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arm: armv7: allow unaligned memory access

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The UEFI spec mandates that unaligned memory access should be enabled if
supported by the CPU architecture.

This patch implements the function unaligned_access() to reset the aligned
access flag in the system control register (SCTLR). It is called when the
bootefi command is invoked.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
[agraf: fix SPDX identifier]
Signed-off-by: Alexander Graf <agraf@suse.de>
This commit is contained in:
Heinrich Schuchardt 2018-04-03 21:59:33 +02:00 committed by Alexander Graf
parent c3b11dea7c
commit 78f90aaeec
2 changed files with 26 additions and 0 deletions
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4
arch/arm/cpu/armv7/Makefile
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@ -12,6 +12,10 @@ obj-y += syslib.o
obj-$(CONFIG_SYS_ARM_MPU) += mpu_v7r.o
ifneq ($(CONFIG_SPL_BUILD),y)
obj-$(CONFIG_EFI_LOADER) += sctlr.o
endif
ifneq ($(CONFIG_SKIP_LOWLEVEL_INIT),y)
obj-y += lowlevel_init.o
endif

22
arch/arm/cpu/armv7/sctlr.S Normal file
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@ -0,0 +1,22 @@
/* SPDX-License-Identifier: GPL-2.0+ */
/*
* Routines to access the system control register
*
* Copyright (c) 2018 Heinrich Schuchardt
*/
#include <linux/linkage.h>
/*
* void allow_unaligned(void) - allow unaligned access
*
* This routine clears the aligned flag in the system control register.
* After calling this routine unaligned access does no longer lead to a
* data abort but is handled by the CPU.
*/
ENTRY(allow_unaligned)
mrc p15, 0, r0, c1, c0, 0 @ load system control register
bic r0, r0, #2 @ clear aligned flag
mcr p15, 0, r0, c1, c0, 0 @ write system control register
bx lr @ return
ENDPROC(allow_unaligned)