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

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Date:	Fri, 22 May 2015 17:29:20 +0200
From:	Maxime Coquelin <mcoquelin.stm32@...il.com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Stefan Agner <stefan@...er.ch>,
	Russell King <linux@....linux.org.uk>, 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

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.

Regards,
Maxime

-------------------------------------------------------------------------------------------------------------

diff --git a/arch/arm/kernel/head-nommu.S b/arch/arm/kernel/head-nommu.S
index aebfbf7..e84bdad 100644
--- a/arch/arm/kernel/head-nommu.S
+++ b/arch/arm/kernel/head-nommu.S
@@ -164,7 +164,8 @@ __after_proc_init:
 #endif
        mcr     p15, 0, r0, c1, c0, 0           @ write control reg
 #endif /* CONFIG_CPU_CP15 */
-       ret     r13
+       mov     r12, r13
+       ret     r12
 ENDPROC(__after_proc_init)
        .ltorg
--
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