diff options
Diffstat (limited to 'Documentation/power')
-rw-r--r-- | Documentation/power/interface.txt | 21 | ||||
-rw-r--r-- | Documentation/power/states.txt | 13 | ||||
-rw-r--r-- | Documentation/power/swsusp.txt | 14 |
3 files changed, 17 insertions, 31 deletions
diff --git a/Documentation/power/interface.txt b/Documentation/power/interface.txt index 74311d7e0f3c..8c5b41bf3f36 100644 --- a/Documentation/power/interface.txt +++ b/Documentation/power/interface.txt | |||
@@ -18,17 +18,10 @@ states. | |||
18 | 18 | ||
19 | 19 | ||
20 | /sys/power/disk controls the operating mode of the suspend-to-disk | 20 | /sys/power/disk controls the operating mode of the suspend-to-disk |
21 | mechanism. Suspend-to-disk can be handled in several ways. The | 21 | mechanism. Suspend-to-disk can be handled in several ways. We have a |
22 | greatest distinction is who writes memory to disk - the firmware or | 22 | few options for putting the system to sleep - using the platform driver |
23 | the kernel. If the firmware does it, we assume that it also handles | 23 | (e.g. ACPI or other pm_ops), powering off the system or rebooting the |
24 | suspending the system. | 24 | system (for testing). |
25 | |||
26 | If the kernel does it, then we have three options for putting the system | ||
27 | to sleep - using the platform driver (e.g. ACPI or other PM | ||
28 | registers), powering off the system or rebooting the system (for | ||
29 | testing). The system will support either 'firmware' or 'platform', and | ||
30 | that is known a priori. But, the user may choose 'shutdown' or | ||
31 | 'reboot' as alternatives. | ||
32 | 25 | ||
33 | Additionally, /sys/power/disk can be used to turn on one of the two testing | 26 | Additionally, /sys/power/disk can be used to turn on one of the two testing |
34 | modes of the suspend-to-disk mechanism: 'testproc' or 'test'. If the | 27 | modes of the suspend-to-disk mechanism: 'testproc' or 'test'. If the |
@@ -44,16 +37,12 @@ is being slow and which device drivers are misbehaving. | |||
44 | Reading from this file will display what the mode is currently set | 37 | Reading from this file will display what the mode is currently set |
45 | to. Writing to this file will accept one of | 38 | to. Writing to this file will accept one of |
46 | 39 | ||
47 | 'firmware' | 40 | 'platform' (only if the platform supports it) |
48 | 'platform' | ||
49 | 'shutdown' | 41 | 'shutdown' |
50 | 'reboot' | 42 | 'reboot' |
51 | 'testproc' | 43 | 'testproc' |
52 | 'test' | 44 | 'test' |
53 | 45 | ||
54 | It will only change to 'firmware' or 'platform' if the system supports | ||
55 | it. | ||
56 | |||
57 | /sys/power/image_size controls the size of the image created by | 46 | /sys/power/image_size controls the size of the image created by |
58 | the suspend-to-disk mechanism. It can be written a string | 47 | the suspend-to-disk mechanism. It can be written a string |
59 | representing a non-negative integer that will be used as an upper | 48 | representing a non-negative integer that will be used as an upper |
diff --git a/Documentation/power/states.txt b/Documentation/power/states.txt index 0931a330d362..34800cc521bf 100644 --- a/Documentation/power/states.txt +++ b/Documentation/power/states.txt | |||
@@ -62,17 +62,18 @@ setup via another operating system for it to use. Despite the | |||
62 | inconvenience, this method requires minimal work by the kernel, since | 62 | inconvenience, this method requires minimal work by the kernel, since |
63 | the firmware will also handle restoring memory contents on resume. | 63 | the firmware will also handle restoring memory contents on resume. |
64 | 64 | ||
65 | If the kernel is responsible for persistently saving state, a mechanism | 65 | For suspend-to-disk, a mechanism called swsusp called 'swsusp' (Swap |
66 | called 'swsusp' (Swap Suspend) is used to write memory contents to | 66 | Suspend) is used to write memory contents to free swap space. |
67 | free swap space. swsusp has some restrictive requirements, but should | 67 | swsusp has some restrictive requirements, but should work in most |
