We need to move to a more flexible timeline that doesn't assume one
fence context per engine, and so allow for a single timeline to be used
across a combination of engines. This means that preallocating a fence
context per engine is now a hindrance, and so we want to introduce the
singular timeline. From the code perspective, this has the notable
advantage of clearing up a lot of mirky semantics and some clumsy
pointer chasing.

By splitting the timeline up into a single entity rather than an array
of per-engine timelines, we can realise the goal of the previous patch
of tracking the timeline alongside the ring.

v2: Tweak wait_for_idle to stop the compiling thinking that ret may be
uninitialised.
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/20180502163839.3248-2-chris@chris-wilson.co.uk

As our early doorbell is split between early allocation and a late setup
after we have a channel to the GuC, it may happen due to a lapse of
programmer judgement that we try to setup an invalid doorbell. Make use
of our has_doorbell() function to check the doorbell does exist for the
client before we try and tell the guc about it. In doing so, we prevent
the compiler from warning about the otherwise unused function in some
configurations.
Reported-by: NMatthias Kaehlcke <mka@chromium.org>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Michel Thierry <michel.thierry@intel.com>
Reviewed-by: NMichel Thierry <michel.thierry@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180501075203.12458-1-chris@chris-wilson.co.uk

Make life easier in upcoming patches by moving the context_pin and
context_unpin vfuncs into inline helpers.

v2: Fixup mock_engine to mark the context as pinned on use.
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/20180430131503.5375-2-chris@chris-wilson.co.uk

Today we only want to pass along the priority to engine->schedule(), but
in the future we want to have much more control over the various aspects
of the GPU during a context's execution, for example controlling the
frequency allowed. As we need an ever growing number of parameters for
scheduling, move those into a struct for convenience.

v2: Move the anonymous struct into its own function for legibility and
ye olde gcc.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180418184052.7129-3-chris@chris-wilson.co.uk

Having moved the priotree struct into i915_scheduler.h, identify it as
the scheduling element and rebrand into i915_sched. This becomes more
useful as we start attaching more information we require to propagate
through the scheduler.

v2: Use i915_sched_node for future distinctiveness
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180418184052.7129-2-chris@chris-wilson.co.uk

Let's avoid having to delve down the pointer chain to see if the i915
device has support for preemption and store that on the engine, which
made the decision in the first place!

v2: Refactor common preemption policy between execlists/guc.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tomasz Lis <tomasz.lis@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NDaniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180403183537.5522-1-chris@chris-wilson.co.uk

We would like to start doing some bookkeeping at the beginning, between
contexts and at the end of execlists submission. We already mark the
beginning and end using EXECLISTS_ACTIVE_USER, to provide an indication
when the HW is idle. This give us a pair of sequence points we can then
expand on for further bookkeeping.

v2: Refactor guc submission to share the same begin/end.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Francisco Jerez <currojerez@riseup.net>
Reviewed-by: NFrancisco Jerez <currojerez@riseup.net>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180331130626.10712-1-chris@chris-wilson.co.uk

We're using those functions in selftests, and the callers are expected
to do the error handling anyways. Let's demote all GuC actions and
doorbell creation to DEBUG_DRIVER.
Signed-off-by: NMichał Winiarski <michal.winiarski@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180319095348.9716-12-michal.winiarski@intel.com

GuC related exported functions should start with "intel_guc_" prefix and
pass intel_guc as the first parameter since its GuC related. Current
guc_ggtt_offset() failed to follow this code convention and this is a
problem for future patches that needs to access intel_guc data to verify
the GGTT offset against the GuC WOPCM top.

This patch renames the guc_ggtt_offset to intel_guc_ggtt_offset and updates
the related code to pass intel_guc pointer to this function call, so that
we can have a unified coding style for GuC code and also enable the future
patches to get GuC related data from intel_guc to do the offset
verification. Meanwhile, this patch also moves the GUC_GGTT_TOP from
intel_guc_regs.h to intel_guc.h since it is not GuC register related
definition.

