By using the out-of-line intel_wait_for_register() not only do we can
efficiency from using the hybrid wait_for() contained within, but we
avoid code bloat from the numerous inlined loops, in total (all patches):

   text    data     bss     dec     hex filename
1078551    4557     416 1083524  108884 drivers/gpu/drm/i915/i915.ko
1070775    4557     416 1075748  106a24 drivers/gpu/drm/i915/i915.ko
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1467297225-21379-47-git-send-email-chris@chris-wilson.co.uk

By using the out-of-line intel_wait_for_register() not only do we can
efficiency from using the hybrid wait_for() contained within, but we
avoid code bloat from the numerous inlined loops, in total (all patches):

   text    data     bss     dec     hex filename
1078551    4557     416 1083524  108884 drivers/gpu/drm/i915/i915.ko
1070775    4557     416 1075748  106a24 drivers/gpu/drm/i915/i915.ko
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1467297225-21379-46-git-send-email-chris@chris-wilson.co.uk

The kernel context exists simply as a placeholder and should never be
executed with a render context. It does not need the golden render
state, as that will always be applied to a user context. By skipping the
initialisation we can avoid issues in attempting to program the golden
render context when trying to make the hardware idle.

v2: Rebase

Testcase: igt/drm_module_reload_basic #byt
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=95634Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1466776558-21516-3-git-send-email-chris@chris-wilson.co.uk

This is so that we have symmetry with intel_lrc.c and avoid a source of
if (i915.enable_execlists) layering violation within i915_gem_context.c -
that is we move the specific handling of the dev_priv->kernel_context
for legacy submission into the legacy submission code.

This depends upon the init/fini ordering between contexts and engines
already defined by intel_lrc.c, and also exporting the context alignment
required for pinning the legacy context.

v2: Separate out pin/unpin context funcs for greater symmetry with
intel_lrc. One more step towards unifying behaviour between the two
classes of engines and towards fixing another bug in i915_switch_context
vs requests.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1466776558-21516-2-git-send-email-chris@chris-wilson.co.uk

This is a WA affecting pooled eu which is a bxt specific feature.
Reviewed-by: NMika Kuoppala <mika.kuoppala@intel.com>
Cc: Winiarski, Michal <michal.winiarski@intel.com>
Cc: Zou, Nanhai <nanhai.zou@intel.com>
Cc: Yang, Rong R <rong.r.yang@intel.com>
Cc: Jeff McGee <jeff.mcgee@intel.com>
Signed-off-by: NArun Siluvery <arun.siluvery@linux.intel.com>
Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>

This patch enables a workaround for a mid thread preemption
issue where a hardware timing problem can prevent the
context restore from happening, leading to a hang.

v2: move to gen9_init_workarounds (Arun)
v3: move to start of gen9_init_workarounds (Arun)
Signed-off-by: NTim Gore <tim.gore@intel.com>
Reviewed-by: NArun Siluvery <arun.siluvery@linux.intel.com>
Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465816501-25557-1-git-send-email-tim.gore@intel.com

There is ambiguity in the documentation between D0 and E0.
Extend this workaround to E0.

References: BSID#779
Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NMatthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465309159-30531-23-git-send-email-mika.kuoppala@intel.com

This is needed for all kbl revision.

v2: Don't add revid checks to generic gen9 init (Arun)

References: HSD#2135593
Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NMatthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465309159-30531-21-git-send-email-mika.kuoppala@intel.com

We need to disable clock gating in this unit to work around
hardware issue causing possible corruption/hang.

v2: name the bit (Ville)
v3: leave the fix enabled for 2227050 and set correct bit (Matthew)
v4: Split out the skl part in separate commit for easier backport

References: HSD#2227156, HSD#2227050
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Matthew Auld <matthew.william.auld@gmail.com>
Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NMatthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465309159-30531-20-git-send-email-mika.kuoppala@intel.com

Add this workaround for both bxt and kbl up to until
rev B0.

References: HSD#2136703
Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NMatthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465309159-30531-16-git-send-email-mika.kuoppala@intel.com

Bspec states that we need to turn off dynamic credit
sharing on kbl revid a0 and b0. This happens by writing bit 28
on 0x4ab8.

