[Intel-gfx] [PATCH] drm/i915: Force HW context restore on resume.

[shuang.he at intel.com]

Tested-By: Intel Graphics QA PRTS (Patch Regression Test System Contact: shuang.he at intel.com)
Task id: 6181
-------------------------------------Summary-------------------------------------
Platform          Delta          drm-intel-nightly          Series Applied
PNV                 -3              276/276              273/276
ILK                 -4              301/301              297/301
SNB                                  316/316              316/316
IVB                 -1              328/328              327/328
BYT                                  285/285              285/285
HSW                                  394/394              394/394
BDW                                  321/321              321/321
-------------------------------------Detailed-------------------------------------
Platform  Test                                drm-intel-nightly          Series Applied
 PNV  igt at gen3_render_linear_blits      FAIL(4)PASS(4)      FAIL(2)
 PNV  igt at gen3_render_tiledx_blits      FAIL(4)PASS(5)      FAIL(1)PASS(1)
 PNV  igt at gen3_render_tiledy_blits      FAIL(4)PASS(4)      FAIL(1)PASS(1)
*ILK  igt at drv_suspend@fence-restore-tiled2untiled      PASS(2)      NO_RESULT(1)
*ILK  igt at drv_suspend@fence-restore-untiled      PASS(2)      NO_RESULT(1)
*ILK  igt at drv_suspend@forcewake      PASS(2)      NO_RESULT(1)
*ILK  igt at gem_workarounds@suspend-resume      PASS(2)      NO_RESULT(1)
 IVB  igt at gem_pwrite_pread@uncached-copy-performance      DMESG_WARN(1)PASS(3)      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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