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Date:   Fri, 13 Oct 2023 12:08:11 +0100
From:   Mark Rutland <mark.rutland@arm.com>
To:     Anshuman Khandual <anshuman.khandual@arm.com>
Cc:     linux-arm-kernel@lists.infradead.org,
        James Clark <james.clark@arm.com>,
        Robin Murphy <robin.murphy@arm.com>,
        Will Deacon <will@kernel.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH V2] drivers: perf: arm_pmuv3: Drop some unused arguments
 from armv8_pmu_init()
Message-ID: <ZSklGz0kQR4D90gj@FVFF77S0Q05N>
References: <20231013040307.1296109-1-anshuman.khandual@arm.com>
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In-Reply-To: <20231013040307.1296109-1-anshuman.khandual@arm.com>
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On Fri, Oct 13, 2023 at 09:33:07AM +0530, Anshuman Khandual wrote:
> There is just a single call site remaining for armv8_pmu_init(), passing on
> NULL pointers for all custom 'struct attribute_group's. These arguments are
> not really getting used, and hence can be dropped. Afterwards the function
> armv8_pmu_init_nogroups() itself becomes redundant, and can also be dropped
> as well.
> 
> The commit e424b1798526 ("arm64: perf: Refactor PMU init callbacks") wanted
> to preserve the notion that non-default sysfs attributes could be used some
> time in the future and hence armv8_pmu_init_nogroups() stayed on but now it
> can be dropped to remove some redundant indirection, simplifying the code.

If you can make that commit message:

| All the PMU init functions want the default sysfs attribute groups, and so
| these all call armv8_pmu_init_nogroups(), with none calling armv8_pmu_init()
| directly. When we introduced armv8_pmu_init_nogroups() in commit:
| 
|   e424b1798526 ("arm64: perf: Refactor PMU init callbacks")
| 
| ... we thought that we might need custom attribute groups in future, but as we
| evidently haven't, we can remove the option.
| 
| This patch folds armv8_pmu_init_nogroups() into armv8_pmu_init(), removing the
| ability to use custome attribute groups and simplifying the code.

Then:

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

Mark.

