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A mirror of the official Linux kernel repository just in case
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Per PCIe r5.0, sec 7.5.3.16, Downstream Ports must disable LTR if the link goes down (the Port goes DL_Down status). This is a problem because the Downstream Port's dev->ltr_path is still set, so we think LTR is still enabled, and we enable LTR in the Endpoint. When it sends LTR messages, they cause Unsupported Request errors at the Downstream Port. This happens in the reset path, where we may enable LTR in pci_restore_pcie_state() even though the Downstream Port disabled LTR because the reset caused a link down event. It also happens in the hot-remove and hot-add path, where we may enable LTR in pci_configure_ltr() even though the Downstream Port disabled LTR when the hot-remove took the link down. In these two scenarios, check the upstream bridge and restore its LTR enable if appropriate. The Unsupported Request may be logged by AER as follows: pcieport 0000:00:1d.0: AER: Uncorrected (Non-Fatal) error received: id=00e8 pcieport 0000:00:1d.0: PCIe Bus Error: severity=Uncorrected (Non-Fatal), type=Transaction Layer, id=00e8(Requester ID) pcieport 0000:00:1d.0: device [8086:9d18] error status/mask=00100000/00010000 pcieport 0000:00:1d.0: [20] Unsupported Request (First) In addition, if LTR is not configured correctly, the link cannot enter the L1.2 state, which prevents some machines from entering the S0ix low power state. [bhelgaas: commit log] Link: https://lore.kernel.org/r/20211012075614.54576-1-mingchuang.qiao@mediatek.com Reported-by: Utkarsh H Patel <utkarsh.h.patel@intel.com> Signed-off-by: Mingchuang Qiao <mingchuang.qiao@mediatek.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com> |
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| 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 | ||
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| 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.