History log of /openbmc/linux/drivers/gpu/drm/i915/gt/intel_lrc.c (Results 51 – 75 of 774)
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# b436a5f8 22-Dec-2020 Chris Wilson <chris@chris-wilson.co.uk>

drm/i915/gt: Track all timelines created using the HWSP

We assume that the contents of the HWSP are lost across suspend, and so
upon resume we must restore critical values such as the timeline seqno

drm/i915/gt: Track all timelines created using the HWSP

We assume that the contents of the HWSP are lost across suspend, and so
upon resume we must restore critical values such as the timeline seqno.
Keep track of every timeline allocated that uses the HWSP as its storage
and so we can then reset all seqno values by walking that list.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201222104242.10993-1-chris@chris-wilson.co.uk

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# a0d3fdb6 18-Dec-2020 Chris Wilson <chris@chris-wilson.co.uk>

drm/i915/gt: Split logical ring contexts from execlist submission

Split the definition, construction and updating of the Logical Ring
Context from the execlist submission interface. The LRC is used

drm/i915/gt: Split logical ring contexts from execlist submission

Split the definition, construction and updating of the Logical Ring
Context from the execlist submission interface. The LRC is used by the
HW, irrespective of our different submission backends.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201219020343.22681-1-chris@chris-wilson.co.uk

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Revision tags: v5.10
# f867b66e 04-Dec-2020 Chris Wilson <chris@chris-wilson.co.uk>

drm/i915/gt: Clear the execlists timers upon reset

Across a reset, we stop the engine but not the timers. This leaves a
window where the timers have inconsistent state with the engine, but
should on

drm/i915/gt: Clear the execlists timers upon reset

Across a reset, we stop the engine but not the timers. This leaves a
window where the timers have inconsistent state with the engine, but
should only result in a spurious timeout. As we cancel the outstanding
events, also cancel their timers.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201204151234.19729-4-chris@chris-wilson.co.uk

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# d997e240 04-Dec-2020 Chris Wilson <chris@chris-wilson.co.uk>

drm/i915/gt: Cancel the preemption timeout on responding to it

We currently presume that the engine reset is successful, cancelling the
expired preemption timer in the process. However, engine reset

drm/i915/gt: Cancel the preemption timeout on responding to it

We currently presume that the engine reset is successful, cancelling the
expired preemption timer in the process. However, engine resets can
fail, leaving the timeout still pending and we will then respond to the
timeout again next time the tasklet fires. What we want is for the
failed engine reset to be promoted to a full device reset, which is
kicked by the heartbeat once the engine stops processing events.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/1168
Fixes: 3a7a92aba8fb ("drm/i915/execlists: Force preemption")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: <stable@vger.kernel.org> # v5.5+
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201204151234.19729-2-chris@chris-wilson.co.uk

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# b9695405 04-Dec-2020 Chris Wilson <chris@chris-wilson.co.uk>

drm/i915/gt: Ignore repeated attempts to suspend request flow across reset

Before reseting the engine, we suspend the execution of the guilty
request, so that we can continue execution with a new co

drm/i915/gt: Ignore repeated attempts to suspend request flow across reset

Before reseting the engine, we suspend the execution of the guilty
request, so that we can continue execution with a new context while we
slowly compress the captured error state for the guilty context. However,
if the reset fails, we will promptly attempt to reset the same request
again, and discover the ongoing capture. Ignore the second attempt to
suspend and capture the same request.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/1168
Fixes: 32ff621fd744 ("drm/i915/gt: Allow temporary suspension of inflight requests")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: <stable@vger.kernel.org> # v5.7+
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201204151234.19729-1-chris@chris-wilson.co.uk

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# a5855989 26-Nov-2020 Chris Wilson <chris@chris-wilson.co.uk>

drm/i915/gt: Check for a completed last request once

Pull the repeated check for the last active request being completed to a
single spot, when deciding whether or not execlist preemption is
require

drm/i915/gt: Check for a completed last request once

Pull the repeated check for the last active request being completed to a
single spot, when deciding whether or not execlist preemption is
required.

