On Monday, September 03, 2012, Rajagopal Venkat wrote:
> Devfreq returns governor predicted frequency as current
> frequency via sysfs interface. But device may not support
> all frequencies that governor predicts.
Do you have any examples, even out of the tree?
> Its driver
> responsibility to maintain current frequency at which device
> is operating. Add a callback in device profile to fix this.
Obviously, there are no users of this callback in the tree right now, so it
may not be regarded as a fix. I'd rather say it's a new mechanism for
drivers to use if their current frequencies differ from the governor-selected
ones.
> Also add a new sysfs node to expose governor predicted next
> target frequency.
>
> Signed-off-by: Rajagopal Venkat <rajagopal.ven...@linaro.org>
> ---
> Documentation/ABI/testing/sysfs-class-devfreq | 7 +++++++
> drivers/devfreq/devfreq.c | 14 ++++++++++++++
> include/linux/devfreq.h | 3 +++
> 3 files changed, 24 insertions(+)
>
> diff --git a/Documentation/ABI/testing/sysfs-class-devfreq
> b/Documentation/ABI/testing/sysfs-class-devfreq
> index 23d78b5..9df5205 100644
> --- a/Documentation/ABI/testing/sysfs-class-devfreq
> +++ b/Documentation/ABI/testing/sysfs-class-devfreq
> @@ -21,6 +21,13 @@ Description:
> The /sys/class/devfreq/.../cur_freq shows the current
> frequency of the corresponding devfreq object.
>
> +What: /sys/class/devfreq/.../target_freq
> +Date: September 2012
> +Contact: MyungJoo Ham <myungjoo....@samsung.com>
It's a bit odd to add someone else as a contact for interfaces that you're
introducing. I'd need MyungJoo Ham's ACK for that.
> +Description:
> + The /sys/class/devfreq/.../target_freq shows the next governor
> + predicted target frequency of the corresponding devfreq object.
> +
> What: /sys/class/devfreq/.../central_polling
> Date: September 2011
> Contact: MyungJoo Ham <myungjoo....@samsung.com>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 3a5f126..55e9046 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -400,6 +400,19 @@ static ssize_t show_governor(struct device *dev,
> static ssize_t show_freq(struct device *dev,
> struct device_attribute *attr, char *buf)
> {
> + unsigned long freq;
> + struct devfreq *devfreq = to_devfreq(dev);
> +
> + if (devfreq->profile->get_cur_freq)
> + if (!devfreq->profile->get_cur_freq(devfreq->dev.parent, &freq))
That should be
+ if (devfreq->profile->get_cur_freq
+ && !devfreq->profile->get_cur_freq(devfreq->dev.parent, &freq))
> + return sprintf(buf, "%lu\n", freq);
> +
Moreover, I suppose it should fall back to the current behavior if
.get_cur_freq() is not present.
> + return sprintf(buf, "<unknown>");
> +}
> +
> +static ssize_t show_target_freq(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> return sprintf(buf, "%lu\n", to_devfreq(dev)->previous_freq);
> }
>
> @@ -503,6 +516,7 @@ static ssize_t show_max_freq(struct device *dev, struct
> device_attribute *attr,
> static struct device_attribute devfreq_attrs[] = {
> __ATTR(governor, S_IRUGO, show_governor, NULL),
> __ATTR(cur_freq, S_IRUGO, show_freq, NULL),
> + __ATTR(target_freq, S_IRUGO, show_target_freq, NULL),
> __ATTR(polling_interval, S_IRUGO | S_IWUSR, show_polling_interval,
> store_polling_interval),
> __ATTR(min_freq, S_IRUGO | S_IWUSR, show_min_freq, store_min_freq),
> diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
> index 7c7e179..d12ed41 100644
> --- a/include/linux/devfreq.h
> +++ b/include/linux/devfreq.h
> @@ -66,6 +66,8 @@ struct devfreq_dev_status {
> * explained above with "DEVFREQ_FLAG_*" macros.
> * @get_dev_status The device should provide the current performance
> * status to devfreq, which is used by governors.
> + * @get_cur_freq The device should provide the current frequency
> + * at which it is operating.
> * @exit An optional callback that is called when devfreq
> * is removing the devfreq object due to error or
> * from devfreq_remove_device() call. If the user
> @@ -79,6 +81,7 @@ struct devfreq_dev_profile {
> int (*target)(struct device *dev, unsigned long *freq, u32 flags);
> int (*get_dev_status)(struct device *dev,
> struct devfreq_dev_status *stat);
> + int (*get_cur_freq)(struct device *dev, unsigned long *freq);
> void (*exit)(struct device *dev);
> };
Thanks,
Rafael
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