9ed9895370
Currently, there is a problem with taking functional dependencies between devices into account. What I mean by a "functional dependency" is when the driver of device B needs device A to be functional and (generally) its driver to be present in order to work properly. This has certain consequences for power management (suspend/resume and runtime PM ordering) and shutdown ordering of these devices. In general, it also implies that the driver of A needs to be working for B to be probed successfully and it cannot be unbound from the device before the B's driver. Support for representing those functional dependencies between devices is added here to allow the driver core to track them and act on them in certain cases where applicable. The argument for doing that in the driver core is that there are quite a few distinct use cases involving device dependencies, they are relatively hard to get right in a driver (if one wants to address all of them properly) and it only gets worse if multiplied by the number of drivers potentially needing to do it. Morever, at least one case (asynchronous system suspend/resume) cannot be handled in a single driver at all, because it requires the driver of A to wait for B to suspend (during system suspend) and the driver of B to wait for A to resume (during system resume). For this reason, represent dependencies between devices as "links", with the help of struct device_link objects each containing pointers to the "linked" devices, a list node for each of them, status information, flags, and an RCU head for synchronization. Also add two new list heads, representing the lists of links to the devices that depend on the given one (consumers) and to the devices depended on by it (suppliers), and a "driver presence status" field (needed for figuring out initial states of device links) to struct device. The entire data structure consisting of all of the lists of link objects for all devices is protected by a mutex (for link object addition/removal and for list walks during device driver probing and removal) and by SRCU (for list walking in other case that will be introduced by subsequent change sets). If CONFIG_SRCU is not selected, however, an rwsem is used for protecting the entire data structure. In addition, each link object has an internal status field whose value reflects whether or not drivers are bound to the devices pointed to by the link or probing/removal of their drivers is in progress etc. That field is only modified under the device links mutex, but it may be read outside of it in some cases (introduced by subsequent change sets), so modifications of it are annotated with WRITE_ONCE(). New links are added by calling device_link_add() which takes three arguments: pointers to the devices in question and flags. In particular, if DL_FLAG_STATELESS is set in the flags, the link status is not to be taken into account for this link and the driver core will not manage it. In turn, if DL_FLAG_AUTOREMOVE is set in the flags, the driver core will remove the link automatically when the consumer device driver unbinds from it. One of the actions carried out by device_link_add() is to reorder the lists used for device shutdown and system suspend/resume to put the consumer device along with all of its children and all of its consumers (and so on, recursively) to the ends of those lists in order to ensure the right ordering between all of the supplier and consumer devices. For this reason, it is not possible to create a link between two devices if the would-be supplier device already depends on the would-be consumer device as either a direct descendant of it or a consumer of one of its direct descendants or one of its consumers and so on. There are two types of link objects, persistent and non-persistent. The persistent ones stay around until one of the target devices is deleted, while the non-persistent ones are removed automatically when the consumer driver unbinds from its device (ie. they are assumed to be valid only as long as the consumer device has a driver bound to it). Persistent links are created by default and non-persistent links are created when the DL_FLAG_AUTOREMOVE flag is passed to device_link_add(). Both persistent and non-persistent device links can be deleted with an explicit call to device_link_del(). Links created without the DL_FLAG_STATELESS flag set are managed by the driver core using a simple state machine. There are 5 states each link can be in: DORMANT (unused), AVAILABLE (the supplier driver is present and functional), CONSUMER_PROBE (the consumer driver is probing), ACTIVE (both supplier and consumer drivers are present and functional), and SUPPLIER_UNBIND (the supplier driver is unbinding). The driver core updates the link state automatically depending on what happens to the linked devices and for each link state specific actions are taken in addition to that. For example, if the supplier driver unbinds from its device, the driver core will also unbind the drivers of all of its consumers automatically under the assumption that they cannot function properly without the supplier. Analogously, the driver core will only allow the consumer driver to bind to its device if the supplier driver is present and functional (ie. the link is in the AVAILABLE state). If that's not the case, it will rely on the existing deferred probing mechanism to wait for the supplier driver to become available. Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
167 lines
4.4 KiB
C
167 lines
4.4 KiB
C
#include <linux/pm_qos.h>
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static inline void device_pm_init_common(struct device *dev)
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{
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if (!dev->power.early_init) {
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spin_lock_init(&dev->power.lock);
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dev->power.qos = NULL;
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dev->power.early_init = true;
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}
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}
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#ifdef CONFIG_PM
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static inline void pm_runtime_early_init(struct device *dev)
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{
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dev->power.disable_depth = 1;
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device_pm_init_common(dev);
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}
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extern void pm_runtime_init(struct device *dev);
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extern void pm_runtime_reinit(struct device *dev);
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extern void pm_runtime_remove(struct device *dev);
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struct wake_irq {
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struct device *dev;
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int irq;
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bool dedicated_irq:1;
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};
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extern void dev_pm_arm_wake_irq(struct wake_irq *wirq);
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extern void dev_pm_disarm_wake_irq(struct wake_irq *wirq);
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#ifdef CONFIG_PM_SLEEP
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extern int device_wakeup_attach_irq(struct device *dev,
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struct wake_irq *wakeirq);
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extern void device_wakeup_detach_irq(struct device *dev);
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extern void device_wakeup_arm_wake_irqs(void);
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extern void device_wakeup_disarm_wake_irqs(void);
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#else
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static inline int
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device_wakeup_attach_irq(struct device *dev,
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struct wake_irq *wakeirq)
