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function description get/ set DP configuration: lane_count, link_rate, spread_spectrum valid lane count value: 1, 2, 4 valid link rate value: 06h = 1.62Gbps per lane 0Ah = 2.7Gbps per lane 0Ch = 3.24Gbps per lane 14h = 5.4Gbps per lane 1Eh = 8.1Gbps per lane debugfs is located at /sys/kernel/debug/dri/0/DP-x/link_settings --- to get dp configuration xxd -l 300 phy_settings It will list current, verified, reported, preferred dp configuration. current -- for current video mode verified --- maximum configuration which pass link training reported --- DP rx report caps (DPCD register offset 0, 1 2) preferred --- user force settings --- set (or force) dp configuration echo <lane_count> <link_rate> for example, to force to 2 lane, 2.7GHz, echo 4 0xa > link_settings spread_spectrum could not be changed dynamically. in case invalid lane count, link rate are force, no hw programming will be done. please check link settings after force operation to see if HW get programming. xxd -l 300 link_settings check current and preferred settings. Signed-off-by: Hersen Wu <hersenxs.wu@amd.com> Reviewed-by: Hersen Wu <hersenxs.wu@amd.com> Acked-by: Harry Wentland <harry.wentland@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.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.