v8:
 - Fixed coding style issues and moved GUC_GGTT_TOP to intel_guc.h (Sagar)
 - Updated commit message to explain to reason and motivation to add
   intel_guc as the first parameter of intel_guc_ggtt_offset (Chris)

v9:
 - Fixed code alignment issue due to line break (Chris)

v10:
 - Removed unnecessary comments, redundant code and avoided reuse variable
   to avoid potential issues (Joonas)

v13:
 - Updated the ordering of s-o-b/cc/r-b tags (Sagar)
Signed-off-by: NJackie Li <yaodong.li@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Sagar Arun Kamble <sagar.a.kamble@intel.com> (v8)
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> (v9)
Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com> (v11)
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> (v12)
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1520987574-19351-1-git-send-email-yaodong.li@intel.com

Since we're inhibiting context save of preempt context, we're no longer
tracking the position of HEAD/TAIL. With GuC, we're adding a new
breadcrumb for each preemption, which means that the HW will do more and
more breadcrumb writes. Eventually the ring is filled, and we're
submitting the preemption context with HEAD==TAIL==0, which won't result
in breadcrumb write, but will trigger hangcheck instead.
Instead of writing a new preempt breadcrumb for each preemption, let's
just fill the ring once at init time (which also saves a couple of
instructions in the tasklet).

v2: Assert that context save restore is inhibited, don't assert on ring
    alignment. (Chris)
v3: Cleanup checkpatch.

Fixes: 517aaffe ("drm/i915/execlists: Inhibit context save/restore for the fake preempt context")
Signed-off-by: NMichał Winiarski <michal.winiarski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180226163800.21745-1-michal.winiarski@intel.comReviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>

Sometimes we need to boost the priority of an in-flight request, which
may lead to the situation where the second submission port then contains
a higher priority context than the first and so we need to inject a
preemption event. To do so we must always check inside
execlists_dequeue() whether there is a priority inversion between the
ports themselves as well as the head of the priority sorted queue, and we
cannot just skip dequeuing if the queue is empty.

As Michał noted, this doesn't simply extend to handling more than 2-port
submission, as we may need to reorder within the array of executing
requests which themselves are lower priority than the first. A task for
later!
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180222142229.14517-1-chris@chris-wilson.co.ukReviewed-by: NMichał Winiarski <michal.winiarski@intel.com>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>

We want to de-emphasize the link between the request (dependency,
execution and fence tracking) from GEM and so rename the struct from
drm_i915_gem_request to i915_request. That is we may implement the GEM
user interface on top of requests, but they are an abstraction for
tracking execution rather than an implementation detail of GEM. (Since
they are not tied to HW, we keep the i915 prefix as opposed to intel.)

In short, the spatch:
@@

@@
- struct drm_i915_gem_request
+ struct i915_request

A corollary to contracting the type name, we also harmonise on using
'rq' shorthand for local variables where space if of the essence and
repetition makes 'request' unwieldy. For globals and struct members,
'request' is still much preferred for its clarity.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180221095636.6649-1-chris@chris-wilson.co.ukReviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: NMichał Winiarski <michal.winiarski@intel.com>
Acked-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>

The continual resubmission model for execlists (and emulated over guc)
requires that we keep feeding requests into the HW in order to generate
more CS interrupts to drain the rest of the queue. Add a couple of
asserts to ensure that we don't skip a cycle and come to a grinding
halt.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180215162553.23348-1-chris@chris-wilson.co.uk

If we remove some hardcoded assumptions about the preempt context having
a fixed id, reserved from use by normal user contexts, we may only
allocate the i915_gem_context when required. Then the subsequent
decisions on using preemption reduce to having the preempt context
available.

v2: Include an assert that we don't allocate the preempt context twice.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Michal Winiarski <michal.winiarski@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Acked-by: NDaniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180207210544.26351-3-chris@chris-wilson.co.ukReviewed-by: NMichel Thierry <michel.thierry@intel.com>

In the next patch, we may only conditionally allocate the preempt-client
if there is a global preempt context and so we need to be prepared in
case the preempt-client itself is NULL.

v2: Grep for more preempt_client.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Michal Winiarski <michal.winiarski@intel.com>
Cc: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180207210544.26351-1-chris@chris-wilson.co.ukReviewed-by: NMichel Thierry <michel.thierry@intel.com>

The Additional Data Struct (ADS) contains objects that are required by
GuC post FW load and are not necessarily submission-only. Even with
submission disabled we may require something inside the ADS, so it
makes more sense for them to be always created.

