1. 10 12月, 2015 2 次提交
  2. 24 11月, 2015 1 次提交
  3. 18 11月, 2015 1 次提交
  4. 19 10月, 2015 1 次提交
  5. 09 10月, 2015 1 次提交
  6. 06 10月, 2015 1 次提交
    • T
      drm/i915: Clean up associated VMAs on context destruction · e9f24d5f
      Tvrtko Ursulin 提交于
      Prevent leaking VMAs and PPGTT VMs when objects are imported
      via flink.
      
      Scenario is that any VMAs created by the importer will be left
      dangling after the importer exits, or destroys the PPGTT context
      with which they are associated.
      
      This is caused by object destruction not running when the
      importer closes the buffer object handle due the reference held
      by the exporter. This also leaks the VM since the VMA has a
      reference on it.
      
      In practice these leaks can be observed by stopping and starting
      the X server on a kernel with fbcon compiled in. Every time
      X server exits another VMA will be leaked against the fbcon's
      frame buffer object.
      
      Also on systems where flink buffer sharing is used extensively,
      like Android, this leak has even more serious consequences.
      
      This version is takes a general approach from the  earlier work
      by Rafael Barbalho (drm/i915: Clean-up PPGTT on context
      destruction) and tries to incorporate the subsequent discussion
      between Chris Wilson and Daniel Vetter.
      
      v2:
      
      Removed immediate cleanup on object retire - it was causing a
      recursive VMA unbind via i915_gem_object_wait_rendering. And
      it is in fact not even needed since by definition context
      cleanup worker runs only after the last context reference has
      been dropped, hence all VMAs against the VM belonging to the
      context are already on the inactive list.
      
      v3:
      
      Previous version could deadlock since VMA unbind waits on any
      rendering on an object to complete. Objects can be busy in a
      different VM which would mean that the cleanup loop would do
      the wait with the struct mutex held.
      
      This is an even simpler approach where we just unbind VMAs
      without waiting since we know all VMAs belonging to this VM
      are idle, and there is nothing in flight, at the point
      context destructor runs.
      
      v4:
      
      Double underscore prefix for __915_vma_unbind_no_wait and a
      commit message typo fix. (Michel Thierry)
      
      Note that this is just a partial/interim fix since we have a bit a
      fundamental issue with cleaning up, e.g.
      
      https://bugs.freedesktop.org/show_bug.cgi?id=87729Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
      Testcase: igt/gem_ppgtt.c/flink-and-exit-vma-leak
      Reviewed-by: NMichel Thierry <michel.thierry@intel.com>
      Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
      Cc: Chris Wilson <chris@chris-wilson.co.uk>
      Cc: Rafael Barbalho <rafael.barbalho@intel.com>
      Cc: Michel Thierry <michel.thierry@intel.com>
      [danvet: Add a note that this isn't everything.]
      Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
      e9f24d5f
  7. 02 9月, 2015 1 次提交
  8. 14 8月, 2015 1 次提交
    • C
      drm/i915: Remove the failed context from the fpriv->context_idr · 37876df6
      Chris Wilson 提交于
      If we encounter an allocation failure during ppggt creation (trivial
      even with 16Gib+ RAM!), we need to remove the dead context from the
      fpriv->context_idr along with the references.
      
      gem_exec_ctx: page allocation failure: order:0, mode:0x8004
      CPU: 3 PID: 27272 Comm: gem_exec_ctx Tainted: G        W       4.2.0-rc5+ #37
       0000000000000000 ffff880086ff7a78 ffffffff816b947a ffff88041ed90038
       0000000000008004 ffff880086ff7b08 ffffffff8114b1a5 ffff880086ff7ac8
       ffffffff8108d848 0000000000000000 ffffffff81ce84b8 0000000000000000
      Call Trace:
       [<ffffffff816b947a>] dump_stack+0x45/0x57
       [<ffffffff8114b1a5>] warn_alloc_failed+0xd5/0x120
       [<ffffffff8108d848>] ? __wake_up+0x48/0x60
       [<ffffffff8114e0ed>] __alloc_pages_nodemask+0x73d/0x8e0
       [<ffffffffc0472238>] ? i915_gem_execbuffer2+0x148/0x240 [i915]
       [<ffffffffc0474240>] __setup_page_dma+0x30/0x110 [i915]
       [<ffffffffc0477f61>] gen8_ppgtt_init+0x31/0x2f0 [i915]
       [<ffffffffc04785e0>] i915_ppgtt_init+0x30/0x80 [i915]
       [<ffffffffc0478928>] i915_ppgtt_create+0x48/0xc0 [i915]
       [<ffffffffc046c9c2>] i915_gem_create_context+0x1c2/0x390 [i915]
       [<ffffffffc046d9cb>] i915_gem_context_create_ioctl+0x5b/0xa0 [i915]
      
