On Thu, Nov 01, 2012 at 09:40:10PM +0800, Fei Yang wrote:
> 2012/11/1 Rob Herring <robherring2@xxxxxxxxx>:
> > On 10/31/2012 08:24 PM, Yangfei (Felix) wrote:
> >> The current "WFI" opcode definiton causes CPU hot-plug feature fails to
> >> work
> >> if the kernel is built with CONFIG_THUMB2_KERNEL/CONFIG_CPU_ENDIAN_BE8
> >> being
> >> defined. An invalid instruction exception will be generated.
> >>
> >> Signed-off-by: yangfei.kernel@xxxxxxxxx
> >> ---
> >> arch/arm/mach-exynos/hotplug.c | 8 +++++++-
> >> arch/arm/mach-realview/hotplug.c | 8 +++++++-
> >> arch/arm/mach-shmobile/hotplug.c | 8 +++++++-
> >> 3 files changed, 21 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/arch/arm/mach-exynos/hotplug.c
> >> b/arch/arm/mach-exynos/hotplug.c
> >> index f4d7dd2..823a0e4 100644
> >> --- a/arch/arm/mach-exynos/hotplug.c
> >> +++ b/arch/arm/mach-exynos/hotplug.c
> >> @@ -18,11 +18,17 @@
> >> #include <asm/cacheflush.h>
> >> #include <asm/cp15.h>
> >> #include <asm/smp_plat.h>
> >> +#include <asm/opcodes.h>
> >>
> >> #include <mach/regs-pmu.h>
> >>
> >> #include "common.h"
> >>
> >> +/*
> >> + * Define opcode of the WFI instruction.
> >> + */
> >> +#define __WFI __inst_arm_thumb16(0xe320f003, 0xbf30)
> >> +
> >> static inline void cpu_enter_lowpower(void)
> >> {
> >> unsigned int v;
> >> @@ -72,7 +78,7 @@ static inline void platform_do_lowpower(unsigned int
> >> cpu, int *spurious)
> >> /*
> >> * here's the WFI
> >> */
> >> - asm(".word 0xe320f003\n"
> >> + asm(__WFI
> >
> > Wouldn't using the actual wfi instruction fix this. There is a wfi()
> > macro.
> >
> > Or just call cpu_do_idle() which will do any other things needed before
> > wfi like a dsb instruction.
> >
> > Rob
> >> :
> >> :
> >> : "memory", "cc");
>
> <Cut>
>
> Hi Rob,
> Thanks for the reply. The way you suggested is more elegant. But
> here we worried about the version of the compiler toolchain used to
> build the kernel. The "WFI" assembler instruction may not be
> recognized if the toolchain is too old. Need the related ARM board
> maintainers to confirm this.
Maybe all the exynos platforms are new enough for this not to be a
problem?
I think mach-exynos is pretty new and v7-only anyway. If so, then it
may be better to put
CFLAGS_hotplug.o := -march=armv7-a
in arch/arm/mach-exynos/Makefile, and use the real "wfi" mnemonic
directly. People should _really_ not be building kernels containig
v7 board support with tools that are too old to support this.
Cheers
---Dave
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