Messages in this thread | | | Subject | Re: [PATCH] PM / devfreq: Add sysfs attributes to simple_ondemand governor | From | Lukasz Luba <> | Date | Mon, 18 Jan 2021 18:26:11 +0000 |
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On 1/18/21 6:14 PM, Greg KH wrote: > On Mon, Jan 18, 2021 at 05:56:06PM +0000, Lukasz Luba wrote: >> >> >> On 1/18/21 5:17 PM, Greg KH wrote: >>> 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 <lukasz.luba@arm.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); >>> >>> sysfs_emit()? >>> >>> Also, you forgot the Documentation/ABI/ updates for new sysfs files :( >> >> True, I will remember next time. >> >>> >>> >>>> +} >>>> + >>>> +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. >> >> I should have used kobject_init_and_add() and the default devfreq >> sysfs group as a parent. > > No, never use "raw" kobjects in the sys/devices/ tree, that is a sure > way to ensure that userspace will never be notified or see your > attributes.
Interesting, I've seen it in the schedutil governor, but might in a different context.
Regards, Lukasz
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