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dff6139015
acpi_pci_bridge_d3(dev) returns "true" if "dev" is a hotplug bridge that
can handle hotplug events while in D3. Previously this meant either:
- "dev" has a _PS0 or _PR0 method (acpi_pci_power_manageable()), or
- The Root Port above "dev" has a _DSD with a "HotPlugSupportInD3"
property with value 1.
This did not consider _PRW, which tells us about wakeup GPEs (ACPI v6.4,
sec 7.3.13). Without a wakeup GPE, from an ACPI perspective the Root Port
has no way of generating wakeup signals, so hotplug events will be lost if
we use D3.
Similarly, it did not consider _S0W, which tells us the deepest D-state
from which a device can wake itself (sec 7.3.20). If _S0W tells us the
device cannot wake from D3, hotplug events will again be lost if we use D3.
Some platforms, e.g., AMD Yellow Carp, supply "HotPlugSupportInD3" without
_PRW or with an _S0W that says the Root Port cannot wake from D3. On those
platforms, we previously put bridges in D3hot, hotplug events were lost,
and hotplugged devices would not be recognized without manually rescanning.
Allow bridges to be put in D3 only if the Root Port can generate wakeup
GPEs (wakeup.flags.valid), it can wake from D3 (_S0W), AND it has the
"HotPlugSupportInD3" property.
Neither Windows 10 nor Windows 11 puts the bridge in D3 when the firmware
is configured this way, and this change aligns the handling of the
situation to be the same.
[bhelgaas: commit log, tidy "HotPlugSupportInD3" check and comment]
Link: https://uefi.org/htmlspecs/ACPI_Spec_6_4_html/07_Power_and_Performance_Mgmt/device-power-management-objects.html?highlight=s0w#s0w-s0-device-wake-state
Link: https://docs.microsoft.com/en-us/windows-hardware/drivers/pci/dsd-for-pcie-root-ports#identifying-pcie-root-ports-supporting-hot-plug-in-d3
Link: https://lore.kernel.org/r/20220401034003.3166-1-mario.limonciello@amd.com
Fixes:
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|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.