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Message-ID: <abc402b1-1253-fe94-94c4-afb1dfb9aebd@gmail.com>
Date: Thu, 13 Oct 2022 04:19:03 +0900
From: Chanwoo Choi <cwchoi00@...il.com>
To: Kant Fan <kant@...winnertech.com>, myungjoo.ham@...sung.com,
kyungmin.park@...sung.com, cw00.choi@...sung.com
Cc: linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] devfreq: governor: Add a private governor_data for
governors in devfreq
On 22. 10. 13. 04:00, Chanwoo Choi wrote:
> Hi,
>
> I'm sorry for late reply. It looks good to me.
> Instead, this patch should contain the 'Fixes' information
> with the following commit because the changed code was merged
> on the patch[1]. Also, need to send it to stable mailing list.
>
> [1] ce26c5bb9569d8b826f01b8620fc16d8da6821e9
> PM / devfreq: Add basic governors
>
> Lastly, I think that need to change the patch title as following:
> - PM / devfreq: governor: Add a private governor_data for governor
>
>
> On 22. 10. 10. 16:22, Kant Fan wrote:
>> The member void *data in the structure devfreq can be overwrite
>> by governor_userspace. For example:
>> 1. The device driver assigned the devfreq governor to simple_ondemand
>> by the function devfreq_add_device() and init the devfreq member
>> void *data to a pointer of a static structure devfreq_simple_ondemand_data
>> by the function devfreq_add_device().
>> 2. The user changed the devfreq governor to userspace by the command
>> "echo userspace > /sys/class/devfreq/.../governor".
>> 3. The governor userspace alloced a dynamic memory for the struct
>> userspace_data and assigend the member void *data of devfreq to
>> this memory by the function userspace_init().
>> 4. The user changed the devfreq governor back to simple_ondemand
>> by the command "echo simple_ondemand > /sys/class/devfreq/.../governor".
>> 5. The governor userspace exited and assigned the member void *data
>> in the structure devfreq to NULL by the function userspace_exit().
>> 6. The governor simple_ondemand fetched the static information of
>> devfreq_simple_ondemand_data in the function
>> devfreq_simple_ondemand_func() but the member void *data of devfreq was
>> assigned to NULL by the function userspace_exit().
>> 7. The information of upthreshold and downdifferential is lost
>> and the governor simple_ondemand can't work correctly.
>>
>> The member void *data in the structure devfreq is designed for
>> a static pointer used in a governor and inited by the function
>> devfreq_add_device(). This patch add an element named governor_data
>> in the devfreq structure which can be used by a governor(E.g userspace)
>> who want to assign a private data to do some private things.
>>
>> Acked-by: MyungJoo Ham <myungjoo.ham@...sung.com>
>>
>> Signed-off-by: Kant Fan <kant@...winnertech.com>
>> ---
>> drivers/devfreq/governor_userspace.c | 12 ++++++------
>> include/linux/devfreq.h | 7 ++++---
>> 2 files changed, 10 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/devfreq/governor_userspace.c b/drivers/devfreq/governor_userspace.c
>> index ab9db7adb3ad..d69672ccacc4 100644
>> --- a/drivers/devfreq/governor_userspace.c
>> +++ b/drivers/devfreq/governor_userspace.c
>> @@ -21,7 +21,7 @@ struct userspace_data {
>>
>> static int devfreq_userspace_func(struct devfreq *df, unsigned long *freq)
>> {
>> - struct userspace_data *data = df->data;
>> + struct userspace_data *data = df->governor_data;
>>
>> if (data->valid)
>> *freq = data->user_frequency;
>> @@ -40,7 +40,7 @@ static ssize_t set_freq_store(struct device *dev, struct device_attribute *attr,
>> int err = 0;
>>
>> mutex_lock(&devfreq->lock);
>> - data = devfreq->data;
>> + data = devfreq->governor_data;
>>
>> sscanf(buf, "%lu", &wanted);
>> data->user_frequency = wanted;
>> @@ -60,7 +60,7 @@ static ssize_t set_freq_show(struct device *dev,
>> int err = 0;
>>
>> mutex_lock(&devfreq->lock);
>> - data = devfreq->data;
>> + data = devfreq->governor_data;
>>
>> if (data->valid)
>> err = sprintf(buf, "%lu\n", data->user_frequency);
>> @@ -91,7 +91,7 @@ static int userspace_init(struct devfreq *devfreq)
>> goto out;
>> }
>> data->valid = false;
>> - devfreq->data = data;
>> + devfreq->governor_data = data;
>>
>> err = sysfs_create_group(&devfreq->dev.kobj, &dev_attr_group);
>> out:
>> @@ -107,8 +107,8 @@ static void userspace_exit(struct devfreq *devfreq)
>> if (devfreq->dev.kobj.sd)
>> sysfs_remove_group(&devfreq->dev.kobj, &dev_attr_group);
>>
>> - kfree(devfreq->data);
>> - devfreq->data = NULL;
>> + kfree(devfreq->governor_data);
>> + devfreq->governor_data = NULL;
>> }
>>
>> static int devfreq_userspace_handler(struct devfreq *devfreq,
>> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
>> index 34aab4dd336c..d265af3fb0a4 100644
>> --- a/include/linux/devfreq.h
>> +++ b/include/linux/devfreq.h
>> @@ -152,8 +152,8 @@ struct devfreq_stats {
>> * @max_state: count of entry present in the frequency table.
>> * @previous_freq: previously configured frequency value.
>> * @last_status: devfreq user device info, performance statistics
>> - * @data: Private data of the governor. The devfreq framework does not
>> - * touch this.
>> + * @data: devfreq core pass to governors, governor should not change it.
In addition, the devfreq driver pass the 'data' from devfreq driver
to governor by using devfreq_add_device. I think that 'devfreq driver'
is more proper
* @data: devfreq driver pass to governors, governor should not change it.
And then, there are extra changes required.
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 63347a5ae599..0c59b7978391 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -776,8 +776,7 @@ static void remove_sysfs_files(struct devfreq *devfreq,
* @dev: the device to add devfreq feature.
* @profile: device-specific profile to run devfreq.
* @governor_name: name of the policy to choose frequency.
- * @data: private data for the governor. The devfreq framework does not
- * touch this value.
+ * @data: devfreq driver pass to governors, governor should not change it.
*/
struct devfreq *devfreq_add_device(struct device *dev,
struct devfreq_dev_profile *profile,
@@ -1011,8 +1010,7 @@ static void devm_devfreq_dev_release(struct device *dev, void *res)
* @dev: the device to add devfreq feature.
* @profile: device-specific profile to run devfreq.
* @governor_name: name of the policy to choose frequency.
- * @data: private data for the governor. The devfreq framework does not
- * touch this value.
+ * @data: devfreq driver pass to governors, governor should not change it.
*
* This function manages automatically the memory of devfreq device using device
* resource management and simplify the free operation for memory of devfreq
--
Best Regards,
Samsung Electronics
Chanwoo Choi
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