From 85dc0b8a4019e38ad4fd0c008f89a5c241805ac2 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Tue, 13 Mar 2012 01:01:39 +0100 Subject: PM / QoS: Make it possible to expose PM QoS latency constraints A runtime suspend of a device (e.g. an MMC controller) belonging to a power domain or, in a more complicated scenario, a runtime suspend of another device in the same power domain, may cause power to be removed from the entire domain. In that case, the amount of time necessary to runtime-resume the given device (e.g. the MMC controller) is often substantially greater than the time needed to run its driver's runtime resume callback. That may hurt performance in some situations, because user data may need to wait for the device to become operational, so we should make it possible to prevent that from happening. For this reason, introduce a new sysfs attribute for devices, power/pm_qos_resume_latency_us, allowing user space to specify the upper bound of the time necessary to bring the (runtime-suspended) device up after the resume of it has been requested. However, make that attribute appear only for the devices whose drivers declare support for it by calling the (new) dev_pm_qos_expose_latency_limit() helper function with the appropriate initial value of the attribute. Signed-off-by: Rafael J. Wysocki Reviewed-by: Kevin Hilman Reviewed-by: Mark Brown Acked-by: Linus Walleij --- drivers/base/power/qos.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 61 insertions(+) (limited to 'drivers/base/power/qos.c') diff --git a/drivers/base/power/qos.c b/drivers/base/power/qos.c index c5d358837461..71855570922d 100644 --- a/drivers/base/power/qos.c +++ b/drivers/base/power/qos.c @@ -41,6 +41,7 @@ #include #include +#include "power.h" static DEFINE_MUTEX(dev_pm_qos_mtx); @@ -166,6 +167,12 @@ void dev_pm_qos_constraints_destroy(struct device *dev) struct dev_pm_qos_request *req, *tmp; struct pm_qos_constraints *c; + /* + * If the device's PM QoS resume latency limit has been exposed to user + * space, it has to be hidden at this point. + */ + dev_pm_qos_hide_latency_limit(dev); + mutex_lock(&dev_pm_qos_mtx); dev->power.power_state = PMSG_INVALID; @@ -445,3 +452,57 @@ int dev_pm_qos_add_ancestor_request(struct device *dev, return error; } EXPORT_SYMBOL_GPL(dev_pm_qos_add_ancestor_request); + +#ifdef CONFIG_PM_RUNTIME +static void __dev_pm_qos_drop_user_request(struct device *dev) +{ + dev_pm_qos_remove_request(dev->power.pq_req); + dev->power.pq_req = 0; +} + +/** + * dev_pm_qos_expose_latency_limit - Expose PM QoS latency limit to user space. + * @dev: Device whose PM QoS latency limit is to be exposed to user space. + * @value: Initial value of the latency limit. + */ +int dev_pm_qos_expose_latency_limit(struct device *dev, s32 value) +{ + struct dev_pm_qos_request *req; + int ret; + + if (!device_is_registered(dev) || value < 0) + return -EINVAL; + + if (dev->power.pq_req) + return -EEXIST; + + req = kzalloc(sizeof(*req), GFP_KERNEL); + if (!req) + return -ENOMEM; + + ret = dev_pm_qos_add_request(dev, req, value); + if (ret < 0) + return ret; + + dev->power.pq_req = req; + ret = pm_qos_sysfs_add(dev); + if (ret) + __dev_pm_qos_drop_user_request(dev); + + return ret; +} +EXPORT_SYMBOL_GPL(dev_pm_qos_expose_latency_limit); + +/** + * dev_pm_qos_hide_latency_limit - Hide PM QoS latency limit from user space. + * @dev: Device whose PM QoS latency limit is to be hidden from user space. + */ +void dev_pm_qos_hide_latency_limit(struct device *dev) +{ + if (dev->power.pq_req) { + pm_qos_sysfs_remove(dev); + __dev_pm_qos_drop_user_request(dev); + } +} +EXPORT_SYMBOL_GPL(dev_pm_qos_hide_latency_limit); +#endif /* CONFIG_PM_RUNTIME */ -- cgit v1.2.3