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, 8 insertions, 8 deletions

diff --git a/arch/arm/mm/proc-arm720.S b/arch/arm/mm/proc-arm720.S
index d42c37f9f5bc..2baa66b3ac9b 100644
--- a/arch/arm/mm/proc-arm720.S
+++ b/arch/arm/mm/proc-arm720.S
@@ -51,14 +51,14 @@
  */
 ENTRY(cpu_arm720_dcache_clean_area)
 ENTRY(cpu_arm720_proc_init)
-		mov	pc, lr
+		ret	lr
 
 ENTRY(cpu_arm720_proc_fin)
 		mrc	p15, 0, r0, c1, c0, 0
 		bic	r0, r0, #0x1000			@ ...i............
 		bic	r0, r0, #0x000e			@ ............wca.
 		mcr	p15, 0, r0, c1, c0, 0		@ disable caches
-		mov	pc, lr
+		ret	lr
 
 /*
  * Function: arm720_proc_do_idle(void)
@@ -66,7 +66,7 @@ ENTRY(cpu_arm720_proc_fin)
  * Purpose : put the processor in proper idle mode
  */
 ENTRY(cpu_arm720_do_idle)
-		mov	pc, lr
+		ret	lr
 
 /*
  * Function: arm720_switch_mm(unsigned long pgd_phys)
@@ -81,7 +81,7 @@ ENTRY(cpu_arm720_switch_mm)
 		mcr	p15, 0, r0, c2, c0, 0		@ update page table ptr
 		mcr	p15, 0, r1, c8, c7, 0		@ flush TLB (v4)
 #endif
-		mov	pc, lr
+		ret	lr
 
 /*
  * Function: arm720_set_pte_ext(pte_t *ptep, pte_t pte, unsigned int ext)
@@ -94,7 +94,7 @@ ENTRY(cpu_arm720_set_pte_ext)
 #ifdef CONFIG_MMU
 	armv3_set_pte_ext wc_disable=0
 #endif
-	mov	pc, lr
+	ret	lr
 
 /*
  * Function: arm720_reset
@@ -112,7 +112,7 @@ ENTRY(cpu_arm720_reset)
 		bic	ip, ip, #0x000f			@ ............wcam
 		bic	ip, ip, #0x2100			@ ..v....s........
 		mcr	p15, 0, ip, c1, c0, 0		@ ctrl register
-		mov	pc, r0
+		ret	r0
 ENDPROC(cpu_arm720_reset)
 		.popsection
 
@@ -128,7 +128,7 @@ __arm710_setup:
 	bic	r0, r0, r5
 	ldr	r5, arm710_cr1_set
 	orr	r0, r0, r5
-	mov	pc, lr				@ __ret (head.S)
+	ret	lr				@ __ret (head.S)
 	.size	__arm710_setup, . - __arm710_setup
 
 	/*
@@ -156,7 +156,7 @@ __arm720_setup:
 	mrc	p15, 0, r0, c1, c0		@ get control register
 	bic	r0, r0, r5
 	orr	r0, r0, r6
-	mov	pc, lr				@ __ret (head.S)
+	ret	lr				@ __ret (head.S)
 	.size	__arm720_setup, . - __arm720_setup
 
 	/*