linux-kernel - Re: [PATCH v3] irqchip: Add support for ARMv7-M's NVIC

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Message-ID: <20130418081555.GV30416@pengutronix.de>
Date:	Thu, 18 Apr 2013 10:15:55 +0200
From:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Thomas Gleixner <tglx@...utronix.de>, kernel@...gutronix.de,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Jonathan Austin <jonathan.austin@....com>,
	Catalin Marinas <catalin.marinas@....com>
Subject: Re: [PATCH v3] irqchip: Add support for ARMv7-M's NVIC

On Wed, Apr 17, 2013 at 10:23:43PM +0200, Arnd Bergmann wrote:
> On Wednesday 17 April 2013, Uwe Kleine-König wrote:
> 
> > This patch triggers two checkpatch warnings:
> > 
> > 	WARNING: Avoid CamelCase: <nvic_do_IRQ>
> > 	WARNING: Avoid CamelCase: <handle_IRQ>
> > 
> > but I think they are OK for consistency?!
> 
> You obviously have no choice for handle_IRQ, but I think the common way to
> name the first-level interrupt handler would be "nvic_handle_irq" here.
The function I called before is asm_do_IRQ which is another instance of
this naming scheme. But I agree that nvic_handle_irq is nicer and will
change to nvic_handle_irq in the next iteration.
 
> > Moreover sparse tells me:
> > 
> > 	drivers/irqchip/irq-nvic.c:58:1: warning: symbol 'nvic_do_IRQ' was not declared. Should it be static?
> > 
> > nvic_do_IRQ is called from assembler only, so a declaration couldn't be
> > shared and I couldn't find a nice place for a declaration. Suggestions
> > welcome.
> 
> Can't you make it static and call set_handle_irq() on it from the
> probe function?
Yeah that works. Then nvic_handle_irq needs to determine the irq itself
which is currently done in the entry code.

> > + * Each bank handles 32 irqs. Only the 16th (= last) bank handles only
> > + * 16 irqs.
> > + */
> > +#define NVIC_MAX_IRQ		((NVIC_MAX_BANKS - 1) * 32 + 16)
> 
> Is this actually inherent to the hardware design, or is the number of irqs
> actually customizable? Also, why do you care about the maximum? You only
> use it to check against the device tree provided value, but I suppose
> you could just as well trust that property to be correct.
I don't provide a value for the number of irqs in the device tree. There
is only the value INTLINESNUM in the V7M_SCS_ICTR register that is used
to determine the number of interrupt banks.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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