[Intel-gfx] [PATCH v4] drm/i915: Avoid GPU Hang when comming out of s3 or s4

[shuang.he at intel.com]

Tested-By: Intel Graphics QA PRTS (Patch Regression Test System Contact: shuang.he at intel.com)
Task id: 6380
-------------------------------------Summary-------------------------------------
Platform          Delta          drm-intel-nightly          Series Applied
PNV                                  276/276              276/276
ILK                 -1              302/302              301/302
SNB                 -1              314/314              313/314
IVB                                  338/338              338/338
BYT                                  286/286              286/286
BDW                 -1              320/320              319/320
-------------------------------------Detailed-------------------------------------
Platform  Test                                drm-intel-nightly          Series Applied
*ILK  igt at kms_flip@flip-vs-dpms-interruptible      PASS(2)      DMESG_WARN(1)
(dmesg patch applied)drm:intel_pch_fifo_underrun_irq_handler[i915]]*ERROR*PCH_transcoder_A_FIFO_underrun at PCH transcoder A FIFO underrun
 SNB  igt at pm_rpm@dpms-mode-unset-non-lpsp      DMESG_WARN(13)PASS(1)      DMESG_WARN(1)
(dmesg patch applied)WARNING:at_drivers/gpu/drm/i915/intel_uncore.c:#assert_device_not_suspended[i915]()@WARNING:.* at .* assert_device_not_suspended+0x
*BDW  igt at gem_fence_thrash@bo-write-verify-y      PASS(2)      DMESG_WARN(1)
(dmesg patch applied)WARNING:at_drivers/gpu/drm/i915/intel_display.c:#assert_plane[i915]()@WARNING:.* at .* assert_plane
assertion_failure at assertion failure
WARNING:at_drivers/gpu/drm/drm_irq.c:#drm_wait_one_vblank[drm]()@WARNING:.* at .* drm_wait_one_vblank+0x
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