Smatch warns of
drivers/gpu/drm/i915/intel_pm.c:1161 g4x_compute_wm() warn: signedness bug returning '(-33554430)'
which is a result of it believing that wm may be INT_MAX following
g4x_tlb_miss_wa(). Just declaring g4x_tlb_miss_wa() as returning an
unsigned integer is not sufficient, we need to tell smatch that wm itself
is unsigned for it to not worry. So mark up the locals we expect to be
non-negative, and so silence smatch.
v2: Mark up vlv_compute_wm_level() as unsigned similarly.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> #v1
Link: https://patchwork.freedesktop.org/patch/msgid/20171107140338.13748-1-chris@chris-wilson.co.uk
Older compilers (gcc-4.9) are not as able to track uninitialised
variables as well as more recent compilers. In particular,
drivers/gpu/drm/i915/intel_dpio_phy.c: In function ‘bxt_ddi_phy_init’:
drivers/gpu/drm/i915/intel_dpio_phy.c:482:25: warning: ‘was_enabled’ may be used uninitialized in this function [-Wmaybe-uninitialized]
In this case, we can rearrange code slightly to make the control flow
clearer to the reader, as well as the compiler. That is we only call
uninit using the same predicate as calling init
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ander Conselvan de Oliveira <ander.conselvan.de.oliveira@intel.com>
Cc: Imre Deak <imre.deak@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171107135324.28300-1-chris@chris-wilson.co.uk
Reviewed-by: Gabriel Krisman Bertazi <krisman@collabora.co.uk>
drivers/gpu/drm/i915/i915_cmd_parser.c:808:23: error: not an lvalue
drivers/gpu/drm/i915/i915_cmd_parser.c:811:23: error: not an lvalue
drivers/gpu/drm/i915/i915_cmd_parser.c:814:23: error: not an lvalue
drivers/gpu/drm/i915/i915_cmd_parser.c:808:23: error: not an lvalue
drivers/gpu/drm/i915/i915_cmd_parser.c:811:23: error: not an lvalue
drivers/gpu/drm/i915/i915_cmd_parser.c:814:23: error: not an lvalue
drivers/gpu/drm/i915/i915_cmd_parser.c:808:23: error: not an lvalue
drivers/gpu/drm/i915/i915_cmd_parser.c:811:23: error: not an lvalue
drivers/gpu/drm/i915/i915_cmd_parser.c:814:23: error: not an lvalue
drivers/gpu/drm/i915/i915_cmd_parser.c:808:23: error: not an lvalue
drivers/gpu/drm/i915/i915_cmd_parser.c:811:23: error: not an lvalue
drivers/gpu/drm/i915/i915_cmd_parser.c:814:23: error: not an lvalue
If we move the shift into each case not only do we kill the warning from
smatch, but we shrink the code slightly:
text data bss dec hex filename
1267906 20587 3168 1291661 13b58d before
1267890 20587 3168 1291645 13b57d after
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Matthew Auld <matthew.william.auld@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171107154055.19460-1-chris@chris-wilson.co.uk
Reviewed-by: Matthew Auld <matthew.william.auld@gmail.com>
Reviewed-by: Gabriel Krisman Bertazi <krisman@collabora.co.uk>
Include GuC and HuC firmware details in captured error state
to provide additional debug information. To reuse existing
uc firmware pretty printer, introduce new drm-printer variant
that works with our i915_error_state_buf output. Also update
uc firmware pretty printer to accept const input.
v2: don't rely on current caps (Chris)
dump correct fw info (Michal)
v3: simplify capture of custom paths (Chris)
v4: improve 'why' comment (Joonas)
trim output if no fw path (Michal)
group code around uc error state (Michal)
v5: use error in cleanup_uc (Michal)
Suggested-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171026173657.49648-1-michal.wajdeczko@intel.com
[ickle: allow printing uc_fw after allocation failure]
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
There is a possibility on gen9 hardware to miss the forcewake ack
message. The recommended workaround is to use another free
bit and toggle it until original bit is successfully acknowledged.
