2016-04-30 13:32 GMT+02:00 Linus Walleij [off-list ref]:

On Fri, Apr 29, 2016 at 1:19 PM, Maxime Coquelin
[off-list ref] wrote:

quoted

It looks like this: http://pastebin.com/raw/cs2WiNKZ
You can directly check section 12.2.5 of the stm32f429 reference manual:
http://www2.st.com/resource/en/reference_manual/dm00031020.pdf

Nice ASCII art, include that into the commit message :)

I will! :)

quoted

For example, we can imagine a board where gpioa0 is used SD's card detect,
and gpiob0 used to control a led.

If we set the mux at request time, gpiob0 request may overwrite the mux
configuration set by gpioa0, whereas it is not used as interrupt.

That is the reason why I did it in .to_irq().

Well now I am even *more* convinced that this should not happen in
.to_irq(). .to_irq() should not do *anything*.

This needs to happen as part of the irqchip setting up the actual
interrupt.

And it seems the problem is that this driver does *not* define its
own irqchip, but it *should*.

What you want to do is implement an hierarchical irqdomain in your
irqchip, which is what other drivers of this type are doing, see:
drivers/gpio/gpio-xgene-sb.c
irq_domain_create_hierarchy() is your friend.

quoted

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It should *also* be done in the set-up path for the irqchip
side, if that line is used without any interaction with the
gpio side of things.

Actually, a line is either used by a GPIO, (exclusive) or another purpose.
In the case of a GPIO line, I think we should always go through the gpio.

This is a textbook example of a hierarchichal irq domain I think.

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The point is that each IRQ that ever get used
has a 1-to-1 relationship to a certain GPIO line, and if that
relationship cannot be resolved from the irqchip side,
something is wrong. The irqchip needs to enable the
GPIO line it is backing to recieve interrupts without any
requirements that .to_irq() have been called first.

Actually, this is not a 1:1 relationship, as for example, exti0 can be connected
to either gpioa0, or gpiob0,..., or gpiok0.

That is what hierarchical irqdomain is for.

You should expose an irqchip from the gpio driver, that give you
unique irq translations for *all* GPIO lines.

Then, at runtime, if the hierarchical irqdomain cannot map
(i.e. mux) the interrupt onto one of the available lines,
you will get an error.

Thanks a lot for this valuable feedback.
I will have a look at hierachical irq domains, and hope to come back this week
with an implementation.

Regards,
Maxime