From: Tony Lindgren <tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org>
Subject: Re: [PATCH] ARM: convert all "mov.* pc, reg" to "bx reg" for ARMv6+
Date: Wed, 2 Jul 2014 02:02:18 -0700
Message-ID: <20140702090218.GV28884@atomide.com>
References: <E1X20Rs-00082S-KI@rmk-PC.arm.linux.org.uk>
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Cc: Andrew Lunn <andrew-g2DYL2Zd6BY@public.gmane.org>, <kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
        <linux-sh-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, Kevin Hilman <khilman-1D3HCaltpLuhEniVeURVKkEOCMrvLtNR@public.gmane.org>,
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        Kukjin
 Kim <kgene.kim-Sze3O3UU22JBDgjK7y7TUQ@public.gmane.org>,
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        Jason Cooper
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        Stephen Warren <swarren-3lzwWm7+Weoh9ZMKESR00Q@public.gmane.org>,
        Marc Zyngier
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        Hans Ulli Kroll <ulli.kroll-gM/Ye1E23mwN+BqQ9rBEUg@public.gmane.org>,
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To: Russell King <rmk+kernel-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>
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* Russell King <rmk+kernel-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org> [140701 09:01]:
> ARMv6 and greater introduced a new instruction ("bx") which can be used
> to return from function calls.  Recent CPUs perform better when the
> "bx lr" instruction is used rather than the "mov pc, lr" instruction,
> and this sequence is strongly recommended to be used by the ARM
> architecture manual (section A.4.1.1).
> 
> We provide a new macro "ret" with all its variants for the condition
> code which will resolve to the appropriate instruction.
> 
> Rather than doing this piecemeal, and miss some instances, change all
> the "mov pc" instances to use the new macro, with the exception of
> the "movs" instruction and the kprobes code.  This allows us to detect
> the "mov pc, lr" case and fix it up - and also gives us the possibility
> of deploying this for other registers depending on the CPU selection.
> 
> Signed-off-by: Russell King <rmk+kernel-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>

Seems to boot fine for omaps:

Tested-by: Tony Lindgren <tony-4v6yS6AI5VpBDgjK7y7TUQ@public.gmane.org>