Messages in this thread | | | Date | Fri, 25 Feb 2011 11:05:29 -0800 | From | Stephen Boyd <> | Subject | Re: [PATCH 1/4] msm: scm: Mark inline asm as volatile |
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On 02/25/2011 03:56 AM, Will Deacon wrote: > Hi Stephen, > > On Thu, 2011-02-24 at 18:44 +0000, Stephen Boyd wrote: >> We don't want the compiler to remove these asm statements or >> reorder them in any way. Mark them as volatile to be sure. >> >> Signed-off-by: Stephen Boyd <sboyd@codeaurora.org> >> --- >> arch/arm/mach-msm/scm.c | 4 ++-- >> 1 files changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/arch/arm/mach-msm/scm.c b/arch/arm/mach-msm/scm.c >> index f4b9bc9..ba57b5a 100644 >> --- a/arch/arm/mach-msm/scm.c >> +++ b/arch/arm/mach-msm/scm.c >> @@ -174,7 +174,7 @@ static u32 smc(u32 cmd_addr) >> register u32 r0 asm("r0") = 1; >> register u32 r1 asm("r1") = (u32)&context_id; >> register u32 r2 asm("r2") = cmd_addr; >> - asm( >> + asm volatile( >> __asmeq("%0", "r0") >> __asmeq("%1", "r0") >> __asmeq("%2", "r1") >> @@ -271,7 +271,7 @@ u32 scm_get_version(void) >> return version; >> >> mutex_lock(&scm_lock); >> - asm( >> + asm volatile( >> __asmeq("%0", "r1") >> __asmeq("%1", "r0") >> __asmeq("%2", "r1") > > > These asm blocks all have sensible looking output constraints. Why > do they need to be marked volatile?
I'm not seeing any different code with or without this so I saw little harm in marking them as volatile. I really don't want the compiler moving them or deleting them so it seemed safer to just mark it volatile to make sure nothing happens to the smc instructions.
-- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
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