linux-kernel - Re: [PATCH v1 17/23] coresight: Discard pm_runtime

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Message-ID: <a4f9b322-befd-4727-b4a0-9894685dea76@arm.com>
Date: Tue, 23 Dec 2025 09:53:27 +0000
From: Suzuki K Poulose <suzuki.poulose@....com>
To: "Rafael J. Wysocki" <rafael@...nel.org>,
 Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Ulf Hansson
 <ulf.hansson@...aro.org>, Brian Norris <briannorris@...omium.org>,
 Mike Leach <mike.leach@...aro.org>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Subject: Re: [PATCH v1 17/23] coresight: Discard pm_runtime_put() return
 values

On 22/12/2025 20:25, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Failing a debugfs write due to pm_runtime_put() returning a negative
> value is not particularly useful.
>   
> Returning an error code from pm_runtime_put() merely means that it has
> not queued up a work item to check whether or not the device can be
> suspended and there are many perfectly valid situations in which that
> can happen, like after writing "on" to the devices' runtime PM "control"
> attribute in sysfs for one example.  It also happens when the kernel
> has been configured with CONFIG_PM unset, in which case
> debug_disable_func() in the coresight driver will always return an
> error.
> 
> For this reason, update debug_disable_func() to simply discard the
> return value of pm_runtime_put(), change its return type to void, and
> propagate that change to debug_func_knob_write().
> 
> This will facilitate a planned change of the pm_runtime_put() return
> type to void in the future.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> 
> This patch is part of a series, but it doesn't depend on anything else
> in that series.  The last patch in the series depends on it.
> 
> It can be applied by itself and if you decide to do so, please let me
> know.
> 
> Otherwise, an ACK or equivalent will be appreciated, but also the lack
> of specific criticism will be eventually regarded as consent.


Happy for you to pick it with your series.

Acked-by: Suzuki K Poulose <suzuki.poulose@....com>


> 
> ---
>   drivers/hwtracing/coresight/coresight-cpu-debug.c |   12 ++++--------
>   1 file changed, 4 insertions(+), 8 deletions(-)
> 
> --- a/drivers/hwtracing/coresight/coresight-cpu-debug.c
> +++ b/drivers/hwtracing/coresight/coresight-cpu-debug.c
> @@ -451,10 +451,10 @@ err:
>   	return ret;
>   }
>   
> -static int debug_disable_func(void)
> +static void debug_disable_func(void)
>   {
>   	struct debug_drvdata *drvdata;
> -	int cpu, ret, err = 0;
> +	int cpu;
>   
>   	/*
>   	 * Disable debug power domains, records the error and keep
> @@ -466,12 +466,8 @@ static int debug_disable_func(void)
>   		if (!drvdata)
>   			continue;
>   
> -		ret = pm_runtime_put(drvdata->dev);
> -		if (ret < 0)
> -			err = ret;
> +		pm_runtime_put(drvdata->dev);
>   	}
> -
> -	return err;
>   }
>   
>   static ssize_t debug_func_knob_write(struct file *f,
> @@ -492,7 +488,7 @@ static ssize_t debug_func_knob_write(str
>   	if (val)
>   		ret = debug_enable_func();
>   	else
> -		ret = debug_disable_func();
> +		debug_disable_func();
>   
>   	if (ret) {
>   		pr_err("%s: unable to %s debug function: %d\n",
> 
> 
>