> CC: James Clark <james.clark@arm.com>
> Cc: Robin Murphy <robin.murphy@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> ---
> This applies on v6.6-rc5
> 
> Changes in V2:
> 
> - Dropped the helper armv8_pmu_init_nogroups()
> - Updated the commit message
> 
> Changes in V1:
> 
> https://lore.kernel.org/all/20231009035638.165270-1-anshuman.khandual@arm.com/
> 
>  drivers/perf/arm_pmuv3.c | 44 +++++++++++-----------------------------
>  1 file changed, 12 insertions(+), 32 deletions(-)
> 
> diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c
> index 8fcaa26f0f8a..c093b6e823f6 100644
> --- a/drivers/perf/arm_pmuv3.c
> +++ b/drivers/perf/arm_pmuv3.c
> @@ -1187,10 +1187,7 @@ static void armv8_pmu_register_sysctl_table(void)
>  }
>  
>  static int armv8_pmu_init(struct arm_pmu *cpu_pmu, char *name,
> -			  int (*map_event)(struct perf_event *event),
> -			  const struct attribute_group *events,
> -			  const struct attribute_group *format,
> -			  const struct attribute_group *caps)
> +			  int (*map_event)(struct perf_event *event))
>  {
>  	int ret = armv8pmu_probe_pmu(cpu_pmu);
>  	if (ret)
> @@ -1212,27 +1209,17 @@ static int armv8_pmu_init(struct arm_pmu *cpu_pmu, char *name,
>  
>  	cpu_pmu->name			= name;
>  	cpu_pmu->map_event		= map_event;
> -	cpu_pmu->attr_groups[ARMPMU_ATTR_GROUP_EVENTS] = events ?
> -			events : &armv8_pmuv3_events_attr_group;
> -	cpu_pmu->attr_groups[ARMPMU_ATTR_GROUP_FORMATS] = format ?
> -			format : &armv8_pmuv3_format_attr_group;
> -	cpu_pmu->attr_groups[ARMPMU_ATTR_GROUP_CAPS] = caps ?
> -			caps : &armv8_pmuv3_caps_attr_group;
> -
> +	cpu_pmu->attr_groups[ARMPMU_ATTR_GROUP_EVENTS] = &armv8_pmuv3_events_attr_group;
> +	cpu_pmu->attr_groups[ARMPMU_ATTR_GROUP_FORMATS] = &armv8_pmuv3_format_attr_group;
> +	cpu_pmu->attr_groups[ARMPMU_ATTR_GROUP_CAPS] = &armv8_pmuv3_caps_attr_group;
>  	armv8_pmu_register_sysctl_table();
>  	return 0;
>  }
>  
> -static int armv8_pmu_init_nogroups(struct arm_pmu *cpu_pmu, char *name,
> -				   int (*map_event)(struct perf_event *event))
> -{
> -	return armv8_pmu_init(cpu_pmu, name, map_event, NULL, NULL, NULL);
> -}
> -
>  #define PMUV3_INIT_SIMPLE(name)						\
>  static int name##_pmu_init(struct arm_pmu *cpu_pmu)			\
>  {									\
> -	return armv8_pmu_init_nogroups(cpu_pmu, #name, armv8_pmuv3_map_event);\
> +	return armv8_pmu_init(cpu_pmu, #name, armv8_pmuv3_map_event);	\
>  }
>  
>  PMUV3_INIT_SIMPLE(armv8_pmuv3)
> @@ -1263,44 +1250,37 @@ PMUV3_INIT_SIMPLE(armv8_nvidia_denver)
>  
>  static int armv8_a35_pmu_init(struct arm_pmu *cpu_pmu)
>  {
> -	return armv8_pmu_init_nogroups(cpu_pmu, "armv8_cortex_a35",
> -				       armv8_a53_map_event);
> +	return armv8_pmu_init(cpu_pmu, "armv8_cortex_a35", armv8_a53_map_event);
>  }
>  
>  static int armv8_a53_pmu_init(struct arm_pmu *cpu_pmu)
>  {
> -	return armv8_pmu_init_nogroups(cpu_pmu, "armv8_cortex_a53",
> -				       armv8_a53_map_event);
> +	return armv8_pmu_init(cpu_pmu, "armv8_cortex_a53", armv8_a53_map_event);
>  }
>  
>  static int armv8_a57_pmu_init(struct arm_pmu *cpu_pmu)
>  {
> -	return armv8_pmu_init_nogroups(cpu_pmu, "armv8_cortex_a57",
> -				       armv8_a57_map_event);
> +	return armv8_pmu_init(cpu_pmu, "armv8_cortex_a57", armv8_a57_map_event);
>  }
>  
>  static int armv8_a72_pmu_init(struct arm_pmu *cpu_pmu)
>  {
> -	return armv8_pmu_init_nogroups(cpu_pmu, "armv8_cortex_a72",
> -				       armv8_a57_map_event);
> +	return armv8_pmu_init(cpu_pmu, "armv8_cortex_a72", armv8_a57_map_event);
>  }
>  
>  static int armv8_a73_pmu_init(struct arm_pmu *cpu_pmu)
>  {
> -	return armv8_pmu_init_nogroups(cpu_pmu, "armv8_cortex_a73",
> -				       armv8_a73_map_event);
> +	return armv8_pmu_init(cpu_pmu, "armv8_cortex_a73", armv8_a73_map_event);
>  }
>  
>  static int armv8_thunder_pmu_init(struct arm_pmu *cpu_pmu)
>  {
> -	return armv8_pmu_init_nogroups(cpu_pmu, "armv8_cavium_thunder",
> -				       armv8_thunder_map_event);
> +	return armv8_pmu_init(cpu_pmu, "armv8_cavium_thunder", armv8_thunder_map_event);
>  }
>  
>  static int armv8_vulcan_pmu_init(struct arm_pmu *cpu_pmu)
>  {
> -	return armv8_pmu_init_nogroups(cpu_pmu, "armv8_brcm_vulcan",
> -				       armv8_vulcan_map_event);
> +	return armv8_pmu_init(cpu_pmu, "armv8_brcm_vulcan", armv8_vulcan_map_event);
>  }
>  
>  static const struct of_device_id armv8_pmu_of_device_ids[] = {
> -- 
> 2.25.1
>