      leading to an oops in i915_gem_context_close. Also note that this
      benchmark should not be running out of memory in the first place...
      
      Testcase: igt/benchmark/gem_exec_ctx -b create # ppgtt >= 2
      Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
      Reviewed-by: NMika Kuoppala <mika.kuoppala@intel.com>
      Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
      37876df6
  9. 14 7月, 2015 1 次提交
    • C
      drm/i915: Store device pointer in contexts for late tracepoint usafe · 9ea4feec
      Chris Wilson 提交于
      [ 1572.417121] BUG: unable to handle kernel NULL pointer dereference at           (null)
      [ 1572.421010] IP: [<ffffffffa00b2514>] ftrace_raw_event_i915_context+0x5d/0x70 [i915]
      [ 1572.424970] PGD 1766a3067 PUD 1767a2067 PMD 0
      [ 1572.428892] Oops: 0000 [#1] SMP
      [ 1572.432787] Modules linked in: ipv6 dm_mod iTCO_wdt iTCO_vendor_support snd_hda_codec_realtek snd_hda_codec_generic snd_hda_intel snd_hda_controller snd_hda_codec snd_hda_core snd_hwdep snd_pcm snd_timer snd soundcore serio_raw pcspkr lpc_ich i2c_i801 mfd_core battery ac acpi_cpufreq i915 button video drm_kms_helper drm
      [ 1572.441720] CPU: 2 PID: 18853 Comm: kworker/u8:0 Not tainted 4.0.0_kcloud_3f0360_20150429+ #588
      [ 1572.446298] Workqueue: i915 i915_gem_retire_work_handler [i915]
      [ 1572.450876] task: ffff880002f428f0 ti: ffff880035724000 task.ti: ffff880035724000
      [ 1572.455557] RIP: 0010:[<ffffffffa00b2514>]  [<ffffffffa00b2514>] ftrace_raw_event_i915_context+0x5d/0x70 [i915]
      [ 1572.460423] RSP: 0018:ffff880035727ce8  EFLAGS: 00010286
      [ 1572.465262] RAX: ffff880073f1643c RBX: ffff880002da9058 RCX: ffff880073e5db40
      [ 1572.470179] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff880035727ce8
      [ 1572.475107] RBP: ffff88007bb11a00 R08: 0000000000000000 R09: 0000000000000000
      [ 1572.480034] R10: 0000000000362200 R11: 0000000000000008 R12: 0000000000000000
      [ 1572.484952] R13: ffff880035727d78 R14: ffff880002dc1c98 R15: ffff880002dc1dc8
      [ 1572.489886] FS:  0000000000000000(0000) GS:ffff88017fd00000(0000) knlGS:0000000000000000
      [ 1572.494883] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
      [ 1572.499859] CR2: 0000000000000000 CR3: 000000017572a000 CR4: 00000000001006e0
      [ 1572.504842] Stack:
      [ 1572.509834]  ffff88017b0090c0 ffff880073f16438 ffff880002da9058 ffff880073f1643c
      [ 1572.514904]  0000000000000246 ffff880100000000 ffff88007bb11a00 ffff880002ddeb10
      [ 1572.519985]  ffff8801759f79c0 ffffffffa0092ff0 0000000000000000 ffff88007bb11a00
      [ 1572.525049] Call Trace:
      [ 1572.530093]  [<ffffffffa0092ff0>] ? i915_gem_context_free+0xa8/0xc1 [i915]
      [ 1572.535227]  [<ffffffffa009b969>] ? i915_gem_request_free+0x4e/0x50 [i915]
      [ 1572.540347]  [<ffffffffa00b5533>] ? intel_execlists_retire_requests+0x14c/0x159 [i915]
      [ 1572.545500]  [<ffffffffa009d9ea>] ? i915_gem_retire_requests+0x9d/0xeb [i915]
      [ 1572.550664]  [<ffffffffa009dd8c>] ? i915_gem_retire_work_handler+0x4c/0x61 [i915]
      [ 1572.555825]  [<ffffffff8104ca7f>] ? process_one_work+0x1b2/0x31d
      [ 1572.560951]  [<ffffffff8104d278>] ? worker_thread+0x24d/0x339
      [ 1572.566033]  [<ffffffff8104d02b>] ? cancel_delayed_work_sync+0xa/0xa
      [ 1572.571140]  [<ffffffff81050b25>] ? kthread+0xce/0xd6
      [ 1572.576191]  [<ffffffff81050a57>] ? kthread_create_on_node+0x162/0x162
      [ 1572.581228]  [<ffffffff8179b3c8>] ? ret_from_fork+0x58/0x90
      [ 1572.586259]  [<ffffffff81050a57>] ? kthread_create_on_node+0x162/0x162
      [ 1572.591318] Code: de 48 89 e7 e8 09 4d 00 e1 48 85 c0 74 27 48 89 68 10 48 8b 55 38 48 89 e7 48 89 50 18 48 8b 55 10 48 8b 12 48 8b 12 48 8b 52 38 <8b> 12 89 50 08 e8 95 4d 00 e1 48 83 c4 30 5b 5d 41 5c c3 41 55
      [ 1572.596981] RIP  [<ffffffffa00b2514>] ftrace_raw_event_i915_context+0x5d/0x70 [i915]
      [ 1572.602464]  RSP <ffff880035727ce8>
      [ 1572.607911] CR2: 0000000000000000
      
      Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=90112#c23Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
      Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
      9ea4feec
  10. 09 7月, 2015 1 次提交
  11. 06 7月, 2015 1 次提交
  12. 23 6月, 2015 11 次提交
  13. 29 5月, 2015 1 次提交
  14. 21 5月, 2015 1 次提交
    • C
      drm/i915: Implement inter-engine read-read optimisations · b4716185
      Chris Wilson 提交于
      Currently, we only track the last request globally across all engines.
      This prevents us from issuing concurrent read requests on e.g. the RCS
      and BCS engines (or more likely the render and media engines). Without
      semaphores, we incur costly stalls as we synchronise between rings -
      greatly impacting the current performance of Broadwell versus Haswell in
      certain workloads (like video decode). With the introduction of
      reference counted requests, it is much easier to track the last request
      per ring, as well as the last global write request so that we can
      optimise inter-engine read read requests (as well as better optimise
      certain CPU waits).
      
      v2: Fix inverted readonly condition for nonblocking waits.
      v3: Handle non-continguous engine array after waits
      v4: Rebase, tidy, rewrite ring list debugging
      v5: Use obj->active as a bitfield, it looks cool
      v6: Micro-optimise, mostly involving moving code around
      v7: Fix retire-requests-upto for execlists (and multiple rq->ringbuf)
      v8: Rebase
      v9: Refactor i915_gem_object_sync() to allow the compiler to better
      optimise it.
      
      Benchmark: igt/gem_read_read_speed
      hsw:gt3e (with semaphores):
      Before: Time to read-read 1024k:		275.794µs
      After:  Time to read-read 1024k:		123.260µs
      
      hsw:gt3e (w/o semaphores):
      Before: Time to read-read 1024k:		230.433µs
      After:  Time to read-read 1024k:		124.593µs
      
      bdw-u (w/o semaphores):             Before          After
      Time to read-read 1x1:            26.274µs       10.350µs
      Time to read-read 128x128:        40.097µs       21.366µs
      Time to read-read 256x256:        77.087µs       42.608µs
      Time to read-read 512x512:       281.999µs      181.155µs
      Time to read-read 1024x1024:    1196.141µs     1118.223µs
      Time to read-read 2048x2048:    5639.072µs     5225.837µs
      Time to read-read 4096x4096:   22401.662µs    21137.067µs
      Time to read-read 8192x8192:   89617.735µs    85637.681µs
      
