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author | Jani Nikula <jani.nikula@intel.com> | 2022-02-08 17:32:09 +0300 |
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committer | Jani Nikula <jani.nikula@intel.com> | 2022-02-11 12:35:37 +0300 |
commit | a421d8a99216d46926609611cdcf260fdf900645 (patch) | |
tree | 2c374da01fc317e353faa0593b70cfdb47be7f3e /drivers/hwmon | |
parent | 92e438619d1603995ecb9f1fb2c322cc304b759d (diff) | |
download | linux-a421d8a99216d46926609611cdcf260fdf900645.tar.xz |
drm/i915/dp: rewrite DP 2.0 128b/132b link training based on errata
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
Diffstat (limited to 'drivers/hwmon')
0 files changed, 0 insertions, 0 deletions