Similarly, we need to access GuC logs and even if GuC submission
is disabled, to debug issues with GuC loading or with whatever we're using
GuC for.

v2: re-wording commit message (Sagar)
Signed-off-by: NSujaritha Sundaresan <sujaritha.sundaresan@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Reviewed-by: NSagar Arun Kamble <sagar.a.kamble@intel.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/1514928025-29659-1-git-send-email-sujaritha.sundaresan@intel.com

We have the selftest that's checking doorbell create/destroy, so there's
no need to check all doorbells delaying the reset every time.
We do want to have that extra sanity check at module load/unload though.
Signed-off-by: NMichał Winiarski <michal.winiarski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: NMichal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: NMichel Thierry <michel.thierry@intel.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171213221352.7173-7-michal.winiarski@intel.com

We can now move the clients allocation to submission_init path, rather
than keeping the condition inside submission_enable called on every
reset.
Signed-off-by: NMichał Winiarski <michal.winiarski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: NMichel Thierry <michel.thierry@intel.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171213221352.7173-6-michal.winiarski@intel.com

Full GPU reset causes GuC to be reset. This means that every time we're
doing a reset, we need to talk to GuC and tell it about doorbells.
Let's separate the communication part (create_doorbell) from our
internal bookkeeping (reserve_doorbell) so that we can cleanly separate
the initialization done at module load from reinitialization done at
reset in the following patch.
While I'm here, let's also add a proper (although slightly asymetric)
cleanup that doesn't try to communicate with GuC after it's already
gone, getting rid of "expected" warnings caused by GuC action failures
on module unload.

Note that I've also removed one of the tests (bitmap out of sync), since
it doesn't make much sense anymore - bitmaps are now not expected to
change during the lifetime of a client.
Signed-off-by: NMichał Winiarski <michal.winiarski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Michel Thierry <michel.thierry@intel.com>
Reviewed-by: NMichel Thierry <michel.thierry@intel.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171213221352.7173-5-michal.winiarski@intel.com

This gets rid of the following lockdep splat:

======================================================
WARNING: possible circular locking dependency detected
4.15.0-rc2-CI-Patchwork_7428+ #1 Not tainted
------------------------------------------------------
debugfs_test/1351 is trying to acquire lock:
 (&dev->struct_mutex){+.+.}, at: [<000000009d90d1a3>] i915_mutex_lock_interruptible+0x47/0x130 [i915]

but task is already holding lock:
 (&mm->mmap_sem){++++}, at: [<000000005df01c1e>] __do_page_fault+0x106/0x560

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #6 (&mm->mmap_sem){++++}:
       __might_fault+0x63/0x90
       _copy_to_user+0x1e/0x70
       filldir+0x8c/0xf0
       dcache_readdir+0xeb/0x160
       iterate_dir+0xe6/0x150
       SyS_getdents+0xa0/0x130
       entry_SYSCALL_64_fastpath+0x1c/0x89

-> #5 (&sb->s_type->i_mutex_key#5){++++}:
       lockref_get+0x9/0x20

-> #4 ((completion)&req.done){+.+.}:
       wait_for_common+0x54/0x210
       devtmpfs_create_node+0x130/0x150
       device_add+0x5ad/0x5e0
       device_create_groups_vargs+0xd4/0xe0
       device_create+0x35/0x40
       msr_device_create+0x22/0x40
       cpuhp_invoke_callback+0xc5/0xbf0
       cpuhp_thread_fun+0x167/0x210
       smpboot_thread_fn+0x17f/0x270
       kthread+0x173/0x1b0
       ret_from_fork+0x24/0x30

-> #3 (cpuhp_state-up){+.+.}:
       cpuhp_issue_call+0x132/0x1c0
       __cpuhp_setup_state_cpuslocked+0x12f/0x2a0
       __cpuhp_setup_state+0x3a/0x50
       page_writeback_init+0x3a/0x5c
       start_kernel+0x393/0x3e2
       secondary_startup_64+0xa5/0xb0

-> #2 (cpuhp_state_mutex){+.+.}:
       __mutex_lock+0x81/0x9b0
       __cpuhp_setup_state_cpuslocked+0x4b/0x2a0
       __cpuhp_setup_state+0x3a/0x50
       page_alloc_init+0x1f/0x26
       start_kernel+0x139/0x3e2
       secondary_startup_64+0xa5/0xb0

