Two corrections to my original report: 1. I stated that the intel-lpss INT3446:00 probe failure at 2.786s is unrelated to the i915 hang. I should not have said that.. I don't actually know whether the two are connected. The LPSS error happens first in the boot sequence and I can't rule out that it contributes to the i915 failure. Worth looking at both together.
2. I said drm_display_helper.ko doesn't export the symbols i915 expects. I didn't actually check the module's symbol table directly. I only confirmed the symbols weren't found under /lib/modules/.../drivers/gpu/. It's possible the symbols are in drm_display_helper but i915 just isn't loading it first. If that's the case then option 2 in my expected behaviour section (missing dependency declaration) is more likely the right fix than a missing export. Sorry for the noise. Chris
