diff options
Diffstat (limited to 'kernel/Documentation/power')
| -rw-r--r-- | kernel/Documentation/power/devices.txt | 7 | ||||
| -rw-r--r-- | kernel/Documentation/power/pci.txt | 51 | ||||
| -rw-r--r-- | kernel/Documentation/power/runtime_pm.txt | 10 | ||||
| -rw-r--r-- | kernel/Documentation/power/suspend-and-cpuhotplug.txt | 6 | ||||
| -rw-r--r-- | kernel/Documentation/power/swsusp.txt | 13 |
5 files changed, 65 insertions, 22 deletions
diff --git a/kernel/Documentation/power/devices.txt b/kernel/Documentation/power/devices.txt index d172bce0f..8ba6625fd 100644 --- a/kernel/Documentation/power/devices.txt +++ b/kernel/Documentation/power/devices.txt @@ -341,6 +341,13 @@ the phases are: and is entirely responsible for bringing the device back to the functional state as appropriate. + Note that this direct-complete procedure applies even if the device is + disabled for runtime PM; only the runtime-PM status matters. It follows + that if a device has system-sleep callbacks but does not support runtime + PM, then its prepare callback must never return a positive value. This + is because all devices are initially set to runtime-suspended with + runtime PM disabled. + 2. The suspend methods should quiesce the device to stop it from performing I/O. They also may save the device registers and put it into the appropriate low-power state, depending on the bus type the device is on, diff --git a/kernel/Documentation/power/pci.txt b/kernel/Documentation/power/pci.txt index 62328d76b..b0e911e0e 100644 --- a/kernel/Documentation/power/pci.txt +++ b/kernel/Documentation/power/pci.txt @@ -979,20 +979,45 @@ every time right after the runtime_resume() callback has returned (alternatively, the runtime_suspend() callback will have to check if the device should really be suspended and return -EAGAIN if that is not the case). -The runtime PM of PCI devices is disabled by default. It is also blocked by -pci_pm_init() that runs the pm_runtime_forbid() helper function. If a PCI -driver implements the runtime PM callbacks and intends to use the runtime PM -framework provided by the PM core and the PCI subsystem, it should enable this -feature by executing the pm_runtime_enable() helper function. However, the -driver should not call the pm_runtime_allow() helper function unblocking -the runtime PM of the device. Instead, it should allow user space or some -platform-specific code to do that (user space can do it via sysfs), although -once it has called pm_runtime_enable(), it must be prepared to handle the +The runtime PM of PCI devices is enabled by default by the PCI core. PCI +device drivers do not need to enable it and should not attempt to do so. +However, it is blocked by pci_pm_init() that runs the pm_runtime_forbid() +helper function. In addition to that, the runtime PM usage counter of +each PCI device is incremented by local_pci_probe() before executing the +probe callback provided by the device's driver. + +If a PCI driver implements the runtime PM callbacks and intends to use the +runtime PM framework provided by the PM core and the PCI subsystem, it needs +to decrement the device's runtime PM usage counter in its probe callback +function. If it doesn't do that, the counter will always be different from +zero for the device and it will never be runtime-suspended. The simplest +way to do that is by calling pm_runtime_put_noidle(), but if the driver +wants to schedule an autosuspend right away, for example, it may call +pm_runtime_put_autosuspend() instead for this purpose. Generally, it +just needs to call a function that decrements the devices usage counter +from its probe routine to make runtime PM work for the device. + +It is important to remember that the driver's runtime_suspend() callback +may be executed right after the usage counter has been decremented, because +user space may already have cuased the pm_runtime_allow() helper function +unblocking the runtime PM of the device to run via sysfs, so the driver must +be prepared to cope with that. + +The driver itself should not call pm_runtime_allow(), though. Instead, it +should let user space or some platform-specific code do that (user space can +do it via sysfs as stated above), but it must be prepared to handle the runtime PM of the device correctly as soon as pm_runtime_allow() is called -(which may happen at any time). [It also is possible that user space causes -pm_runtime_allow() to be called via sysfs before the driver is loaded, so in -fact the driver has to be prepared to handle the runtime PM of the device as -soon as it calls pm_runtime_enable().] +(which may happen at