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diff --git a/Documentation/power/pm.txt b/Documentation/power/pm.txt deleted file mode 100644 index be841507e43..00000000000 --- a/Documentation/power/pm.txt +++ /dev/null @@ -1,257 +0,0 @@ - Linux Power Management Support - -This document briefly describes how to use power management with your -Linux system and how to add power management support to Linux drivers. - -APM or ACPI? ------------- -If you have a relatively recent x86 mobile, desktop, or server system, -odds are it supports either Advanced Power Management (APM) or -Advanced Configuration and Power Interface (ACPI). ACPI is the newer -of the two technologies and puts power management in the hands of the -operating system, allowing for more intelligent power management than -is possible with BIOS controlled APM. - -The best way to determine which, if either, your system supports is to -build a kernel with both ACPI and APM enabled (as of 2.3.x ACPI is -enabled by default). If a working ACPI implementation is found, the -ACPI driver will override and disable APM, otherwise the APM driver -will be used. - -No, sorry, you cannot have both ACPI and APM enabled and running at -once. Some people with broken ACPI or broken APM implementations -would like to use both to get a full set of working features, but you -simply cannot mix and match the two. Only one power management -interface can be in control of the machine at once. Think about it.. - -User-space Daemons ------------------- -Both APM and ACPI rely on user-space daemons, apmd and acpid -respectively, to be completely functional. Obtain both of these -daemons from your Linux distribution or from the Internet (see below) -and be sure that they are started sometime in the system boot process. -Go ahead and start both. If ACPI or APM is not available on your -system the associated daemon will exit gracefully. - - apmd: http://worldvisions.ca/~apenwarr/apmd/ - acpid: http://acpid.sf.net/ - -Driver Interface -- OBSOLETE, DO NOT USE! -----------------************************* - -Note: pm_register(), pm_access(), pm_dev_idle() and friends are -obsolete. Please do not use them. Instead you should properly hook -your driver into the driver model, and use its suspend()/resume() -callbacks to do this kind of stuff. - -If you are writing a new driver or maintaining an old driver, it -should include power management support. Without power management -support, a single driver may prevent a system with power management -capabilities from ever being able to suspend (safely). - -Overview: -1) Register each instance of a device with "pm_register" -2) Call "pm_access" before accessing the hardware. - (this will ensure that the hardware is awake and ready) -3) Your "pm_callback" is called before going into a - suspend state (ACPI D1-D3) or after resuming (ACPI D0) - from a suspend. -4) Call "pm_dev_idle" when the device is not being used - (optional but will improve device idle detection) -5) When unloaded, unregister the device with "pm_unregister" - -/* - * Description: Register a device with the power-management subsystem - * - * Parameters: - * type - device type (PCI device, system device, ...) - * id - instance number or unique identifier - * cback - request handler callback (suspend, resume, ...) - * - * Returns: Registered PM device or NULL on error - * - * Examples: - * dev = pm_register(PM_SYS_DEV, PM_SYS_VGA, vga_callback); - * - * struct pci_dev *pci_dev = pci_find_dev(...); - * dev = pm_register(PM_PCI_DEV, PM_PCI_ID(pci_dev), callback); - */ -struct pm_dev *pm_register(pm_dev_t type, unsigned long id, pm_callback cback); - -/* - * Description: Unregister a device with the power management subsystem - * - * Parameters: - * dev - PM device previously returned from pm_register - */ -void pm_unregister(struct pm_dev *dev); - -/* - * Description: Unregister all devices with a matching callback function - * - * Parameters: - * cback - previously registered request callback - * - * Notes: Provided for easier porting from old APM interface - */ -void pm_unregister_all(pm_callback cback); - -/* - * Power management request callback - * - * Parameters: - * dev - PM device previously returned from pm_register - * rqst - request type - * data - data, if any, associated with the request - * - * Returns: 0 if the request is successful - * EINVAL if the request is not supported - * EBUSY if the device is now busy and cannot handle the request - * ENOMEM if the device was unable to handle the request due to memory - * - * Details: The device request callback will be called before the - * device/system enters a suspend state (ACPI D1-D3) or - * or after the device/system resumes from suspend (ACPI D0). - * For PM_SUSPEND, the ACPI D-state being entered is passed - * as the "data" argument to the callback. The device - * driver should save (PM_SUSPEND) or restore (PM_RESUME) - * device context when the request callback is called. - * - * Once a driver returns 0 (success) from a suspend - * request, it should not process any further requests or - * access