linux-kernel - Re: [PATCH v2 1/5] perf/arm_cspmu: Add arm_cspmu_acpi_dev

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Message-ID: <331bea5f-cfab-49fb-87e4-7ec31523c2c3@arm.com>
Date: Thu, 25 Sep 2025 09:30:55 +0100
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Besar Wicaksono <bwicaksono@...dia.com>, will@...nel.org,
 robin.murphy@....com, ilkka@...amperecomputing.com
Cc: linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-tegra@...r.kernel.org, mark.rutland@....com, treding@...dia.com,
 jonathanh@...dia.com, vsethi@...dia.com, rwiley@...dia.com,
 sdonthineni@...dia.com
Subject: Re: [PATCH v2 1/5] perf/arm_cspmu: Add arm_cspmu_acpi_dev_get

On 23/09/2025 01:18, Besar Wicaksono wrote:
> Add interface to get ACPI device associated with the
> PMU. This ACPI device may contain additional properties
> not covered by the standard properties.
> 

Ok, but who needs this ? I couldn't see any users in the series.
Did I miss something ?

> Signed-off-by: Besar Wicaksono <bwicaksono@...dia.com>
> ---
>   drivers/perf/arm_cspmu/arm_cspmu.c | 22 ++++++++++++++++++++++
>   drivers/perf/arm_cspmu/arm_cspmu.h |  9 +++++++++
>   2 files changed, 31 insertions(+)
> 
> diff --git a/drivers/perf/arm_cspmu/arm_cspmu.c b/drivers/perf/arm_cspmu/arm_cspmu.c
> index efa9b229e701..75b2d80f783e 100644
> --- a/drivers/perf/arm_cspmu/arm_cspmu.c
> +++ b/drivers/perf/arm_cspmu/arm_cspmu.c
> @@ -1090,6 +1090,28 @@ static int arm_cspmu_acpi_get_cpus(struct arm_cspmu *cspmu)
>   
>   	return 0;
>   }
> +
> +struct acpi_device *arm_cspmu_acpi_dev_get(const struct arm_cspmu *cspmu)
> +{
> +	char hid[16];
> +	char uid[16];
> +	struct acpi_device *adev;
> +	const struct acpi_apmt_node *apmt_node;
> +
> +	apmt_node = arm_cspmu_apmt_node(cspmu->dev);
> +	if (!apmt_node || apmt_node->type != ACPI_APMT_NODE_TYPE_ACPI)
> +		return NULL;
> +
> +	memset(hid, 0, sizeof(hid));
> +	memset(uid, 0, sizeof(uid));
> +
> +	memcpy(hid, &apmt_node->inst_primary, sizeof(apmt_node->inst_primary));
> +	sprintf(uid, "%u", apmt_node->inst_secondary);
> +
> +	adev = acpi_dev_get_first_match_dev(hid, uid, -1);
> +	return adev;
> +}
> +EXPORT_SYMBOL_GPL(arm_cspmu_acpi_dev_get);
>   #else
>   static int arm_cspmu_acpi_get_cpus(struct arm_cspmu *cspmu)
>   {
> diff --git a/drivers/perf/arm_cspmu/arm_cspmu.h b/drivers/perf/arm_cspmu/arm_cspmu.h
> index 19684b76bd96..9c5f11f98acd 100644
> --- a/drivers/perf/arm_cspmu/arm_cspmu.h
> +++ b/drivers/perf/arm_cspmu/arm_cspmu.h
> @@ -8,6 +8,7 @@
>   #ifndef __ARM_CSPMU_H__
>   #define __ARM_CSPMU_H__
>   
> +#include <linux/acpi.h>
>   #include <linux/bitfield.h>
>   #include <linux/cpumask.h>
>   #include <linux/device.h>
> @@ -222,4 +223,12 @@ int arm_cspmu_impl_register(const struct arm_cspmu_impl_match *impl_match);
>   /* Unregister vendor backend. */
>   void arm_cspmu_impl_unregister(const struct arm_cspmu_impl_match *impl_match);
>   
> +#if defined(CONFIG_ACPI)
> +/**
> + * Get ACPI device associated with the PMU.
> + * The caller is responsible for calling acpi_dev_put() on the returned device.
> + */
> +struct acpi_device *arm_cspmu_acpi_dev_get(const struct arm_cspmu *cspmu);
> +#endif
If we need this, why not add an empty stub for !CONFIG_ACPI case ? 
Similar to what we do for other cases.

Suzuki

> +
>   #endif /* __ARM_CSPMU_H__ */