diff options
Diffstat (limited to 'Documentation/power')
| -rw-r--r-- | Documentation/power/interface.txt | 13 | ||||
| -rw-r--r-- | Documentation/power/pci.txt | 4 | ||||
| -rw-r--r-- | Documentation/power/s2ram.txt | 56 | ||||
| -rw-r--r-- | Documentation/power/states.txt | 2 | ||||
| -rw-r--r-- | Documentation/power/swsusp-and-swap-files.txt | 60 | ||||
| -rw-r--r-- | Documentation/power/swsusp.txt | 20 | ||||
| -rw-r--r-- | Documentation/power/userland-swsusp.txt | 64 |
7 files changed, 189 insertions, 30 deletions
diff --git a/Documentation/power/interface.txt b/Documentation/power/interface.txt index a66bec2..74311d7 100644 --- a/Documentation/power/interface.txt +++ b/Documentation/power/interface.txt @@ -30,6 +30,17 @@ testing). The system will support either 'firmware' or 'platform', and that is known a priori. But, the user may choose 'shutdown' or 'reboot' as alternatives. +Additionally, /sys/power/disk can be used to turn on one of the two testing +modes of the suspend-to-disk mechanism: 'testproc' or 'test'. If the +suspend-to-disk mechanism is in the 'testproc' mode, writing 'disk' to +/sys/power/state will cause the kernel to disable nonboot CPUs and freeze +tasks, wait for 5 seconds, unfreeze tasks and enable nonboot CPUs. If it is +in the 'test' mode, writing 'disk' to /sys/power/state will cause the kernel +to disable nonboot CPUs and freeze tasks, shrink memory, suspend devices, wait +for 5 seconds, resume devices, unfreeze tasks and enable nonboot CPUs. Then, +we are able to look in the log messages and work out, for example, which code +is being slow and which device drivers are misbehaving. + Reading from this file will display what the mode is currently set to. Writing to this file will accept one of @@ -37,6 +48,8 @@ to. Writing to this file will accept one of 'platform' 'shutdown' 'reboot' + 'testproc' + 'test' It will only change to 'firmware' or 'platform' if the system supports it. diff --git a/Documentation/power/pci.txt b/Documentation/power/pci.txt index 24edf25..c750f9f 100644 --- a/Documentation/power/pci.txt +++ b/Documentation/power/pci.txt @@ -153,7 +153,7 @@ Description: events, which is implicit if it doesn't even support it in the first place). - Note that the PMC Register in the device's PM Capabilties has a bitmask + Note that the PMC Register in the device's PM Capabilities has a bitmask of the states it supports generating PME# from. D3hot is bit 3 and D3cold is bit 4. So, while a value of 4 as the state may not seem semantically correct, it is. @@ -268,7 +268,7 @@ to wake the system up. (However, it is possible that a device may support some non-standard way of generating a wake event on sleep.) Bits 15:11 of the PMC (Power Mgmt Capabilities) Register in a device's -PM Capabilties describe what power states the device supports generating a +PM Capabilities describe what power states the device supports generating a wake event from: +------------------+ diff --git a/Documentation/power/s2ram.txt b/Documentation/power/s2ram.txt new file mode 100644 index 0000000..b05f512 --- /dev/null +++ b/Documentation/power/s2ram.txt @@ -0,0 +1,56 @@ + How to get s2ram working + ~~~~~~~~~~~~~~~~~~~~~~~~ + 2006 Linus Torvalds + 2006 Pavel Machek + +1) Check suspend.sf.net, program s2ram there has long whitelist of + "known ok" machines, along with tricks to use on each one. + +2) If that does not help, try reading tricks.txt and + video.txt. Perhaps problem is as simple as broken module, and + simple module unload can fix it. + +3) You can use Linus' TRACE_RESUME infrastructure, described below. + + Using TRACE_RESUME + ~~~~~~~~~~~~~~~~~~ + +I've been working at making the machines I have able to STR, and almost +always it's a driver that is buggy. Thank God for the suspend/resume +debugging - the thing that Chuck tried to disable. That's often the _only_ +way to debug these things, and it's actually pretty powerful (but +time-consuming - having to insert TRACE_RESUME() markers into the device +driver that doesn't resume and recompile and reboot). + +Anyway, the way to debug this for people who are interested (have a +machine that doesn't boot) is: + + - enable PM_DEBUG, and PM_TRACE + + - use a script like this: + + #!/bin/sh + sync + echo 1 > /sys/power/pm_trace + echo mem > /sys/power/state + + to suspend + + - if it doesn't come back up (which is usually the problem), reboot by + holding the power button down, and look at the dmesg output for things + like + + Magic number: 4:156:725 + hash matches drivers/base/power/resume.c:28 + hash matches device 0000:01:00.0 + + which means that the last trace event was just before trying to resume + device 0000:01:00.0. Then figure out what driver is controlling that + device (lspci and /sys/devices/pci* is your friend), and see if you can + fix it, disable it, or trace into its resume function. + +For example, the above happens to be the VGA device on my EVO, which I +used to run with "radeonfb" (it's an ATI Radeon mobility). It turns out +that "radeonfb" simply cannot resume that device - it tries to set the +PLL's, and it just _hangs_. Using the regular VGA console and letting X +resume it instead works fine. diff --git a/Documentation/power/states.txt b/Documentation/power/states.txt index 3e5e5d3..0931a33 100644 --- a/Documentation/power/states.txt +++ b/Documentation/power/states.txt @@ -62,7 +62,7 @@ setup via another operating system for it to use. Despite the inconvenience, this method requires minimal work by the kernel, since the firmware will also handle restoring memory contents on resume. -If the kernel is responsible for persistantly saving state, a mechanism +If the kernel is responsible for persistently saving state, a mechanism called 'swsusp' (Swap Suspend) is used to write memory contents to free swap space. swsusp has some restrictive requirements, but should work in most cases. Some, albeit outdated, documentation can be found diff --git a/Documentation/power/swsusp-and-swap-files.txt b/Documentation/power/swsusp-and-swap-files.txt new file mode 100644 index 0000000..06f911a --- /dev/null +++ b/Documentation/power/swsusp-and-swap-files.txt @@ -0,0 +1,60 @@ +Using swap files with software suspend (swsusp) + (C) 2006 Rafael J. Wysocki <rjw@sisk.pl> + +The Linux kernel handles swap files almost in the same way as it handles swap +partitions and there are only two differences between these two types of swap +areas: +(1) swap files need not be contiguous, +(2) the header of a swap file is not in the first block of the partition that +holds it. From the swsusp's point of view (1) is not a problem, because it is +already taken care of by the swap-handling code, but (2) has to be taken into +consideration. + +In principle the location of a swap file's header may be determined with the +help of appropriate filesystem driver. Unfortunately, however, it requires the +filesystem holding the swap file to be mounted, and if this filesystem is +journaled, it cannot be mounted during resume from disk. For this reason to +identify a swap file swsusp uses the name of the partition that holds the file +and the offset from the beginning of the partition at which the swap file's +header is located. For convenience, this offset is expressed in <PAGE_SIZE> +units. + +In order to use a swap file with swsusp, you need to: + +1) Create the swap file and make it active, eg. + +# dd if=/dev/zero of=<swap_file_path> bs=1024 count=<swap_file_size_in_k> +# mkswap <swap_file_path> +# swapon <swap_file_path> + +2) Use an application that will bmap the swap file with the help of the +FIBMAP ioctl and determine the location of the file's swap header, as the +offset, in <PAGE_SIZE> units, from the beginning of the partition which +holds the swap file. + +3) Add the following parameters to the kernel command line: + +resume=<swap_file_partition> resume_offset=<swap_file_offset> + +where <swap_file_partition> is the partition on which the swap file is located +and <swap_file_offset> is the offset of the swap header determined by the +application in 2) (of course, this step may be carried out automatically +by the same application that determies the swap file's header offset using the +FIBMAP ioctl) + +OR + +Use a userland suspend application that will set the partition and offset +with the help of the SNAPSHOT_SET_SWAP_AREA ioctl described in +Documentation/power/userland-swsusp.txt (this is the only method to suspend +to a swap file allowing the resume to be initiated from an initrd or initramfs +image). + +Now, swsusp will use the swap file in the same way in which it would use a swap +partition. In particular, the swap file has to be active (ie. be present in +/proc/swaps) so that it can be used for suspending. + +Note that if the swap file used for suspending is deleted and recreated, +the location of its header need not be the same as before. Thus every time +this happens the value of the "resume_offset=" kernel command line parameter +has to be updated. diff --git a/Documentation/power/swsusp.txt b/Documentation/power/swsusp.txt index 9ea2208..0761ff6 100644 --- a/Documentation/power/swsusp.txt +++ b/Documentation/power/swsusp.txt @@ -153,7 +153,7 @@ add: If the thread is needed for writing the image to storage, you should instead set the PF_NOFREEZE process flag when creating the thread (and -be very carefull). +be very careful). Q: What is the difference between "platform", "shutdown" and @@ -297,20 +297,12 @@ system is shut down or suspended. Additionally use the encrypted suspend image to prevent sensitive data from being stolen after resume. -Q: Why can't we suspend to a swap file? +Q: Can I suspend to a swap file? -A: Because accessing swap file needs the filesystem mounted, and -filesystem might do something wrong (like replaying the journal) -during mount. - -There are few ways to get that fixed: - -1) Probably could be solved by modifying every filesystem to support -some kind of "really read-only!" option. Patches welcome. - -2) suspend2 gets around that by storing absolute positions in on-disk -image (and blocksize), with resume parameter pointing directly to -suspend header. +A: Generally, yes, you can. However, it requires you to use the "resume=" and +"resume_offset=" kernel command line parameters, so the resume from a swap file +cannot be initiated from an initrd or initramfs image. See +swsusp-and-swap-files.txt for details. Q: Is there a maximum system RAM size that is supported by swsusp? diff --git a/Documentation/power/userland-swsusp.txt b/Documentation/power/userland-swsusp.txt index 64755e9..000556c 100644 --- a/Documentation/power/userland-swsusp.txt +++ b/Documentation/power/userland-swsusp.txt @@ -9,9 +9,8 @@ done it already. Now, to use the userland interface for software suspend you need special utilities that will read/write the system memory snapshot from/to the kernel. Such utilities are available, for example, from -<http://www.sisk.pl/kernel/utilities/suspend>. You may want to have -a look at them if you are going to develop your own suspend/resume -utilities. +<http://suspend.sourceforge.net>. You may want to have a look at them if you +are going to develop your own suspend/resume utilities. The interface consists of a character device providing the open(), release(), read(), and write() operations as well as several ioctl() @@ -21,9 +20,9 @@ be read from /sys/class/misc/snapshot/dev. The device can be open either for reading or for writing. If open for reading, it is considered to be in the suspend mode. Otherwise it is -assumed to be in the resume mode. The device cannot be open for reading -and writing. It is also impossible to have the device open more than once -at a time. +assumed to be in the resume mode. The device cannot be open for simultaneous +reading and writing. It is also impossible to have the device open more than +once at a time. The ioctl() commands recognized by the device are: @@ -69,9 +68,46 @@ SNAPSHOT_FREE_SWAP_PAGES - free all swap pages allocated with SNAPSHOT_SET_SWAP_FILE - set the resume partition (the last ioctl() argument should specify the device's major and minor numbers in the old two-byte format, as returned by the stat() function in the .st_rdev - member of the stat structure); it is recommended to always use this - call, because the code to set the resume partition could be removed from - future kernels + member of the stat structure) + +SNAPSHOT_SET_SWAP_AREA - set the resume partition and the offset (in <PAGE_SIZE> + units) from the beginning of the partition at which the swap header is + located (the last ioctl() argument should point to a struct + resume_swap_area, as defined in kernel/power/power.h, containing the + resume device specification, as for the SNAPSHOT_SET_SWAP_FILE ioctl(), + and the offset); for swap partitions the offset is always 0, but it is + different to zero for swap files (please see + Documentation/swsusp-and-swap-files.txt for details). + The SNAPSHOT_SET_SWAP_AREA ioctl() is considered as a replacement for + SNAPSHOT_SET_SWAP_FILE which is regarded as obsolete. It is + recommended to always use this call, because the code to set the resume + partition may be removed from future kernels + +SNAPSHOT_S2RAM - suspend to RAM; using this call causes the kernel to + immediately enter the suspend-to-RAM state, so this call must always + be preceded by the SNAPSHOT_FREEZE call and it is also necessary + to use the SNAPSHOT_UNFREEZE call after the system wakes up. This call + is needed to implement the suspend-to-both mechanism in which the + suspend image is first created, as though the system had been suspended + to disk, and then the system is suspended to RAM (this makes it possible + to resume the system from RAM if there's enough battery power or restore + its state on the basis of the saved suspend image otherwise) + +SNAPSHOT_PMOPS - enable the usage of the pmops->prepare, pmops->enter and + pmops->finish methods (the in-kernel swsusp knows these as the "platform + method") which are needed on many machines to (among others) speed up + the resume by letting the BIOS skip some steps or to let the system + recognise the correct state of the hardware after the resume (in + particular on many machines this ensures that unplugged AC + adapters get correctly detected and that kacpid does not run wild after + the resume). The last ioctl() argument can take one of the three + values, defined in kernel/power/power.h: + PMOPS_PREPARE - make the kernel carry out the + pm_ops->prepare(PM_SUSPEND_DISK) operation + PMOPS_ENTER - make the kernel power off the system by calling + pm_ops->enter(PM_SUSPEND_DISK) + PMOPS_FINISH - make the kernel carry out the + pm_ops->finish(PM_SUSPEND_DISK) operation The device's read() operation can be used to transfer the snapshot image from the kernel. It has the following limitations: @@ -91,10 +127,12 @@ unfreeze user space processes frozen by SNAPSHOT_UNFREEZE if they are still frozen when the device is being closed). Currently it is assumed that the userland utilities reading/writing the -snapshot image from/to the kernel will use a swap partition, called the resume -partition, as storage space. However, this is not really required, as they -can use, for example, a special (blank) suspend partition or a file on a partition -that is unmounted before SNAPSHOT_ATOMIC_SNAPSHOT and mounted afterwards. +snapshot image from/to the kernel will use a swap parition, called the resume +partition, or a swap file as storage space (if a swap file is used, the resume +partition is the partition that holds this file). However, this is not really +required, as they can use, for example, a special (blank) suspend partition or +a file on a partition that is unmounted before SNAPSHOT_ATOMIC_SNAPSHOT and +mounted afterwards. These utilities SHOULD NOT make any assumptions regarding the ordering of data within the snapshot image, except for the image header that MAY be |
