To ease the frequent and ugly pointer dance of
&request->gem_context->engine[request->engine->id] during request
submission, store that pointer as request->hw_context. One major
advantage that we will exploit later is that this decouples the logical
context state from the engine itself.

v2: Set mock_context->ops so we don't crash and burn in selftests.
    Cleanups from Tvrtko.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Acked-by: NZhenyu Wang <zhenyuw@linux.intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180517212633.24934-3-chris@chris-wilson.co.uk

In the next patch, we want to store the intel_context pointer inside
i915_request, as it is frequently access via a convoluted dance when
submitting the request to hw. Having two context pointers inside
i915_request leads to confusion so first rename the existing
i915_gem_context pointer to i915_request.gem_context.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180517212633.24934-1-chris@chris-wilson.co.uk

The HWACK bit more generically solves the problem of resubmitting ESLP
while the hardware is still processing the current ELSP write. We no
longer need to check port[0].count itself.

References: ba74cb10 ("drm/i915/execlists: Delay writing to ELSP until HW has processed the previous write")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Michel Thierry <michel.thierry@intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180517115647.17205-1-chris@chris-wilson.co.uk

We cannot call kthread_park() from softirq context, so let's avoid it
entirely during the reset. We wanted to suspend the signaler so that it
would not mark a request as complete at the same time as we marked it as
being in error. Instead of parking the signaling, stop the engine from
advancing so that the GPU doesn't emit the breadcrumb for our chosen
"guilty" request.

v2: Refactor setting STOP_RING so that we don't have the same code thrice
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Michałt Winiarski <michal.winiarski@intel.com>
CC: Michel Thierry <michel.thierry@intel.com>
Cc: Jeff McGee <jeff.mcgee@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180516183355.10553-8-chris@chris-wilson.co.uk

Catch up with the inflight CSB events, after disabling the tasklet
before deciding which request was truly guilty of hanging the GPU.
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: Jeff McGee <jeff.mcgee@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180516183355.10553-7-chris@chris-wilson.co.uk

Pull the CSB event processing into its own routine so that we can reuse
it during reset to flush any missed interrupts/events.
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: Jeff McGee <jeff.mcgee@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180516183355.10553-6-chris@chris-wilson.co.uk

In the next patch, we will make the execlists reset prepare callback
take into account preemption by flushing the context-switch handler.
This is not applicable to the GuC submission backend, so split the two
into their own backend callbacks.
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: Jeff McGee <jeff.mcgee@intel.com>
Reviewed-by: NJeff McGee <jeff.mcgee@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180516183355.10553-5-chris@chris-wilson.co.uk

In preparation to more carefully handling incomplete preemption during
reset by execlists, we move the existing code wholesale to the backends
under a couple of new reset vfuncs.
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: Jeff McGee <jeff.mcgee@intel.com>
Reviewed-by: NJeff McGee <jeff.mcgee@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180516183355.10553-4-chris@chris-wilson.co.uk

As a complement to inject_preempt_context(), follow up with the function
to handle its completion. This will be useful should we wish to extend
the duties of the preempt-context for execlists.

v2: And do the same for the guc.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Jeff McGee <jeff.mcgee@intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Reviewed-by: Jeff McGee <jeff.mcgee@intel.com> #v1
Link: https://patchwork.freedesktop.org/patch/msgid/20180516183355.10553-3-chris@chris-wilson.co.uk

We assume that the CSB is written using the normal ringbuffer
coherency protocols, as outlined in kernel/events/ring_buffer.c:

    *   (HW)                              (DRIVER)
    *
    *   if (LOAD ->data_tail) {            LOAD ->data_head
    *                      (A)             smp_rmb()       (C)
    *      STORE $data                     LOAD $data
    *      smp_wmb()       (B)             smp_mb()        (D)
    *      STORE ->data_head               STORE ->data_tail
    *   }

So we assume that the HW fulfils its ordering requirements (B), and so
we should use a complimentary rmb (C) to ensure that our read of its
WRITE pointer is completed before we start accessing the data.

