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  1. 25 7月, 2019 1 次提交
  3. 23 7月, 2019 1 次提交
    • C
      drm/i915: Rely on spinlock protection for GPU error capture · 3bdd4f84
      由 Chris Wilson 提交于 
      Trust that we now have adequate protection over the low level structures
via the engine->active.lock to allow ourselves to capture the GPU error
state without the heavy hammer of stop_machine(). Sadly this does mean
that we have to forgo some of the lesser used information (not derived
from the active state) that is not controlled by the active locks. This
includes the list of buffers in the ppGTT and pinned globally in the
GGTT. Originally this was used to manually verify relocations, but
hasn't been required for sometime and modern mesa now has the habit of
ensuring that all interesting buffers within a batch are captured in their
entirety (that are the auxiliary state buffers, but not the textures).

A useful side-effect is that this allows us to restore error capturing
for Braswell and Broxton.

v2: Use pagevec for a typical arbitrary number of preallocated pages
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190722222847.24178-1-chris@chris-wilson.co.uk
      3bdd4f84
  5. 16 7月, 2019 1 次提交
  7. 14 7月, 2019 1 次提交
  9. 21 6月, 2019 3 次提交
  11. 20 6月, 2019 1 次提交
    • C
      drm/i915/execlists: Preempt-to-busy · 22b7a426
      由 Chris Wilson 提交于 
      When using a global seqno, we required a precise stop-the-workd event to
handle preemption and unwind the global seqno counter. To accomplish
this, we would preempt to a special out-of-band context and wait for the
machine to report that it was idle. Given an idle machine, we could very
precisely see which requests had completed and which we needed to feed
back into the run queue.

However, now that we have scrapped the global seqno, we no longer need
to precisely unwind the global counter and only track requests by their
per-context seqno. This allows us to loosely unwind inflight requests
while scheduling a preemption, with the enormous caveat that the
requests we put back on the run queue are still _inflight_ (until the
preemption request is complete). This makes request tracking much more
messy, as at any point then we can see a completed request that we
believe is not currently scheduled for execution. We also have to be
careful not to rewind RING_TAIL past RING_HEAD on preempting to the
running context, and for this we use a semaphore to prevent completion
of the request before continuing.

To accomplish this feat, we change how we track requests scheduled to
the HW. Instead of appending our requests onto a single list as we
submit, we track each submission to ELSP as its own block. Then upon
receiving the CS preemption event, we promote the pending block to the
inflight block (discarding what was previously being tracked). As normal
CS completion events arrive, we then remove stale entries from the
inflight tracker.

v2: Be a tinge paranoid and ensure we flush the write into the HWS page
for the GPU semaphore to pick in a timely fashion.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190620142052.19311-1-chris@chris-wilson.co.uk
      22b7a426
  13. 17 6月, 2019 1 次提交
  15. 15 6月, 2019 1 次提交
  17. 13 6月, 2019 1 次提交
  19. 12 6月, 2019 1 次提交
  21. 11 6月, 2019 1 次提交
  23. 10 6月, 2019 1 次提交
  25. 07 6月, 2019 2 次提交
  27. 29 5月, 2019 2 次提交
    • J
      Revert "drm/i915: Expand subslice mask" · a10f361d
      由 Jani Nikula 提交于 
      This reverts commit 1ac159e2 ("drm/i915: Expand subslice mask"),
which kills ICL due to GEM_BUG_ON() sanity checks before CI even gets a
chance to do anything.

The commit exposes an issue in commit 1e40d4ae ("drm/i915/cnl:
Implement WaProgramMgsrForCorrectSliceSpecificMmioReads"), which will
also need to be addressed.

There's a proposed fix [1], but considering the seeming uncertainty with
the fix as well as the size of the regressing commit (in this context,
the one that actually brings down ICL), this warrants a revert to get
ICL working, and gives us time to get all of this right without
rushing. Even if this means shooting the messenger.