68 | work in most cases. Some, albeit outdated, documentation can be found | 68 | cases. Some, albeit outdated, documentation can be found in |
69 | in Documentation/power/swsusp.txt. | 69 | Documentation/power/swsusp.txt. Alternatively, userspace can do most |
70 | of the actual suspend to disk work, see userland-swsusp.txt. | ||
70 | 71 | ||
71 | Once memory state is written to disk, the system may either enter a | 72 | Once memory state is written to disk, the system may either enter a |
72 | low-power state (like ACPI S4), or it may simply power down. Powering | 73 | low-power state (like ACPI S4), or it may simply power down. Powering |
73 | down offers greater savings, and allows this mechanism to work on any | 74 | down offers greater savings, and allows this mechanism to work on any |
74 | system. However, entering a real low-power state allows the user to | 75 | system. However, entering a real low-power state allows the user to |
75 | trigger wake up events (e.g. pressing a key or opening a laptop lid). | 76 | trigger wake up events (e.g. pressing a key or opening a laptop lid). |
76 | 77 | ||
77 | A transition from Suspend-to-Disk to the On state should take about 30 | 78 | A transition from Suspend-to-Disk to the On state should take about 30 |
78 | seconds, though it's typically a bit more with the current | 79 | seconds, though it's typically a bit more with the current |
diff --git a/Documentation/power/swsusp.txt b/Documentation/power/swsusp.txt index 0761ff6c57ed..c55bd5079b90 100644 --- a/Documentation/power/swsusp.txt +++ b/Documentation/power/swsusp.txt | |||
@@ -156,8 +156,7 @@ instead set the PF_NOFREEZE process flag when creating the thread (and | |||
156 | be very careful). | 156 | be very careful). |
157 | 157 | ||
158 | 158 | ||
159 | Q: What is the difference between "platform", "shutdown" and | 159 | Q: What is the difference between "platform" and "shutdown"? |
160 | "firmware" in /sys/power/disk? | ||
161 | 160 | ||
162 | A: | 161 | A: |
163 | 162 | ||
@@ -166,11 +165,8 @@ shutdown: save state in linux, then tell bios to powerdown | |||
166 | platform: save state in linux, then tell bios to powerdown and blink | 165 | platform: save state in linux, then tell bios to powerdown and blink |
167 | "suspended led" | 166 | "suspended led" |
168 | 167 | ||
169 | firmware: tell bios to save state itself [needs BIOS-specific suspend | 168 | "platform" is actually right thing to do where supported, but |
170 | partition, and has very little to do with swsusp] | 169 | "shutdown" is most reliable (except on ACPI systems). |
171 | |||
172 | "platform" is actually right thing to do, but "shutdown" is most | ||
173 | reliable. | ||
174 | 170 | ||
175 | Q: I do not understand why you have such strong objections to idea of | 171 | Q: I do not understand why you have such strong objections to idea of |
176 | selective suspend. | 172 | selective suspend. |
@@ -388,8 +384,8 @@ while the system is asleep, maintaining the connection, using true sleep | |||
388 | modes like "suspend-to-RAM" or "standby". (Don't write "disk" to the | 384 | modes like "suspend-to-RAM" or "standby". (Don't write "disk" to the |
389 | /sys/power/state file; write "standby" or "mem".) We've not seen any | 385 | /sys/power/state file; write "standby" or "mem".) We've not seen any |
390 | hardware that can use these modes through software suspend, although in | 386 | hardware that can use these modes through software suspend, although in |
391 | theory some systems might support "platform" or "firmware" modes that | 387 | theory some systems might support "platform" modes that won't break the |
392 | won't break the USB connections. | 388 | USB connections. |
393 | 389 | ||
394 | Remember that it's always a bad idea to unplug a disk drive containing a | 390 | Remember that it's always a bad idea to unplug a disk drive containing a |
395 | mounted filesystem. That's true even when your system is asleep! The | 391 | mounted filesystem. That's true even when your system is asleep! The |