The final mb (D) is implied by the uncached mmio we perform to inform
the HW of our READ pointer.

References: https://bugs.freedesktop.org/show_bug.cgi?id=105064
References: https://bugs.freedesktop.org/show_bug.cgi?id=105888
References: https://bugs.freedesktop.org/show_bug.cgi?id=106185
Fixes: 767a983a ("drm/i915/execlists: Read the context-status HEAD from the HWSP")
References: 61bf9719 ("drm/i915/cnl: Use mmio access to context status buffer")
Suggested-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Rafael Antognolli <rafael.antognolli@intel.com>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: Timo Aaltonen <tjaalton@ubuntu.com>
Tested-by: NTimo Aaltonen <tjaalton@ubuntu.com>
Acked-by: NMichel Thierry <michel.thierry@intel.com>
Acked-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180511121147.31915-1-chris@chris-wilson.co.uk

Inherit workarounds from previous platforms that are still valid for
Icelake.

v2: GEN7_ROW_CHICKEN2 is masked
v3:
  - Since it has been fixed already in upstream, removed the TODO
    comment about WA_SET_BIT for WaInPlaceDecompressionHang.
  - Squashed with this patch:
      drm/i915/icl: add icelake_init_clock_gating()
    from Paulo Zanoni <paulo.r.zanoni@intel.com>
  - Squashed with this patch:
      drm/i915/icl: WaForceEnableNonCoherent
    from Oscar Mateo <oscar.mateo@intel.com>
  - WaPushConstantDereferenceHoldDisable is now Wa_1604370585 and
    applies to B0 as well.
  - WaPipeControlBefore3DStateSamplePattern WABB was being applied
    to ICL incorrectly.
v4:
  - Wrap the commit message
  - s/dev_priv/p to please checkpatch
v5: Rebased on top of the WA refactoring
v6: Rebased on top of further whitelist registers refactoring (Michel)
v7: Added WaRsForcewakeAddDelayForAck
v8: s/ICL_HDC_CHICKEN0/ICL_HDC_MODE (Mika)
v9:
  - C, not lisp (Chris)
  - WaIncreaseDefaultTLBEntries is the same for GEN > 9_LP (Tvrtko)
Signed-off-by: NOscar Mateo <oscar.mateo@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Tomasz Lis <tomasz.lis@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Signed-off-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1525814984-20039-2-git-send-email-oscar.mateo@intel.com

Prepare to allow the execlists submission to be run from underneath a
hardirq timer context (and not just the current softirq context) as is
required for fast preemption resets and context switches.
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/20180508210318.10274-1-chris@chris-wilson.co.uk

Add some onion to populate_lr_context.

v2: prefer err_unpin_ctx
    drop the fixes tag, worst case we just spew a warn before everything
    is cleaned up and balance is restored
Signed-off-by: NMatthew Auld <matthew.auld@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180301114639.510-1-matthew.auld@intel.com

When rescheduling a change of dependencies, they all need to be added to
the same priolist (at least the ones on the same engine!). Since we
likely want to move a batch of requests, keep the priolist around.

v2: Throw in an assert to catch trivial errors quickly.
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/20180508003046.2633-2-chris@chris-wilson.co.uk

lookup_priolist() no longer attaches the request into the priolist, it
just returns the priolist for the given priority instead. Drop the
unused parameter.
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/20180508003046.2633-1-chris@chris-wilson.co.uk

Limit the arbitration (where preemption may occur) to inside the batch,
and prevent it from happening on the pipecontrols/flushes we use to
write the breadcrumb seqno. Once the user batch is complete, we have
nothing left to do but serialise and emit the breadcrumb; switching
contexts at this point is futile so don't.
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: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NMichel Thierry <michel.thierry@intel.com>
Reviewed-by: NLionel Landwerlin <lionel.g.landwerlin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180503195416.22498-1-chris@chris-wilson.co.uk