<3>[    9.426327] intel_sseu_get_subslices:46 GEM_BUG_ON(slice >= sseu->max_slices)
<4>[    9.426355] ------------[ cut here ]------------
<2>[    9.426357] kernel BUG at drivers/gpu/drm/i915/gt/intel_sseu.c:46!
<4>[    9.426371] invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
<4>[    9.426377] CPU: 1 PID: 364 Comm: systemd-udevd Not tainted 5.2.0-rc2-CI-CI_DRM_6159+ #1
<4>[    9.426385] Hardware name: Intel Corporation Ice Lake Client Platform/IceLake U DDR4 SODIMM PD RVP TLC, BIOS ICLSFWR1.R00.3183.A00.1905020411 05/02/2019
<4>[    9.426444] RIP: 0010:intel_sseu_get_subslices+0x8a/0xe0 [i915]
<4>[    9.426452] Code: d5 76 b7 e0 48 8b 35 9d 24 21 00 49 c7 c0 07 f0 72 a0 b9 2e 00 00 00 48 c7 c2 00 8e 6d a0 48 c7 c7 a5 14 5b a0 e8 36 3c be e0 <0f> 0b 48 c7 c1 80 d5 6f a0 ba 30 00 00 00 48 c7 c6 00 8e 6d a0 48
<4>[    9.426468] RSP: 0018:ffffc9000037b9c8 EFLAGS: 00010282
<4>[    9.426475] RAX: 000000000000000f RBX: 0000000000000000 RCX: 0000000000000000
<4>[    9.426482] RDX: 0000000000000001 RSI: 0000000000000008 RDI: ffff88849e346f98
<4>[    9.426490] RBP: ffff88848a200000 R08: 0000000000000004 R09: ffff88849d50b000
<4>[    9.426497] R10: 0000000000000000 R11: ffff88849e346f98 R12: ffff88848a209e78
<4>[    9.426505] R13: 0000000003000000 R14: ffff88848a20b1a8 R15: 0000000000000000
<4>[    9.426513] FS:  00007f73d5ae8680(0000) GS:ffff88849fc80000(0000) knlGS:0000000000000000
<4>[    9.426521] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
<4>[    9.426527] CR2: 0000561417b01260 CR3: 0000000494764003 CR4: 0000000000760ee0
<4>[    9.426535] PKRU: 55555554
<4>[    9.426538] Call Trace:
<4>[    9.426585]  wa_init_mcr+0xd5/0x110 [i915]
<4>[    9.426597]  ? lock_acquire+0xa6/0x1c0
<4>[    9.426645]  icl_gt_workarounds_init+0x21/0x1a0 [i915]
<4>[    9.426694]  ? i915_driver_load+0xfcf/0x18a0 [i915]
<4>[    9.426739]  gt_init_workarounds+0x14c/0x230 [i915]
<4>[    9.426748]  ? _raw_spin_unlock_irq+0x24/0x50
<4>[    9.426789]  intel_gt_init_workarounds+0x1b/0x30 [i915]
<4>[    9.426835]  i915_driver_load+0xfd7/0x18a0 [i915]
<4>[    9.426843]  ? lock_acquire+0xa6/0x1c0
<4>[    9.426850]  ? __pm_runtime_resume+0x4f/0x80
<4>[    9.426857]  ? _raw_spin_unlock_irqrestore+0x4c/0x60
<4>[    9.426863]  ? _raw_spin_unlock_irqrestore+0x4c/0x60
<4>[    9.426870]  ? lockdep_hardirqs_on+0xe3/0x1b0
<4>[    9.426915]  i915_pci_probe+0x29/0xa0 [i915]
<4>[    9.426923]  pci_device_probe+0x9e/0x120
<4>[    9.426930]  really_probe+0xea/0x3c0
<4>[    9.426936]  driver_probe_device+0x10b/0x120
<4>[    9.426942]  device_driver_attach+0x4a/0x50
<4>[    9.426948]  __driver_attach+0x97/0x130
<4>[    9.426954]  ? device_driver_attach+0x50/0x50
<4>[    9.426960]  bus_for_each_dev+0x74/0xc0
<4>[    9.426966]  bus_add_driver+0x13f/0x210
<4>[    9.426971]  ? 0xffffffffa083b000
<4>[    9.426976]  driver_register+0x56/0xe0
<4>[    9.426982]  ? 0xffffffffa083b000
<4>[    9.426987]  do_one_initcall+0x58/0x300
<4>[    9.426994]  ? do_init_module+0x1d/0x1f6
<4>[    9.427001]  ? rcu_read_lock_sched_held+0x6f/0x80
<4>[    9.427007]  ? kmem_cache_alloc_trace+0x261/0x290
<4>[    9.427014]  do_init_module+0x56/0x1f6
<4>[    9.427020]  load_module+0x24d1/0x2990
<4>[    9.427032]  ? __se_sys_finit_module+0xd3/0xf0
<4>[    9.427037]  __se_sys_finit_module+0xd3/0xf0
<4>[    9.427047]  do_syscall_64+0x55/0x1c0
<4>[    9.427053]  entry_SYSCALL_64_after_hwframe+0x49/0xbe
<4>[    9.427059] RIP: 0033:0x7f73d5609839
<4>[    9.427064] Code: 00 f3 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 1f f6 2c 00 f7 d8 64 89 01 48
<4>[    9.427082] RSP: 002b:00007ffdf34477b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
<4>[    9.427091] RAX: ffffffffffffffda RBX: 00005559fd5d7b40 RCX: 00007f73d5609839
<4>[    9.427099] RDX: 0000000000000000 RSI: 00007f73d52e8145 RDI: 000000000000000f
<4>[    9.427106] RBP: 00007f73d52e8145 R08: 0000000000000000 R09: 00007ffdf34478d0
<4>[    9.427114] R10: 000000000000000f R11: 0000000000000246 R12: 0000000000000000
<4>[    9.427121] R13: 00005559fd5c90f0 R14: 0000000000020000 R15: 00005559fd5d7b40
<4>[    9.427131] Modules linked in: i915(+) mei_hdcp x86_pkg_temp_thermal coretemp snd_hda_intel crct10dif_pclmul crc32_pclmul snd_hda_codec snd_hwdep e1000e snd_hda_core ghash_clmulni_intel ptp snd_pcm cdc_ether usbnet mii pps_core mei_me mei prime_numbers btusb btrtl btbcm btintel bluetooth ecdh_generic ecc
<4>[    9.427254] ---[ end trace af3eeb543bd66e66 ]---

