Jian-Hong Pan c37cc784af PCI: vmd: Set devices to D0 before enabling PM L1 Substates
[ Upstream commit d660410631 ]

The remapped PCIe Root Port and the child device have PM L1 Substates
capability, but they are disabled originally.

Here is a failed example on ASUS B1400CEAE:

  Capabilities: [900 v1] L1 PM Substates
        L1SubCap: PCI-PM_L1.2+ PCI-PM_L1.1- ASPM_L1.2+ ASPM_L1.1- L1_PM_Substates+
                  PortCommonModeRestoreTime=32us PortTPowerOnTime=10us
        L1SubCtl1: PCI-PM_L1.2- PCI-PM_L1.1- ASPM_L1.2+ ASPM_L1.1-
                   T_CommonMode=0us LTR1.2_Threshold=101376ns
        L1SubCtl2: T_PwrOn=50us

Enable PCI-PM L1 PM Substates for devices below VMD while they are in D0
(see PCIe r6.0, sec 5.5.4).

Link: https://lore.kernel.org/r/20241001083438.10070-4-jhp@endlessos.org
Link: https://bugzilla.kernel.org/show_bug.cgi?id=218394
Signed-off-by: Jian-Hong Pan <jhp@endlessos.org>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2024-12-14 20:00:14 +01:00
2024-12-14 19:59:57 +01:00
2024-12-14 20:00:03 +01:00
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2024-12-11 16:13:43 +01:00
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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.
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