References: HSD#2225601, HSD#2226938, HSD#2225763
Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NMatthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465309159-30531-15-git-send-email-mika.kuoppala@intel.com

Extend the scope of this workaround, already used in skl,
to also take effect in kbl.

v2: Fix KBL_REVID_E0 (Matthew)

References: HSD#2132677
Cc: Matthew Auld <matthew.william.auld@gmail.com>
Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NMatthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465309159-30531-12-git-send-email-mika.kuoppala@intel.com

Add this workaround for kbl revid A0 only.

v2: rebase
v3: carve out a non related workaround (Chris)

References: HSD#1911714
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NMatthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465309159-30531-9-git-send-email-mika.kuoppala@intel.com

We need this crucial workaround from skl also to all kbl revisions.
Lack of it was causing system hangs on skl enabling so this is
a must have.

v2: Don't add revid checks to gen9 init workarounds (Arun)

References: HSD#2126660
Cc: Arun Siluvery <arun.siluvery@linux.intel.com>
Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NMatthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465309159-30531-8-git-send-email-mika.kuoppala@intel.com

Past evidence with system hangs and hsds tie
WaForceEnableNonCoherent and WaDisableHDCInvalidation to
WaForceContextSaveRestoreNonCoherent. Documentation
states that WaForceContextSaveRestoreNonCoherent would
not be needed on skl past E0 but evidence proved otherwise. See
commit <510650e8> ("drm/i915/skl: Fix spurious gpu hang with gt3/gt4
revs"). In this scope consider kbl to be skl with a bigger revision than
E0 so play it safe and bind these two workarounds to the
WaForceContextSaveRestoreNonCoherent, and apply to all gen9.

v2: fix comment (Matthew)

References: HSD#2134449, HSD#2131413
Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NMatthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465309159-30531-7-git-send-email-mika.kuoppala@intel.com

The revision id range for this workaround has changed. So apply
it to all revids on all gen9.

References: HSD#2134449
Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NMatthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465309159-30531-6-git-send-email-mika.kuoppala@intel.com

Kabylake is part of gen9 family so init the generic gen9
workarounds for it.

v2: rebase
Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NMatthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465309159-30531-3-git-send-email-mika.kuoppala@intel.com

We need to disable clock gating in this unit to work around
hardware issue causing possible corruption/hang.

v2: name the bit (Ville)
v3: leave the fix enabled for 2227050 and set correct bit (Matthew)

References: HSD#2227156, HSD#2227050
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Matthew Auld <matthew.william.auld@gmail.com>
Reviewed-by: NMatthew Auld <matthew.auld@intel.com>
Signed-off-by: NMika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465309159-30531-2-git-send-email-mika.kuoppala@intel.com

Kernel only need to add a register to HW whitelist, required for a
preemption related issue.

Reference: HSD#2131039
Reviewed-by: NJeff McGee <jeff.mcgee@intel.com>
Signed-off-by: NArun Siluvery <arun.siluvery@linux.intel.com>
Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465203169-16591-1-git-send-email-arun.siluvery@linux.intel.com

Following a GPU hang, we break out of the request loop in order to
unlock the struct_mutex for use by the GPU reset. However, if we retire
all the requests at that moment, we cannot identify the guilty request
after performing the reset.

v2: Not automatically retiring requests forces us to recheck for
available ringspace.

Fixes: f4457ae7 ("drm/i915: Prevent leaking of -EIO from i915_wait_request()")
Testcase: igt/gem_reset_stats/ban-*
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Tested-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NMika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1463137042-9669-4-git-send-email-chris@chris-wilson.co.uk
(cherry picked from commit e075a32f)
Signed-off-by: NJani Nikula <jani.nikula@intel.com>

Combine the near identical implementations of intel_logical_ring_begin()
and intel_ring_begin() - the only difference is that the logical wait
has to check for a matching ring (which is assumed by legacy).

