On Thu, Aug 18, 2011 at 3:27 AM, MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx> wrote:
> The patch enables to register notifier_block for an OPP-device in order
> to get notified for any changes in the availability of OPPs of the
> device. For example, if a new OPP is inserted or enable/disable status
> of an OPP is changed, the notifier is executed.
>
> This enables the usage of opp_add, opp_enable, and opp_disable to
> directly take effect with any connected entities such as CPUFREQ or
> DEVFREQ.
>
> Signed-off-by: MyungJoo Ham <myungjoo.ham@xxxxxxxxxxx>
> Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
>
> ---
> Added at devfreq patch set v6 replacing devfreq_update calls at OPP.
> ---
> drivers/base/power/opp.c | 28 ++++++++++++++++++++++++++++
> include/linux/opp.h | 12 ++++++++++++
> 2 files changed, 40 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c
> index b23de18..39e16c3 100644
> --- a/drivers/base/power/opp.c
> +++ b/drivers/base/power/opp.c
> @@ -73,6 +73,7 @@ struct opp {
> * RCU usage: nodes are not modified in the list of device_opp,
> * however addition is possible and is secured by dev_opp_list_lock
> * @dev: device pointer
> + * @head: notifier head to notify the OPP availability changes.
> * @opp_list: list of opps
> *
> * This is an internal data structure maintaining the link to opps attached to
> @@ -83,6 +84,8 @@ struct device_opp {
> struct list_head node;
>
> struct device *dev;
> + struct srcu_notifier_head head;
> +
> struct list_head opp_list;
> };
>
> @@ -404,6 +407,7 @@ int opp_add(struct device *dev, unsigned long freq, unsigned long u_volt)
> }
>
> dev_opp->dev = dev;
> + srcu_init_notifier_head(&dev_opp->head);
> INIT_LIST_HEAD(&dev_opp->opp_list);
>
> /* Secure the device list modification */
> @@ -428,6 +432,11 @@ int opp_add(struct device *dev, unsigned long freq, unsigned long u_volt)
> list_add_rcu(&new_opp->node, head);
> mutex_unlock(&dev_opp_list_lock);
>
> + /*
> + * Notify the changes in the availability of the operable
> + * frequency/voltage list.
> + */
> + srcu_notifier_call_chain(&dev_opp->head, OPP_EVENT_ADD, new_opp);
> return 0;
> }
>
> @@ -504,6 +513,11 @@ static int opp_set_availability(struct device *dev, unsigned long freq,
> mutex_unlock(&dev_opp_list_lock);
> synchronize_rcu();
I'm not an RCU expert. Is the above synchronize_rcu call still needed
with the addition of the srcu_notifier_call_chain below? The newly
added src_notifier_call_chain will result in the following call graph:
srcu_notifier_call_chain
-> __srcu_notifier_call_chain
-> srcu_read_lock
-> __srcu_read_lock
-> srcu_barrier
>
> + /* Notify the change of the OPP availability */
> + srcu_notifier_call_chain(&dev_opp->head, availability_req ?
> + OPP_EVENT_ENABLE : OPP_EVENT_DISABLE,
Nitpick: I'm not a fan of conditional statements as func parameters.
> + new_opp);
> +
> /* clean up old opp */
> new_opp = opp;
> goto out;
> @@ -512,6 +526,7 @@ unlock:
> mutex_unlock(&dev_opp_list_lock);
> out:
> kfree(new_opp);
> +
Nitpick: unnecessary whitespace addition.
> return r;
> }
>
> @@ -643,3 +658,16 @@ void opp_free_cpufreq_table(struct device *dev,
> *table = NULL;
> }
> #endif /* CONFIG_CPU_FREQ */
> +
> +/** opp_get_notifier() - find notifier_head of the device with opp
> + * @dev: device pointer used to lookup device OPPs.
> + */
> +struct srcu_notifier_head *opp_get_notifier(struct device *dev)
> +{
> + struct device_opp *dev_opp = find_device_opp(dev);
> +
> + if (IS_ERR(dev_opp))
> + return ERR_PTR(PTR_ERR(dev_opp)); /* matching type */
> +
> + return &dev_opp->head;
> +}
> diff --git a/include/linux/opp.h b/include/linux/opp.h
> index 7020e97..53d4538 100644
> --- a/include/linux/opp.h
> +++ b/include/linux/opp.h
> @@ -16,9 +16,14 @@
>
> #include <linux/err.h>
> #include <linux/cpufreq.h>
> +#include <linux/notifier.h>
>
> struct opp;
>
> +enum opp_event {
> + OPP_EVENT_ADD, OPP_EVENT_ENABLE, OPP_EVENT_DISABLE, OPP_EVENT_MAX
I don't see OPP_EVENT_MAX used anywhere else in the code. What is it's purpose?
Regards,
Mike
> +};
> +
> #if defined(CONFIG_PM_OPP)
>
> unsigned long opp_get_voltage(struct opp *opp);
> @@ -40,6 +45,8 @@ int opp_enable(struct device *dev, unsigned long freq);
>
> int opp_disable(struct device *dev, unsigned long freq);
>
> +struct srcu_notifier_head *opp_get_notifier(struct device *dev);
> +
> #else
> static inline unsigned long opp_get_voltage(struct opp *opp)
> {
> @@ -89,6 +96,11 @@ static inline int opp_disable(struct device *dev, unsigned long freq)
> {
> return 0;
> }
> +
> +struct srcu_notifier_head *opp_get_notifier(struct device *dev)
> +{
> + return ERR_PTR(-EINVAL);
> +}
> #endif /* CONFIG_PM */
>
> #if defined(CONFIG_CPU_FREQ) && defined(CONFIG_PM_OPP)
> --
> 1.7.4.1
>
>
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