diff options
| author | Russell King <rmk+kernel@arm.linux.org.uk> | 2014-06-30 11:29:12 -0400 |
|---|---|---|
| committer | Russell King <rmk+kernel@arm.linux.org.uk> | 2014-07-18 07:29:04 -0400 |
| commit | 6ebbf2ce437b33022d30badd49dc94d33ecfa498 (patch) | |
| tree | bc015e35b456a28bb0e501803a454dc0c0d3291a /arch/arm/lib/delay-loop.S | |
| parent | af040ffc9ba1e079ee4c0748aff64fa3d4716fa5 (diff) | |
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/lib/delay-loop.S')
| -rw-r--r-- | arch/arm/lib/delay-loop.S | 18 |
1 files changed, 9 insertions, 9 deletions
diff --git a/arch/arm/lib/delay-loop.S b/arch/arm/lib/delay-loop.S index bc1033b897b4..518bf6e93f78 100644 --- a/arch/arm/lib/delay-loop.S +++ b/arch/arm/lib/delay-loop.S | |||
| @@ -35,7 +35,7 @@ ENTRY(__loop_const_udelay) @ 0 <= r0 <= 0x7fffff06 | |||
| 35 | mul r0, r2, r0 @ max = 2^32-1 | 35 | mul r0, r2, r0 @ max = 2^32-1 |
| 36 | add r0, r0, r1, lsr #32-6 | 36 | add r0, r0, r1, lsr #32-6 |
| 37 | movs r0, r0, lsr #6 | 37 | movs r0, r0, lsr #6 |
| 38 | moveq pc, lr | 38 | reteq lr |
| 39 | 39 | ||
| 40 | /* | 40 | /* |
| 41 | * loops = r0 * HZ * loops_per_jiffy / 1000000 | 41 | * loops = r0 * HZ * loops_per_jiffy / 1000000 |
| @@ -46,23 +46,23 @@ ENTRY(__loop_const_udelay) @ 0 <= r0 <= 0x7fffff06 | |||
| 46 | ENTRY(__loop_delay) | 46 | ENTRY(__loop_delay) |
| 47 | subs r0, r0, #1 | 47 | subs r0, r0, #1 |
| 48 | #if 0 | 48 | #if 0 |
| 49 | movls pc, lr | 49 | retls lr |
| 50 | subs r0, r0, #1 | 50 | subs r0, r0, #1 |
| 51 | movls pc, lr | 51 | retls lr |
| 52 | subs r0, r0, #1 | 52 | subs r0, r0, #1 |
| 53 | movls pc, lr | 53 | retls lr |
| 54 | subs r0, r0, #1 | 54 | subs r0, r0, #1 |
| 55 | movls pc, lr | 55 | retls lr |
| 56 | subs r0, r0, #1 | 56 | subs r0, r0, #1 |
| 57 | movls pc, lr | 57 | retls lr |
| 58 | subs r0, r0, #1 | 58 | subs r0, r0, #1 |
| 59 | movls pc, lr | 59 | retls lr |
| 60 | subs r0, r0, #1 | 60 | subs r0, r0, #1 |
| 61 | movls pc, lr | 61 | retls lr |
| 62 | subs r0, r0, #1 | 62 | subs r0, r0, #1 |
| 63 | #endif | 63 | #endif |
| 64 | bhi __loop_delay | 64 | bhi __loop_delay |
| 65 | mov pc, lr | 65 | ret lr |
| 66 | ENDPROC(__loop_udelay) | 66 | ENDPROC(__loop_udelay) |
| 67 | ENDPROC(__loop_const_udelay) | 67 | ENDPROC(__loop_const_udelay) |
| 68 | ENDPROC(__loop_delay) | 68 | ENDPROC(__loop_delay) |