-> #1 (cpu_hotplug_lock.rw_sem){++++}:
       cpus_read_lock+0x34/0xa0
       apply_workqueue_attrs+0xd/0x40
       __alloc_workqueue_key+0x2c7/0x4e1
       intel_guc_submission_init+0x10c/0x650 [i915]
       intel_uc_init_hw+0x29e/0x460 [i915]
       i915_gem_init_hw+0xca/0x290 [i915]
       i915_gem_init+0x115/0x3a0 [i915]
       i915_driver_load+0x9a8/0x16c0 [i915]
       i915_pci_probe+0x2e/0x90 [i915]
       pci_device_probe+0x9c/0x120
       driver_probe_device+0x2a3/0x480
       __driver_attach+0xd9/0xe0
       bus_for_each_dev+0x57/0x90
       bus_add_driver+0x168/0x260
       driver_register+0x52/0xc0
       do_one_initcall+0x39/0x150
       do_init_module+0x56/0x1ef
       load_module+0x231c/0x2d70
       SyS_finit_module+0xa5/0xe0
       entry_SYSCALL_64_fastpath+0x1c/0x89

-> #0 (&dev->struct_mutex){+.+.}:
       lock_acquire+0xaf/0x200
       __mutex_lock+0x81/0x9b0
       i915_mutex_lock_interruptible+0x47/0x130 [i915]
       i915_gem_fault+0x201/0x760 [i915]
       __do_fault+0x15/0x70
       __handle_mm_fault+0x85b/0xe40
       handle_mm_fault+0x14f/0x2f0
       __do_page_fault+0x2d1/0x560
       page_fault+0x22/0x30

other info that might help us debug this:

Chain exists of:
  &dev->struct_mutex --> &sb->s_type->i_mutex_key#5 --> &mm->mmap_sem

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&mm->mmap_sem);
                               lock(&sb->s_type->i_mutex_key#5);
                               lock(&mm->mmap_sem);
  lock(&dev->struct_mutex);

 *** DEADLOCK ***

1 lock held by debugfs_test/1351:
 #0:  (&mm->mmap_sem){++++}, at: [<000000005df01c1e>] __do_page_fault+0x106/0x560

stack backtrace:
CPU: 2 PID: 1351 Comm: debugfs_test Not tainted 4.15.0-rc2-CI-Patchwork_7428+ #1
Hardware name:                  /NUC6i5SYB, BIOS SYSKLi35.86A.0057.2017.0119.1758 01/19/2017
Call Trace:
 dump_stack+0x5f/0x86
 print_circular_bug+0x230/0x3b0
 check_prev_add+0x439/0x7b0
 ? lockdep_init_map_crosslock+0x20/0x20
 ? unwind_get_return_address+0x16/0x30
 ? __lock_acquire+0x1385/0x15a0
 __lock_acquire+0x1385/0x15a0
 lock_acquire+0xaf/0x200
 ? i915_mutex_lock_interruptible+0x47/0x130 [i915]
 __mutex_lock+0x81/0x9b0
 ? i915_mutex_lock_interruptible+0x47/0x130 [i915]
 ? i915_mutex_lock_interruptible+0x47/0x130 [i915]
 ? i915_mutex_lock_interruptible+0x47/0x130 [i915]
 i915_mutex_lock_interruptible+0x47/0x130 [i915]
 ? __pm_runtime_resume+0x4f/0x80
 i915_gem_fault+0x201/0x760 [i915]
 __do_fault+0x15/0x70
 __handle_mm_fault+0x85b/0xe40
 handle_mm_fault+0x14f/0x2f0
 __do_page_fault+0x2d1/0x560
 page_fault+0x22/0x30
RIP: 0033:0x7f98d6f49116
RSP: 002b:00007ffd6ffc3278 EFLAGS: 00010283
RAX: 00007f98d39a2bc0 RBX: 0000000000000000 RCX: 0000000000001680
RDX: 0000000000001680 RSI: 00007ffd6ffc3400 RDI: 00007f98d39a2bc0
RBP: 00007ffd6ffc33a0 R08: 0000000000000000 R09: 00000000000005a0
R10: 000055e847c2a830 R11: 0000000000000002 R12: 0000000000000001
R13: 000055e847c1d040 R14: 00007ffd6ffc3400 R15: 00007f98d6752ba0

v2: Init preempt_work unconditionally (Chris)
v3: Mention that we need the enable_guc=1 for lockdep splat (Chris)

Testcase: igt/debugfs_test/read_all_entries # with i915.enable_guc=1
Signed-off-by: NMichał Winiarski <michal.winiarski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171213221352.7173-2-michal.winiarski@intel.com

We need shared data for actions (e.g. guc suspend/resume), and we're
using those with GuC submission disabled.
Let's introduce intel_guc_init and move shared data alloc there.

