[U-Boot] [RFC] interrupt handling

[Stefan Roese <sr@denx.de>]

Hi Albert,

On 22.06.2013 11:58, Albert ARIBAUD wrote:
> From time to time there is discussion about the need for proper
> interrupt support in U-Boot.
> 
> Right now, the only thing left in the source code which remotely looks
> like interrupt support is a few code sections compiled conditionally
> under CONFIG_USE_IRQ, and it does not constitute a good approach to
> interrupt support, if only for the following reasons:
> 
> - CONFIG_USE_IRQ is very general and imprecise as far as overall
>   meaning goes. It does not say "allow drivers to use IRQs", or "IRQs
>   are provided by supporting this specific interrupt controller", or
>   "this driver requires IRQs to work". It does not help us either that
>   the option was never documented...
> 
> - CONFIG_USE_IRQ is, OTOH, very specific as far as interrupt types go.
>   IRQ is an acronym known in ARM for a specific type of interrupt, but
>   ARM also knows FIQ. IRQ may have a different meaning for another
>   architecture, and each platform has its own classification and
>   attributes for interrupts.
> 
> - no API is defined for registering interrupt controller or interrupt
>   client drivers.
> 
> But the worst part is, CONFIG_USE_IRQ is never *ever* defined. :)
> 
> So I am tempted to start this RFC with a first question: do we *need*
> interrupts in the first place, and if we do, do we need an organized
> interrupts subsystem or do we keep an ad hoc approach?

I know that interrupts are currently used on PowerPC for the PPC4xx
ethernet driver (emac). This could be reworked to of cause, but I just
wanted to point this out.

I have no idea if interrupts are used on any ARM platform though.

Thanks,
Stefan