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Message-ID: <e09da2a0-f4cc-d93e-07a5-3551004fed83@samsung.com>
Date: Mon, 18 Jan 2021 15:49:20 +0900
From: Chanwoo Choi <cw00.choi@...sung.com>
To: Lukasz Luba <lukasz.luba@....com>, linux-kernel@...r.kernel.org,
linux-pm@...r.kernel.org
Cc: myungjoo.ham@...sung.com, kyungmin.park@...sung.com
Subject: Re: [PATCH] PM / devfreq: Add sysfs attributes to simple_ondemand
governor
Hi Lukasz,
I has been developed[1] the sysfs attributes for upthreshold and downdifferential.
But, I has not yet posted it[1]. I'll post my approach with some changes.
[1] https://git.kernel.org/pub/scm/linux/kernel/git/chanwoo/linux.git/commit/?h=devfreq-testing&id=e7c59dfb4afebe0c96de54516e9be23d76d96492
On 1/16/21 2:05 AM, Lukasz Luba wrote:
> The simple_ondemand devfreq governor is used by quite a few devices, like
> GPUs, DSPs, memory controllers, etc. It implements algorithm which tries
> to predict the device frequency based on past statistics. There are two
> tunables for the algorithm: 'upthreshold' and 'downdifferential'. These
> tunables change the behavior of the decision, e.g. how fast to increase
> the frequency or how rapidly limit the frequency. These values might be
> different based on the application which is currently running, e.g.
> different behavior is needed for a game than for web browsing or clean
> desktop. The patch exports these two tunables so they can be adjusted
> based on current need. There is also a check with the allowed ranges
> to make sure the values are correct and safe.
>
> Signed-off-by: Lukasz Luba <lukasz.luba@....com>
> ---
> drivers/devfreq/governor_simpleondemand.c | 135 ++++++++++++++++++++++
> 1 file changed, 135 insertions(+)
>
> diff --git a/drivers/devfreq/governor_simpleondemand.c b/drivers/devfreq/governor_simpleondemand.c
> index d57b82a2b570..4b3c182e0a49 100644
> --- a/drivers/devfreq/governor_simpleondemand.c
> +++ b/drivers/devfreq/governor_simpleondemand.c
> @@ -15,6 +15,7 @@
> /* Default constants for DevFreq-Simple-Ondemand (DFSO) */
> #define DFSO_UPTHRESHOLD (90)
> #define DFSO_DOWNDIFFERENCTIAL (5)
> +#define DFSO_MAX_VALUE (100)
> static int devfreq_simple_ondemand_func(struct devfreq *df,
> unsigned long *freq)
> {
> @@ -84,15 +85,149 @@ static int devfreq_simple_ondemand_func(struct devfreq *df,
> return 0;
> }
>
> +static ssize_t upthreshold_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct devfreq_simple_ondemand_data *data;
> + struct devfreq *df = to_devfreq(dev);
> +
> + if (!df->data)
> + return -EINVAL;
> +
> + data = df->data;
> +
> + return sprintf(buf, "%d\n", data->upthreshold);
> +}
> +
> +static ssize_t upthreshold_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct devfreq_simple_ondemand_data *data;
> + struct devfreq *df = to_devfreq(dev);
> + unsigned int value;
> + int ret;
> +
> + if (!df->data)
> + return -EINVAL;
> +
> + data = df->data;
> +
> + ret = kstrtouint(buf, 10, &value);
> + if (ret < 0)
> + return -EINVAL;
> +
> + mutex_lock(&df->lock);
> +
> + if (value > DFSO_MAX_VALUE || value <= data->downdifferential) {
> + mutex_unlock(&df->lock);
> + return -EINVAL;
> + }
> +
> + data->upthreshold = value;
> + mutex_unlock(&df->lock);
> +
> + return count;
> +}
> +static DEVICE_ATTR_RW(upthreshold);
> +
> +static ssize_t downdifferential_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + struct devfreq_simple_ondemand_data *data;
> + struct devfreq *df = to_devfreq(dev);
> +
> + if (!df->data)
> + return -EINVAL;
> +
> + data = df->data;
> +
> + return sprintf(buf, "%d\n", data->downdifferential);
> +}
> +
> +static ssize_t downdifferential_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t count)
> +{
> + struct devfreq_simple_ondemand_data *data;
> + struct devfreq *df = to_devfreq(dev);
> + unsigned int value;
> + int ret;
> +
> + if (!df->data)
> + return -EINVAL;
> +
> + data = df->data;
> +
> + ret = kstrtouint(buf, 10, &value);
> + if (ret < 0)
> + return -EINVAL;
> +
> + mutex_lock(&df->lock);
> +
> + if (value > DFSO_MAX_VALUE || value >= data->upthreshold) {
> + mutex_unlock(&df->lock);
> + return -EINVAL;
> + }
> +
> + data->downdifferential = value;
> + mutex_unlock(&df->lock);
> +
> + return count;
> +}
> +static DEVICE_ATTR_RW(downdifferential);
> +
> +static void devfreq_simple_ondemand_sysfs_setup(struct devfreq *df)
> +{
> + struct devfreq_simple_ondemand_data *data;
> + int ret;
> +
> + if (!df->data) {
> + /* The memory will be freed automatically */
> + df->data = devm_kzalloc(&df->dev,
> + sizeof(struct devfreq_simple_ondemand_data),
> + GFP_KERNEL);
> + if (!df->data) {
> + dev_warn(&df->dev, "Unable to allocate memory");
> + return;
> + }
> + }
> +
> + data = df->data;
> +
> + /* After new allocation setup default values, since they are used */
> + if (!data->upthreshold)
> + data->upthreshold = DFSO_UPTHRESHOLD;
> +
> + if (!data->downdifferential)
> + data->downdifferential = DFSO_DOWNDIFFERENCTIAL;
> +
> + ret = sysfs_create_file(&df->dev.kobj, &dev_attr_upthreshold.attr);
> + if (ret < 0)
> + dev_warn(&df->dev, "Unable to create 'upthreshold' attr\n");
> +
> + ret = sysfs_create_file(&df->dev.kobj, &dev_attr_downdifferential.attr);
> + if (ret < 0)
> + dev_warn(&df->dev, "Unable to create 'downdifferential' attr\n");
> +}
> +
> +static void devfreq_simple_ondemand_sysfs_remove(struct devfreq *df)
> +{
> + sysfs_remove_file(&df->dev.kobj, &dev_attr_upthreshold.attr);
> + sysfs_remove_file(&df->dev.kobj, &dev_attr_downdifferential.attr);
> +}
> +
> static int devfreq_simple_ondemand_handler(struct devfreq *devfreq,
> unsigned int event, void *data)
> {
> switch (event) {
> case DEVFREQ_GOV_START:
> devfreq_monitor_start(devfreq);
> + devfreq_simple_ondemand_sysfs_setup(devfreq);
> break;
>
> case DEVFREQ_GOV_STOP:
> + devfreq_simple_ondemand_sysfs_remove(devfreq);
> devfreq_monitor_stop(devfreq);
> break;
>
>
--
Best Regards,
Chanwoo Choi
Samsung Electronics
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