linux-kernel - Re: [PATCH 3/8] perf/arm_cspmu: Add arm_cspmu_acpi_dev

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Message-ID: <3e96b16f-a53f-438b-fcd9-2e1b6fef2136@os.amperecomputing.com>
Date: Thu, 29 Jan 2026 14:23:14 -0800 (PST)
From: Ilkka Koskinen <ilkka@...amperecomputing.com>
To: Besar Wicaksono <bwicaksono@...dia.com>
cc: will@...nel.org, suzuki.poulose@....com, robin.murphy@....com, 
    ilkka@...amperecomputing.com, 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, 
    skelley@...dia.com, ywan@...dia.com, mochs@...dia.com, nirmoyd@...dia.com
Subject: Re: [PATCH 3/8] perf/arm_cspmu: Add arm_cspmu_acpi_dev_get


Hi Besar,

On Mon, 26 Jan 2026, 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.
>
> Signed-off-by: Besar Wicaksono <bwicaksono@...dia.com>
> ---
> drivers/perf/arm_cspmu/arm_cspmu.c | 24 +++++++++++++++++++++++-
> drivers/perf/arm_cspmu/arm_cspmu.h | 17 ++++++++++++++++-
> 2 files changed, 39 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/perf/arm_cspmu/arm_cspmu.c b/drivers/perf/arm_cspmu/arm_cspmu.c
> index 34430b68f602..dadc9b765d80 100644
> --- a/drivers/perf/arm_cspmu/arm_cspmu.c
> +++ b/drivers/perf/arm_cspmu/arm_cspmu.c
> @@ -16,7 +16,7 @@
>  * The user should refer to the vendor technical documentation to get details
>  * about the supported events.
>  *
> - * Copyright (c) 2022-2023, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
> + * Copyright (c) 2022-2026, NVIDIA CORPORATION & AFFILIATES. All rights reserved.
>  *
>  */
>
> @@ -1132,6 +1132,28 @@ 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));
> +	snprintf(uid, sizeof(uid), "%u", apmt_node->inst_secondary);
> +
> +	adev = acpi_dev_get_first_match_dev(hid, uid, -1);
> +	return adev;

I'd probably just do

 	return acpi_dev_get_first_match_dev(hid, uid, -1);

but it doesn't really matter. Regardless,

 	Reviewed-by: Ilkka Koskinen <ilkka@...amperecomputing.com>

Cheers, Ilkka