In doing so, we remove the tasklet kick, introduced with the completion
checks in commit 35f3fd8182ba ("drm/i915/execlists: Workaround switching
back to a completed context"), if we find the request was completed but
have not yet seen the corresponding CS event. This was devolving into a
busy spin of the tasklet while we waited for the event as the delivery
was not as instantaneous as expected. Under load this is sufficient to
exhaust the tasklet softirq timeslice, and force ksoftirqd. Quite
noticeable overhead for no apparent improvement in latency.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201126140407.31952-2-chris@chris-wilson.co.uk

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# b8e2bd98 26-Nov-2020 Chris Wilson <chris@chris-wilson.co.uk>

drm/i915/gt: Decouple completed requests on unwind

Since the introduction of preempt-to-busy, requests can complete in the
background, even while they are not on the engine->active.requests list.
As

drm/i915/gt: Decouple completed requests on unwind

Since the introduction of preempt-to-busy, requests can complete in the
background, even while they are not on the engine->active.requests list.
As such, the engine->active.request list itself is not in strict
retirement order, and we have to scan the entire list while unwinding to
not miss any. However, if the request is completed we currently leave it
on the list [until retirement], but we could just as simply remove it
and stop treating it as active. We would only have to then traverse it
once while unwinding in quick succession.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201126140407.31952-1-chris@chris-wilson.co.uk

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# 46eecfcc 23-Nov-2020 Chris Wilson <chris@chris-wilson.co.uk>

drm/i915/gt: Free stale request on destroying the virtual engine

Since preempt-to-busy, we may unsubmit a request while it is still on
the HW and completes asynchronously. That means it may be retir

drm/i915/gt: Free stale request on destroying the virtual engine

Since preempt-to-busy, we may unsubmit a request while it is still on
the HW and completes asynchronously. That means it may be retired and in
the process destroy the virtual engine (as the user has closed their
context), but that engine may still be holding onto the unsubmitted
compelted request. Therefore we need to potentially cleanup the old
request on destroying the virtual engine. We also have to keep the
virtual_engine alive until after the sibling's execlists_dequeue() have
finished peeking into the virtual engines, for which we serialise with
RCU.

v2: Be paranoid and flush the tasklet as well.
v3: And flush the tasklet before the engines, as the tasklet may
re-attach an rb_node after our removal from the siblings.

Fixes: 6d06779e8672 ("drm/i915: Load balancing across a virtual engine")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201123113717.20500-4-chris@chris-wilson.co.uk

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# b5b349b9 19-Nov-2020 Chris Wilson <chris@chris-wilson.co.uk>

drm/i915: Lift waiter/signaler iterators

Lift the list iteration defines for traversing the signaler/waiter lists
into i915_scheduler.h for reuse.

Signed-off-by: Chris Wilson <chris@chris-wilson.co

drm/i915: Lift waiter/signaler iterators

Lift the list iteration defines for traversing the signaler/waiter lists
into i915_scheduler.h for reuse.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201119165616.10834-5-chris@chris-wilson.co.uk

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# 562675d0 19-Nov-2020 Chris Wilson <chris@chris-wilson.co.uk>

drm/i915/gt: Update request status flags for debug pretty-printer

We plan to expand upon the number of available statuses for when we
pretty-print the requests along the timelines, and so need a new

drm/i915/gt: Update request status flags for debug pretty-printer

We plan to expand upon the number of available statuses for when we
pretty-print the requests along the timelines, and so need a new set of
flags. We have settled upon:

Unready [U]
- initial status after being submitted, the request is not
ready for execution as it is waiting for external fences

Ready [R]
- all fences the request was waiting on have been signaled,
and the request is now ready for execution and will be
in a backend queue

- a ready request may still need to wait on semaphores
[internal fences]

Ready/virtual [V]
- same as ready, but queued over multiple backends

Executing [E]
- the request has been transferred from the backend queue and
submitted for execution on HW

- a completed request may still be regarded as executing, its
status may not be updated until it is retired and removed
from the lists

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201119165616.10834-3-chris@chris-wilson.co.uk

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# 1f0e785a 19-Nov-2020 Chris Wilson <chris@chris-wilson.co.uk>

drm/i915: Lift i915_request_show()

Extract i915_request_show for reuse in other request chain pretty
printers.