[1] http://patchwork.freedesktop.org/patch/msgid/20190528200655.11605-1-chris@chris-wilson.co.uk

References: https://intel-gfx-ci.01.org/tree/drm-tip/CI_DRM_6159/fi-icl-u2/pstore0-1517155098_Oops_1.log
References: 1e40d4ae ("drm/i915/cnl: Implement WaProgramMgsrForCorrectSliceSpecificMmioReads")
Fixes: 1ac159e2 ("drm/i915: Expand subslice mask")
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Oscar Mateo <oscar.mateo@intel.com>
Cc: Stuart Summers <stuart.summers@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Yunwei Zhang <yunwei.zhang@intel.com>
Acked-by: NDaniel Vetter <daniel@ffwll.ch>
Signed-off-by: NJani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190529082150.31526-1-jani.nikula@intel.com
      a10f361d
    • S
      drm/i915: Expand subslice mask · 1ac159e2
      由 Stuart Summers 提交于 
      Currently, the subslice_mask runtime parameter is stored as an
array of subslices per slice. Expand the subslice mask array to
better match what is presented to userspace through the
I915_QUERY_TOPOLOGY_INFO ioctl. The index into this array is
then calculated:
  slice * subslice stride + subslice index / 8

v2: fix spacing in set_sseu_info args
    use set_sseu_info to initialize sseu data when building
    device status in debugfs
    rename variables in intel_engine_types.h to avoid checkpatch
    warnings
v3: update headers in intel_sseu.h
v4: add const to some sseu_dev_info variables
    use sseu->eu_stride for EU stride calculations
v5: address review comments from Tvrtko and Daniele
v6: remove extra space in intel_sseu_get_subslices
    return the correct subslice enable in for_each_instdone
    add GEM_BUG_ON to ensure user doesn't pass invalid ss_mask size
    use printk formatted string for subslice mask
v7: remove string.h header and rebase

Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Acked-by: NLionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: NDaniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: NStuart Summers <stuart.summers@intel.com>
Signed-off-by: NManasi Navare <manasi.d.navare@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190524154022.13575-6-stuart.summers@intel.com
      1ac159e2
  29. 28 5月, 2019 2 次提交
  31. 03 5月, 2019 1 次提交
  33. 30 4月, 2019 2 次提交
  35. 17 4月, 2019 1 次提交
    • P
      drm/i915: add GEN2_ prefix to the I{E, I, M, S}R registers · 9d9523d8
      由 Paulo Zanoni 提交于 
      This discussion started because we use token pasting in the
GEN{2,3}_IRQ_INIT and GEN{2,3}_IRQ_RESET macros, so gen2-4 passes an
empty argument to those macros, making the code a little weird. The
original proposal was to just add a comment as the empty argument, but
Ville suggested we just add a prefix to the registers, and that indeed
sounds like a more elegant solution.

