[PATCH] ARM: head: Remove boot-time HYP mode check for v5 and below

Dave Martin dave.martin at linaro.org
Fri Dec 7 08:45:59 EST 2012

The kernel can only be entered on HYP mode on CPUs which actually
support it, i.e.  >= ARMv7.  pre-v6 platform support cannot coexist
in the same kernel as support for v7 and higher, so there is no
advantage in having the HYP mode check on pre-v6 hardware.

At least one pre-v6 board is known to fail when the HYP mode check
code is present, although the exact cause remains unknown and may
be unrelated.  [1]

This patch restores the old behaviour for pre-v6 platforms, whereby
the CPSR is forced directly to SVC mode with IRQs and FIQs masked.
All kernels capable of booting on v7 hardware will retain the
check, so this should not impair functionality.

[1] http://lists.arm.linux.org.uk/lurker/message/20121130.013814.19218413.en.html
([ARM] head.S change broke platform device registration?)

Signed-off-by: Dave Martin <dave.martin at linaro.org>
 arch/arm/include/asm/assembler.h |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h
index 2ef9581..eb87200 100644
--- a/arch/arm/include/asm/assembler.h
+++ b/arch/arm/include/asm/assembler.h
@@ -250,6 +250,7 @@
  * Beware, it also clobers LR.
 .macro safe_svcmode_maskall reg:req
+#if __LINUX_ARM_ARCH__ >= 6
 	mrs	\reg , cpsr
 	mov	lr , \reg
 	and	lr , lr , #MODE_MASK
@@ -266,6 +267,13 @@ THUMB(	orr	\reg , \reg , #PSR_T_BIT	)
 1:	msr	cpsr_c, \reg
+ * workaround for possibly broken pre-v6 hardware
+ * (akita, Sharp Zaurus C-1000, PXA270-based)
+ */
+	setmode	PSR_F_BIT | PSR_I_BIT | SVC_MODE, \reg

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