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Currently the aardvark driver trains link in PCIe gen2 mode. This may cause some buggy gen1 cards (such as Compex WLE900VX) to be unstable or even not detected. Moreover when ASPM code tries to retrain link second time, these cards may stop responding and link goes down. If gen1 is used this does not happen. Unconditionally forcing gen1 is not a good solution since it may have performance impact on gen2 cards. To overcome this, read 'max-link-speed' property (as defined in PCI device tree bindings) and use this as max gen mode. Then iteratively try link training at this mode or lower until successful. After successful link training choose final controller gen based on Negotiated Link Speed from Link Status register, which should match card speed. Link: https://lore.kernel.org/r/20200430080625.26070-5-pali@kernel.org Tested-by: Tomasz Maciej Nowak <tmn505@gmail.com> Signed-off-by: Pali Rohár <pali@kernel.org> Signed-off-by: Marek Behún <marek.behun@nic.cz> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Reviewed-by: Rob Herring <robh@kernel.org> Acked-by: Thomas Petazzoni <thomas.petazzoni@bootlin.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.
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.