I build a kernel based on v5.12-rc4, and cherry-pick below commit, this issue is fixed.
3f3a9bc1f6df drm/i915/ilk-glk: Fix link training on links with LTTPRs
And I tried to cherry-pick the other two commits. It's still good.
ab03631087f5 drm/i915: Disable LTTPR support when the LTTPR rev < 1.4
7dffbdedb96a drm/i915: Disable LTTPR support when the DPCD rev < 1.4
I build a kernel based on v5.12-rc4, and cherry-pick below commit, this issue is fixed.
3f3a9bc1f6df drm/i915/ilk-glk: Fix link training on links with LTTPRs
And I tried to cherry-pick the other two commits. It's still good.
ab03631087f5 drm/i915: Disable LTTPR support when the LTTPR rev < 1.4
7dffbdedb96a drm/i915: Disable LTTPR support when the DPCD rev < 1.4