linux-kernel - Re: [PATCH v2 2/5] arch_topology: update CPU map to use the new API

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Message-ID: <20250711102539.000065b6@huawei.com>
Date: Fri, 11 Jul 2025 10:25:39 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Alireza Sanaee <alireza.sanaee@...wei.com>
CC: <krzk@...nel.org>, <robh@...nel.org>, <coresight@...ts.linaro.org>,
	<devicetree@...r.kernel.org>, <dianders@...omium.org>,
	<james.clark@...aro.org>, <linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>, <linux-perf-users@...r.kernel.org>,
	<linuxarm@...wei.com>, <mark.rutland@....com>, <mike.leach@...aro.org>,
	<ruanjinjie@...wei.com>, <saravanak@...gle.com>,
	<shameerali.kolothum.thodi@...wei.com>
Subject: Re: [PATCH v2 2/5] arch_topology: update CPU map to use the new API

On Tue, 8 Jul 2025 16:14:59 +0100
Alireza Sanaee <alireza.sanaee@...wei.com> wrote:

> Cleans up the cpu-map generation using the created API.
> 
> Signed-off-by: Alireza Sanaee <alireza.sanaee@...wei.com>
> ---
>  drivers/base/arch_topology.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> index 1037169abb45..ccc73bfae90d 100644
> --- a/drivers/base/arch_topology.c
> +++ b/drivers/base/arch_topology.c
> @@ -473,19 +473,19 @@ static unsigned int max_smt_thread_num = 1;
>   */
>  static int __init get_cpu_for_node(struct device_node *node)
>  {
> +	struct device_node *cpu_node;

Initialize to NULL.  Whilst we can see that it will always be initalized
static analysis tools and compilers probably can't.

>  	int cpu;
> -	struct device_node *cpu_node __free(device_node) =
> -		of_parse_phandle(node, "cpu", 0);
>  
> -	if (!cpu_node)
> -		return -1;
> -
> -	cpu = of_cpu_node_to_id(cpu_node);
> -	if (cpu >= 0)
> +	cpu = of_cpu_phandle_to_id(node, &cpu_node, 0);
> +	if (cpu >= 0) {
>  		topology_parse_cpu_capacity(cpu_node, cpu);
> -	else
> +		of_node_put(cpu_node);
> +	} else if (cpu == -ENODEV) {
>  		pr_info("CPU node for %pOF exist but the possible cpu range is :%*pbl\n",
>  			cpu_node, cpumask_pr_args(cpu_possible_mask));
> +		of_node_put(cpu_node);
> +	} else
> +		return -1;

I'd be tempted to make this more conventional with error path out of line.

	cpu = of_cpu_phandle_to_id(node, &cpu_node, 0);
	if (cpu == -ENODEV) {
  		pr_info("CPU node for %pOF exist but the possible cpu range is :%*pbl\n",
  			cpu_node, cpumask_pr_args(cpu_possible_mask));
		return -ENODEV;
	} else if (cpu < 0) {
`		return -1;  /* to keep ABI - it's odd but not something we should touch! */
// note this avoids need for the helper to return -1, it can return -EINVAL to indicate
// an invalid parameter.
	}

	topology_parse_cpu_capacity(cpu_node, cpu);
	of_node_put(cpu_node);

	return cpu;
	

>  
>  	return cpu;
>  }