Move the tracepoint into the common execlists_context_schedule_out() and
call it from preemption completion as well. A small bit of refactoring
code should help with when tracing, or else we end up with requests
mysteriously disappearing and some being emitted to HW multiple times.
Reported-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
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/20180502230202.6848-1-chris@chris-wilson.co.uk

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

In the future, we want to move a request between engines. To achieve
this, we first realise that we have two timelines in effect here. The
first runs through the GTT is required for ordering vma access, which is
tracked currently by engine. The second is implied by sequential
execution of commands inside the ringbuffer. This timeline is one that
maps to userspace's expectations when submitting requests (i.e. given the
same context, batch A is executed before batch B). As the rings's
timelines map to userspace and the GTT timeline an implementation
detail, move the timeline from the GTT into the ring itself (per-context
in logical-ring-contexts/execlists, or a global per-engine timeline for
the shared ringbuffers in legacy submission.

The two timelines are still assumed to be equivalent at the moment (no
migrating requests between engines yet) and so we can simply move from
one to the other without adding extra ordering.

v2: Reinforce that one isn't allowed to mix the engine execution
timeline with the client timeline from userspace (on the ring).
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/20180502163839.3248-1-chris@chris-wilson.co.uk

Due to the latency of the tasklet running from ksoftirqd, by the time we
process the execlist dequeue may be a long time behind the GPU. If the
request was completed when we ran reschedule, we will not have tweaked
its priority, but if it is still listed as being in-flight for dequeue
we will use it as a reference for the rest of the queue, including
requests from its own context which will now be at higher priority. This
can cause us to issue a preempt-to-idle request, even though the request
we want to preempt is already complete.
Reported-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180501122131.19435-1-chris@chris-wilson.co.ukReviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>

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

Previously, we just reset the ring register in the context image such
that we could skip over the broken batch and emit the closing
breadcrumb. However, on resume the context image and GPU state would be
reloaded, which may have been left in an inconsistent state by the
reset. The presumption was that at worst it would just cause another
reset and skip again until it recovered, however it seems just as likely
to cause an unrecoverable hang. Instead of risking loading an incomplete
context image, restore it back to the default state.

v2: Fix up off-by-one from including the ppHSWP in with the register
state.
v3: Use a ring local to compact a few lines.
v4: Beware setting the ring local before checking for a NULL request.

References: https://bugs.freedesktop.org/show_bug.cgi?id=105304Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Michel Thierry <michel.thierry@intel.com> #v2
Link: https://patchwork.freedesktop.org/patch/msgid/20180428111532.15819-1-chris@chris-wilson.co.uk

Interrupt handling in Gen11 is quite different from previous platforms.

v2: Rebased (Michel)
v3: Rebased with wiggle
v4: Rebased, remove TODO warning correctly (Daniele)
v5: Rebased, made gen11_gtiir const while at it (Michel)
v6: Rebased
v7: Adapt to the style currently in upstream
Suggested-by: NMichel Thierry <michel.thierry@intel.com>
Signed-off-by: NRodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: NMichel Thierry <michel.thierry@intel.com>
Signed-off-by: NOscar Mateo <oscar.mateo@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.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/1524605995-22324-1-git-send-email-oscar.mateo@intel.com

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

Add a selftest to ensure that we restore the whitelisted registers after
rewrite the registers everytime they might be scrubbed, e.g. module
load, reset and resume. For the other volatile workaround registers, we
export their presence via debugfs and check in igt/gem_workarounds.
However, we don't export the whitelist and rather than do so, let's test
them directly in the kernel.

