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57d12fc6f7
Previously the driver used pcie_get_minimum_link() to warn when the NIC is in a slot that can't supply as much bandwidth as the NIC could use. pcie_get_minimum_link() can be misleading because it finds the slowest link and the narrowest link (which may be different links) without considering the total bandwidth of each link. For a path with a 16 GT/s x1 link and a 2.5 GT/s x16 link, it returns 2.5 GT/s x1, which corresponds to 250 MB/s of bandwidth, not the true available bandwidth of about 1969 MB/s for a 16 GT/s x1 link. Use pcie_print_link_status() to report PCIe link speed and possible limitations instead of implementing this in the driver itself. This finds the slowest link in the path to the device by computing the total bandwidth of each link and compares that with the capabilities of the device. The dmesg change is: - PCIe link speed is %s, device supports %s - PCIe link width is x%d, device supports x%d + %u.%03u Gb/s available PCIe bandwidth (%s x%d link) or, if the device is capable of better performance than is available in the current slot: - A slot with more lanes and/or higher speed is suggested for optimal performance. + %u.%03u Gb/s available PCIe bandwidth, limited by %s x%d link at %s (capable of %u.%03u Gb/s with %s x%d link) Signed-off-by: Bjorn Helgaas <bhelgaas@google.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 Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
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.