Some future gen9 revs might or might not fix the underlying issue but
using fallback forcewake bit dance can be considered as harmless:
without the ack timeout we never reach the fallback bit forcewake.
Thus as of now we adopt a blanket approach for all gen9 and leave
the bypassing the fallback bit approach for future patches if
corresponding hw revisions do appear.
Commit 83e3337204 ("drm/i915: Increase maximum polling time to 50ms
for forcewake request/clear ack") did increase the forcewake timeout.
If the issue was a delayed ack, future work could include finding
a suitable timeout value both for primary ack and reserve toggle
to reduce the worst case latency.
v2: use bit 15, naming, comment (Chris), only wait fallback ack
v3: fix return on fallback, backoff after fallback write (Chris)
v4: udelay on first pass, grammar (Chris)
v4: s/reserve/fallback
References: HSDES #1604254524
References: https://bugs.freedesktop.org/show_bug.cgi?id=102051
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171102094836.2506-1-mika.kuoppala@linux.intel.com
This patch adds per engine reset and recovery (TDR) support when GuC is
used to submit workloads to GPU.
In the case of i915 directly submission to ELSP, driver manages hang
detection, recovery and resubmission. With GuC submission these tasks
are shared between driver and GuC. i915 is still responsible for detecting
a hang, and when it does it only requests GuC to reset that Engine. GuC
internally manages acquiring forcewake and idling the engine before
resetting it.
Once the reset is successful, i915 takes over again and handles the
resubmission. The scheduler in i915 knows which requests are pending so
after resetting a engine, pending workloads/requests are resubmitted
again.
v2: s/i915_guc_request_engine_reset/i915_guc_reset_engine/ to match the
non-guc function names.
v3: Removed debug message about engine restarting from which request,
since the new baseline do it regardless of submission mode. (Chris)
v4: Rebase.
v5: Do not pass unnecessary reporting flags to the fw (Jeff);
tasklet_schedule(&execlists->irq_tasklet) handles the resubmit; rebase.
v6: Rename the existing reset engine function and share a similar
interface between guc and non-guc paths (Chris).
Signed-off-by: Michel Thierry <michel.thierry@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171031225309.10888-1-michel.thierry@intel.com
Reviewed-by: Jeff McGee <jeff.mcgee@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
If GuC firmware performs an engine reset while that engine had a
preemption pending, it will set the terminated attribute bit on our
preemption stage descriptor. GuC firmware retains all pending work
items for a high-priority GuC client, unlike the normal-priority GuC
client where work items are dropped. It wants to make sure the preempt-
to-idle work doesn't run when scheduling resumes, and uses this bit to
inform its scheduler and presumably us as well. Our job is to clear it
for the next preemption after reset, otherwise that and future
preemptions will never complete. We'll just clear it every time.
Signed-off-by: Jeff McGee <jeff.mcgee@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171101221630.25086-1-jeff.mcgee@intel.com
Reviewed-by: Michel Thierry <michel.thierry@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
In case the object has changed tiling between calls to execbuf, we need
to check if the existing offset inside the GTT matches the new tiling
constraint. We even need to do this for "unfenced" tiled objects, where
the 3D commands use an implied fence and so the object still needs to
match the physical fence restrictions on alignment (only required for
gen2 and early gen3).
In commit 2889caa923 ("drm/i915: Eliminate lots of iterations over
the execobjects array"), the idea was to remove the second guessing and
only set the NEEDS_MAP flag when required. However, the entire check
for an unusable offset for fencing was removed and not just the
secondary check. I.e.
/* avoid costly ping-pong once a batch bo ended up non-mappable */
if (entry->flags & __EXEC_OBJECT_NEEDS_MAP &&
!i915_vma_is_map_and_fenceable(vma))
return !only_mappable_for_reloc(entry->flags);
was entirely removed as the ping-pong between execbuf passes was fixed,
but its primary purpose in forcing unaligned unfenced access to be
rebound was forgotten.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103502
Fixes: 2889caa923 ("drm/i915: Eliminate lots of iterations over the execobjects array")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171031103607.17836-1-chris@chris-wilson.co.uk
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
encoder->type isn't genreally safe around DDI ports, so let's
replace some uses in the audio code with the crtc state's
output_types instead.
