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author | Linus Torvalds <torvalds@linux-foundation.org> | 2019-07-16 06:44:49 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2019-07-16 06:44:49 +0300 |
commit | fb4da215ed92f564f7ca090bb81a199b0d6cab8a (patch) | |
tree | 38d4e18e1db026bec42c8b58ee40a245db313af3 /Documentation/power/interface.rst | |
parent | 2a3c389a0fde49b241430df806a34276568cfb29 (diff) | |
parent | 7b4b0f6b34d893be569da81ffad865a9d3a7d014 (diff) | |
download | linux-fb4da215ed92f564f7ca090bb81a199b0d6cab8a.tar.xz |
Merge tag 'pci-v5.3-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci
Pull PCI updates from Bjorn Helgaas:
"Enumeration changes:
- Evaluate PCI Boot Configuration _DSM to learn if firmware wants us
to preserve its resource assignments (Benjamin Herrenschmidt)
- Simplify resource distribution (Nicholas Johnson)
- Decode 32 GT/s link speed (Gustavo Pimentel)
Virtualization:
- Fix incorrect caching of VF config space size (Alex Williamson)
- Fix VF driver probing sysfs knobs (Alex Williamson)
Peer-to-peer DMA:
- Fix dma_virt_ops check (Logan Gunthorpe)
Altera host bridge driver:
- Allow building as module (Ley Foon Tan)
Armada 8K host bridge driver:
- add PHYs support (Miquel Raynal)
DesignWare host bridge driver:
- Export APIs to support removable loadable module (Vidya Sagar)
- Enable Relaxed Ordering erratum workaround only on Tegra20 &
Tegra30 (Vidya Sagar)
Hyper-V host bridge driver:
- Fix use-after-free in eject (Dexuan Cui)
Mobiveil host bridge driver:
- Clean up and fix many issues, including non-identify mapped
windows, 64-bit windows, multi-MSI, class code, INTx clearing (Hou
Zhiqiang)
Qualcomm host bridge driver:
- Use clk bulk API for 2.4.0 controllers (Bjorn Andersson)
- Add QCS404 support (Bjorn Andersson)
- Assert PERST for at least 100ms (Niklas Cassel)
R-Car host bridge driver:
- Add r8a774a1 DT support (Biju Das)
Tegra host bridge driver:
- Add support for Gen2, opportunistic UpdateFC and ACK (PCIe protocol
details) AER, GPIO-based PERST# (Manikanta Maddireddy)
- Fix many issues, including power-on failure cases, interrupt
masking in suspend, UPHY settings, AFI dynamic clock gating,
pending DLL transactions (Manikanta Maddireddy)
Xilinx host bridge driver:
- Fix NWL Multi-MSI programming (Bharat Kumar Gogada)
Endpoint support:
- Fix 64bit BAR support (Alan Mikhak)
- Fix pcitest build issues (Alan Mikhak, Andy Shevchenko)
Bug fixes:
- Fix NVIDIA GPU multi-function power dependencies (Abhishek Sahu)
- Fix NVIDIA GPU HDA enablement issue (Lukas Wunner)
- Ignore lockdep for sysfs "remove" (Marek Vasut)
Misc:
- Convert docs to reST (Changbin Du, Mauro Carvalho Chehab)"
* tag 'pci-v5.3-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci: (107 commits)
PCI: Enable NVIDIA HDA controllers
tools: PCI: Fix installation when `make tools/pci_install`
PCI: dwc: pci-dra7xx: Fix compilation when !CONFIG_GPIOLIB
PCI: Fix typos and whitespace errors
PCI: mobiveil: Fix INTx interrupt clearing in mobiveil_pcie_isr()
PCI: mobiveil: Fix infinite-loop in the INTx handling function
PCI: mobiveil: Move PCIe PIO enablement out of inbound window routine
PCI: mobiveil: Add upper 32-bit PCI base address setup in inbound window
PCI: mobiveil: Add upper 32-bit CPU base address setup in outbound window
PCI: mobiveil: Mask out hardcoded bits in inbound/outbound windows setup
PCI: mobiveil: Clear the control fields before updating it
PCI: mobiveil: Add configured inbound windows counter
PCI: mobiveil: Fix the valid check for inbound and outbound windows
PCI: mobiveil: Clean-up program_{ib/ob}_windows()
PCI: mobiveil: Remove an unnecessary return value check
PCI: mobiveil: Fix error return values
PCI: mobiveil: Refactor the MEM/IO outbound window initialization
PCI: mobiveil: Make some register updates more readable
PCI: mobiveil: Reformat the code for readability
dt-bindings: PCI: mobiveil: Change gpio_slave and apb_csr to optional
...
