Hi Rob,
2017-08-11 2:23 GMT+09:00 Rob Herring <robh+dt@xxxxxxxxxx>:
> On Thu, Jul 6, 2017 at 4:58 PM, Masahiro Yamada
> <yamada.masahiro@xxxxxxxxxxxxx> wrote:
>> Hi IRQ experts, DT exports,
>>
>>
>> I have a question about CONFIG_IRQ_DOMAIN_HIERARCHY.
>>
>> When IRQ domains are hierarchy,
>> how can we specify IRQ number re-mapping between the
>> parent irqchip and the child irqchip?
>>
>> The following figure shows a simplified example.
>>
>> |----------| |----------| |----------|
>> | parent | | child | | IRQ |
>> | IRQ chip | <----- | IRQ chip |<----- | consumer |
>> | | | | | Device |
>> |----------| |----------| |----------|
>>
>> Perhaps, we may describe DT like follows
>>
>> gic: interrupt-controller {
>> ...
>> interrupt-controller;
>> #interrupt-cells = <3>;
>> };
>>
>> child_intc: child-interrupt-controller {
>> ...
>> interrupt-parent = <&gic>;
>> interrupts = <0 50 0>, <0 51 0>, <0 52 0>, <0 53 0>;
>> interrupt-controller;
>> #interrupt-cells = <2>;
>> };
>>
>> i2c: i2c {
>> ...
>> interrupt-parent = <&child_intc>;
>> interrupts = <0 4>;
>> };
>>
>>
>> In this example, the I2C controller takes HWIRQ=0 of the child_intc device.
>> This goes through the child IRQ chip,
>> then connected to HWIRQ=50 of the parent intc.
>>
>> The DT above describes the hardware connection well,
>> but it actually does not work.
>>
>> The root irqchip is usually declared with IRQCHIP_DECLARE().
>> So, IRQ resources are allocated when platform devices are populated from DT.
>> This means IRQ allocation happens before drivers are probed.
>>
>> of_pupulate_default_populate() does not know the fact about irqdomain hierarchy.
>
> This has not been true for some time now. The irqs are resolved at
> probe time rather than statically created resources and deferred probe
> is supported if one of the interrupt controllers is not yet
> initialized.
Yes, it is true if the irqchip is a platform driver instead of
IRQCHIP_DECLARE(),
but irqdomain hierarchy always wants to disable the static resource allocation.
>> interrupt-ranges = <0 0 0 50 0 4>;
>>
>> This means <0 0>, <0 1>, <0 2>, <0 3> in the child
>> should be mapped to <0 50 0>, <0 51 0>, <0 52 0>, <0 53 0> in the parent,
>> respectively.
>
> interrupt-map property does this. See here[1].
>
> Rob
>
> [1] http://elinux.org/Device_Tree_Usage#Advanced_Interrupt_Mapping
Thanks for the pointer.
I read it and of_irq_parse_raw() implementation as well.
The interrupt-map would not work for the irqdomain hierarchy
because the interrupt-map transforms irq-spec based on "reg" property.
In this case, no relation between the irqchip and its irq-consumers
(between "child_intc" and "i2c") in therms of the physical address view.
Some irq-consumers have address cell size 1,
and other irq-consumers have address cells size 2.
--
Best Regards
Masahiro Yamada
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