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PCIe Link Retraining can alter Link Speed. pcie_retrain_link() that performs the Link Training is called from bwctrl and ASPM driver. While bwctrl listens for Link Bandwidth Management Status (LBMS) to pick up changes in Link Speed, there is a race between pcie_reset_lbms() clearing LBMS after the Link Training and pcie_bwnotif_irq() reading the Link Status register. If LBMS is already cleared when the irq handler reads the register, the interrupt handler will return early with IRQ_NONE and won't update the Link Speed. When Link Speed update originates from bwctrl, pcie_bwctrl_change_speed() ensures Link Speed is updated after the retraining. ASPM driver, however, calls pcie_retrain_link() but does not update the Link Speed after retraining which can result in stale Link Speed. Also, it is possible to have ASPM support with CONFIG_PCIEPORTBUS=n in which case bwctrl will not be built in (and thus won't update the Link Speed at all). To ensure Link Speed is not left stale after Link Training, move the call to pcie_update_link_speed() from pcie_bwctrl_change_speed() into pcie_retrain_link(). Suggested-by: Lukas Wunner <lukas@wunner.de> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org> Reviewed-by: Lukas Wunner <lukas@wunner.de> Link: https://lore.kernel.org/linux-pci/aBCjpfyYmlkJ12AZ@wunner.de Link: https://lore.kernel.org/r/20250514132821.15705-1-ilpo.jarvinen@linux.intel.com |
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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 reStructuredText 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.