linux-kernel - Re: [RFC PATCH 01/14] cpufreq: cpufreq-cpu0: add dt node parsing for 'cooling-zones'

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Message-ID: <20130827092931.GB19893@e106331-lin.cambridge.arm.com>
Date:	Tue, 27 Aug 2013 10:29:32 +0100
From:	Mark Rutland <mark.rutland@....com>
To:	Eduardo Valentin <eduardo.valentin@...com>
Cc:	"swarren@...dotorg.org" <swarren@...dotorg.org>,
	Pawel Moll <Pawel.Moll@....com>,
	"ian.campbell@...rix.com" <ian.campbell@...rix.com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"linux@...ck-us.net" <linux@...ck-us.net>,
	"rui.zhang@...el.com" <rui.zhang@...el.com>,
	"wni@...dia.com" <wni@...dia.com>,
	"durgadoss.r@...el.com" <durgadoss.r@...el.com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	"cpufreq@...r.kernel.org" <cpufreq@...r.kernel.org>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>
Subject: Re: [RFC PATCH 01/14] cpufreq: cpufreq-cpu0: add dt node parsing
 for 'cooling-zones'

On Sat, Aug 24, 2013 at 12:15:42AM +0100, Eduardo Valentin wrote:
> This patch changes the cpufreq-cpu0 driver to consider if
> a cpu needs cooling (with cpufreq). In case the cooling is needed,
> it can be flagged at the cpu0 device tree node, with the list
> of zones property 'cooling-zones'.
> 
> In case this list of zones is present, the driver will
> load a cpufreq cooling device in the system. The cpufreq-cpu0
> driver is not interested in determining how the system should
> be using the cooling device. The driver is responsible
> only of loading the cooling device.
> 
> Describing how the cooling device will be used can be
> accomplished by setting up a thermal zone that references
> and is composed by the cpufreq cooling device.
> 
> Cc: "Rafael J. Wysocki" <rjw@...k.pl>
> Cc: Viresh Kumar <viresh.kumar@...aro.org>
> Cc: Grant Likely <grant.likely@...aro.org>
> Cc: Rob Herring <rob.herring@...xeda.com>
> Cc: cpufreq@...r.kernel.org
> Cc: linux-pm@...r.kernel.org
> Cc: linux-kernel@...r.kernel.org
> Cc: devicetree-discuss@...ts.ozlabs.org
> Signed-off-by: Eduardo Valentin <eduardo.valentin@...com>
> ---
>  Documentation/devicetree/bindings/cpufreq/cpufreq-cpu0.txt |  4 ++++
>  drivers/cpufreq/cpufreq-cpu0.c                             | 12 ++++++++++++
>  2 files changed, 16 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/cpufreq/cpufreq-cpu0.txt b/Documentation/devicetree/bindings/cpufreq/cpufreq-cpu0.txt
> index 051f764..add50f7 100644
> --- a/Documentation/devicetree/bindings/cpufreq/cpufreq-cpu0.txt
> +++ b/Documentation/devicetree/bindings/cpufreq/cpufreq-cpu0.txt
> @@ -15,6 +15,9 @@ Optional properties:
>  - clock-latency: Specify the possible maximum transition latency for clock,
>    in unit of nanoseconds.
>  - voltage-tolerance: Specify the CPU voltage tolerance in percentage.
> +- cooling-zones: A list of thermal zones phandles. The generic cpu
> +  cooling (freq clipping) is loaded by the generic cpufreq-cpu0 driver
> +  in case the device tree node has this list.

Bindings should not describe the behaviour of any kernel (and for that
reason I'm not very keen on the current cpufreq-cpu0 binding document).

Bindings should simply describe the hardware. This addition could
instead be:

 - cooling-zones: a list of thermal zone phandles.

However, as the thermal zone binding doesn't seem to have appeared by
this patch, it should get moved later anyway...

Thanks,
Mark.

>  
>  Examples:
>  
> @@ -33,6 +36,7 @@ cpus {
>  			198000  850000
>  		>;
>  		clock-latency = <61036>; /* two CLK32 periods */
> +		cooling-zones = <&cpu_thermal>;
>  	};
>  
>  	cpu@1 {
> diff --git a/drivers/cpufreq/cpufreq-cpu0.c b/drivers/cpufreq/cpufreq-cpu0.c
> index ad1fde2..ede6487 100644
> --- a/drivers/cpufreq/cpufreq-cpu0.c
> +++ b/drivers/cpufreq/cpufreq-cpu0.c
> @@ -20,6 +20,9 @@
>  #include <linux/platform_device.h>
>  #include <linux/regulator/consumer.h>
>  #include <linux/slab.h>
> +#include <linux/thermal.h>
> +#include <linux/cpu_cooling.h>
> +#include <linux/cpumask.h>
>  
>  static unsigned int transition_latency;
>  static unsigned int voltage_tolerance; /* in percentage */
> @@ -28,6 +31,7 @@ static struct device *cpu_dev;
>  static struct clk *cpu_clk;
>  static struct regulator *cpu_reg;
>  static struct cpufreq_frequency_table *freq_table;
> +static struct thermal_cooling_device *cdev;
>  
>  static int cpu0_verify_speed(struct cpufreq_policy *policy)
>  {
> @@ -268,6 +272,13 @@ static int cpu0_cpufreq_probe(struct platform_device *pdev)
>  		goto out_free_table;
>  	}
>  
> +	/*
> +	 * For now, just loading the cooling device;
> +	 * thermal DT code takes care of matching them.
> +	 */
> +	if (of_find_property(np, "cooling-zones", NULL))
> +		cdev = cpufreq_cooling_register(cpu_present_mask);
> +
>  	of_node_put(np);
>  	of_node_put(parent);
>  	return 0;
> @@ -283,6 +294,7 @@ out_put_parent:
>  
>  static int cpu0_cpufreq_remove(struct platform_device *pdev)
>  {
> +	cpufreq_cooling_unregister(cdev);
>  	cpufreq_unregister_driver(&cpu0_cpufreq_driver);
>  	opp_free_cpufreq_table(cpu_dev, &freq_table);
>  
> -- 
> 1.8.2.1.342.gfa7285d
> 
> 
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