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    SubjectRe: [PATCH 2/4] msm: scm: Fix improper register assignment
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    On Thu, 2011-02-24 at 18:44 +0000, Stephen Boyd wrote:
    > Assign the registers used in the inline assembly immediately
    > before the inline assembly block. This ensures the compiler
    > doesn't optimize away dead register assignments when it
    > shouldn't.
    >
    > Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
    > ---
    > arch/arm/mach-msm/scm.c | 7 +++++--
    > 1 files changed, 5 insertions(+), 2 deletions(-)
    >
    > diff --git a/arch/arm/mach-msm/scm.c b/arch/arm/mach-msm/scm.c
    > index ba57b5a..5eddf54 100644
    > --- a/arch/arm/mach-msm/scm.c
    > +++ b/arch/arm/mach-msm/scm.c
    > @@ -264,13 +264,16 @@ u32 scm_get_version(void)
    > {
    > int context_id;
    > static u32 version = -1;
    > - register u32 r0 asm("r0") = 0x1 << 8;
    > - register u32 r1 asm("r1") = (u32)&context_id;
    > + register u32 r0 asm("r0");
    > + register u32 r1 asm("r1");
    >
    > if (version != -1)
    > return version;
    >
    > mutex_lock(&scm_lock);
    > +
    > + r0 = 0x1 << 8;
    > + r1 = (u32)&context_id;
    > asm volatile(
    > __asmeq("%0", "r1")
    > __asmeq("%1", "r0")


    Whoa, have you seen the compiler `optimise' the original assignments
    away? Since there is a use in the asm block, the definition shouldn't
    be omitted. What toolchain are you using?

    Will



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