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SubjectRe: [PATCH v4 6/6] gpio: uniphier: add UniPhier GPIO controller driver
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On 09/12/2017 07:03 AM, Linus Walleij wrote:
> On Thu, Sep 7, 2017 at 1:42 PM, Masahiro Yamada
> <yamada.masahiro@socionext.com> wrote:
>
>> This GPIO controller device is used on UniPhier SoCs.
>>
>> It also serves as an interrupt controller, but interrupt signals are
>> just delivered to the parent irqchip without any latching or OR'ing.
>> This is implemented by using hierarchy IRQ domain.
>>
>> Implementation note:
>> Unfortunately, the IRQ mapping from this controller to the parent is
>> random. (48, 49, ..., 63, 154, 155, ...)
>> If "interrupts" property is used, IRQ resources may be statically
>> allocated when platform devices are populated from DT. This can be
>> a problem for the hierarchy IRQ domain because IRQ allocation must
>> happen from the outer-most domain up to the root domain in order to
>> build up the stacked IRQ. (https://lkml.org/lkml/2017/7/6/758)
>> Solutions to work around it could be to hard-code parent hwirqs or
>> to invent a driver-specific DT property.
>>
>> Here, the new API irq_domain_push_irq() was merged by v4.14-rc1.
>> It allows to add irq_data to the existing hierarchy. It will help
>> to make this driver work whether the parent has already initialized
>> the hierarchy or not.
>>
>> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
>> ---
>>
>> Changes in v4:
>> - Add COMPILE_TEST and select IRQ_DOMAIN_HIERARCHY
>> - Reimplement irqchip part by using irq_domain_push_irq()
>
> Awesome improvement. There was a build error and I also
> would like David Daney to have a look at this so we know we
> use things the right way,

It looks correct to me.

I haven't verified it, but I think the OF device-tree probing code for
the platform devices will automatically xlat-and-map all those irqs, so
that the irq_domain_push_irq() is required to get the domain hierarchy
properly configured. It would be similar to the PCI case where we
configure all the MSI-X and then do the irq_domain_push_irq() in the
Cavium ThunderX driver.

If interrupt handling has been verified to work with this driver, I
would say that we are probably using things "the right way".

David.



> but overall I am happy after this
> so I hope I will be able to apply next version.
>
> Yours,
> Linus Walleij
>

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