ARM: convert all "mov.* pc, reg" to "bx reg" for ARMv6+

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.

Reported-by: Will Deacon <will.deacon@arm.com>
Tested-by: Stephen Warren <swarren@nvidia.com> # Tegra Jetson TK1
Tested-by: Robert Jarzmik <robert.jarzmik@free.fr> # mioa701_bootresume.S
Tested-by: Andrew Lunn <andrew@lunn.ch> # Kirkwood
Tested-by: Shawn Guo <shawn.guo@freescale.com>
Tested-by: Tony Lindgren <tony@atomide.com> # OMAPs
Tested-by: Gregory CLEMENT <gregory.clement@free-electrons.com> # Armada XP, 375, 385
Acked-by: Sekhar Nori <nsekhar@ti.com> # DaVinci
Acked-by: Christoffer Dall <christoffer.dall@linaro.org> # kvm/hyp
Acked-by: Haojian Zhuang <haojian.zhuang@gmail.com> # PXA3xx
Acked-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com> # Xen
Tested-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de> # ARMv7M
Tested-by: Simon Horman <horms+renesas@verge.net.au> # Shmobile
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 4 insertions, 4 deletions

diff --git a/arch/arm/mach-tegra/sleep.S b/arch/arm/mach-tegra/sleep.S
index 8d06213fbc47..f024a5109e8e 100644
--- a/arch/arm/mach-tegra/sleep.S
+++ b/arch/arm/mach-tegra/sleep.S
@@ -87,7 +87,7 @@ ENTRY(tegra_init_l2_for_a15)
 	mcrne	p15, 0x1, r0, c9, c0, 2
 _exit_init_l2_a15:
 
-	mov	pc, lr
+	ret	lr
 ENDPROC(tegra_init_l2_for_a15)
 
 /*
@@ -111,7 +111,7 @@ ENTRY(tegra_sleep_cpu_finish)
 	add	r3, r3, r0
 	mov	r0, r1
 
-	mov	pc, r3
+	ret	r3
 ENDPROC(tegra_sleep_cpu_finish)
 
 /*
@@ -139,7 +139,7 @@ ENTRY(tegra_shut_off_mmu)
 	moveq	r3, #0
 	streq	r3, [r2, #L2X0_CTRL]
 #endif
-	mov	pc, r0
+	ret	r0
 ENDPROC(tegra_shut_off_mmu)
 	.popsection
 
@@ -156,6 +156,6 @@ ENTRY(tegra_switch_cpu_to_pllp)
 	str	r0, [r5, #CLK_RESET_CCLK_BURST]
 	mov	r0, #0
 	str	r0, [r5, #CLK_RESET_CCLK_DIVIDER]
-	mov	pc, lr
+	ret	lr
 ENDPROC(tegra_switch_cpu_to_pllp)
 #endif