path: root/Documentation
diff options
authorRafael J. Wysocki <rjw@sisk.pl>2008-02-23 19:13:25 +0100
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-23 10:40:04 -0800
commit3a2d5b700132f35401f1d9e22fe3c2cab02c2549 (patch)
treead991428c41aee92a5f78b06bf73430af0e6f7ae /Documentation
parent39273b58a409cd6d65c9732bdca00bacd1626672 (diff)
PM: Introduce PM_EVENT_HIBERNATE callback state
During the last step of hibernation in the "platform" mode (with the help of ACPI) we use the suspend code, including the devices' ->suspend() methods, to prepare the system for entering the ACPI S4 system sleep state. But at least for some devices the operations performed by the ->suspend() callback in that case must be different from its operations during regular suspend. For this reason, introduce the new PM event type PM_EVENT_HIBERNATE and pass it to the device drivers' ->suspend() methods during the last phase of hibernation, so that they can distinguish this case and handle it as appropriate. Modify the drivers that handle PM_EVENT_SUSPEND in a special way and need to handle PM_EVENT_HIBERNATE in the same way. These changes are necessary to fix a hibernation regression related to the i915 driver (ref. http://lkml.org/lkml/2008/2/22/488). Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> Acked-by: Pavel Machek <pavel@ucw.cz> Tested-by: Jeff Chua <jeff.chua.linux@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
1 files changed, 8 insertions, 5 deletions
diff --git a/Documentation/power/devices.txt b/Documentation/power/devices.txt
index c53d2636191..461e4f1dbec 100644
--- a/Documentation/power/devices.txt
+++ b/Documentation/power/devices.txt
@@ -310,9 +310,12 @@ used with suspend-to-disk:
PM_EVENT_SUSPEND -- quiesce the driver and put hardware into a low-power
state. When used with system sleep states like "suspend-to-RAM" or
"standby", the upcoming resume() call will often be able to rely on
- state kept in hardware, or issue system wakeup events. When used
- instead with suspend-to-disk, few devices support this capability;
- most are completely powered off.
+ state kept in hardware, or issue system wakeup events.
+ PM_EVENT_HIBERNATE -- Put hardware into a low-power state and enable wakeup
+ events as appropriate. It is only used with hibernation
+ (suspend-to-disk) and few devices are able to wake up the system from
+ this state; most are completely powered off.
PM_EVENT_FREEZE -- quiesce the driver, but don't necessarily change into
any low power mode. A system snapshot is about to be taken, often
@@ -329,8 +332,8 @@ used with suspend-to-disk:
wakeup events nor DMA are allowed.
To enter "standby" (ACPI S1) or "Suspend to RAM" (STR, ACPI S3) states, or
-the similarly named APM states, only PM_EVENT_SUSPEND is used; for "Suspend
-to Disk" (STD, hibernate, ACPI S4), all of those event codes are used.
+the similarly named APM states, only PM_EVENT_SUSPEND is used; the other event
+codes are used for hibernation ("Suspend to Disk", STD, ACPI S4).
There's also PM_EVENT_ON, a value which never appears as a suspend event
but is sometimes used to record the "not suspended" device state.