[Linux-Xtensa] Re: [patch 09/12] xtensa: allow platform and variant to initialize own irq chips

[Daniel Glöckner]

Hi Chris,

On 04/23/2009 10:03 PM, Chris Zankel wrote:
> Daniel Glöckner wrote:
>> On 04/23/2009 07:20 PM, Chris Zankel wrote:
>>>> Another possibility would be to select VARIANT_IRQ_SWITCH (or a
>>>> dedicated new
>>>> Kconfig option) in all SoCs that need additional IRQs.
>>> Wasn't the original code before your patch just doing that?
>>
>> Yes, but I wanted to decouple variant IRQs from the functionality
>> provided by CONFIG_VARIANT_IRQ_SWITCH.
> 
> Could you elaborate a bit more on this? What's the (intended) difference
> between VARIANT_IRQ_SWITCH and VARIANT_IRQ?

VARIANT_IRQ_SWITCH provides callbacks that may be used by the variant to perform
actions when a core interrupt is enabled/disabled.
We use it to setup IRQ routing.

VARIANT_IRQ would allow variants to define additional irq_chips.

> I need to look a bit closers, but can't the variant code simply define
> its own irq_chip? We might need some tweaking in xtensa-irq.c for the
> cascaded interrupts, or the variant-irq.c has to register a handler with
> it.

Let's see..
The variant would need to be able to increase NR_IRQS and it would need to have
the opportunity to call set_irq_chip from inside init_IRQ.

That's exactly what this patch does.

  Daniel

-- 
Dipl.-Math. Daniel Glöckner, emlix GmbH, http://www.emlix.com
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