Subject: Re: [PATCH] powerpc/oprofile: Fix error in oprofile power7_marked_instr_event() function

From: Paul Mackerras <[email-masked]>
Date: Sat, 5 Jan 2013 11:55:50 +1100

On Thu, Nov 29, 2012 at 08:42:03AM -0800, Carl E. Love wrote:
> powerpc/oprofile: Fix error in oprofile power7_marked_instr_event() function
> 
> The calculation for the left shift of the mask OPROFILE_PM_PMCSEL_MSK has an
> error.  The calculation is should be to shift left by (max_cntrs - cntr) times
> the width of the pmsel field width.  However, the #define OPROFILE_MAX_PMC_NUM
> was used instead of OPROFILE_PMSEL_FIELD_WIDTH.  This patch fixes the
> calculation.
> 
> Signed-off-by: Carl Love <[email-masked]>
> ---
>  arch/powerpc/oprofile/op_model_power4.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/oprofile/op_model_power4.c b/arch/powerpc/oprofile/op_model_power4.c
> index 315f949..f444b94 100644
> --- a/arch/powerpc/oprofile/op_model_power4.c
> +++ b/arch/powerpc/oprofile/op_model_power4.c
> @@ -52,7 +52,7 @@ static int power7_marked_instr_event(u64 mmcr1)
>  	for (pmc = 0; pmc < 4; pmc++) {
>  		psel = mmcr1 & (OPROFILE_PM_PMCSEL_MSK
>  				<< (OPROFILE_MAX_PMC_NUM - pmc)
> -				* OPROFILE_MAX_PMC_NUM);
> +				* OPROFILE_PMSEL_FIELD_WIDTH);
>  		psel = (psel >> ((OPROFILE_MAX_PMC_NUM - pmc)
>  				 * OPROFILE_PMSEL_FIELD_WIDTH)) & ~1ULL;

Apart from the fact that those two statements would be simpler and
better as:

		psel = mmcr1 >> ((OPROFILE_MAX_PMC_NUM - pmc)
  				 * OPROFILE_PMSEL_FIELD_WIDTH);
		psel &= OPROFILE_PM_PMCSEL_MSK & ~1ULL;

the change looks correct, so:

Acked-by: Paul Mackerras <[email-masked]>