any time, even before the driver is loaded). + +When the driver's remove callback runs, it has to balance the decrementation +of the device's runtime PM usage counter at the probe time. For this reason, +if it has decremented the counter in its probe callback, it must run +pm_runtime_get_noresume() in its remove callback. [Since the core carries +out a runtime resume of the device and bumps up the device's usage counter +before running the driver's remove callback, the runtime PM of the device +is effectively disabled for the duration of the remove execution and all +runtime PM helper functions incrementing the device's usage counter are +then effectively equivalent to pm_runtime_get_noresume().] The runtime PM framework works by processing requests to suspend or resume devices, or to check if they are idle (in which cases it is reasonable to diff --git a/kernel/Documentation/power/runtime_pm.txt b/kernel/Documentation/power/runtime_pm.txt index 44fe1d28a..0784bc3a2 100644 --- a/kernel/Documentation/power/runtime_pm.txt +++ b/kernel/Documentation/power/runtime_pm.txt @@ -445,10 +445,6 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h: bool pm_runtime_status_suspended(struct device *dev); - return true if the device's runtime PM status is 'suspended' - bool pm_runtime_suspended_if_enabled(struct device *dev); - - return true if the device's runtime PM status is 'suspended' and its - 'power.disable_depth' field is equal to 1 - void pm_runtime_allow(struct device *dev); - set the power.runtime_auto flag for the device and decrease its usage counter (used by the /sys/devices/.../power/control interface to @@ -556,6 +552,12 @@ helper functions described in Section 4. In that case, pm_runtime_resume() should be used. Of course, for this purpose the device's runtime PM has to be enabled earlier by calling pm_runtime_enable(). +Note, if the device may execute pm_runtime calls during the probe (such as +if it is registers with a subsystem that may call back in) then the +pm_runtime_get_sync() call paired with a pm_runtime_put() call will be +appropriate to ensure that the device is not put back to sleep during the +probe. This can happen with systems such as the network device layer. + It may be desirable to suspend the device once ->probe() has finished. Therefore the driver core uses the asyncronous pm_request_idle() to submit a request to execute the subsystem-level idle callback for the device at that diff --git a/kernel/Documentation/power/suspend-and-cpuhotplug.txt b/kernel/Documentation/power/suspend-and-cpuhotplug.txt index 2850df3bf..2fc909502 100644 --- a/kernel/Documentation/power/suspend-and-cpuhotplug.txt +++ b/kernel/Documentation/power/suspend-and-cpuhotplug.txt @@ -72,7 +72,7 @@ More details follow: | v Disable regular cpu hotplug - by setting cpu_hotplug_disabled=1 + by increasing cpu_hotplug_disabled | v Release cpu_add_remove_lock @@ -89,7 +89,7 @@ Resuming back is likewise, with the counterparts being (in the order of execution during resume): * enable_nonboot_cpus() which involves: | Acquire cpu_add_remove_lock - | Reset cpu_hotplug_disabled to 0, thereby enabling regular cpu hotplug + | Decrease cpu_hotplug_disabled, thereby enabling regular cpu hotplug | Call _cpu_up() [for all those cpus in the frozen_cpus mask, in a loop] | Release cpu_add_remove_lock v @@ -120,7 +120,7 @@ after the entire cycle is complete (i.e., suspend + resume). Acquire cpu_add_remove_lock | v - If cpu_hotplug_disabled is 1 + If cpu_hotplug_disabled > 0 return gracefully | | diff --git a/kernel/Documentation/power/swsusp.txt b/kernel/Documentation/power/swsusp.txt index f732a8321..8cc17ca71 100644 --- a/kernel/Documentation/power/swsusp.txt +++ b/kernel/Documentation/power/swsusp.txt @@ -410,8 +410,17 @@ Documentation/usb/persist.txt. Q: Can I suspend-to-disk using a swap partition under LVM? -A: No. You can suspend successfully, but you'll not be able to -resume. uswsusp should be able to work with LVM. See suspend.sf.net. +A: Yes and No. You can suspend successfully, but the kernel will not be able +to resume on its own. You need an initramfs that can recognize the resume +situation, activate the logical volume containing the swap volume (but not +touch any filesystems!), and eventually call + +echo -n "$major:$minor" > /sys/power/resume + +where $major and $minor are the respective major and minor device numbers of +the swap volume. + +uswsusp works with LVM, too. See http://suspend.sourceforge.net/ Q: I upgraded the kernel from 2.6.15 to 2.6.16. Both kernels were compiled with the similar configuration files. Anyway I found that |