linux-kernel - Re: [PATCH v1 3/7] cpu_cooling: Add generic driver ready callback

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Date:   Thu, 10 Jan 2019 11:44:50 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Amit Kucheria <amit.kucheria@...aro.org>
Cc:     linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        bjorn.andersson@...aro.org, edubezval@...il.com,
        andy.gross@...aro.org, tdas@...eaurora.org, swboyd@...omium.org,
        dianders@...omium.org, mka@...omium.org,
        Amit Daniel Kachhap <amit.kachhap@...il.com>,
        Javi Merino <javi.merino@...nel.org>,
        Zhang Rui <rui.zhang@...el.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        "open list:THERMAL/CPU_COOLING" <linux-pm@...r.kernel.org>
Subject: Re: [PATCH v1 3/7] cpu_cooling: Add generic driver ready callback

On 10-01-19, 05:30, Amit Kucheria wrote:
> All cpufreq drivers do similar things to register as a cooling device.
> Provide a generic call back so we can get rid of duplicated code in the
> drivers.
> 
> Signed-off-by: Amit Kucheria <amit.kucheria@...aro.org>
> Suggested-by: Stephen Boyd <swboyd@...omium.org>
> ---
>  drivers/thermal/cpu_cooling.c | 18 ++++++++++++++++++
>  include/linux/cpu_cooling.h   |  9 +++++++++
>  2 files changed, 27 insertions(+)

We may be doing this differently, but I found some other issues with
the patch.

> diff --git a/drivers/thermal/cpu_cooling.c b/drivers/thermal/cpu_cooling.c
> index dfd23245f778..5154ffc12332 100644
> --- a/drivers/thermal/cpu_cooling.c
> +++ b/drivers/thermal/cpu_cooling.c
> @@ -694,6 +694,7 @@ __cpufreq_cooling_register(struct device_node *np,
>  
>  	cpufreq_cdev->clipped_freq = cpufreq_cdev->freq_table[0].frequency;
>  	cpufreq_cdev->cdev = cdev;
> +	policy->cooldev = cdev;

Why was this required ? The below routine was already doing it...

>  
>  	mutex_lock(&cooling_list_lock);
>  	/* Register the notifier for first cpufreq cooling device */
> @@ -785,6 +786,23 @@ of_cpufreq_cooling_register(struct cpufreq_policy *policy)
>  }
>  EXPORT_SYMBOL_GPL(of_cpufreq_cooling_register);
>  
> +/**
> + * generic_cpufreq_ready - generic driver callback to register a thermal_cooling_device
> + * @policy: cpufreq policy
> + */
> +void generic_cpufreq_ready(struct cpufreq_policy *policy)
> +{
> +	struct thermal_cooling_device **cdev = &policy->cooldev;
> +
> +	*cdev = of_cpufreq_cooling_register(policy);

... here

> +	if (IS_ERR(*cdev)) {

We never get an error here, only NULL.

> +		pr_err("Failed to register cpufreq cooling device for CPU%d: %ld\n",
> +		       policy->cpu, PTR_ERR(cdev));

The of_cpufreq_cooling_register() routine already prints enough error
messages on failures.

> +		cdev = NULL;

This is a meaningless statement, perhaps you wanted to do *cdev = NULL
:)

-- 
viresh