linux-kernel - Re: [PATCH 1/2] cpufreq: Add stop callback to cpufreq

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Date:	Thu, 20 Mar 2014 08:01:48 -0700
From:	Dirk Brandewie <dirk.brandewie@...il.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
CC:	dirk.brandewie@...il.com, linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org, patrick.marlier@...il.com,
	viresh.kumar@...aro.org, srivatsa.bhat@...ux.vnet.ibm.com,
	Dirk Brandewie <dirk.j.brandewie@...el.com>
Subject: Re: [PATCH 1/2] cpufreq: Add stop callback to cpufreq_driver interface

On 03/19/2014 08:28 PM, Rafael J. Wysocki wrote:
> On Wednesday, March 19, 2014 11:31:31 PM Rafael J. Wysocki wrote:
>> On Wednesday, March 19, 2014 08:45:53 AM dirk.brandewie@...il.com wrote:
>>> From: Dirk Brandewie <dirk.j.brandewie@...el.com>
>>>
>>> This callback allows the driver to do clean up before the CPU is
>>> completely down and its state cannot be modified.  This is used
>>> by the intel_pstate driver to reduce the requested P state prior to
>>> the core going away.  This is required because the requested P state
>>> of the offline core is used to select the package P state. This
>>> effectively sets the floor package P state to the requested P state on
>>> the offline core.
>>>
>>> Signed-off-by: Dirk Brandewie <dirk.j.brandewie@...el.com>
>
> To speed up things a bit I changed the name of the new callback to ->stop_cpu
> and made it void.
>
> I also modified patch [2/2] accordingly and queued the both of them up for 3.15.
>
> Please check the bleeding-edge branch.
>
> I wouldn't like to need to do anything like that any more in the future, though.

Sorry had appointments yesterday afternoon.

bleeding-edge looks good


>
>>> ---
>>>   Documentation/cpu-freq/cpu-drivers.txt | 8 +++++++-
>>>   drivers/cpufreq/cpufreq.c              | 3 ++-
>>>   include/linux/cpufreq.h                | 1 +
>>>   3 files changed, 10 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/Documentation/cpu-freq/cpu-drivers.txt b/Documentation/cpu-freq/cpu-drivers.txt
>>> index 8b1a445..79def80 100644
>>> --- a/Documentation/cpu-freq/cpu-drivers.txt
>>> +++ b/Documentation/cpu-freq/cpu-drivers.txt
>>> @@ -61,7 +61,13 @@ target_index		-	See below on the differences.
>>>
>>>   And optionally
>>>
>>> -cpufreq_driver.exit -		A pointer to a per-CPU cleanup function.
>>> +cpufreq_driver.exit -		A pointer to a per-CPU cleanup
>>> +		    		function called during CPU_POST_DEAD
>>> +		    		phase of cpu hotplug process.
>>> +
>>> +cpufreq_driver.stop -		A pointer to a per-CPU stop function
>>> +			    	called during CPU_DOWN_PREPARE phase of
>>> +				cpu hotplug process.
>>>
>>>   cpufreq_driver.resume -		A pointer to a per-CPU resume function
>>>   				which is called with interrupts disabled
>>> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
>>> index cf485d9..bb20292 100644
>>> --- a/drivers/cpufreq/cpufreq.c
>>> +++ b/drivers/cpufreq/cpufreq.c
>>> @@ -1336,7 +1336,8 @@ static int __cpufreq_remove_dev_prepare(struct device *dev,
>>>   						__func__, new_cpu, cpu);
>>>   			}
>>>   		}
>>> -	}
>>> +	} else if (cpufreq_driver->stop && cpufreq_driver->setpolicy)
>>> +		cpufreq_driver->stop(policy);
>>
>> Nit: Why is it an int function if the only caller doesn't check the
>> return value?  It should be void.
>>
>>>
>>>   	return 0;
>>>   }
>>> diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
>>> index 4d89e0e..ff8db19 100644
>>> --- a/include/linux/cpufreq.h
>>> +++ b/include/linux/cpufreq.h
>>> @@ -224,6 +224,7 @@ struct cpufreq_driver {
>>>   	int	(*bios_limit)	(int cpu, unsigned int *limit);
>>>
>>>   	int	(*exit)		(struct cpufreq_policy *policy);
>>> +	int	(*stop)		(struct cpufreq_policy *policy);
>>>   	int	(*suspend)	(struct cpufreq_policy *policy);
>>>   	int	(*resume)	(struct cpufreq_policy *policy);
>>>   	struct freq_attr	**attr;
>>>
>>
>>
>

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