For a bonus point, quietly change the seqno format from %llx to %lld to
match everywhe

drm/i915: Lift i915_request_show()

Extract i915_request_show for reuse in other request chain pretty
printers.

For a bonus point, quietly change the seqno format from %llx to %lld to
match everywhere else.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201119165616.10834-2-chris@chris-wilson.co.uk

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# 45e50f48 18-Nov-2020 Chris Wilson <chris@chris-wilson.co.uk>

drm/i915/gt: Remember to free the virtual breadcrumbs

Since we allocate some breadcrumbs for the virtual engine, and the
virtual engine has a custom destructor, we also need to free the
breadcrumbs

drm/i915/gt: Remember to free the virtual breadcrumbs

Since we allocate some breadcrumbs for the virtual engine, and the
virtual engine has a custom destructor, we also need to free the
breadcrumbs after use.

Fixes: b3786b29379c ("drm/i915/gt: Distinguish the virtual breadcrumbs from the irq breadcrumbs")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201118133839.1783-1-chris@chris-wilson.co.uk

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# d33fcd79 17-Nov-2020 Chris Wilson <chris@chris-wilson.co.uk>

drm/i915/gt: Ignore dt==0 for reporting underflows

The presumption was that some time would always elapse between recording
the start and the finish of a context switch. This turns out to be a
regul

drm/i915/gt: Ignore dt==0 for reporting underflows

The presumption was that some time would always elapse between recording
the start and the finish of a context switch. This turns out to be a
regular occurrence and emitting a debug statement superfluous.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201117113103.21480-4-chris@chris-wilson.co.uk

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# bda30024 04-Nov-2020 Tvrtko Ursulin <tvrtko.ursulin@intel.com>

drm/i915: Improve record of hung engines in error state

Between events which trigger engine and GPU resets and capturing the error
state we lose information on which engine triggered the reset. Impr

drm/i915: Improve record of hung engines in error state

Between events which trigger engine and GPU resets and capturing the error
state we lose information on which engine triggered the reset. Improve
this by passing in the hung engine mask down to error capture.

Result is that the list of engines in user visible "GPU HANG: ecode
<gen>:<engines>:<ecode>, <process>" is now a list of hanging and not just
active engines. Most importantly the displayed process is now the one
which was actually hung.

v2:
* Stub prototype. (Chris)

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20201104134743.916027-1-tvrtko.ursulin@linux.intel.com

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# 09212e81 02-Nov-2020 Chris Wilson <chris@chris-wilson.co.uk>

drm/i915/gt: Flush xcs before tgl breadcrumbs

In a simple test case that writes to scratch and then busy-waits for the
batch to be signaled, we observe that the signal is before the write is
posted.

drm/i915/gt: Flush xcs before tgl breadcrumbs

In a simple test case that writes to scratch and then busy-waits for the
batch to be signaled, we observe that the signal is before the write is
posted. That is bad news.

Splitting the flush + write_dword into two separate flush_dw prevents
the issue from being reproduced, we can presume the post-sync op is not
so post-sync.

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/216
Testcase: igt/gem_exec_fence/parallel
Testcase: igt/i915_selftest/live/gt_timelines
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: stable@vger.kernel.org
Acked-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201102221057.29626-2-chris@chris-wilson.co.uk

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Revision tags: v5.8.17
# c10f6019 22-Oct-2020 Chris Wilson <chris@chris-wilson.co.uk>

drm/i915/gt: Use the local HWSP offset during submission

We wrap the timeline on construction of the next request, but there may
still be requests in flight that have not yet finalized the breadcrum

drm/i915/gt: Use the local HWSP offset during submission

We wrap the timeline on construction of the next request, but there may
still be requests in flight that have not yet finalized the breadcrumb.
(The breadcrumb is delayed as we need engine-local offsets, and for the
virtual engine that is not known until execution.) As such, by the time
we write to the timeline's HWSP offset it may have changed, and we
should use the value we preserved in the request instead.

