drm/i915: Disable LTTPR support when the DPCD rev < 1.4

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By the specification the 0xF0000-0xF02FF range is only valid when the
DPCD revision is 1.4 or higher. Disable LTTPR support if this isn't so.

Trying to detect LTTPRs returned corrupted values for the above DPCD
range at least on a Skylake host with an LG 43UD79-B monitor with a DPCD
revision 1.2 connected.

v2: Add the actual version check.
v3: Fix s/DRPX/DPRX/ typo.

Fixes: 7b2a4ab8b0 ("drm/i915: Switch to LTTPR transparent mode link training")
Cc: <stable@vger.kernel.org> # v5.11
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210317190149.4032966-1-imre.deak@intel.com
(cherry picked from commit 264613b406)
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

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Imre Deak 2021-03-17 21:01:49 +02:00 • committed by Rodrigo Vivi

parent 3f3a9bc1f6

commit 7dffbdedb9

3 changed files with 39 additions and 15 deletions

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4

drivers/gpu/drm/i915/display/intel_dp.c

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48

drivers/gpu/drm/i915/display/intel_dp_link_training.c

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2

drivers/gpu/drm/i915/display/intel_dp_link_training.h

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