Actually in these cases encoder->type would work since the DP
SST case is only relevant for VLV/CHV and encoder->type==DP
is a thing on those platforms. The DP MST cases would work
as well since MST encoder->type==DP_MST always. But I think
it's best to try and minimize the encoder->type use in general
to avoid showing a bad example to people.
Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171030184654.17429-2-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Eliminate the partially duplicated DDI readout code from MST, and
instead just call intel_ddi_get_config(). As a nice bonus we get
more cross checking as intel_ddi_get_config() will populate
output_types based on the actual mode of the DDI port.
Additonally intel_ddi_get_config() must be changed to get the crtc
from the passed in crtc state rather than from the encoder->crtc link.
encoder->crtc really shouldn't be used anyway.
v2: Rebased on BXT MST latency_optim fix
Make intel_ddi_clock_get() static
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171027193128.14483-7-ville.syrjala@linux.intel.com
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Pass an old crtc state to intel_ddi_post_disable() from the MST code.
Note that this crtc state won't necessaitly match the one that was
passed to intel_ddi_pre_enable() if the first stream to be enabled isn't
the last stream to be disabled. But this is fine since the states should
be identical in every important way. This does mean people frobbing
the DDI pre_enable/post_disable hooks have to pay attention in what
parts of the state they consult.
The alternative would be to inline the relevant code into the MST code.
That is actually what we used to do for pre_enable before
commit e081c8463a ("drm/i915: Remove duplicate DDI enabling logic
from MST path"). For post_disable we've always called the DDI hook.
v2: Pimp up the comments explaining the MST issues
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171027193128.14483-6-ville.syrjala@linux.intel.com
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Currently the DDI encoder->type will change at runtime depending on
what kind of hotplugs we've processed. That's quite bad since we can't
really trust that that current value of encoder->type actually matches
the type of signal we're trying to drive through it.
Let's eliminate that problem by declaring that non-eDP DDI port will
always have the encoder type as INTEL_OUTPUT_DDI. This means the code
can no longer try to distinguish DP vs. HDMI based on encoder->type.
We'll leave eDP as INTEL_OUTPUT_EDP, since it'll never change and
there's a bunch of code that relies on that value to identify eDP
encoders.
We'll introduce a new encoder .compute_output_type() hook. This allows
us to compute the full output_types before any encoder .compute_config()
hooks get called, thus those hooks can rely on output_types being
correct, which is useful for cloning on oldr platforms. For now we'll
just look at the connector type and pick the correct mode based on that.
In the future the new hook could be used to implement dynamic switching
between LS and PCON modes for LSPCON.
v2: Fix BXT/GLK PPS explosion with DSI/MST encoders
v3: Avoid the PPS warn on pure HDMI/DVI DDI encoders by checking dp.output_reg
v4: Rebase
v5: Populate output_types in .get_config() rather than in the caller
v5: Split out populating output_types in .get_config() (Maarten)
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171027193128.14483-3-ville.syrjala@linux.intel.com
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Starting from version 204 VBT can specify the max TMDS clock we are
allowed to use with HDMI ports. Parse that information and take it
into account when filtering modes and computing a crtc state.
