linux/arch/arm/lib/io-readsb.S
Russell King 6ebbf2ce43 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>
2014-07-18 12:29:04 +01:00

124 lines
2.4 KiB
ArmAsm

/*
* linux/arch/arm/lib/io-readsb.S
*
* Copyright (C) 1995-2000 Russell King
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/linkage.h>
#include <asm/assembler.h>
.Linsb_align: rsb ip, ip, #4
cmp ip, r2
movgt ip, r2
cmp ip, #2
ldrb r3, [r0]
strb r3, [r1], #1
ldrgeb r3, [r0]
strgeb r3, [r1], #1
ldrgtb r3, [r0]
strgtb r3, [r1], #1
subs r2, r2, ip
bne .Linsb_aligned
ENTRY(__raw_readsb)
teq r2, #0 @ do we have to check for the zero len?
reteq lr
ands ip, r1, #3
bne .Linsb_align
.Linsb_aligned: stmfd sp!, {r4 - r6, lr}
subs r2, r2, #16
bmi .Linsb_no_16
.Linsb_16_lp: ldrb r3, [r0]
ldrb r4, [r0]
ldrb r5, [r0]
mov r3, r3, put_byte_0
ldrb r6, [r0]
orr r3, r3, r4, put_byte_1
ldrb r4, [r0]
orr r3, r3, r5, put_byte_2
ldrb r5, [r0]
orr r3, r3, r6, put_byte_3
ldrb r6, [r0]
mov r4, r4, put_byte_0
ldrb ip, [r0]
orr r4, r4, r5, put_byte_1
ldrb r5, [r0]
orr r4, r4, r6, put_byte_2
ldrb r6, [r0]
orr r4, r4, ip, put_byte_3
ldrb ip, [r0]
mov r5, r5, put_byte_0
ldrb lr, [r0]
orr r5, r5, r6, put_byte_1
ldrb r6, [r0]
orr r5, r5, ip, put_byte_2
ldrb ip, [r0]
orr r5, r5, lr, put_byte_3
ldrb lr, [r0]
mov r6, r6, put_byte_0
orr r6, r6, ip, put_byte_1
ldrb ip, [r0]
orr r6, r6, lr, put_byte_2
orr r6, r6, ip, put_byte_3
stmia r1!, {r3 - r6}
subs r2, r2, #16
bpl .Linsb_16_lp
tst r2, #15
ldmeqfd sp!, {r4 - r6, pc}
.Linsb_no_16: tst r2, #8
beq .Linsb_no_8
ldrb r3, [r0]
ldrb r4, [r0]
ldrb r5, [r0]
mov r3, r3, put_byte_0
ldrb r6, [r0]
orr r3, r3, r4, put_byte_1
ldrb r4, [r0]
orr r3, r3, r5, put_byte_2
ldrb r5, [r0]
orr r3, r3, r6, put_byte_3
ldrb r6, [r0]
mov r4, r4, put_byte_0
ldrb ip, [r0]
orr r4, r4, r5, put_byte_1
orr r4, r4, r6, put_byte_2
orr r4, r4, ip, put_byte_3
stmia r1!, {r3, r4}
.Linsb_no_8: tst r2, #4
beq .Linsb_no_4
ldrb r3, [r0]
ldrb r4, [r0]
ldrb r5, [r0]
ldrb r6, [r0]
mov r3, r3, put_byte_0
orr r3, r3, r4, put_byte_1
orr r3, r3, r5, put_byte_2
orr r3, r3, r6, put_byte_3
str r3, [r1], #4
.Linsb_no_4: ands r2, r2, #3
ldmeqfd sp!, {r4 - r6, pc}
cmp r2, #2
ldrb r3, [r0]
strb r3, [r1], #1
ldrgeb r3, [r0]
strgeb r3, [r1], #1
ldrgtb r3, [r0]
strgtb r3, [r1]
ldmfd sp!, {r4 - r6, pc}
ENDPROC(__raw_readsb)