From 40a5f8be2f482783de0f1f0fe856660e489734a8 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Fri, 23 Dec 2011 01:23:52 +0100 Subject: [PATCH] PM / QoS: Introduce dev_pm_qos_add_ancestor_request() Some devices, like the I2C controller on SH7372, are not necessary for providing power to their children or forwarding wakeup signals (and generally interrupts) from them. They are only needed by their children when there's some data to transfer, so they may be suspended for the majority of time and resumed on demand, when the children have data to send or receive. For this purpose, however, their power.ignore_children flags have to be set, or the PM core wouldn't allow them to be suspended while their children were active. Unfortunately, in some situations it may take too much time to resume such devices so that they can assist their children in transferring data. For example, if such a device belongs to a PM domain which goes to the "power off" state when that device is suspended, it may take too much time to restore power to the domain in response to the request from one of the device's children. In that case, if the parent's resume time is critical, the domain should stay in the "power on" state, although it still may be desirable to power manage the parent itself (e.g. by manipulating its clock). In general, device PM QoS may be used to address this problem. Namely, if the device's children added PM QoS latency constraints for it, they would be able to prevent it from being put into an overly deep low-power state. However, in some cases the devices needing to be serviced are not the immediate children of a "children-ignoring" device, but its grandchildren or even less direct descendants. In those cases, the entity wanting to add a PM QoS request for a given device's ancestor that ignores its children will have to find it in the first place, so introduce a new helper function that may be used to achieve that. This function, dev_pm_qos_add_ancestor_request(), will search for the first ancestor of the given device whose power.ignore_children flag is set and will add a device PM QoS latency request for that ancestor on behalf of the caller. The request added this way may be removed with the help of dev_pm_qos_remove_request() in the future, like any other device PM QoS latency request. Signed-off-by: Rafael J. Wysocki --- drivers/base/power/qos.c | 25 +++++++++++++++++++++++++ include/linux/pm_qos.h | 5 +++++ 2 files changed, 30 insertions(+) diff --git a/drivers/base/power/qos.c b/drivers/base/power/qos.c index 86de6c5..edf7687 100644 --- a/drivers/base/power/qos.c +++ b/drivers/base/power/qos.c @@ -412,3 +412,28 @@ int dev_pm_qos_remove_global_notifier(struct notifier_block *notifier) return blocking_notifier_chain_unregister(&dev_pm_notifiers, notifier); } EXPORT_SYMBOL_GPL(dev_pm_qos_remove_global_notifier); + +/** + * dev_pm_qos_add_ancestor_request - Add PM QoS request for device's ancestor. + * @dev: Device whose ancestor to add the request for. + * @req: Pointer to the preallocated handle. + * @value: Constraint latency value. + */ +int dev_pm_qos_add_ancestor_request(struct device *dev, + struct dev_pm_qos_request *req, s32 value) +{ + struct device *ancestor = dev->parent; + int error = -ENODEV; + + while (ancestor && !ancestor->power.ignore_children) + ancestor = ancestor->parent; + + if (ancestor) + error = dev_pm_qos_add_request(ancestor, req, value); + + if (error) + req->dev = NULL; + + return error; +} +EXPORT_SYMBOL_GPL(dev_pm_qos_add_ancestor_request); diff --git a/include/linux/pm_qos.h b/include/linux/pm_qos.h index 83b0ea3..fe247b3 100644 --- a/include/linux/pm_qos.h +++ b/include/linux/pm_qos.h @@ -91,6 +91,8 @@ int dev_pm_qos_add_global_notifier(struct notifier_block *notifier); int dev_pm_qos_remove_global_notifier(struct notifier_block *notifier); void dev_pm_qos_constraints_init(struct device *dev); void dev_pm_qos_constraints_destroy(struct device *dev); +int dev_pm_qos_add_ancestor_request(struct device *dev, + struct dev_pm_qos_request *req, s32 value); #else static inline int pm_qos_update_target(struct pm_qos_constraints *c, struct plist_node *node, @@ -150,6 +152,9 @@ static inline void dev_pm_qos_constraints_destroy(struct device *dev) { dev->power.power_state = PMSG_INVALID; } +static inline int dev_pm_qos_add_ancestor_request(struct device *dev, + struct dev_pm_qos_request *req, s32 value) + { return 0; } #endif #endif -- 2.7.4