linux-kernel - Re: [PATCH 3/5] coresight: cti: Use of_cpu_phandle_to

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Message-ID: <20250708093623.0000363e@huawei.com>
Date: Tue, 8 Jul 2025 09:36:23 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Alireza Sanaee <alireza.sanaee@...wei.com>
CC: <mark.rutland@....com>, <robh@...nel.org>, <coresight@...ts.linaro.org>,
	<devicetree@...r.kernel.org>, <dianders@...omium.org>,
	<james.clark@...aro.org>, <krzk@...nel.org>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
	<linux-perf-users@...r.kernel.org>, <linuxarm@...wei.com>,
	<mike.leach@...aro.org>, <ruanjinjie@...wei.com>, <saravanak@...gle.com>,
	<shameerali.kolothum.thodi@...wei.com>, <suzuki.poulose@....com>
Subject: Re: [PATCH 3/5] coresight: cti: Use of_cpu_phandle_to_id for
 grabbing CPU id

On Mon, 7 Jul 2025 16:04:12 +0100
Alireza Sanaee <alireza.sanaee@...wei.com> wrote:

> Use the newly created API to grab CPU id.
> 
> Signed-off-by: Alireza Sanaee <alireza.sanaee@...wei.com>
Here is the justification for allowing the node parameter to be null.

> ---
>  .../hwtracing/coresight/coresight-cti-platform.c  | 15 +++------------
>  1 file changed, 3 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/hwtracing/coresight/coresight-cti-platform.c b/drivers/hwtracing/coresight/coresight-cti-platform.c
> index d0ae10bf6128..cd821e926792 100644
> --- a/drivers/hwtracing/coresight/coresight-cti-platform.c
> +++ b/drivers/hwtracing/coresight/coresight-cti-platform.c
> @@ -41,21 +41,12 @@
>   */
>  static int of_cti_get_cpu_at_node(const struct device_node *node)
>  {
> +	struct device_node *dn = NULL;
>  	int cpu;
> -	struct device_node *dn;
>  
> -	if (node == NULL)
> -		return -1;
> -
> -	dn = of_parse_phandle(node, "cpu", 0);
> -	/* CTI affinity defaults to no cpu */
> -	if (!dn)
> -		return -1;
> -	cpu = of_cpu_node_to_id(dn);
> +	cpu = of_cpu_phandle_to_id(node, &dn, 0);
>  	of_node_put(dn);

With change suggested on patch 1 this becomes

static int of_cti_get_cpu_at_node(const struct device_node *node)
{
	int cpu = of_cpu_phandle_to_id(node, NULL, 0);

	return (cpu < 0) ? -1 : cpu;
}

> -
> -	/* No Affinity  if no cpu nodes are found */
> -	return (cpu < 0) ? -1 : cpu;
> +	return cpu;

This an result in -ENODEV hence juggle above.  No idea
why the caller will care but I guess it does or this code
would not be here!

>  }
>  
>  #else