linux-kernel - Re: [PATCH soc] ARM: use ARM_SINGLE

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Date:	Fri, 22 May 2015 18:56:51 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Maxime Coquelin <mcoquelin.stm32@...il.com>
Cc:	Arnd Bergmann <arnd@...db.de>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Stefan Agner <stefan@...er.ch>, manabian@...il.com,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>, olof@...om.net
Subject: Re: [PATCH soc] ARM: use ARM_SINGLE_ARMV7M for ARMv7-M platforms

On Fri, May 22, 2015 at 05:29:20PM +0200, Maxime Coquelin wrote:
> 2015-05-22 16:50 GMT+02:00 Arnd Bergmann <arnd@...db.de>:
> > [one small request as I have four armv7-m folks on Cc already:
> >  could one of you try to fix the warning that I get with every
> >  single build: "/git/arm-soc/arch/arm/kernel/head-nommu.S: Assembler
> > messages: /git/arm-soc/arch/arm/kernel/head-nommu.S:167: Warning:
> > Use of r13 as a source register is deprecated when r15 is the
> > destination register."]
> 
> Moving r13 to r12 and returning r12 seems to do the job (see below).
> But I don't know if there is a more elegant way, and if it is also
> valid for other architectures than armv7-m.
> I can propose a patch if someone can confirm it is valid.

Please follow the ARM code example, rather than inventing alternative
solutions to the same problem that was solved there.  We use r3 for
this there:

        mov     r3, r13
        ret     r3

Consistency _is_ important.

Thanks.

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