      Testcase: igt/gem_concurrent_blit (read-read and friends)
      Cc: Lionel Landwerlin <lionel.g.landwerlin@linux.intel.com>
      Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
      Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
      Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com> [v8]
      [danvet: s/\<rq\>/req/g]
      Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
      b4716185
  15. 24 4月, 2015 2 次提交
  16. 21 4月, 2015 1 次提交
  17. 10 4月, 2015 1 次提交
  18. 20 3月, 2015 3 次提交
    • B
      drm/i915: Initialize all contexts · 6702cf16
      Ben Widawsky 提交于
      The problem is we're going to switch to a new context, which could be
      the default context. The plan was to use restore inhibit, which would be
      fine, except if we are using dynamic page tables (which we will). If we
      use dynamic page tables and we don't load new page tables, the previous
      page tables might go away, and future operations will fault.
      
      CTXA runs.
      switch to default, restore inhibit
      CTXA dies and has its address space taken away.
      Run CTXB, tries to save using the context A's address space - this
      fails.
      
      The general solution is to make sure every context has it's own state,
      and its own address space. For cases when we must restore inhibit, first
      thing we do is load a valid address space. I thought this would be
      enough, but apparently there are references within the context itself
      which will refer to the old address space - therefore, we also must
      reinitialize.
      
      v2: to->ppgtt is only valid in full ppgtt.
      v3: Rebased.
      v4: Make post PDP update clearer.
      Signed-off-by: NBen Widawsky <ben@bwidawsk.net>
      Signed-off-by: Michel Thierry <michel.thierry@intel.com> (v2+)
      Reviewed-by: NMika Kuoppala <mika.kuoppala@intel.com>
      Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
      6702cf16
    • B
      drm/i915: Track page table reload need · 563222a7
      Ben Widawsky 提交于
      This patch was formerly known as, "Force pd restore when PDEs change,
      gen6-7." I had to change the name because it is needed for GEN8 too.
      
      The real issue this is trying to solve is when a new object is mapped
      into the current address space. The GPU does not snoop the new mapping
      so we must do the gen specific action to reload the page tables.
      
      GEN8 and GEN7 do differ in the way they load page tables for the RCS.
      GEN8 does so with the context restore, while GEN7 requires the proper
      load commands in the command streamer. Non-render is similar for both.
      
      Caveat for GEN7
      The docs say you cannot change the PDEs of a currently running context.
      We never map new PDEs of a running context, and expect them to be
      present - so I think this is okay. (We can unmap, but this should also
      be okay since we only unmap unreferenced objects that the GPU shouldn't
      be tryingto va->pa xlate.) The MI_SET_CONTEXT command does have a flag
      to signal that even if the context is the same, force a reload. It's
      unclear exactly what this does, but I have a hunch it's the right thing
      to do.
      
      The logic assumes that we always emit a context switch after mapping new
      PDEs, and before we submit a batch. This is the case today, and has been
      the case since the inception of hardware contexts. A note in the comment
      let's the user know.
      
      It's not just for gen8. If the current context has mappings change, we
      need a context reload to switch
      
      v2: Rebased after ppgtt clean up patches. Split the warning for aliasing
      and true ppgtt options. And do not break aliasing ppgtt, where to->ppgtt
      is always null.
      
      v3: Invalidate PPGTT TLBs inside alloc_va_range.
      
      v4: Rename ppgtt_invalidate_tlbs to mark_tlbs_dirty and move
      pd_dirty_rings from i915_address_space to i915_hw_ppgtt. Fixes when
      neither ctx->ppgtt and aliasing_ppgtt exist.
      
      v5: Removed references to teardown_va_range.
      
      v6: Updated needs_pd_load_pre/post.
      
      v7: Fix pd_dirty_rings check in needs_pd_load_post, and update/move
      comment about updated PDEs to object_pin/bind (Mika).
      
      Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
      Signed-off-by: NBen Widawsky <ben@bwidawsk.net>
      Signed-off-by: Michel Thierry <michel.thierry@intel.com> (v2+)
      Reviewed-by: NMika Kuoppala <mika.kuoppala@intel.com>
      Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
      563222a7
    • B
      drm/i915: Extract context switch skip and add pd load logic · 317b4e90
      Ben Widawsky 提交于
      In Gen8, PDPs are saved and restored with legacy contexts (legacy contexts
      only exist on the render ring). So change the ordering of LRI vs MI_SET_CONTEXT
      for the initialization of the context. Also the only cases in which we
      need to manually update the PDPs are when MI_RESTORE_INHIBIT has been
      set in MI_SET_CONTEXT (i.e. when the context is not yet initialized or
      it is the default context).
      
      Legacy submission is not available post GEN8, so it isn't necessary to
      add extra checks for newer generations.
      
      v2: Use new functions to replace the logic right away (Daniel)
      v3: Add missing pd load logic.
      v4: Add warning in case pd_load_pre & pd_load_post are true, and add
      missing trace_switch_mm. Cleaned up pd_load conditions. Add more
      information about when is pd_load_post needed. (Mika)
      Signed-off-by: NBen Widawsky <ben@bwidawsk.net>
      Signed-off-by: Michel Thierry <michel.thierry@intel.com> (v2+)
      Reviewed-by: NMika Kuoppala <mika.kuoppala@intel.com>
      Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
      317b4e90
  19. 24 2月, 2015 1 次提交
  20. 08 1月, 2015 1 次提交
  21. 07 1月, 2015 1 次提交
  22. 16 12月, 2014 1 次提交
    • C
      drm/i915: Disable PSMI sleep messages on all rings around context switches · 2c550183
      Chris Wilson 提交于
      There exists a current workaround to prevent a hang on context switch
      should the ring go to sleep in the middle of the restore,
      WaProgramMiArbOnOffAroundMiSetContext (applicable to all gen7+). In
      spite of disabling arbitration (which prevents the ring from powering
      down during the critical section) we were still hitting hangs that had
      the hallmarks of the known erratum. That is we are still seeing hangs
      "on the last instruction in the context restore". By comparing -nightly
      (broken) with requests (working), we were able to deduce that it was the
      semaphore LRI cross-talk that reproduced the original failure. The key
      was that requests implemented deferred semaphore signalling, and
      disabling that, i.e. emitting the semaphore signal to every other ring
      after every batch restored the frequent hang.  Explicitly disabling PSMI
      sleep on the RCS ring was insufficient, all the rings had to be awake to
      prevent the hangs. Fortunately, we can reduce the wakelock to the
      MI_SET_CONTEXT operation itself, and so should be able to limit the extra
      power implications.
      
      Since the MI_ARB_ON_OFF workaround is listed for all gen7 and above
      products, we should apply this extra hammer for all of the same
      platforms despite so far that we have only been able to reproduce the
      hang on certain ivb and hsw models. The last question is whether we want
      to always use the extra hammer or only when we know semaphores are in
      operation. At the moment, we only use LRI on non-RCS rings for
      semaphores, but that may change in the future with the possibility of
      reintroducing this bug under subtle conditions.
      
      v2: Make it explicit that the PSMI LRI are an extension to the original
      workaround for the other rings.
      v3: Bikeshedding variable names and whitespacing
      
      Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=80660
      Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=83677
      Cc: Simon Farnsworth <simon@farnz.org.uk>
      Cc: Daniel Vetter <daniel@ffwll.ch>
      Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
      Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
      Tested-by: NPeter Frühberger <fritsch@xbmc.org>
      Reviewed-by: NDaniel Vetter <daniel@ffwll.ch>
      Cc: stable@vger.kernel.org
      Signed-off-by: NJani Nikula <jani.nikula@intel.com>
      2c550183
  23. 15 12月, 2014 1 次提交
    • T
      drm/i915: Infrastructure for supporting different GGTT views per object · fe14d5f4
      Tvrtko Ursulin 提交于
      Things like reliable GGTT mappings and mirrored 2d-on-3d display will need
      to map objects into the same address space multiple times.
      
