ARCv2: Enable unaligned access in early ASM code

BugLink: https://bugs.launchpad.net/bugs/1837813
commit 252f6e8eae909bc075a1b1e3b9efb095ae4c0b56 upstream.

It is currently done in arc_init_IRQ() which might be too late
considering gcc 7.3.1 onwards (GNU 2018.03) generates unaligned
memory accesses by default

Cc: stable@vger.kernel.org #4.4+
Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
[vgupta: rewrote changelog]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/arch/arc/kernel/head.S b/arch/arc/kernel/head.S
index 8b90d25a15cca8ebd334402848d98aa22f07b8bf..26e33a8b2d188cd2994873249d4cae87fdd4021c 100644 (file)
--- a/arch/arc/kernel/head.S
+++ b/arch/arc/kernel/head.S
@@ -17,6 +17,7 @@
 #include <asm/entry.h>
 #include <asm/arcregs.h>
 #include <asm/cache.h>
+#include <asm/irqflags.h>
 
 .macro CPU_EARLY_SETUP
 
@@ -47,6 +48,15 @@
        sr      r5, [ARC_REG_DC_CTRL]
 
 1:
+
+#ifdef CONFIG_ISA_ARCV2
+       ; Unaligned access is disabled at reset, so re-enable early as
+       ; gcc 7.3.1 (ARC GNU 2018.03) onwards generates unaligned access
+       ; by default
+       lr      r5, [status32]
+       bset    r5, r5, STATUS_AD_BIT
+       kflag   r5
+#endif
 .endm
 
        .section .init.text, "ax",@progbits