[U-Boot] [PATCH v2 2/3] arm: armv7: allow unaligned memory access

[Heinrich Schuchardt]

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 at gmx.de>
---
 arch/arm/cpu/armv7/Makefile |  4 ++++
 arch/arm/cpu/armv7/sctlr.S  | 23 +++++++++++++++++++++++
 2 files changed, 27 insertions(+)
 create mode 100644 arch/arm/cpu/armv7/sctlr.S

diff --git a/arch/arm/cpu/armv7/Makefile b/arch/arm/cpu/armv7/Makefile
index b14ee54519..cdb56e490b 100644
--- a/arch/arm/cpu/armv7/Makefile
+++ b/arch/arm/cpu/armv7/Makefile
@@ -12,6 +12,10 @@ obj-y	+= cache_v7.o cache_v7_asm.o
 obj-y	+= cpu.o cp15.o
 obj-y	+= syslib.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
diff --git a/arch/arm/cpu/armv7/sctlr.S b/arch/arm/cpu/armv7/sctlr.S
new file mode 100644
index 0000000000..cfdb7d2a52
--- /dev/null
+++ b/arch/arm/cpu/armv7/sctlr.S
@@ -0,0 +1,23 @@
+/*
+ *  Routines to access the system control register
+ *
+ *  Copyright (c) 2018 Heinrich Schuchardt
+ *
+ *  SPDX-License-Identifier:     GPL-2.0+
+ */
+
+#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)
-- 
2.16.3