[Intel-gfx] [PATCH] drm/i915: Workaround to avoid lite restore with HEAD==TAIL

[shuang.he at intel.com]

Tested-By: Intel Graphics QA PRTS (Patch Regression Test System Contact: shuang.he at intel.com)
Task id: 6171
-------------------------------------Summary-------------------------------------
Platform          Delta          drm-intel-nightly          Series Applied
PNV                 -3              270/270              267/270
ILK                                  303/303              303/303
SNB                 -21              304/304              283/304
IVB                                  337/337              337/337
BYT                 -1              287/287              286/287
HSW                                  361/361              361/361
BDW                                  309/309              309/309
-------------------------------------Detailed-------------------------------------
Platform  Test                                drm-intel-nightly          Series Applied
*PNV  igt at gem_fence_thrash@bo-write-verify-none      PASS(2)      FAIL(1)PASS(1)
*PNV  igt at gem_fence_thrash@bo-write-verify-threaded-none      PASS(3)      CRASH(1)PASS(1)
 PNV  igt at gem_userptr_blits@coherency-sync      CRASH(5)PASS(3)      CRASH(1)PASS(1)
 SNB  igt at kms_cursor_crc@cursor-size-change      NSPT(3)PASS(1)      NSPT(2)
 SNB  igt at kms_mmio_vs_cs_flip@setcrtc_vs_cs_flip      NSPT(3)PASS(1)      NSPT(2)
 SNB  igt at kms_mmio_vs_cs_flip@setplane_vs_cs_flip      NSPT(3)PASS(1)      NSPT(2)
 SNB  igt at kms_rotation_crc@primary-rotation      NSPT(3)PASS(1)      NSPT(2)
 SNB  igt at kms_rotation_crc@sprite-rotation      NSPT(3)PASS(3)      NSPT(2)
 SNB  igt at pm_rpm@cursor      NSPT(3)PASS(1)      NSPT(2)
 SNB  igt at pm_rpm@cursor-dpms      NSPT(3)PASS(1)      NSPT(2)
 SNB  igt at pm_rpm@dpms-mode-unset-non-lpsp      NSPT(3)PASS(1)      NSPT(2)
 SNB  igt at pm_rpm@dpms-non-lpsp      NSPT(3)PASS(1)      NSPT(2)
 SNB  igt at pm_rpm@drm-resources-equal      NSPT(3)PASS(1)      NSPT(2)
 SNB  igt at pm_rpm@fences      NSPT(3)PASS(1)      NSPT(2)
 SNB  igt at pm_rpm@fences-dpms      NSPT(3)PASS(1)      NSPT(2)
 SNB  igt at pm_rpm@gem-execbuf      NSPT(3)PASS(1)      NSPT(2)
 SNB  igt at pm_rpm@gem-mmap-cpu      NSPT(3)PASS(1)      NSPT(2)
 SNB  igt at pm_rpm@gem-mmap-gtt      NSPT(3)PASS(1)      NSPT(2)
 SNB  igt at pm_rpm@gem-pread      NSPT(3)PASS(1)      NSPT(2)
 SNB  igt at pm_rpm@i2c      NSPT(3)PASS(1)      NSPT(2)
 SNB  igt at pm_rpm@modeset-non-lpsp      NSPT(3)PASS(1)      NSPT(2)
 SNB  igt at pm_rpm@modeset-non-lpsp-stress-no-wait      NSPT(3)PASS(1)      NSPT(2)
 SNB  igt at pm_rpm@pci-d3-state      NSPT(3)PASS(1)      NSPT(2)
 SNB  igt at pm_rpm@rte      NSPT(3)PASS(1)      NSPT(2)
*BYT  igt at gem_exec_bad_domains@conflicting-write-domain      PASS(3)      FAIL(1)PASS(1)
Note: You need to pay more attention to line start with '*'