      Added a GGTT view concept and linked it with the VMA to distinguish between
      multiple instances per address space.
      
      New objects and GEM functions which do not take this new view as a parameter
      assume the default of zero (I915_GGTT_VIEW_NORMAL) which preserves the
      previous behaviour.
      
      This now means that objects can have multiple VMA entries so the code which
      assumed there will only be one also had to be modified.
      
      Alternative GGTT views are supposed to borrow DMA addresses from obj->pages
      which is DMA mapped on first VMA instantiation and unmapped on the last one
      going away.
      
      v2:
          * Removed per view special casing in i915_gem_ggtt_prepare /
            finish_object in favour of creating and destroying DMA mappings
            on first VMA instantiation and last VMA destruction. (Daniel Vetter)
          * Simplified i915_vma_unbind which does not need to count the GGTT views.
            (Daniel Vetter)
          * Also moved obj->map_and_fenceable reset under the same check.
          * Checkpatch cleanups.
      
      v3:
          * Only retire objects once the last VMA is unbound.
      
      v4:
          * Keep scatter-gather table for alternative views persistent for the
            lifetime of the VMA.
          * Propagate binding errors to callers and handle appropriately.
      
      v5:
          * Explicitly look for normal GGTT view in i915_gem_obj_bound to align
            usage in i915_gem_object_ggtt_unpin. (Michel Thierry)
          * Change to single if statement in i915_gem_obj_to_ggtt. (Michel Thierry)
          * Removed stray semi-colon in i915_gem_object_set_cache_level.
      
      For: VIZ-4544
      Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
      Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
      Reviewed-by: NMichel Thierry <michel.thierry@intel.com>
      [danvet: Drop hunk from i915_gem_shrink since it's just prettification
      but upsets a __must_check warning.]
      Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
      fe14d5f4
  24. 08 12月, 2014 1 次提交
  25. 03 12月, 2014 2 次提交
    • T
      drm/i915: Fix startup failure in LRC mode after recent init changes · e7778be1
      Thomas Daniel 提交于
      A previous commit introduced engine init changes:
      
          commit 372ee59699d9 ("drm/i915: Only init engines once")
      
      This broke execlists as intel_lr_context_render_state_init was trying to emit
      commands to the RCS for the default context before the ring->init_hw was called.
      
      Made a new gen8_init_rcs_context function and assign in to render ring
      init_context.  Moved call to intel_logical_ring_workarounds_emit into
      gen8_init_rcs_context to maintain previous functionality.
      
      Moved call to render_state_init from lr_context_deferred_create into
      gen8_init_rcs_context, and modified deferred_create to call ring->init_context
      for non-default contexts.
      
      Modified i915_gem_context_enable to call ring->init_context for the default
      context.
      
      So init_context will now always be called when the hw is ready - in
      i915_gem_context_enable for the default context and in lr_context_deferred_create
      for other contexts.
      Signed-off-by: NThomas Daniel <thomas.daniel@intel.com>
      Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
      e7778be1
    • J
      drm/i915: Remove the now redundant 'obj->ring' · 41c52415
      John Harrison 提交于
      The ring member of the object structure was always updated with the
      last_read_seqno member. Thus with the conversion to last_read_req, obj->ring is
      now a direct copy of obj->last_read_req->ring. This makes it somewhat redundant
      and potentially misleading (especially as there was no comment to explain its
      purpose).
      
      This checkin removes the redundant field. Many uses were simply testing for
      non-null to see if the object is active on the GPU. Some of these have been
      converted to check 'obj->active' instead. Others (where the last_read_req is
      about to be used anyway) have been changed to check obj->last_read_req. The rest
      simply pull the ring out from the request structure and proceed as before.
      
      For: VIZ-4377
      Signed-off-by: NJohn Harrison <John.C.Harrison@Intel.com>
      Reviewed-by: NThomas Daniel <Thomas.Daniel@intel.com>
      Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
      41c52415