Diffstat (limited to 'Documentation/power/interface.rst')
-rw-r--r-- | Documentation/power/interface.rst | 79 |
1 files changed, 79 insertions, 0 deletions
diff --git a/Documentation/power/interface.rst b/Documentation/power/interface.rst new file mode 100644 index 000000000000..8d270ed27228 --- /dev/null +++ b/Documentation/power/interface.rst @@ -0,0 +1,79 @@ +=========================================== +Power Management Interface for System Sleep +=========================================== + +Copyright (c) 2016 Intel Corp., Rafael J. Wysocki <rafael.j.wysocki@intel.com> + +The power management subsystem provides userspace with a unified sysfs interface +for system sleep regardless of the underlying system architecture or platform. +The interface is located in the /sys/power/ directory (assuming that sysfs is +mounted at /sys). + +/sys/power/state is the system sleep state control file. + +Reading from it returns a list of supported sleep states, encoded as: + +- 'freeze' (Suspend-to-Idle) +- 'standby' (Power-On Suspend) +- 'mem' (Suspend-to-RAM) +- 'disk' (Suspend-to-Disk) + +Suspend-to-Idle is always supported. Suspend-to-Disk is always supported +too as long the kernel has been configured to support hibernation at all +(ie. CONFIG_HIBERNATION is set in the kernel configuration file). Support +for Suspend-to-RAM and Power-On Suspend depends on the capabilities of the +platform. + +If one of the strings listed in /sys/power/state is written to it, the system +will attempt to transition into the corresponding sleep state. Refer to +Documentation/admin-guide/pm/sleep-states.rst for a description of each of +those states. + +/sys/power/disk controls the operating mode of hibernation (Suspend-to-Disk). +Specifically, it tells the kernel what to do after creating a hibernation image. + +Reading from it returns a list of supported options encoded as: + +- 'platform' (put the system into sleep using a platform-provided method) +- 'shutdown' (shut the system down) +- 'reboot' (reboot the system) +- 'suspend' (trigger a Suspend-to-RAM transition) +- 'test_resume' (resume-after-hibernation test mode) + +The currently selected option is printed in square brackets. + +The 'platform' option is only available if the platform provides a special +mechanism to put the system to sleep after creating a hibernation image (ACPI +does that, for example). The 'suspend' option is available if Suspend-to-RAM +is supported. Refer to Documentation/power/basic-pm-debugging.rst for the +description of the 'test_resume' option. + +To select an option, write the string representing it to /sys/power/disk. + +/sys/power/image_size controls the size of hibernation images. + +It can be written a string representing a non-negative integer that will be +used as a best-effort upper limit of the image size, in bytes. The hibernation +core will do its best to ensure that the image size will not exceed that number. +However, if that turns out to be impossible to achieve, a hibernation image will +still be created and its size will be as small as possible. In particular, +writing '0' to this file will enforce hibernation images to be as small as +possible. + +Reading from this file returns the current image size limit, which is set to +around 2/5 of available RAM by default. + +/sys/power/pm_trace controls the PM trace mechanism saving the last suspend +or resume event point in the RTC across reboots. + +It helps to debug hard lockups or reboots due to device driver failures that +occur during system suspend or resume (which is more common) more effectively. + +If /sys/power/pm_trace contains '1', the fingerprint of each suspend/resume +event point in turn will be stored in the RTC memory (overwriting the actual +RTC information), so it will survive a system crash if one occurs right after +storing it and it can be used later to identify the driver that caused the crash +to happen (see Documentation/power/s2ram.rst for more information). + +Initially it contains '0' which may be changed to '1' by writing a string +representing a nonzero integer into it. |