see any problem with me continuing with the above temp fix?

No, because you only use request_irq() to set up the GPIO line properly,
but you don't actually share the interrupt between linux and Xenomai,
which is ok.

Philippe,
I don't understand your response (below). It is too deep in
Adeos/Xenomai technical details.
After the issues are worked out on -core, please report back to -help
to let us know what we are to do.

In short, Xenomai does not fully configure an interrupt line the way
request_irq() does, this is the problem. Having the per-IRQ chip
set_type() handler called is required to set the xxxDETECT bits in your
case, and our low-level code (i.e. rthal_irq_request indirectly called
from rtdm_irq_request) does not do that.

It would also help if you could better describe the meaning of the
rtdm_irq_request() flags and whether the Linux request_irq() flags
have any implications to Adeos.

They have none. The edge flag is purely Xenomai-related. When shared IRQ
support is enabled, the EDGE flags passed to rtdm_irq_request() just
gives a hint to the Xenomai interrupt dispatcher for dealing with edge
interrupt handlers properly.

For example, I was quite surprised that both the request_irq() and
rtdm_irq_request() to the same IRQ succeeded even though neither
included a SHARE flag. This seems to require a rt driver to call both
routines to protect its xxxDetect registers.

This is a current flaw in the Xenomai interrupt management routines;
they should allow the IRQ trigger info to be defined when requesting an
IRQ (via rtdm_irq_request) the same way request_irq() does on the linux
side, but they do not support this yet.

request_irq and rtdm_irq_request are not supposed to work together; IRQ
sharing between linux and Xenomai is not formally defined, because it is
semantically wrong. Actually, a real-time interrupt hooked via
rtdm_irq_request should not be grabbed via request_irq() at the same
time for handling the IRQ. This would mean that both linux and the rt
domain share that interrupt, which would introduce a flaw, since a
dependency would exist between the non-rt linux handling and the rt
handling of the same IRQ. Think of a level-triggered IRQ, requiring
linux to handle it before it is unmasked anew. To prevent an interrupt
storm, the rt domain would then have to wait for the non-rt one (i.e.
linux) to unmask the interrupt channel (i.e. maybe a non-rt device is
requiring attention), thus introducing an unbounded latency.

Regards,
Bob Feretich

On 8/9/2010 10:35 PM, Philippe Gerum wrote:

On Mon, 2010-08-09 at 19:19 +0200, Gilles Chanteperdrix wrote:

Philippe Gerum wrote:

On Mon, 2010-08-09 at 13:50 +0200, Gilles Chanteperdrix wrote:

Philippe Gerum wrote:

On Mon, 2010-08-09 at 02:54 -0700, Bob Feretich wrote:

I am converting my second driver to RTDM. This one receives a
negativing going edge triggered interrupt on GPIO133 of the 
OMAP3
chip.

I have...
ret = rtdm_irq_request(&adis_data_rdy_irq_handle, irq, 
                   adis_data_rdy_irq_handler, 
                   RTDM_IRQTYPE_EDGE, 
                   "asuspidvr", ctx);
then...
ret = rtdm_irq_enable(&adis_data_rdy_irq_handle);

but the interrupt handler is never invoked.

cat /proc/xenomai/irq shows:
IRQ         CPU0
 37:       15815         [timer]
 39:           0         asuspidvr
 48:           0         asuspidvr
 91:           0         asuspidvr
293:           0         asuspidvr
418:           0         [virtual]

IRQ 293 in the interrupt that should be happening.

I can see the pulses on the input pin and the non-rt version of 
the
driver sees the interrupts, so that excludes hardware issues and
u-boot pin configuration issues.

Any suggestions?
Regards,
Bob Feretich


__

For some reason, that IRQ line may not be properly enabled by the 
core
code. Could you introduce this patch? If a valid routine is 
reported in
the kernel log message, you could locate it by address, from a 
kernel
image objdump.

There may also be more to do than enabling the irq line, such as
programming the hardware to enable irq for this gpio, set the type
(edge, level) and so on. You can try and call request_irq, then 
free_irq
before calling rtdm_request_irq to see if request_irq would trigger 
some
actions that rtdm_request_irq does not trigger.

If you mean that beagle_twl_gpio_setup() still has to be called at 
this
point, then we probably have something broken at ipipe level.

I was rather thinking about gpio_irq_type, which is normally called
through "set_irq_type". I wonder however, if calling this function for
an irq registered through rtdm will not screw things up, especially
since it changes the flow handler, or do nothing because the irq has not
been registered with request_irq.

chip->set_type() should be called when setting the IRQ trigger; this one
completely depends on the per-chip routine. In the gpio_irq_type(), that
should be fine, since we relay the settings through
__fixup_irq_handler(), which is Adeos-defined.

Xenomai is not currently setting the IRQ trigger when requesting an
interrupt, which is the problem. However, set_type() handlers are often
required to run in secondary mode; this means than any call on behalf of
rtdm_irq_request() would restrict the latter to secondary mode only,
which is not currently the case.

This means that we should probably force this requirement on
rthal_irq_request() at some point, because connecting a Xenomai
interrupt descriptor to the Linux core may impose secondary mode on us.

PS: switching the discussion to -core where it belongs now.