The test we use is to read the registers back from the CS (this helps us
be sure that the registers will be valid for MI_LRI etc). In order to
generate the expected list, we split intel_whitelist_workarounds_emit
into two phases, the first to build the list and the second to apply.
Inside the test, we only build the list and then check that list against
the hw.

v2: Filter out pre-gen8 as they do not have RING_NONPRIV.
v3: Drop unused engine parameter, no plans to use it now or future.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Oscar Mateo <oscar.mateo@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: NOscar Mateo <oscar.mateo@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180414122754.569-1-chris@chris-wilson.co.uk

There are different kind of workarounds (those that modify registers that
live in the context image, those that modify global registers, those that
whitelist registers, etc...) and they have different requirements in terms
of where they are applied and how. Also, by splitting them apart, it should
be easier to decide where a new workaround should go.

v2:
  - Add multiple MISSING_CASE
  - Rebased

v3:
  - Rename mmio_workarounds to gt_workarounds (Chris, Mika)
  - Create empty placeholders for BDW and CHV GT WAs
  - Rebased

v4: Rebased

v5:
 - Rebased
 - FORCE_TO_NONPRIV register exists since BDW, so make a path
   for it to achieve universality, even if empty (Chris)
Signed-off-by: NOscar Mateo <oscar.mateo@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
[ickle: appease checkpatch]
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/1523376767-18480-2-git-send-email-oscar.mateo@intel.com

This has grown to be a sizable amount of code, so move it to
its own file before we try to refactor anything. For the moment,
we are leaving behind the WA BB code and the WAs that get applied
(incorrectly) in init_clock_gating, but we will deal with it later.

v2: Use intel_ prefix for code that deals with the hardware (Chris)
v3: Rebased
v4:
  - Rebased
  - New license header
v5:
  - Rebased
  - Added some organisational notes to the file (Chris)
v6: Include DOC section in the documentation build (Jani)
Signed-off-by: NOscar Mateo <oscar.mateo@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
[ickle: appease checkpatch, mostly]
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/1523376767-18480-1-git-send-email-oscar.mateo@intel.com

We can refine our current execlists->queue_priority if we inspect
ELSP[1] rather than the head of the unsubmitted queue. Currently, we use
the unsubmitted queue and say that if a subsequent request is more
important than the current queue, we will rerun the submission tasklet
to evaluate the need for preemption. However, we only want to preempt if
we need to jump ahead of a currently executing request in ELSP. The
second reason for running the submission tasklet is amalgamate requests
into the active context on ELSP[0] to avoid a stall when ELSP[0] drains.
(Though repeatedly amalgamating requests into the active context and
triggering many lite-restore is off question gain, the goal really is to
put a context into ELSP[1] to cover the interrupt.) So if instead of
looking at the head of the queue, we look at the context in ELSP[1] we
can answer both of the questions more accurately -- we don't need to
rerun the submission tasklet unless our new request is important enough
to feed into, at least, ELSP[1].

v2: Add some comments from the discussion with Tvrtko.
v3: More commentary to cross-reference queue_request()

References: f6322edd ("drm/i915/preemption: Allow preemption between submission ports")
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>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180411103929.27374-1-chris@chris-wilson.co.uk

Include fence context and seqno in low level tracing so it is easier to
follow flows of individual requests when things go bad.

Also added tracing on the reset side of things.

v2:
 Chris Wilson:
 * Standardize global_seqno and seqno as global.
 * Include current hws seqno in execlists_cancel_port_requests.

v3:
 * Fix port printk format for all builds.
Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> # v2
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180406123514.5809-1-tvrtko.ursulin@linux.intel.com

Before adding a new feature to execlists submission, we should endeavour
to cover the baseline behaviour with selftests. So start the ball
rolling.
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: Jeff McGee <jeff.mcgee@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180404093329.5383-1-chris@chris-wilson.co.uk

When cancelling the requests and clearing out the ports following a
successful preemption completion, also clear the active flag. I had
assumed that all preemptions would be followed by an immediate dequeue
(preserving the active user flag), but under rare circumstances we may
be triggering a preemption for the second port only for it to have
completed before the preemotion kicks in; leaving execlists->active set
even though the system is now idle.

