A recent bspec update added a restriction on when DC states can be enabled:
[Before enabling DC states:]
"""
PG2 can be kept enabled only because PGB requires PG2.
Do not use PG2 functions, such as type-C DDIs.
DMC will dynamically control PG1, PGA, PG2, PGB.
"""
Accordingly prevent DC states if PW2 (aka PG2) is enabled for any other
functionality.
Bpsec: 49193
Fixes: 88c4879384 ("drm/i915: Use separate "DC off" power well for ADL-P and DG2")
Reported-by: Kai Vehmanen <kai.vehmanen@intel.com>
Tested-by: Ambica Pramod <ambica.pramod@intel.com>
Reviewed-by: Uma Shankar <uma.shankar@intel.com>
Signed-off-by: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230606172822.1891897-1-imre.deak@intel.com
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