Now doing this is kinda against our rules for register naming since we
only add gens or platform names as register prefixes when the given
gen/platform changes a register that already existed before. On the
other hand, we have so many instances of IIR/IMR in comments that
adding a prefix would make the users of these register more easily
findable, in addition to make our token pasting macros actually
readable. So IMHO opening an exception here is worth it.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190410235344.31199-4-paulo.r.zanoni@intel.com
      9d9523d8
  37. 05 4月, 2019 1 次提交
  39. 02 4月, 2019 2 次提交
    • C
      drm/i915: Move intel_engine_mask_t around for use by i915_request_types.h · 3a891a62
      由 Chris Wilson 提交于 
      We want to use intel_engine_mask_t inside i915_request.h, which means
extracting it from the general header file mess and placing it inside a
types.h. A knock on effect is that the compiler wants to warn about
type-contraction of ALL_ENGINES into intel_engine_maskt_t, so prepare
for the worst.

v2: Use intel_engine_mask_t consistently
v3: Move I915_NUM_ENGINES to its natural home at the end of the enum
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190401162641.10963-1-chris@chris-wilson.co.ukReviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
      3a891a62
    • T
      drm/i915: Introduce concept of a sub-platform · 805446c8
      由 Tvrtko Ursulin 提交于 
      Concept of a sub-platform already exist in our code (like ULX and ULT
platform variants and similar),implemented via the macros which check a
list of device ids to determine a match.

With this patch we consolidate device ids checking into a single function
called during early driver load.

A few low bits in the platform mask are reserved for sub-platform
identification and defined as a per-platform namespace.

At the same time it future proofs the platform_mask handling by preparing
the code for easy extending, and tidies the very verbose WARN strings
generated when IS_PLATFORM macros are embedded into a WARN type
statements.

v2: Fixed IS_SUBPLATFORM. Updated commit msg.
v3: Chris was right, there is an ordering problem.

v4:
 * Catch-up with new sub-platforms.
 * Rebase for RUNTIME_INFO.
 * Drop subplatform mask union tricks and convert platform_mask to an
   array for extensibility.

v5:
 * Fix subplatform check.
 * Protect against forgetting to expand subplatform bits.
 * Remove platform enum tallying.
 * Add subplatform to error state. (Chris)
 * Drop macros and just use static inlines.
 * Remove redundant IRONLAKE_M. (Ville)

v6:
 * Split out Ironlake change.
 * Optimize subplatform check.
 * Use __always_inline. (Lucas)
 * Add platform_mask comment. (Paulo)
 * Pass stored runtime info in error capture. (Chris)

v7:
 * Rebased for new AML ULX device id.
 * Bump platform mask array size for EHL.
 * Stop mentioning device ids in intel_device_subplatform_init by using
   the trick of splitting macros i915_pciids.h. (Jani)
 * AML seems to be either a subplatform of KBL or CFL so express it like
   that.

v8:
 * Use one device id table per subplatform. (Jani)
Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Suggested-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Jose Souza <jose.souza@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Acked-by: NJani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190327142328.31780-1-tvrtko.ursulin@linux.intel.com
      805446c8
  41. 27 3月, 2019 1 次提交
  43. 21 3月, 2019 1 次提交
  45. 19 3月, 2019 1 次提交
  47. 16 3月, 2019 1 次提交
  49. 06 3月, 2019 2 次提交
  51. 05 3月, 2019 1 次提交
  53. 26 2月, 2019 2 次提交
  55. 19 2月, 2019 1 次提交
    • C
      drm/i915: Use time based guilty context banning · 7f4127c4
      由 Chris Wilson 提交于 
      Currently, we accumulate each time a context hangs the GPU, offset
against the number of requests it submits, and if that score exceeds a
certain threshold, we ban that context from submitting any more requests
(cancelling any work in flight). In contrast, we use a simple timer on
the file, that if we see more than a 9 hangs faster than 60s apart in
total across all of its contexts, we will ban the client from creating
any more contexts. This leads to a confusing situation where the file
may be banned before the context, so lets use a simple timer scheme for
each.

