I'm running a bit low on ideas, but one thing would be to stop all drm clients (i.e. X) and check whether it still hangs. We still need to load the drm/i915.ko driver, because only when we load and enable rc6 can the cpu die actually reach the lowest power state, i.e. I want to check whether this might be an issue outside of the gpu, only brought to light due to the low power state.
I'm running a bit low on ideas, but one thing would be to stop all drm clients (i.e. X) and check whether it still hangs. We still need to load the drm/i915.ko driver, because only when we load and enable rc6 can the cpu die actually reach the lowest power state, i.e. I want to check whether this might be an issue outside of the gpu, only brought to light due to the low power state.