For v6, wfi is architected as a defined MCR instruction, so
use that definition.
Doing a no-op instead of wfi() is probably bad, so for older
processors than v6, wfi() is not defined. If needed, some CPU-
specific wfi() will have to be defined elsewhere.
Signed-off-by: Dave Martin <dave.martin@xxxxxxxxxx>
---
--------------------------------------------------------------------
v2 notes:
The first version of this patch incorrectly specified the write
buffer drain MCR (c7, c5, 4) instead of WFI (c7, c0, 5). Now fixed.
I hang my head in shame!
The first version of this patch attempted to define wfe() and sev()
to empty asms also for pre-v6K processors. Having thought about
this some more, I think that it may be better to wait until this
is actually needed before attempting to define these to anything.
Having no definition (giving a build error) seems safer than
having a wrong definition.
arch/arm/include/asm/system.h | 3 +++
1 files changed, 3 insertions(+), 0 deletions(-)
diff --git a/arch/arm/include/asm/system.h b/arch/arm/include/asm/system.h
index 97f6d60..f39cf09 100644
--- a/arch/arm/include/asm/system.h
+++ b/arch/arm/include/asm/system.h
@@ -129,6 +129,9 @@ extern unsigned int user_debug;
#define sev() __asm__ __volatile__ ("sev" : : : "memory")
#define wfe() __asm__ __volatile__ ("wfe" : : : "memory")
#define wfi() __asm__ __volatile__ ("wfi" : : : "memory")
+#elif __LINUX_ARM_ARCH__ == 6
+#define wfi() __asm__ __volatile__ ("mcr p15, 0, %0, c7, c0, 4" \
+ : : "r" (0) : "memory")
#endif
#if __LINUX_ARM_ARCH__ >= 7
--
1.7.1
--
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