Also take the opportunity to sort the platform check if ladder
from new to old.
v2: Add defines for the values into intel_vbt_defs.h (Jani)
Don't fall back to 0 silently for unknown values (Jani)
Skip the debug print for the 0 case (Jani)
Cc: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171030145702.23662-1-ville.syrjala@linux.intel.com
Kasan spotted
[IGT] gem_tiled_pread_pwrite: exiting, ret=0
==================================================================
BUG: KASAN: use-after-free in __i915_gem_object_reset_page_iter+0x15c/0x170 [i915]
Read of size 8 at addr ffff8801359da310 by task kworker/3:2/182
CPU: 3 PID: 182 Comm: kworker/3:2 Tainted: G U 4.14.0-rc6-CI-Custom_3340+ #1
Hardware name: Intel Corp. Geminilake/GLK RVP1 DDR4 (05), BIOS GELKRVPA.X64.0062.B30.1708222146 08/22/2017
Workqueue: events __i915_gem_free_work [i915]
Call Trace:
dump_stack+0x68/0xa0
print_address_description+0x78/0x290
? __i915_gem_object_reset_page_iter+0x15c/0x170 [i915]
kasan_report+0x23d/0x350
__asan_report_load8_noabort+0x19/0x20
__i915_gem_object_reset_page_iter+0x15c/0x170 [i915]
? i915_gem_object_truncate+0x100/0x100 [i915]
? lock_acquire+0x380/0x380
__i915_gem_object_put_pages+0x30d/0x530 [i915]
__i915_gem_free_objects+0x551/0xbd0 [i915]
? lock_acquire+0x13e/0x380
__i915_gem_free_work+0x4e/0x70 [i915]
process_one_work+0x6f6/0x1590
? pwq_dec_nr_in_flight+0x2b0/0x2b0
worker_thread+0xe6/0xe90
? pci_mmcfg_check_reserved+0x110/0x110
kthread+0x309/0x410
? process_one_work+0x1590/0x1590
? kthread_create_on_node+0xb0/0xb0
ret_from_fork+0x27/0x40
Allocated by task 1801:
save_stack_trace+0x1b/0x20
kasan_kmalloc+0xee/0x190
kasan_slab_alloc+0x12/0x20
kmem_cache_alloc+0xdc/0x2e0
radix_tree_node_alloc.constprop.12+0x48/0x330
__radix_tree_create+0x274/0x480
__radix_tree_insert+0xa2/0x610
i915_gem_object_get_sg+0x224/0x670 [i915]
i915_gem_object_get_page+0xb5/0x1c0 [i915]
i915_gem_pread_ioctl+0x822/0xf60 [i915]
drm_ioctl_kernel+0x13f/0x1c0
drm_ioctl+0x6cf/0x980
do_vfs_ioctl+0x184/0xf30
SyS_ioctl+0x41/0x70
entry_SYSCALL_64_fastpath+0x1c/0xb1
Freed by task 37:
save_stack_trace+0x1b/0x20
kasan_slab_free+0xaf/0x190
kmem_cache_free+0xbf/0x340
radix_tree_node_rcu_free+0x79/0x90
rcu_process_callbacks+0x46d/0xf40
__do_softirq+0x21c/0x8d3
The buggy address belongs to the object at ffff8801359da0f0
which belongs to the cache radix_tree_node of size 576
The buggy address is located 544 bytes inside of
576-byte region [ffff8801359da0f0, ffff8801359da330)
The buggy address belongs to the page:
page:ffffea0004d67600 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0
flags: 0x8000000000008100(slab|head)
raw: 8000000000008100 0000000000000000 0000000000000000 0000000100110011
raw: ffffea0004b52920 ffffea0004b38020 ffff88015b416a80 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff8801359da200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801359da280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801359da300: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
^
ffff8801359da380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8801359da400: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
Disabling lock debugging due to kernel taint
which looks like the slab containing the radixtree iter was freed as we
traversed the tree, taking the rcu read lock across the loop should
prevent that (deferring all the frees until the end).
