On Fri, Jan 15, 2021 at 05:05:30PM +0000, 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 <[email protected]>
> ---
> 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);
sysfs_emit()?
Also, you forgot the Documentation/ABI/ updates for new sysfs files :(
> +}
> +
> +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");
You just raced with userspace and lost :(
Please use the default sysfs groups so that it all works properly.
Huge hint, when calling sysfs_* from a driver, that usually means you
are doing something wrong.
thanks,
greg k-h
