[Intel-gfx] [PATCH] drm: Defer disabling the vblank IRQ until the next interrupt (for instant-off)

[shuang.he at intel.com]

Tested-By: PRC QA PRTS (Patch Regression Test System Contact: shuang.he at intel.com)
Task id: 6120
-------------------------------------Summary-------------------------------------
Platform          Delta          drm-intel-nightly          Series Applied
PNV                                  272/272              272/272
ILK                                  302/302              302/302
SNB                                  303/303              303/303
IVB                                  338/338              338/338
BYT                 -1              287/287              286/287
HSW                 -1              361/361              360/361
BDW                                  308/308              308/308
-------------------------------------Detailed-------------------------------------
Platform  Test                                drm-intel-nightly          Series Applied
*BYT  igt at gem_exec_bad_domains@conflicting-write-domain      PASS(12)      FAIL(1)PASS(1)
*HSW  igt at gem_storedw_loop_blt      PASS(2)      DMESG_WARN(1)PASS(1)
(dmesg patch applied)drm:i915_hangcheck_elapsed[i915]]*ERROR*Hangcheck_timer_elapsed...blitter_ring_idle at Hangcheck timer elapsed... blitter ring idle
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