Reported-by: Tomi Sarvela <tomi.p.sarvela@intel.com>
Fixes: d1b48c1e71 ("drm/i915: Replace execbuf vma ht with an idr")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171026130032.10677-2-chris@chris-wilson.co.uk
Reviewed-by: Matthew Auld <matthew.william.auld@gmail.com>
Kasan spotted
[IGT] gem_tiled_pread_pwrite: exiting, ret=0
==================================================================
BUG: KASAN: use-after-free in __i915_gem_object_reset_page_iter+0x15c/0x170 [i915]
Read of size 8 at addr ffff8801359da310 by task kworker/3:2/182
CPU: 3 PID: 182 Comm: kworker/3:2 Tainted: G U 4.14.0-rc6-CI-Custom_3340+ #1
Hardware name: Intel Corp. Geminilake/GLK RVP1 DDR4 (05), BIOS GELKRVPA.X64.0062.B30.1708222146 08/22/2017
Workqueue: events __i915_gem_free_work [i915]
Call Trace:
dump_stack+0x68/0xa0
print_address_description+0x78/0x290
? __i915_gem_object_reset_page_iter+0x15c/0x170 [i915]
kasan_report+0x23d/0x350
__asan_report_load8_noabort+0x19/0x20
__i915_gem_object_reset_page_iter+0x15c/0x170 [i915]
? i915_gem_object_truncate+0x100/0x100 [i915]
? lock_acquire+0x380/0x380
__i915_gem_object_put_pages+0x30d/0x530 [i915]
__i915_gem_free_objects+0x551/0xbd0 [i915]
? lock_acquire+0x13e/0x380
__i915_gem_free_work+0x4e/0x70 [i915]
process_one_work+0x6f6/0x1590
? pwq_dec_nr_in_flight+0x2b0/0x2b0
worker_thread+0xe6/0xe90
? pci_mmcfg_check_reserved+0x110/0x110
kthread+0x309/0x410
? process_one_work+0x1590/0x1590
? kthread_create_on_node+0xb0/0xb0
ret_from_fork+0x27/0x40
Allocated by task 1801:
save_stack_trace+0x1b/0x20
kasan_kmalloc+0xee/0x190
kasan_slab_alloc+0x12/0x20
kmem_cache_alloc+0xdc/0x2e0
radix_tree_node_alloc.constprop.12+0x48/0x330
__radix_tree_create+0x274/0x480
__radix_tree_insert+0xa2/0x610
i915_gem_object_get_sg+0x224/0x670 [i915]
i915_gem_object_get_page+0xb5/0x1c0 [i915]
i915_gem_pread_ioctl+0x822/0xf60 [i915]
drm_ioctl_kernel+0x13f/0x1c0
drm_ioctl+0x6cf/0x980
do_vfs_ioctl+0x184/0xf30
SyS_ioctl+0x41/0x70
entry_SYSCALL_64_fastpath+0x1c/0xb1
Freed by task 37:
save_stack_trace+0x1b/0x20
kasan_slab_free+0xaf/0x190
kmem_cache_free+0xbf/0x340
radix_tree_node_rcu_free+0x79/0x90
rcu_process_callbacks+0x46d/0xf40
__do_softirq+0x21c/0x8d3
The buggy address belongs to the object at ffff8801359da0f0
which belongs to the cache radix_tree_node of size 576
The buggy address is located 544 bytes inside of
576-byte region [ffff8801359da0f0, ffff8801359da330)
The buggy address belongs to the page:
page:ffffea0004d67600 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0
flags: 0x8000000000008100(slab|head)
raw: 8000000000008100 0000000000000000 0000000000000000 0000000100110011
raw: ffffea0004b52920 ffffea0004b38020 ffff88015b416a80 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff8801359da200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff8801359da280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801359da300: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
^
ffff8801359da380: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff8801359da400: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================
Disabling lock debugging due to kernel taint
which looks like the slab containing the radixtree iter was freed as we
traversed the tree, taking the rcu read lock across the loop should
prevent that (deferring all the frees until the end).
Reported-by: Tomi Sarvela <tomi.p.sarvela@intel.com>
Fixes: 96d7763452 ("drm/i915: Use a radixtree for random access to the object's backing storage")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171026130032.10677-1-chris@chris-wilson.co.uk
Reviewed-by: Matthew Auld <matthew.william.auld@gmail.com>
