| Message ID | 20201015191003.1413-1-ilina@codeaurora.org |
|---|---|
| Headers | show |
| Series | Better domain idle from device wakeup patterns | expand |
On Thu, Oct 15 2020 at 13:10 -0600, Lina Iyer wrote: >Some devices may have a predictable interrupt pattern while executing >usecases. An example would be the VSYNC interrupt associated with >display devices. A 60 Hz display could cause a interrupt every 16 ms. If >the device were in a PM domain, the domain would need to be powered up >for device to resume and handle the interrupt. > >Entering a domain idle state saves power, only if the residency of the >idle state is met. Without knowing the idle duration of the domain, the >governor would just choose the deepest idle state that matches the QoS >requirements. The domain might be powered off just as the device is >expecting to wake up. If devices could inform runtime PM of their next >event, the parent PM domain's idle duration can be determined. > >So let's add the pm_runtime_set_next_wake() API for the device to notify >runtime PM of the impending wakeup and document it's usage. > >Signed-off-by: Lina Iyer <ilina@codeaurora.org> >--- >Changes in v2: > - Update documentation > - Remove runtime PM enabled check > - Update commit text >--- > Documentation/power/runtime_pm.rst | 23 ++++++++++++++++++++--- > drivers/base/power/runtime.c | 24 ++++++++++++++++++++++++ > include/linux/pm.h | 2 ++ > include/linux/pm_runtime.h | 1 + > 4 files changed, 47 insertions(+), 3 deletions(-) > >diff --git a/Documentation/power/runtime_pm.rst b/Documentation/power/runtime_pm.rst >index 0553008b6279..a1c472e5bb04 100644 >--- a/Documentation/power/runtime_pm.rst >+++ b/Documentation/power/runtime_pm.rst >@@ -515,6 +515,12 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h: > power.use_autosuspend isn't set, otherwise returns the expiration time > in jiffies > >+ `int pm_runtime_set_next_event(struct device *dev, ktime_t next);` >+ - inform runtime PM of the next event on the device. Devices that are >+ sensitive to their domain idle enter/exit latencies may provide this >+ information for use by the PM domain governor. The domain governor would >+ use this information to calculate it's sleep length. >+ > It is safe to execute the following helper functions from interrupt context: > > - pm_request_idle() >@@ -545,6 +551,7 @@ functions may also be used in interrupt context: > - pm_runtime_put_sync() > - pm_runtime_put_sync_suspend() > - pm_runtime_put_sync_autosuspend() >+- pm_runtime_set_next_event() > > 5. Runtime PM Initialization, Device Probing and Removal > ======================================================== >@@ -639,9 +646,19 @@ suspend routine). It may be necessary to resume the device and suspend it again > in order to do so. The same is true if the driver uses different power levels > or other settings for runtime suspend and system sleep. > >-During system resume, the simplest approach is to bring all devices back to full >-power, even if they had been suspended before the system suspend began. There >-are several reasons for this, including: >+When a device enters idle at runtime, it may trigger the runtime PM up the >+hierarchy and if device has a predictable interrupt pattern, we can even do a >+better job at determining the parent's idle state. For example, a display >+device gets a VSYNC interrupt every 16 ms when running at 60 Hz. When it's PM >+domain is powering down and happens to be at the boundary of the VSYNC >+interrupt, it may not be efficient to power off the domain. Knowing the next >+wake up (when available) for devices in the domain we can determine the idle >+duration of the domain. By comparing idle duration with the residencies of the >+domain idle states, we can be efficient in both power and performance. >+ >+During system resume, the simplest approach is to bring all devices back to >+full power, even if they had been suspended before the system suspend began. >+There are several reasons for this, including: > Looks like an unintended change. Will fix it in the next spin. > * The device might need to switch power levels, wake-up settings, etc. > >diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c >index 8143210a5c54..5d2ebacfd35e 100644 >--- a/drivers/base/power/runtime.c >+++ b/drivers/base/power/runtime.c >@@ -122,6 +122,27 @@ u64 pm_runtime_suspended_time(struct device *dev) > } > EXPORT_SYMBOL_GPL(pm_runtime_suspended_time); > >+/** >+ * pm_runtime_set_next_wakeup_event - Notify PM framework of an impending event. >+ * @dev: Device to handle >+ * @next: impending interrupt/wakeup for the device >+ */ >+int pm_runtime_set_next_event(struct device *dev, ktime_t next) >+{ >+ unsigned long flags; >+ int ret = -EINVAL; >+ >+ spin_lock_irqsave(&dev->power.lock, flags); >+ if (ktime_before(ktime_get(), next)) { >+ dev->power.next_event = next; >+ ret = 0; >+ } >+ spin_unlock_irqrestore(&dev->power.lock, flags); >+ >+ return ret; >+} >+EXPORT_SYMBOL_GPL(pm_runtime_set_next_event); >+ > /** > * pm_runtime_deactivate_timer - Deactivate given device's suspend timer. > * @dev: Device to handle. >@@ -1415,6 +1436,9 @@ void pm_runtime_enable(struct device *dev) > "Enabling runtime PM for inactive device (%s) with active children\n", > dev_name(dev)); > >+ /* Reset the next wakeup for the device */ >+ dev->power.next_event = KTIME_MAX; >+ > spin_unlock_irqrestore(&dev->power.lock, flags); > } > EXPORT_SYMBOL_GPL(pm_runtime_enable); >diff --git a/include/linux/pm.h b/include/linux/pm.h >index a30a4b54df52..9051658674a4 100644 >--- a/include/linux/pm.h >+++ b/include/linux/pm.h >@@ -8,6 +8,7 @@ > #ifndef _LINUX_PM_H > #define _LINUX_PM_H > >+#include <linux/ktime.h> > #include <linux/list.h> > #include <linux/workqueue.h> > #include <linux/spinlock.h> >@@ -616,6 +617,7 @@ struct dev_pm_info { > u64 active_time; > u64 suspended_time; > u64 accounting_timestamp; >+ ktime_t next_event; > #endif > struct pm_subsys_data *subsys_data; /* Owned by the subsystem. */ > void (*set_latency_tolerance)(struct device *, s32); >diff --git a/include/linux/pm_runtime.h b/include/linux/pm_runtime.h >index 6245caa18034..af6d35178335 100644 >--- a/include/linux/pm_runtime.h >+++ b/include/linux/pm_runtime.h >@@ -59,6 +59,7 @@ extern void pm_runtime_get_suppliers(struct device *dev); > extern void pm_runtime_put_suppliers(struct device *dev); > extern void pm_runtime_new_link(struct device *dev); > extern void pm_runtime_drop_link(struct device *dev); >+extern int pm_runtime_set_next_event(struct device *dev, ktime_t next); > > /** > * pm_runtime_get_if_in_use - Conditionally bump up runtime PM usage counter. >-- >The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, >a Linux Foundation Collaborative Project >