In the process some debug messages are culled as there were following a
WARN if we hit an actual error.

v2: Updated commentary
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461833819-3991-12-git-send-email-chris@chris-wilson.co.uk
(cherry picked from commit 987046ad)
Signed-off-by: NJani Nikula <jani.nikula@intel.com>

With the introduction of a distinct engine->id vs the hardware id, we need
to fix up the value we use for selecting the target engine when signaling
a semaphore. Note that these values can be merged with engine->guc_id.

Fixes: de1add36
Cc: stable@vger.kernel.org # v4.6
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461932305-14637-3-git-send-email-chris@chris-wilson.co.uk
(cherry picked from commit 215a7e32)
Signed-off-by: NJani Nikula <jani.nikula@intel.com>

Faced with sporadic machine hangs on gen7, that mimic the issue of
concurrent writes to the same cacheline and seem to start with
commit 9b9ed309 (drm/i915: Remove forcewake dance from seqno/irq
barrier on legacy gen6+), let us restore the spinlock around the mmio
read.

Fixes: 9b9ed309 (drm/i915: Remove forcewake dance from seqno/irq...)
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461744121-27051-1-git-send-email-chris@chris-wilson.co.ukTested-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NMika Kuoppala <mika.kuoppala@intel.com>
(cherry picked from commit bcbdb6d0)
Signed-off-by: NJani Nikula <jani.nikula@intel.com>

Following a GPU hang, we break out of the request loop in order to
unlock the struct_mutex for use by the GPU reset. However, if we retire
all the requests at that moment, we cannot identify the guilty request
after performing the reset.

v2: Not automatically retiring requests forces us to recheck for
available ringspace.

Fixes: f4457ae7 ("drm/i915: Prevent leaking of -EIO from i915_wait_request()")
Testcase: igt/gem_reset_stats/ban-*
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Tested-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NMika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1463137042-9669-4-git-send-email-chris@chris-wilson.co.uk

To be used for more efficient Gen range checking.

v2: Remove spurious chunk. (Chris Wilson)
v3: Rebase.
v4: Renamed from INTEL_GEN_RANGE and added GEN_FOREVER.
Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> (v3)
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Dave Gordon <david.s.gordon@intel.com>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1462874228-6601-1-git-send-email-tvrtko.ursulin@linux.intel.com

This way optimization from a previous patch works even better.

v2: Rebase.
Signed-off-by: NTvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>

   text	   data	    bss	    dec	    hex	filename
6309351	3578714	 696320	10584385	 a18141	vmlinux
6308391	3578714	 696320	10583425	 a17d81	vmlinux

Almost 1KiB of code reduction.

v2: More s/INTEL_INFO()->gen/INTEL_GEN()/ and IS_GENx() conversions

   text	   data	    bss	    dec	    hex	filename
6304579	3578778	 696320	10579677	 a16edd	vmlinux
6303427	3578778	 696320	10578525	 a16a5d	vmlinux

Now over 1KiB!
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1462545621-30125-3-git-send-email-chris@chris-wilson.co.uk

No need for hard-coding the register value, the corresponding fields are
defined properly in BSpec.

No functional change.

v2:
- Rebased on BXT L3 SQC tuning patch merged meanwhile.

CC: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NImre Deak <imre.deak@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com> (v1)
Link: http://patchwork.freedesktop.org/patch/msgid/1462280061-1457-3-git-send-email-imre.deak@intel.com

When the engine idles waiting upon a semaphore, it loses its
pagetables and we must reload them before executing the batch.

v2: Restrict w/a to non-RCS rings (RCS works correctly apparently).
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461932305-14637-5-git-send-email-chris@chris-wilson.co.uk

In order for the MI_SEMAPHORE_SIGNAL command to wait until after the
pipecontrol writing the signal value is complete, we have to pause the
CS inside the PIPE_CONTROL with the CS_STALL bit.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461932305-14637-4-git-send-email-chris@chris-wilson.co.uk

With the introduction of a distinct engine->id vs the hardware id, we need
to fix up the value we use for selecting the target engine when signaling
a semaphore. Note that these values can be merged with engine->guc_id.

