[PATCH 2/3][RFC] devfreq: Add suspend and resume apis

On 20 August 2012 15:49, MyungJoo Ham myungjoo.ham@samsung.com wrote:

...

This patch adds suspend and resume apis needed for devices which can idle. Suspend/resume apis are called from driver to suspend/resume devfreq load monitoring of that device.

Signed-off-by: Rajagopal Venkat rajagopal.venkat@linaro.org

1. Some devfreq devices may need their own code to do suspend/resume; e.g.,

setting a specific frequency for suspend (especially with suspend-to-RAM).

Assuming device driver is using devfreq ondemand governor, when driver detects idleness perhaps through runtime-pm, let driver set specific frequency and then suspend its devfreq. Also let driver resume its devfreq when device is back online.

2. Are these new APIs (devfreq_suspend/resume_device()) intended to be

used by runtime_pm and pm(Suspend-to-RAM) callbacks of the parent devices? If so, could you consider use the structure of runtime-pm (I don't have an idea on how to do this for now)? For example, when a device is being suspended, devfreq device's suspend is also called without calling it explicitly at the device driver's suspend callback.

These new apis are not coupled with runtime-pm. Though runtime-pm is good candidate for detecting idleness, drivers can have their own logic. So its at device drivers discretion when to call devfreq_suspend_device() and devfreq_resume_device().

3. As in the patch 1/3, could you consider to integrate class-wide

features in devfreq.c, not in a governor?

Yes, these apis are part of devfreq core. Core sends events to governors for taking specific actions. Again, only governor knows what to do with DEVFREQ_GOV_SUSPEND and DEVFREQ_GOV_RESUME events. For instance ondemand cancels/queues delayed work.

Cheers! MyungJoo

...

---

drivers/devfreq/devfreq.c | 30 ++++++++++++++++++++++++++++++ drivers/devfreq/governor_simpleondemand.c | 15 +++++++++++++++ include/linux/devfreq.h | 16 ++++++++++++++++ 3 files changed, 61 insertions(+)

diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c index 5aa23a8..375b5aa1 100644 --- a/drivers/devfreq/devfreq.c +++ b/drivers/devfreq/devfreq.c @@ -233,6 +233,36 @@ int devfreq_remove_device(struct devfreq *devfreq) } EXPORT_SYMBOL(devfreq_remove_device);

+/**

• • devfreq_suspend_device() - Suspend devfreq of a device.
• • @devfreq the devfreq instance to be suspended
• */

+int devfreq_suspend_device(struct devfreq *devfreq) +{

• if (!devfreq)
  

•         return -EINVAL;
  

• devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_SUSPEND);
  

• return 0;
  

+} +EXPORT_SYMBOL(devfreq_suspend_device);

+/**

• • devfreq_resume_device() - Resume devfreq of a device.
• • @devfreq the devfreq instance to be resumed
• */

+int devfreq_resume_device(struct devfreq *devfreq) +{

• if (!devfreq)
  

•         return -EINVAL;
  

• devfreq->governor->event_handler(devfreq, DEVFREQ_GOV_RESUME);
  

• return 0;
  

+} +EXPORT_SYMBOL(devfreq_resume_device);

static ssize_t show_governor(struct device *dev, struct device_attribute *attr, char *buf) { diff --git a/drivers/devfreq/governor_simpleondemand.c b/drivers/devfreq/governor_simpleondemand.c index 7c70c30..95e4db9 100644 --- a/drivers/devfreq/governor_simpleondemand.c +++ b/drivers/devfreq/governor_simpleondemand.c @@ -221,6 +221,21 @@ static int devfreq_simple_ondemand_func(struct devfreq *df, ondemand_exit(df); break;

• case DEVFREQ_GOV_SUSPEND:
  

•         if (delayed_work_pending(&data->work)) {
  

•                 data->stop_queuing = true;
  

•                 cancel_delayed_work_sync(&data->work);
  

•         }
  

•         break;
  

• case DEVFREQ_GOV_RESUME:
  

•         if (!delayed_work_pending(&data->work)) {
  

•                 data->stop_queuing = false;
  

•                 queue_delayed_work(devfreq_wq, &data->work,
  

•                         msecs_to_jiffies(df->profile->polling_ms));
  

•         }
  

•         break;
  

• case DEVFREQ_GOV_LIMITS:
          if (delayed_work_pending(&data->work)) {
                  mutex_lock(&df->lock);
  

diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h index 600cc2e..7c6517f 100644 --- a/include/linux/devfreq.h +++ b/include/linux/devfreq.h @@ -56,6 +56,8 @@ struct devfreq_dev_status { #define DEVFREQ_GOV_START 0x1 #define DEVFREQ_GOV_STOP 0x2 #define DEVFREQ_GOV_LIMITS 0x3 +#define DEVFREQ_GOV_SUSPEND 0x4 +#define DEVFREQ_GOV_RESUME 0x5

/**

• struct devfreq_dev_profile - Devfreq's user device profile

@@ -155,6 +157,10 @@ extern struct devfreq *devfreq_add_device(struct device *dev, void *data); extern int devfreq_remove_device(struct devfreq *devfreq);

+extern int devfreq_suspend_device(struct devfreq *devfreq);

+extern int devfreq_resume_device(struct devfreq *devfreq);

/* Helper functions for devfreq user device driver with OPP. */ extern struct opp *devfreq_recommended_opp(struct device *dev, unsigned long *freq, u32 flags); @@ -207,6 +213,16 @@ static int devfreq_remove_device(struct devfreq *devfreq) return 0; }

+static int devfreq_suspend_device(struct devfreq *devfreq) +{

• return 0;
  

+}

+extern int devfreq_resume_device(struct devfreq *devfreq) +{

• return 0;
  

+}

static struct opp *devfreq_recommended_opp(struct device *dev, unsigned long *freq, u32 flags) { -- 1.7.11.3

-- Regards, Rajagopal