This fixes GPF during module unload with HuC, but without GuC submission:

BUG: unable to handle kernel NULL pointer dereference at 000000005aee7809
IP: intel_guc_suspend+0x34/0x140 [i915]
PGD 0 P4D 0
Oops: 0000 [#1] PREEMPT SMP
Modules linked in: i915(O-) netconsole x86_pkg_temp_thermal
intel_powerclamp coretemp crct10dif_pclmul crc32_pclmul ghash_clmulni_intel
mei_me i2c_i801 mei prime_numbers [last unloaded: i915]
CPU: 2 PID: 2794 Comm: rmmod Tainted: G     U  W  O 4.15.0-rc2+ #297
Hardware name: /NUC6i5SYB, BIOS SYSKLi35.86A.0054.2016.0930.1102 09/30/2016
task: 0000000055945c61 task.stack: 00000000264ccb43
RIP: 0010:intel_guc_suspend+0x34/0x140 [i915]
RSP: 0018:ffffc90000483df8 EFLAGS: 00010286
RAX: 0000000000000000 RBX: ffff880829180000 RCX: 0000000000000000
RDX: 0000000000000006 RSI: ffff880844c2c938 RDI: ffff880844c2c000
RBP: ffff880829180000 R08: 00000000a29c58c1 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: ffffffffa040ba40
R13: ffffffffa040bab0 R14: ffff88084a195060 R15: 000055df3ef357a0
FS:  00007ff43c043740(0000) GS:ffff88084e200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000000000f9 CR3: 000000083f179005 CR4: 00000000003606e0
Call Trace:
 i915_gem_suspend+0x9d/0x130 [i915]
 ? i915_driver_unload+0x68/0x180 [i915]
 i915_driver_unload+0x70/0x180 [i915]
 i915_pci_remove+0x15/0x20 [i915]
 pci_device_remove+0x36/0xb0
 device_release_driver_internal+0x15f/0x220
 driver_detach+0x3a/0x80
 bus_remove_driver+0x58/0xd0
 pci_unregister_driver+0x29/0x90
 SyS_delete_module+0x150/0x1e0
 entry_SYSCALL_64_fastpath+0x23/0x9a
RIP: 0033:0x7ff43b51b5c7
RSP: 002b:00007ffe6825a758 EFLAGS: 00000206 ORIG_RAX: 00000000000000b0
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007ff43b51b5c7
RDX: 000000000000000a RSI: 0000000000000800 RDI: 000055df3ef35808
RBP: 0000000000000000 R08: 00007ffe682596d1 R09: 0000000000000000
R10: 00007ff43b594880 R11: 0000000000000206 R12: 000055df3ef357a0
R13: 00007ffe68259740 R14: 000055df3ef35260 R15: 000055df3ef357a0
Code: 00 00 02 74 03 31 c0 c3 53 48 89 fb 48 83 ec 10 e8 52 0f
f8 ff 48 b8 01 05 00 00 02 00 00 00 48 89 44 24 04 48 8b 83 00 12 00 00 <f6> 80
f9 00 00 00 01 0f 84 a7 00 00 00 f6 80 98 00 00 00 01 0f
RIP: intel_guc_suspend+0x34/0x140 [i915] RSP: ffffc90000483df8
CR2: 00000000000000f9
---[ end trace 23a192a61d937a3e ]---

Fixes: b8e5eb96 ("drm/i915/guc: Allocate separate shared data object for GuC communication")
Signed-off-by: NMichał Winiarski <michal.winiarski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171213221352.7173-1-michal.winiarski@intel.com

Sagar noticed the check can be consolidated between the engine stats
implementation and the PMU.

