[U-Boot] [RFC] interrupt handling

From: Lukasz Majewski <l.majewski@samsung.com>
To: u-boot@lists.denx.de
Subject: [U-Boot] [RFC] interrupt handling
Date: Mon, 24 Jun 2013 14:23:56 +0200	[thread overview]
Message-ID: <20130624142356.448f15ee@amdc308.digital.local> (raw)
In-Reply-To: <51C58631.60803@denx.de>

Hi Stefan,

> 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.

For me it looks, like a fundamental decision to support interrupts on
ARM. Do we need them - it's an open question. Does anyone have good use
case for it?

On the other hand I remember that Marek was struggling to introduce new
driver model. It was also a fundamental change and as fair as I know we
don't have it yet finished. 

Anyway it is a good discussion topic :-)

> 
> Thanks,
> Stefan
> 
> _______________________________________________
> U-Boot mailing list
> U-Boot at lists.denx.de
> http://lists.denx.de/mailman/listinfo/u-boot

-- 
Best regards,

Lukasz Majewski

Samsung R&D Institute Poland (SRPOL) | Linux Platform Group