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The DP 2.0 errata completely overhauls the 128b/132b link training, with no provisions for backward compatibility with the original DP 2.0 specification. The changes are too intrusive to consider reusing the same code for both 8b/10b and 128b/132b, mainly because the LTTPR channel equalisation is done concurrently instead of serialized. NOTES: * It's a bit unclear when to wait for DP_INTERLANE_ALIGN_DONE and per-lane DP_LANE_SYMBOL_LOCKED. Figure xx4 in the SCR implies the LANEx_CHANNEL_EQ_DONE sequence may end with either 0x77,0x77,0x85 *or* 0x33,0x33,0x84 (for four lane configuration in DPCD 0x202..0x204) i.e. without the above bits set. Text elsewhere seems contradictory or incomplete. * We read entire link status (6 bytes) everywhere instead of individual DPCD addresses. * There are some subtle ambiguities or contradictions in the order of some DPCD access and TPS signal enables/disables. It's also not clear whether these are significant. v4: - Wait for intra-hop clear after link training end (Ville) - Wait instead of single check for intra-hop clear before link train v3: - Use msecs_to_jiffies_timeout() (Ville) - Read status at the beginning of interlane align done loop (Ville) - Try to simplify timeout flag use where possible (Ville) v2: - Always try one last time after timeouts to avoid races (Ville) - Extend timeout to cover the entire LANEx_EQ_DONE sequence (Ville) - Also check for eq interlane align done in LANEx_CDS_DONE Sequence (Ville) - Check for Intra-hop status before link training Cc: Uma Shankar <uma.shankar@intel.com> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> Signed-off-by: Jani Nikula <jani.nikula@intel.com> Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20220208143209.2997337-1-jani.nikula@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.