My first choice was a static inline helper but that got into include
ordering mess quickly fast so I went with a macro instead. At some point
we should perhaps looking into taking out the non-ringubffer bits from
intel_ringbuffer.h into a new intel_engine.h or something.

v2: Use engine->flags. (Chris Wilson)
v3: Rebase and mark GuC as not yet supported. (Chris Wilson)
v4: Move flag setting to intel_engines_reset_default_submission.
    (Chris Wilson)
v5: Move flag setting to logical_ring_setup.
v6: intel_engines_reset_default_submission is the wrong place to set the
    flag - it needs to be in execlists_set_default_submission. (Sagar)
v7: Flag setting in logical_ring_setup is not required. (Chris)
Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Suggested-by: NSagar Arun Kamble <sagar.a.kamble@intel.com>
Cc: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Sagar Arun Kamble <sagar.a.kamble@intel.com> (v6)
Link: https://patchwork.freedesktop.org/patch/msgid/20171129102805.22690-1-tvrtko.ursulin@linux.intel.com

Since we know that the port is empty, we do not need to extract the
count from the old request it and copy it over to the new request, or
attempt to unref the NULL old request pointer.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Reviewed-by: NMichał Winiarski <michal.winiarski@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171124130031.20761-1-chris@chris-wilson.co.uk

Our execlist emulation is intended to only use a maximum of 2 ports per
engine, so as to not overflow the wq. (By knowing the limits, we can
avoid having to handle the wq exhaustion.) However, upon adding
preemption, we lost the skip over the first port if set for the
non-preemption path. Restore it.
Reported-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Fixes: c41937fd ("drm/i915/guc: Preemption! With GuC")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171124133745.5173-1-chris@chris-wilson.co.ukReviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: NMichał Winiarski <michal.winiarski@intel.com>

The first test aims to check guc_init_doorbell_hw, changing the existing
guc clients and doorbells state before calling it.

The second test tries to create as many clients as it is currently possible
(currently limited to max number of doorbells) and exercise the doorbell
alloc/dealloc code.

Since our usage mode require very few clients/doorbells, this code has
been exercised very lightly and it's good to have a simple test for it.

As reference, this test already helped identify the bug fixed by
commit 7f1ea2ac ("drm/i915/guc: Fix doorbell id selection").

v2: Extend number of clients; check for client allocation failure when
number of doorbells is exceeded; validate client properties; reuse
guc_init_doorbell_hw (Chris).

v3: guc_init_doorbell_hw test added per Chris suggestion.

v4: Try to explain why guc_init_doorbell_hw exist and comment some
details in the subtest.

v5: Remove redundant pr_info at the beginning of each subtest (Chris);
rebase (s/i915_guc_client/intel_guc_client/).
Signed-off-by: NMichel Thierry <michel.thierry@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171116220632.1909-1-michel.thierry@intel.comSigned-off-by: NChris Wilson <chris@chris-wilson.co.uk>

With all component structures and functions named appropriately, change
the names of GuC submission source files. There were bunch of style issues
in guc_submission.c that are highlighted now by checkpatch. Fix those.
Update name in Documentation/gpu. (Joonas)

v2: Rebase.

v3: Rebase.
Signed-off-by: NSagar Arun Kamble <sagar.a.kamble@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Michal Winiarski <michal.winiarski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Acked-by: NChris Wilson <chris@chris-wilson.co.uk>
Acked-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Acked-by: NOscar Mateo <oscar.mateo@intel.com>
Reviewed-by: NMichal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1510839162-25197-6-git-send-email-sagar.a.kamble@intel.comSigned-off-by: NChris Wilson <chris@chris-wilson.co.uk>

GuC submission clients are currently being used in kernel only hence
update the structure name to intel_guc_client.
Signed-off-by: NSagar Arun Kamble <sagar.a.kamble@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Michal Winiarski <michal.winiarski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Acked-by: NChris Wilson <chris@chris-wilson.co.uk>
Acked-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Acked-by: NOscar Mateo <oscar.mateo@intel.com>
Reviewed-by: NMichal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1510839162-25197-5-git-send-email-sagar.a.kamble@intel.comSigned-off-by: NChris Wilson <chris@chris-wilson.co.uk>

i915 GuC submission is hardware interface and GuC APIs that are not user
facing should be named intel_guc* hence we change GuC submission related
functions name prefix to intel_guc. Also changed the parameter to these
functions to intel_guc struct.

