Messages in this thread Patch in this message | | | Date | Mon, 18 Jan 2021 19:14:32 +0100 | From | Greg KH <> | Subject | Re: [PATCH] PM / devfreq: Add sysfs attributes to simple_ondemand governor |
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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.
thanks,
greg k-h
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