If the context submits 3 hanging requests within a 120s period, declare
it forbidden to ever send more requests.

This has the advantage of not being easy to repair by simply sending
empty requests, but has the disadvantage that if the context is idle
then it is forgiven. However, if the context is idle, it is not
disrupting the system, but a hog can evade the request counting and
cause much more severe disruption to the system.

Updating ban_score from request retirement is dubious as the retirement
is purposely not in sync with request submission (i.e. we try and batch
retirement to reduce overhead and avoid latency on submission), which
leads to surprising situations where we can forgive a hang immediately
due to a backlog of requests from before the hang being retired
afterwards.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NMika Kuoppala <mika.kuoppala@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190219122215.8941-2-chris@chris-wilson.co.uk
      7f4127c4
  57. 06 2月, 2019 1 次提交
  59. 30 1月, 2019 2 次提交
    • C
      drm/i915: Drop fake breadcrumb irq · 789659f4
      由 Chris Wilson 提交于 
      Missed breadcrumb detection is defunct due to the tight coupling with
dma_fence signaling and the myriad ways we may signal fences from
everywhere but from an interrupt, i.e. we frequently signal a fence
before we even see its interrupt. This means that even if we miss an
interrupt for a fence, it still is signaled before our breadcrumb
hangcheck fires, so simplify the breadcrumb hangchecking by moving it
into the GPU hangcheck and forgo fake interrupts.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190129205230.19056-3-chris@chris-wilson.co.uk
      789659f4
    • C
      drm/i915: Replace global breadcrumbs with per-context interrupt tracking · 52c0fdb2
      由 Chris Wilson 提交于 
      A few years ago, see commit 688e6c72 ("drm/i915: Slaughter the
thundering i915_wait_request herd"), the issue of handling multiple
clients waiting in parallel was brought to our attention. The
requirement was that every client should be woken immediately upon its
request being signaled, without incurring any cpu overhead.

To handle certain fragility of our hw meant that we could not do a
simple check inside the irq handler (some generations required almost
unbounded delays before we could be sure of seqno coherency) and so
request completion checking required delegation.

Before commit 688e6c72, the solution was simple. Every client
waiting on a request would be woken on every interrupt and each would do
a heavyweight check to see if their request was complete. Commit
688e6c72 introduced an rbtree so that only the earliest waiter on
the global timeline would woken, and would wake the next and so on.
(Along with various complications to handle requests being reordered
along the global timeline, and also a requirement for kthread to provide
a delegate for fence signaling that had no process context.)

The global rbtree depends on knowing the execution timeline (and global
seqno). Without knowing that order, we must instead check all contexts
queued to the HW to see which may have advanced. We trim that list by
only checking queued contexts that are being waited on, but still we
keep a list of all active contexts and their active signalers that we
inspect from inside the irq handler. By moving the waiters onto the fence
signal list, we can combine the client wakeup with the dma_fence
signaling (a dramatic reduction in complexity, but does require the HW
being coherent, the seqno must be visible from the cpu before the
interrupt is raised - we keep a timer backup just in case).

Having previously fixed all the issues with irq-seqno serialisation (by
inserting delays onto the GPU after each request instead of random delays
on the CPU after each interrupt), we can rely on the seqno state to
perfom direct wakeups from the interrupt handler. This allows us to
preserve our single context switch behaviour of the current routine,
with the only downside that we lose the RT priority sorting of wakeups.
In general, direct wakeup latency of multiple clients is about the same
(about 10% better in most cases) with a reduction in total CPU time spent
in the waiter (about 20-50% depending on gen). Average herd behaviour is
improved, but at the cost of not delegating wakeups on task_prio.

v2: Capture fence signaling state for error state and add comments to
warm even the most cold of hearts.
v3: Check if the request is still active before busywaiting
v4: Reduce the amount of pointer misdirection with list_for_each_safe
and using a local i915_request variable inside the loops
v5: Add a missing pluralisation to a purely informative selftest message.

References: 688e6c72 ("drm/i915: Slaughter the thundering i915_wait_request herd")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190129205230.19056-2-chris@chris-wilson.co.uk
      52c0fdb2