v2: Using local guc variable in intel_uc_fini_hw. (Michal Wajdeczko)
Rebase.
Suggested-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NSagar Arun Kamble <sagar.a.kamble@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Michal Winiarski <michal.winiarski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Acked-by: NChris Wilson <chris@chris-wilson.co.uk>
Acked-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Acked-by: NOscar Mateo <oscar.mateo@intel.com>
Reviewed-by: NMichal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1510839162-25197-4-git-send-email-sagar.a.kamble@intel.comSigned-off-by: NChris Wilson <chris@chris-wilson.co.uk>

i915_guc_submit, i915_guc_dequeue, i915_guc_submission_park and
i915_guc_submission_upark are functions internal to GuC submission
hence remove "i915_" prefix.
Suggested-by: NMichal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: NSagar Arun Kamble <sagar.a.kamble@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Michal Winiarski <michal.winiarski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: NMichal Wajdeczko <michal.wajdeczko@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1510839162-25197-3-git-send-email-sagar.a.kamble@intel.comSigned-off-by: NChris Wilson <chris@chris-wilson.co.uk>

intel_lrc_irq_handler and i915_guc_irq_handler are HW submission related
tasklet functions. Name them with "submission_tasklet" suffix and
remove intel/i915 prefix as they are static. Also rename irq_tasklet
as just tasklet for clarity.

v2: s/_bh/_tasklet (Chris)
Suggested-by: NMichal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: NSagar Arun Kamble <sagar.a.kamble@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Michal Winiarski <michal.winiarski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: NMichal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/1510839162-25197-2-git-send-email-sagar.a.kamble@intel.comSigned-off-by: NChris Wilson <chris@chris-wilson.co.uk>

Back in commit a4b2b015 ("drm/i915: Don't mark an execlists
context-switch when idle") we noticed the presence of late
context-switch interrupts. We were able to filter those out by looking
at whether the ELSP remained active, but in commit beecec90
("drm/i915/execlists: Preemption!") that became problematic as we now
anticipate receiving a context-switch event for preemption while ELSP
may be empty. To restore the spurious interrupt suppression, add a
counter for the expected number of pending context-switches and skip if
we do not need to handle this interrupt to make forward progress.

v2: Don't forget to switch on for preempt.
v3: Reduce the counter to a on/off boolean tracker. Declare the HW as
active when we first submit, and idle after the final completion event
(with which we confirm the HW says it is idle), and track each source
of activity separately. With a finite number of sources, it should aide
us in debugging which gets stuck.

Fixes: beecec90 ("drm/i915/execlists: Preemption!")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Michal Winiarski <michal.winiarski@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171023213237.26536-3-chris@chris-wilson.co.ukReviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
(cherry picked from commit 4a118ecb)
Signed-off-by: NJani Nikula <jani.nikula@intel.com>

Silence smatch by demonstrating that guc->stage_desc_pool is allocated
following a successful guc_stage_desc_pool_create(),

drivers/gpu/drm/i915/i915_guc_submission.c:1293 i915_guc_submission_init() error: we previously assumed 'guc->stage_desc_pool' could be null (see line 1261)
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Oscar Mateo <oscar.mateo@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171106114833.31199-1-chris@chris-wilson.co.ukReviewed-by: NMichal Wajdeczko <michal.wajdeczko@intel.com>

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: NJeff McGee <jeff.mcgee@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171101221630.25086-1-jeff.mcgee@intel.comReviewed-by: NMichel Thierry <michel.thierry@intel.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>

Pretty similar to what we have on execlists.
We're reusing most of the GEM code, however, due to GuC quirks we need a
couple of extra bits.
Preemption is implemented as GuC action, and actions can be pretty slow.
Because of that, we're using a mutex to serialize them. Since we're
requesting preemption from the tasklet, the task of creating a workitem
and wrapping it in GuC action is delegated to a worker.

To distinguish that preemption has finished, we're using additional
piece of HWSP, and since we're not getting context switch interrupts,
we're also adding a user interrupt.

