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authorRussell King <rmk+kernel@arm.linux.org.uk>2014-06-30 19:29:12 +0400
committerRussell King <rmk+kernel@arm.linux.org.uk>2014-07-18 15:29:04 +0400
commit6ebbf2ce437b33022d30badd49dc94d33ecfa498 (patch)
treebc015e35b456a28bb0e501803a454dc0c0d3291a /arch/arm/mm/proc-v6.S
parentaf040ffc9ba1e079ee4c0748aff64fa3d4716fa5 (diff)
downloadlinux-6ebbf2ce437b33022d30badd49dc94d33ecfa498.tar.xz
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>
Diffstat (limited to 'arch/arm/mm/proc-v6.S')
-rw-r--r--arch/arm/mm/proc-v6.S16
1 files changed, 8 insertions, 8 deletions
diff --git a/arch/arm/mm/proc-v6.S b/arch/arm/mm/proc-v6.S
index 32b3558321c4..d0390f4b3f18 100644
--- a/arch/arm/mm/proc-v6.S
+++ b/arch/arm/mm/proc-v6.S
@@ -36,14 +36,14 @@
#define PMD_FLAGS_SMP PMD_SECT_WBWA|PMD_SECT_S
ENTRY(cpu_v6_proc_init)
- mov pc, lr
+ ret lr
ENTRY(cpu_v6_proc_fin)
mrc p15, 0, r0, c1, c0, 0 @ ctrl register
bic r0, r0, #0x1000 @ ...i............
bic r0, r0, #0x0006 @ .............ca.
mcr p15, 0, r0, c1, c0, 0 @ disable caches
- mov pc, lr
+ ret lr
/*
* cpu_v6_reset(loc)
@@ -62,7 +62,7 @@ ENTRY(cpu_v6_reset)
mcr p15, 0, r1, c1, c0, 0 @ disable MMU
mov r1, #0
mcr p15, 0, r1, c7, c5, 4 @ ISB
- mov pc, r0
+ ret r0
ENDPROC(cpu_v6_reset)
.popsection
@@ -77,14 +77,14 @@ ENTRY(cpu_v6_do_idle)
mov r1, #0
mcr p15, 0, r1, c7, c10, 4 @ DWB - WFI may enter a low-power mode
mcr p15, 0, r1, c7, c0, 4 @ wait for interrupt
- mov pc, lr
+ ret lr
ENTRY(cpu_v6_dcache_clean_area)
1: mcr p15, 0, r0, c7, c10, 1 @ clean D entry
add r0, r0, #D_CACHE_LINE_SIZE
subs r1, r1, #D_CACHE_LINE_SIZE
bhi 1b
- mov pc, lr
+ ret lr
/*
* cpu_v6_switch_mm(pgd_phys, tsk)
@@ -113,7 +113,7 @@ ENTRY(cpu_v6_switch_mm)
#endif
mcr p15, 0, r1, c13, c0, 1 @ set context ID
#endif
- mov pc, lr
+ ret lr
/*
* cpu_v6_set_pte_ext(ptep, pte, ext)
@@ -131,7 +131,7 @@ ENTRY(cpu_v6_set_pte_ext)
#ifdef CONFIG_MMU
armv6_set_pte_ext cpu_v6
#endif
- mov pc, lr
+ ret lr
/* Suspend/resume support: taken from arch/arm/mach-s3c64xx/sleep.S */
.globl cpu_v6_suspend_size
@@ -241,7 +241,7 @@ __v6_setup:
mcreq p15, 0, r5, c1, c0, 1 @ write aux control reg
orreq r0, r0, #(1 << 21) @ low interrupt latency configuration
#endif
- mov pc, lr @ return to head.S:__ret
+ ret lr @ return to head.S:__ret
/*
* V X F I D LR