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authorLinus Torvalds <torvalds@linux-foundation.org>2019-07-16 06:44:49 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2019-07-16 06:44:49 +0300
commitfb4da215ed92f564f7ca090bb81a199b0d6cab8a (patch)
tree38d4e18e1db026bec42c8b58ee40a245db313af3 /Documentation/power/interface.rst
parent2a3c389a0fde49b241430df806a34276568cfb29 (diff)
parent7b4b0f6b34d893be569da81ffad865a9d3a7d014 (diff)
downloadlinux-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 ...
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+===========================================
+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.