We can clear the flag inside the common execlists_cancel_port_requests()
as the other users also expect the semantics of active being cleared.

Fixes: f6322edd ("drm/i915/preemption: Allow preemption between submission ports")
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>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180324125829.27026-1-chris@chris-wilson.co.uk
(cherry picked from commit eed7ec52)
Signed-off-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>

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

When we include a request's global_seqno in a GEM_TRACE it often helps
to know how that relates to the current breadcrumb as seen by the
hardware.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180327210157.16896-3-chris@chris-wilson.co.ukReviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>

Tvrtko uncovered a fun issue with recovering from a wedge device. In his
tests, he wedged the driver by injecting an unrecoverable hang whilst a
batch was spinning. As we reset the gpu in the middle of the spinner,
when resumed it would continue on from the next instruction in the ring
and write it's breadcrumb. However, on wedging we updated our
bookkeeping to indicate that the GPU had completed executing and would
restart from after the breadcrumb; so the emission of the stale
breadcrumb from before the reset came as a bit of a surprise.

A simple fix is to when rebinding the context into the GPU, we update
the ring register state in the context image to match our bookkeeping.
We already have to update the RING_START and RING_TAIL, so updating
RING_HEAD as well is trivial. This works because whenever we unbind the
context, we keep the bookkeeping in check; and on wedging we unbind all
contexts.

Testcase: igt/gem_eio
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>
Link: https://patchwork.freedesktop.org/patch/msgid/20180327210136.16750-1-chris@chris-wilson.co.ukTested-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>

If the request is still waiting on external fences, it has not yet been
submitted to the HW queue and so we can forgo kicking the submission
tasklet when re-evaluating its priority.

This should have no impact other than reducing the number of tasklet
wakeups under signal heavy workloads (e.g. switching between engines).

v2: Use prebaked container_of()

References: f6322edd ("drm/i915/preemption: Allow preemption between submission ports")
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/20180326115044.2505-2-chris@chris-wilson.co.ukReviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>

When cancelling the requests and clearing out the ports following a
successful preemption completion, also clear the active flag. I had
assumed that all preemptions would be followed by an immediate dequeue
(preserving the active user flag), but under rare circumstances we may
be triggering a preemption for the second port only for it to have
completed before the preemotion kicks in; leaving execlists->active set
even though the system is now idle.

We can clear the flag inside the common execlists_cancel_port_requests()
as the other users also expect the semantics of active being cleared.

Fixes: f6322edd ("drm/i915/preemption: Allow preemption between submission ports")
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>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180324125829.27026-1-chris@chris-wilson.co.uk

We were relying on the uncached reads when processing the CSB to provide
ourselves with the serialisation with the interrupt handler (so we could
detect new interrupts in the middle of processing the old one). However,
in commit 767a983a ("drm/i915/execlists: Read the context-status HEAD
from the HWSP") those uncached reads were eliminated (on one path at
least) and along with them our serialisation. The result is that we
would very rarely miss notification of a new interrupt and leave a
context-switch unprocessed, hanging the GPU.

Fixes: 767a983a ("drm/i915/execlists: Read the context-status HEAD from the HWSP")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: NMichel Thierry <michel.thierry@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180321091027.21034-1-chris@chris-wilson.co.uk
(cherry picked from commit 9153e6b7)
Signed-off-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>

Commit 0f36a85c ("drm/i915: Flush pending interrupt following a GPU
reset") got confused and only applied the flush to the set-wedge path
(which itself is proving troublesome), but we also need the
serialisation on the regular reset path. Oops.

Move the interrupt into reset_irq() and make it common to the reset and
final set-wedge.

v2: reset_irq() after port cancellation, as we assert that
execlists->active is sane for cancellation (and is being reset by
reset_irq).

References: 0f36a85c ("drm/i915: Flush pending interrupt following a GPU reset")
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Jeff McGee <jeff.mcgee@intel.com>
Reviewed-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180323101824.14645-1-chris@chris-wilson.co.uk