linux-kernel - Re: [PATCH v3 5/7] arm64: perf: Clean up armv8pmu_select

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Date:   Fri, 29 Jun 2018 14:29:23 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Suzuki K Poulose <suzuki.poulose@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        will.deacon@....com, robin.murphy@....com, julien.thierry@....com
Subject: Re: [PATCH v3 5/7] arm64: perf: Clean up armv8pmu_select_counter

On Tue, Jun 19, 2018 at 11:15:40AM +0100, Suzuki K Poulose wrote:
> armv8pmu_select_counter always returns the passed idx. So
> let us make that void and get rid of the pointless checks.
> 
> Suggested-by: Mark Rutland <mark.rutland@....com>
> Cc: Will Deacon <will.deacon@....com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>

Acked-by: Mark Rutland <mark.rutland@....com>

Mark.

> ---
>  arch/arm64/kernel/perf_event.c | 29 +++++++++++++++++++----------
>  1 file changed, 19 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c
> index 66a2ffd..9ce3729 100644
> --- a/arch/arm64/kernel/perf_event.c
> +++ b/arch/arm64/kernel/perf_event.c
> @@ -503,13 +503,17 @@ static inline int armv8pmu_counter_has_overflowed(u32 pmnc, int idx)
>  	return pmnc & BIT(ARMV8_IDX_TO_COUNTER(idx));
>  }
>  
> -static inline int armv8pmu_select_counter(int idx)
> +static inline void armv8pmu_select_counter(int idx)
>  {
>  	u32 counter = ARMV8_IDX_TO_COUNTER(idx);
>  	write_sysreg(counter, pmselr_el0);
>  	isb();
> +}
>  
> -	return idx;
> +static inline u32 armv8pmu_read_evcntr(int idx)
> +{
> +	armv8pmu_select_counter(idx);
> +	return read_sysreg(pmxevcntr_el0);
>  }
>  
>  static inline u64 armv8pmu_read_counter(struct perf_event *event)
> @@ -524,12 +528,18 @@ static inline u64 armv8pmu_read_counter(struct perf_event *event)
>  			smp_processor_id(), idx);
>  	else if (idx == ARMV8_IDX_CYCLE_COUNTER)
>  		value = read_sysreg(pmccntr_el0);
> -	else if (armv8pmu_select_counter(idx) == idx)
> -		value = read_sysreg(pmxevcntr_el0);
> +	else
> +		value = armv8pmu_read_evcntr(idx);
>  
>  	return value;
>  }
>  
> +static inline void armv8pmu_write_evcntr(int idx, u32 value)
> +{
> +	armv8pmu_select_counter(idx);
> +	write_sysreg(value, pmxevcntr_el0);
> +}
> +
>  static inline void armv8pmu_write_counter(struct perf_event *event, u64 value)
>  {
>  	struct arm_pmu *cpu_pmu = to_arm_pmu(event->pmu);
> @@ -547,16 +557,15 @@ static inline void armv8pmu_write_counter(struct perf_event *event, u64 value)
>  		 */
>  		value |= 0xffffffff00000000ULL;
>  		write_sysreg(value, pmccntr_el0);
> -	} else if (armv8pmu_select_counter(idx) == idx)
> -		write_sysreg(value, pmxevcntr_el0);
> +	} else
> +		armv8pmu_write_evcntr(idx, value);
>  }
>  
>  static inline void armv8pmu_write_evtype(int idx, u32 val)
>  {
> -	if (armv8pmu_select_counter(idx) == idx) {
> -		val &= ARMV8_PMU_EVTYPE_MASK;
> -		write_sysreg(val, pmxevtyper_el0);
> -	}
> +	armv8pmu_select_counter(idx);
> +	val &= ARMV8_PMU_EVTYPE_MASK;
> +	write_sysreg(val, pmxevtyper_el0);
>  }
>  
>  static inline int armv8pmu_enable_counter(int idx)
> -- 
> 2.7.4
>