arm: armv7: allow unaligned memory access

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>

arch/arm/cpu/armv7/Makefile

@@ -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

arch/arm/cpu/armv7/sctlr.S

@@ -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)