linux-kernel - Re: [PATCH V2 7/8] ARM: cpuidle: Register per cpuidle device

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Message-ID: <550AEC3C.5090200@linaro.org>
Date:	Thu, 19 Mar 2015 16:33:16 +0100
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Lina Iyer <lina.iyer@...aro.org>
CC:	rjw@...ysocki.net, lorenzo.pieralisi@....com,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Catalin.Marinas@....com, robherring2@...il.com, arnd@...db.de,
	devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH V2 7/8] ARM: cpuidle: Register per cpuidle device

On 03/19/2015 04:31 PM, Lina Iyer wrote:
> On Wed, Mar 18 2015 at 12:46 -0600, Daniel Lezcano wrote:
>> Some architectures have some cpus which does not support idle states.
>>
>> Let the underlying low level code to return -ENOSYS when it is not
>> possible to set an idle state.
>>
>> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
>> ---
>> drivers/cpuidle/cpuidle-arm.c | 45
>> +++++++++++++++++++++++++++++++++++++++++--
>> 1 file changed, 43 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/cpuidle/cpuidle-arm.c
>> b/drivers/cpuidle/cpuidle-arm.c
>> index 1c94b88..0682ed0 100644
>> --- a/drivers/cpuidle/cpuidle-arm.c
>> +++ b/drivers/cpuidle/cpuidle-arm.c
>> @@ -17,11 +17,14 @@
>> #include <linux/kernel.h>
>> #include <linux/module.h>
>> #include <linux/of.h>
>> +#include <linux/slab.h>
>>
>> #include <asm/cpuidle.h>
>>
>> #include "dt_idle_states.h"
>>
>> +static DEFINE_PER_CPU(struct cpuidle_device, *cpuidle_arm_dev);
>
> Is a per-cpu variable needed? There seems to be no per-cpu access, other
> than at init.

:)

Actually it is the cpuidle framework which is using the per cpu variable.

>> +
>> /*
>>  * arm_enter_idle_state - Programs CPU to enter the specified state
>>  *
>> @@ -94,6 +97,7 @@ static int __init arm_idle_init(void)
>> {
>>     int cpu, ret;
>>     struct cpuidle_driver *drv = &arm_idle_driver;
>> +    struct cpuidle_device *dev;
>>
>>     /*
>>      * Initialize idle states data, starting at index 1.
>> @@ -105,18 +109,55 @@ static int __init arm_idle_init(void)
>>     if (ret <= 0)
>>         return ret ? : -ENODEV;
>>
>> +    ret = cpuidle_register_driver(drv);
>> +    if (ret) {
>> +        pr_err("Failed to register cpuidle driver\n");
>> +        return ret;
>> +    }
>> +
>>     /*
>>      * Call arch CPU operations in order to initialize
>>      * idle states suspend back-end specific data
>>      */
>>     for_each_possible_cpu(cpu) {
>>         ret = arm_cpuidle_init(cpu);
>> +
>> +        /* This cpu does not support any idle states */
>> +        if (ret == -ENOSYS)
>> +            continue;
>> +
>>         if (ret) {
>>             pr_err("CPU %d failed to init idle CPU ops\n", cpu);
>> -            return ret;
>> +            goto out_fail;
>> +        }
>> +
>> +        dev = kzalloc(sizeof(*dev), GFP_KERNEL);
>> +        if (!dev) {
>> +            pr_err("Failed to allocate cpuidle device\n");
>> +            goto out_fail;
>> +        }
>> +
>> +        dev->cpu = cpu;
>> +        per_cpu(cpuidle_arm_dev, cpu) = dev;
>> +
>> +        ret = cpuidle_register_device(dev);
>> +        if (ret) {
>> +            pr_err("Failed to register cpuidle device for CPU %d\n",
>> +                   cpu);
>> +            kfree(dev);
>> +            goto out_fail;
>>         }
>>     }
>> +out:
>> +    return ret;
>>
>> -    return cpuidle_register(drv, NULL);
>> +out_fail:
>> +    for (cpu--; cpu <= 0; cpu--) {
>> +        dev = per_cpu(cpuidle_arm_dev, cpu);
>> +        cpuidle_unregister_device(dev);
>> +        kfree(dev);
>> +    }
>> +    cpuidle_unregister_driver(drv);
>> +    goto out;
>> }
>> device_initcall(arm_idle_init);
>> --
>> 1.9.1
>>


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