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{
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return 0;
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}
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static inline void device_wakeup_detach_irq(struct device *dev)
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{
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}
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static inline void device_wakeup_arm_wake_irqs(void)
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{
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}
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static inline void device_wakeup_disarm_wake_irqs(void)
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{
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}
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#endif /* CONFIG_PM_SLEEP */
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/*
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* sysfs.c
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*/
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extern int dpm_sysfs_add(struct device *dev);
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extern void dpm_sysfs_remove(struct device *dev);
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extern void rpm_sysfs_remove(struct device *dev);
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extern int wakeup_sysfs_add(struct device *dev);
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extern void wakeup_sysfs_remove(struct device *dev);
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extern int pm_qos_sysfs_add_resume_latency(struct device *dev);
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extern void pm_qos_sysfs_remove_resume_latency(struct device *dev);
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extern int pm_qos_sysfs_add_flags(struct device *dev);
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extern void pm_qos_sysfs_remove_flags(struct device *dev);
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extern int pm_qos_sysfs_add_latency_tolerance(struct device *dev);
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extern void pm_qos_sysfs_remove_latency_tolerance(struct device *dev);
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#else /* CONFIG_PM */
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static inline void pm_runtime_early_init(struct device *dev)
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{
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device_pm_init_common(dev);
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}
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static inline void pm_runtime_init(struct device *dev) {}
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static inline void pm_runtime_reinit(struct device *dev) {}
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static inline void pm_runtime_remove(struct device *dev) {}
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static inline int dpm_sysfs_add(struct device *dev) { return 0; }
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static inline void dpm_sysfs_remove(struct device *dev) {}
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static inline void rpm_sysfs_remove(struct device *dev) {}
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static inline int wakeup_sysfs_add(struct device *dev) { return 0; }
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static inline void wakeup_sysfs_remove(struct device *dev) {}
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static inline int pm_qos_sysfs_add(struct device *dev) { return 0; }
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static inline void pm_qos_sysfs_remove(struct device *dev) {}
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static inline void dev_pm_arm_wake_irq(struct wake_irq *wirq)
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{
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}
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static inline void dev_pm_disarm_wake_irq(struct wake_irq *wirq)
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{
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}
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#endif
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#ifdef CONFIG_PM_SLEEP
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/* kernel/power/main.c */
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extern int pm_async_enabled;
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/* drivers/base/power/main.c */
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extern struct list_head dpm_list; /* The active device list */
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static inline struct device *to_device(struct list_head *entry)
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{
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return container_of(entry, struct device, power.entry);
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}
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extern void device_pm_sleep_init(struct device *dev);
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extern void device_pm_add(struct device *);
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extern void device_pm_remove(struct device *);
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extern void device_pm_move_before(struct device *, struct device *);
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extern void device_pm_move_after(struct device *, struct device *);
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extern void device_pm_move_last(struct device *);
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extern void device_pm_check_callbacks(struct device *dev);
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static inline bool device_pm_initialized(struct device *dev)
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{
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return dev->power.in_dpm_list;
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}
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#else /* !CONFIG_PM_SLEEP */
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static inline void device_pm_sleep_init(struct device *dev) {}
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static inline void device_pm_add(struct device *dev) {}
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static inline void device_pm_remove(struct device *dev)
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{
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pm_runtime_remove(dev);
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}
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static inline void device_pm_move_before(struct device *deva,
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struct device *devb) {}
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static inline void device_pm_move_after(struct device *deva,
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struct device *devb) {}
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static inline void device_pm_move_last(struct device *dev) {}
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static inline void device_pm_check_callbacks(struct device *dev) {}
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static inline bool device_pm_initialized(struct device *dev)
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{
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return device_is_registered(dev);
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}
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#endif /* !CONFIG_PM_SLEEP */
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static inline void device_pm_init(struct device *dev)
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{
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device_pm_init_common(dev);
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device_pm_sleep_init(dev);
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pm_runtime_init(dev);
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}
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