The fact that our special preempt context has completed unfortunately
doesn't mean that we're ready to submit new work. We also need to wait
for GuC to finish its own processing.

v2: Don't compile out the wait for GuC, handle workqueue flush on reset,
no need for ordered workqueue, put on a reviewer hat when looking at my own
patches (Chris)
Move struct work around in intel_guc, move user interruput outside of
conditional (Michał)
Keep ring around rather than chase though intel_context

v3: Extract WA for flushing ggtt writes to a helper (Chris)
Keep work_struct in intel_guc rather than engine (Michał)
Use ordered workqueue for inject_preempt worker to avoid GuC quirks.

v4: Drop now unused INTEL_GUC_PREEMPT_OPTION_IMMEDIATE (Daniele)
Drop stray newlines, use container_of for intel_guc in worker,
check for presence of workqueue when flushing it, rather than
enable_guc_submission modparam, reorder preempt postprocessing (Chris)

v5: Make wq NULL after destroying it

v6: Swap struct guc_preempt_work members (Michał)
Signed-off-by: NMichał Winiarski <michal.winiarski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jeff McGee <jeff.mcgee@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Oscar Mateo <oscar.mateo@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171026133558.19580-1-michal.winiarski@intel.com

We also want to support preemption with GuC submission backend.
In order to do that, we need to remember the priority, like we do on
execlists path.

v2: Remove completed prio == INT_MAX optimization
Signed-off-by: NMichał Winiarski <michal.winiarski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jeff McGee <jeff.mcgee@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171025200020.16636-10-michal.winiarski@intel.com

We're using a special preempt context for HW to preempt into. We don't
want to emit any requests there, but we still need to wrap this context
into a valid GuC work item.
Let's cleanup the functions operating on GuC work items.
We can extract guc_request_add - responsible for adding GuC work item and
ringing the doorbell, and guc_wq_item_append - used by the function
above, not tied to the concept of gem request.
Signed-off-by: NMichał Winiarski <michal.winiarski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jeff McGee <jeff.mcgee@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Oscar Mateo <oscar.mateo@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJeff McGee <jeff.mcgee@intel.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171025200020.16636-7-michal.winiarski@intel.com

This second client is created with priority KMD_HIGH, and marked
as preemptive. This will allow us to request preemption using GuC actions.

v2: Extract clients creation into a helper, debugfs fixups. (Michał)
Recreate doorbell on init. (Daniele)
Move clients into an array.

v3: And move clients back from an array, to get rid of the enum (Michał)

v4: Use is_high_priority, move DRM_ERROR into __create_doorbell, move
GEM_BUG_ON inside guc_clients_create (Michał)

v5: Split the BUG_ON (Michał)

v6: Cleanup after error during doorbell reinit (Michał)
Signed-off-by: NDave Gordon <david.s.gordon@intel.com>
Signed-off-by: NMichał Winiarski <michal.winiarski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Jeff McGee <jeff.mcgee@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Oscar Mateo <oscar.mateo@intel.com>
Reviewed-by: NMichal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171026141737.31656-1-michal.winiarski@intel.com

We were using first page of kernel context render state for sharing data
with GuC. While it's justified by the fact that those pages are not used
(note, GuC still enforces this layout and refuses to work if we remove
the extra page in front), it's also confusing (why are we using this
particular page?). Let's allocate a separate object instead.

v2: Drop kernel_context from GuC suspend/resume action handlers (Michel)
Suggested-by: NDaniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: NMichał Winiarski <michal.winiarski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Jeff McGee <jeff.mcgee@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Oscar Mateo <oscar.mateo@intel.com>
Reviewed-by: NDaniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171025200020.16636-4-michal.winiarski@intel.com

Since it's a two-step process, we can have a cleaner error handling in
the caller if we do the allocations in a helper.
Signed-off-by: NMichał Winiarski <michal.winiarski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Jeff McGee <jeff.mcgee@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Oscar Mateo <oscar.mateo@intel.com>
Reviewed-by: NDaniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171025200020.16636-3-michal.winiarski@intel.com

Apparently, this value is reserved and may be interpreted as changing
doorbell ownership. Even though we're not observing any side effects
now, let's skip over it to be consistent with the spec.

v2: Apply checkpatch (Sagar)
Suggested-by: NSagar Arun Kamble <sagar.a.kamble@intel.com>
Signed-off-by: NMichał Winiarski <michal.winiarski@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Reviewed-by: NSagar Arun Kamble <sagar.a.kamble@intel.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171025200020.16636-2-michal.winiarski@intel.com