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[ Upstream commit cdea98bf1faef23166262825ce44648be6ebff42 ] The Asus B1400 with original shipped firmware versions and VMD disabled cannot resume from suspend: the NVMe device becomes unresponsive and inaccessible. This appears to be an untested D3cold transition by the vendor; Intel socwatch shows that Windows leaves the NVMe device and parent bridge in D0 during suspend, even though these firmware versions have StorageD3Enable=1. The NVMe device and parent PCI bridge both share the same "PXP" ACPI power resource, which gets turned off as both devices are put into D3cold during suspend. The _OFF() method calls DL23() which sets a L23E bit at offset 0xe2 into the PCI configuration space for this root port. This is the specific write that the _ON() routine is unable to recover from. This register is not documented in the public chipset datasheet. Disallow D3cold on the PCI bridge to enable successful suspend/resume. Link: https://bugzilla.kernel.org/show_bug.cgi?id=215742 Link: https://lore.kernel.org/r/20240228075316.7404-1-drake@endlessos.org Signed-off-by: Daniel Drake <drake@endlessos.org> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Acked-by: Jian-Hong Pan <jhp@endlessos.org> Acked-by: Rafael J. Wysocki <rafael@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
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.