the device hardware until a call to "pm_access" is made. - */ -typedef int (*pm_callback)(struct pm_dev *dev, pm_request_t rqst, void *data); - -Driver Details --------------- -This is just a quick Q&A as a stopgap until a real driver writers' -power management guide is available. - -Q: When is a device suspended? - -Devices can be suspended based on direct user request (eg. laptop lid -closes), system power policy (eg. sleep after 30 minutes of console -inactivity), or device power policy (eg. power down device after 5 -minutes of inactivity) - -Q: Must a driver honor a suspend request? - -No, a driver can return -EBUSY from a suspend request and this -will stop the system from suspending. When a suspend request -fails, all suspended devices are resumed and the system continues -to run. Suspend can be retried at a later time. - -Q: Can the driver block suspend/resume requests? - -Yes, a driver can delay its return from a suspend or resume -request until the device is ready to handle requests. It -is advantageous to return as quickly as possible from a -request as suspend/resume are done serially. - -Q: What context is a suspend/resume initiated from? - -A suspend or resume is initiated from a kernel thread context. -It is safe to block, allocate memory, initiate requests -or anything else you can do within the kernel. - -Q: Will requests continue to arrive after a suspend? - -Possibly. It is the driver's responsibility to queue(*), -fail, or drop any requests that arrive after returning -success to a suspend request. It is important that the -driver not access its device until after it receives -a resume request as the device's bus may no longer -be active. - -(*) If a driver queues requests for processing after - resume be aware that the device, network, etc. - might be in a different state than at suspend time. - It's probably better to drop requests unless - the driver is a storage device. - -Q: Do I have to manage bus-specific power management registers - -No. It is the responsibility of the bus driver to manage -PCI, USB, etc. power management registers. The bus driver -or the power management subsystem will also enable any -wake-on functionality that the device has. - -Q: So, really, what do I need to do to support suspend/resume? - -You need to save any device context that would -be lost if the device was powered off and then restore -it at resume time. When ACPI is active, there are -three levels of device suspend states; D1, D2, and D3. -(The suspend state is passed as the "data" argument -to the device callback.) With D3, the device is powered -off and loses all context, D1 and D2 are shallower power -states and require less device context to be saved. To -play it safe, just save everything at suspend and restore -everything at resume. - -Q: Where do I store device context for suspend? - -Anywhere in memory, kmalloc a buffer or store it -in the device descriptor. You are guaranteed that the -contents of memory will be restored and accessible -before resume, even when the system suspends to disk. - -Q: What do I need to do for ACPI vs. APM vs. etc? - -Drivers need not be aware of the specific power management -technology that is active. They just need to be aware -of when the overlying power management system requests -that they suspend or resume. - -Q: What about device dependencies? - -When a driver registers a device, the power management -subsystem uses the information provided to build a -tree of device dependencies (eg. USB device X is on -USB controller Y which is on PCI bus Z) When power -management wants to suspend a device, it first sends -a suspend request to its driver, then the bus driver, -and so on up to the system bus. Device resumes -proceed in the opposite direction. - -Q: Who do I contact for additional information about - enabling power management for my specific driver/device? - -ACPI Development mailing list: linux-acpi@vger.kernel.org - -System Interface -- OBSOLETE, DO NOT USE! -----------------************************* -If you are providing new power management support to Linux (ie. -adding support for something like APM or ACPI), you should -communicate with drivers through the existing generic power -management interface. - -/* - * Send a request to all devices - * - * Parameters: - * rqst - request type - * data - data, if any, associated with the request - * - * Returns: 0 if the request is successful - * See "pm_callback" return for errors - * - * Details: Walk list of registered devices and call pm_send - * for each until complete or an error is encountered. - * If an error is encountered for a suspend request, - * return all devices to the state they were in before - * the suspend request. - */ -int pm_send_all(pm_request_t rqst, void *data); - -/* - * Find a matching device - * - * Parameters: - * type - device type (PCI device, system device, or 0 to match all devices) - * from - previous match or NULL to start from the beginning - * - * Returns: Matching device or NULL if none found - */ -struct pm_dev *pm_find(pm_dev_t type, struct pm_dev *from); |