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The MST link BW reported by branch devices via the ENUM_PATH_RESOURCES message depends on the channel coding and link rate/lane count parameters programmed to DPCD. This is the case at least for some branch devices, while for others the reported BW is independent of the link parameters. In any case the DP standard requires the branch device to adjust the returned value to both account for the different way the BW for FEC is accounted for (included in the returned value for non-UHBR and not included for UHBR rates) and to limit the returned value to the (trained) link BW between the source and first downstream branch device, see DP v2.0/v2.1 Figure 2-94, DP v2.1 5.9.7. Presumedly this is also the reason why the standard requires the DPCD link rate/lane count values being up-to-date before sending the ENUM_PATH_RESOURCES message, see DP v2.1 2.14.9.4. Based on the above reprobe the MST topology after the link is retrained with new link parameters to make sure that the MST link BW tracked in the MST topology state (via each topology port's full_pbn value) is up-to-date. The next patch will make sure that the MST link BW is also kept up-to-date if the link is disabled. Reviewed-by: Suraj Kandpal <suraj.kandpal@intel.com> Signed-off-by: Imre Deak <imre.deak@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20240722165503.2084999-13-imre.deak@intel.com
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.