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The BIOS of at least one ASUS-Z170M system with an SKL I have programs the 101b WRPLL PDIV divider value, which is the encoding for PDIV=7 with bit#0 incorrectly set. This happens with the "3840x2160": 30 262750 3840 3888 3920 4000 2160 2163 2168 2191 0x48 0x9 HDMI mode (scaled from a 1024x768 src fb) set by BIOS and the ref_clock=24000, dco_integer=383, dco_fraction=5802, pdiv=7, qdiv=1, kdiv=1 WRPLL parameters (assuming PDIV=7 was the intended setting). This corresponds to 262749 PLL frequency/port clock. Later the driver sets the same mode for which it calculates the same dco_int/dco_frac/div WRPLL parameters (with the correct PDIV=7 encoding). Based on the above, let's assume that PDIV=7 was intended and the HW just ignores bit#0 in the PDIV register field for this setting, treating 100b and 101b encodings the same way. While at it add the MISSING_CASE() for the p0,p2 divider decodings. v2: (Ville) - Add a define for the incorrect divider value. - Emit only a debug message when detecting the incorrect divider value. - Use fallthrough from the incorrect divider value case. - Add the MISSING_CASE()s. v3: Return 0 freq for incorrect divider values. (Ville) Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Signed-off-by: Imre Deak <imre.deak@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20201006013555.1488262-1-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 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.