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Re: Using irq-crossbar.c

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  Re: Using irq-crossbar.c Sebastian Frias <sf84@laposte.net> - 2016-06-13 17:20 +0200
    Re: Using irq-crossbar.c Marc Zyngier <marc.zyngier@arm.com> - 2016-06-13 18:30 +0200

#1420975 — Re: Using irq-crossbar.c

Hi Marc,

Thanks for your input, please find my comments below.

On 06/11/2016 11:58 AM, Marc Zyngier wrote:
>> I think Sebastian is even more baffled by the DT mess
>> (sorry, intricacies) than I am.
> 
> This mess is what has saved us from the apocalypse 5 years ago, and
> describing a complex system is not easy (what a surprise...). If you
> just want to apply recipes without understanding the underlying
> constraints, you're in for a lot of pain.

Nobody said we wanted a recipe, but it would help to have examples of each of the configurations supported.
Indeed, there is effort in writing the DT bindings and even Documentation/IRQ-domain.txt yet I did not see example drivers for the different configurations.
Also, it is difficult to know what is the recommended way, since old APIs are kept for a while.

APIs are usually extended/designed around specific cases, so there must be examples, but they are not easy to find.

> 
>> The base file he was referring to is:
>>
>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/tango4-common.dtsi
> 
> I know which file that is, it is mentioned in the diff. I was merely
> trying to point out the glaring mistakes that could be enough for a
> interrupt controller hierarchy to be completely non-functional:
> 
> - Your crossbar doesn't have a #interrupt-cells property. How do you
>   expect the interrupt specifiers to be interpreted?

Thanks for the pointer, actually, after adding "#interrupt-cells = <3>;" I can see the driver getting requests for domain maps and xlates :-)

> - You've changed the default interrupt controller to be your crossbar.
>   Which means that all the sub-nodes are inheriting it. Have you
>   checked that this was valid for all of these nodes?

What do you mean with "valid for all these nodes"? All HW irq lines go to the crossbar.

> 
> And as it has been pointed out before, you seem to be reusing an
> existing driver. Do you know for sure that the usage constraints are
> similar?

It is not being reused as is, I just thought (incorrectly apparently) that it was a good example for our case.

Best regards,

Sebastian

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#1421043

On 13/06/16 16:15, Sebastian Frias wrote:

>>> The base file he was referring to is:
>>>
>>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/tango4-common.dtsi
>>
>> I know which file that is, it is mentioned in the diff. I was merely
>> trying to point out the glaring mistakes that could be enough for a
>> interrupt controller hierarchy to be completely non-functional:
>>
>> - Your crossbar doesn't have a #interrupt-cells property. How do you
>>   expect the interrupt specifiers to be interpreted?
> 
> Thanks for the pointer, actually, after adding "#interrupt-cells =
> <3>;" I can see the driver getting requests for domain maps and
> xlates :-)

OK, we're getting somewhere.

>> - You've changed the default interrupt controller to be your crossbar.
>>   Which means that all the sub-nodes are inheriting it. Have you
>>   checked that this was valid for all of these nodes?
> 
> What do you mean with "valid for all these nodes"? All HW irq lines go to the crossbar.

All the interrupt lines *in the system*? Or just those that are in the
nodes below the "soc" section?

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...

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