Fixes: de1add36Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461932305-14637-3-git-send-email-chris@chris-wilson.co.uk

For legacy ringbuffer mode, we need the new ordered breadcrumb emission
tried and tested on execlists in order to avoid the dreaded "missed
interrupt" syndrome. A secondary advantage of the execlists method is
that it writes to an arbitrary address, useful if one wants to write a
breadcrumb elsewhere.

This fix is taken from commit 7c17d377 (drm/i915: Use ordered seqno
write interrupt generation on gen8+ execlists).
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461932305-14637-1-git-send-email-chris@chris-wilson.co.uk

At the start of request emission, we flush some space for the request,
estimating the typical size for the request body. The tail is now much
larger than the typical body, so we can shrink the flush slightly.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461917226-9132-2-git-send-email-chris@chris-wilson.co.uk

Rather than being interrupted when we run out of space halfway through
the request, and having to restart from the beginning (and returning to
userspace), flush a little more free space when we prepare the request.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461833819-3991-15-git-send-email-chris@chris-wilson.co.uk

In the next patches, we want to move the work out of freeing the request
and into its retirement (so that we can free the request without
requiring the struct_mutex). This means that we cannot rely on
unreferencing the request to completely teardown the request any more
and so we need to manually unwind the failed allocation. In doing so, we
reorder the allocation in order to make the unwind simple (and ensure
that we don't try to unwind a partial request that may have modified
global state) and so we end up pushing the initial preallocation down
into the engine request initialisation functions where we have the
requisite control over the state of the request.

Moving the initial preallocation into the engine is less than ideal: it
moves logic to handle a specific problem with request handling out of
the common code. On the other hand, it does allow those backends
significantly more flexibility in performing its allocations.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: NTvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461833819-3991-14-git-send-email-chris@chris-wilson.co.uk

Now that we share intel_ring_begin(), reserving space for the tail of
the request is identical between legacy/execlists and so the tautology
can be removed. In the process, we move the reserved space tracking
from the ringbuffer on to the request. This is to enable us to reorder
the reserved space allocation in the next patch.
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461833819-3991-13-git-send-email-chris@chris-wilson.co.uk

Combine the near identical implementations of intel_logical_ring_begin()
and intel_ring_begin() - the only difference is that the logical wait
has to check for a matching ring (which is assumed by legacy).

In the process some debug messages are culled as there were following a
WARN if we hit an actual error.

v2: Updated commentary
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461833819-3991-12-git-send-email-chris@chris-wilson.co.uk

Similarly to i915_gem_object_pin_map on LLC platforms, we can
use the new VMA based io mapping on !LLC to amoritize the cost
of ringbuffer pinning and unpinning.
Signed-off-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: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461833819-3991-6-git-send-email-chris@chris-wilson.co.uk

Propagate the real error from drm_gem_object_init(). Note this also
fixes some confusion in the error return from i915_gem_alloc_object...

v2:
(Matthew Auld)
  - updated new users of gem_alloc_object from latest drm-nightly
  - replaced occurrences of IS_ERR_OR_NULL() with IS_ERR()
v3:
(Joonas Lahtinen)
  - fix double "From:" in commit message
  - add goto teardown path
v4:
(Matthew Auld)
  - rebase with i915_gem_alloc_object name change
Signed-off-by: NMatthew Auld <matthew.auld@intel.com>
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461587533-8841-1-git-send-email-matthew.auld@intel.com
[Joonas: Removed spurious " = NULL" from _init() function]
Signed-off-by: NJoonas Lahtinen <joonas.lahtinen@linux.intel.com>

Faced with sporadic machine hangs on gen7, that mimic the issue of
concurrent writes to the same cacheline and seem to start with
commit 9b9ed309 (drm/i915: Remove forcewake dance from seqno/irq
barrier on legacy gen6+), let us restore the spinlock around the mmio
read.

Fixes: 9b9ed309 (drm/i915: Remove forcewake dance from seqno/irq...)
Signed-off-by: NChris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461744121-27051-1-git-send-email-chris@chris-wilson.co.ukTested-by: NMika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: NMika Kuoppala <mika.kuoppala@intel.com>