Though the window is small and infrequent (at full flow we can expect a
timeline's seqno to wrap once every 30 minutes), the impact of writing
the old seqno into the new HWSP is severe: the old requests are never
completed, and the new requests are completed before they are even
submitted.

Fixes: ebece7539242 ("drm/i915: Keep timeline HWSP allocated until idle across the system")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: <stable@vger.kernel.org> # v5.2+
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201022064127.10159-1-chris@chris-wilson.co.uk

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Revision tags: v5.8.16
# 89db9537 15-Oct-2020 Chris Wilson <chris@chris-wilson.co.uk>

drm/i915/gt: Confirm the context survives execution

Repeat our sanitychecks from before execution to after execution. One
expects that if we were to see these, the gpu would already be on fire,
but

drm/i915/gt: Confirm the context survives execution

Repeat our sanitychecks from before execution to after execution. One
expects that if we were to see these, the gpu would already be on fire,
but the timing may be informative.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201015190816.31763-1-chris@chris-wilson.co.uk

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Revision tags: v5.8.15, v5.9, v5.8.14
# bb65548e 02-Oct-2020 Chris Wilson <chris@chris-wilson.co.uk>

drm/i915/gt: Undo forced context restores after trivial preemptions

We may try to preempt the currently executing request, only to find that
after unravelling all the dependencies that the original

drm/i915/gt: Undo forced context restores after trivial preemptions

We may try to preempt the currently executing request, only to find that
after unravelling all the dependencies that the original executing
context is still the earliest in the topological sort and re-submitted
back to HW (if we do detect some change in the ELSP that requires
re-submission). However, due to the way we check for wrap-around during
the unravelling, we mark any context that has been submitted just once
(i.e. with the rq->wa_tail set, but the ring->tail earlier) as
potentially wrapping and requiring a forced restore on resubmission.
This was expected to be not a problem, as it was anticipated that most
unwinding for preemption would result in a context switch and the few
that did not would be lost in the noise. It did not take long for
someone to find one particular workload where the cost of those extra
context restores was measurable.

However, since we know the wa_tail is of fixed size, and we know that a
request must be larger than the wa_tail itself, we can safely maintain
the check for request wrapping and check against a slightly future point
in the ring that includes an expected wa_tail. (That is if the
ring->tail is already set to rq->wa_tail, including another 8 bytes in
the check does not invalidate the incremental wrap detection.)

Fixes: 8ab3a3812aa9 ("drm/i915/gt: Incrementally check for rewinding")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Bruce Chang <yu.bruce.chang@intel.com>
Cc: Ramalingam C <ramalingam.c@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: <stable@vger.kernel.org> # v5.4+
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201002083425.4605-1-chris@chris-wilson.co.uk

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# 6ca7217d 15-Oct-2020 Chris Wilson <chris@chris-wilson.co.uk>

drm/i915/gt: Delay execlist processing for tgl

When running gem_exec_nop, it floods the system with many requests (with
the goal of userspace submitting faster than the HW can process a single
empty

drm/i915/gt: Delay execlist processing for tgl

When running gem_exec_nop, it floods the system with many requests (with
the goal of userspace submitting faster than the HW can process a single
empty batch). This causes the driver to continually resubmit new
requests onto the end of an active context, a flood of lite-restore
preemptions. If we time this just right, Tigerlake hangs.

Inserting a small delay between the processing of CS events and
submitting the next context, prevents the hang. Naturally it does not
occur with debugging enabled. The suspicion then is that this is related
to the issues with the CS event buffer, and inserting an mmio read of
the CS pointer status appears to be very successful in preventing the
hang. Other registers, or uncached reads, or plain mb, do not prevent
the hang, suggesting that register is key -- but that the hang can be
prevented by a simple udelay, suggests it is just a timing issue like
that encountered by commit 233c1ae3c83f ("drm/i915/gt: Wait for CSB
entries on Tigerlake"). Also note that the hang is not prevented by
applying CTX_DESC_FORCE_RESTORE, or by inserting a delay on the GPU
between requests.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Bruce Chang <yu.bruce.chang@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: stable@vger.kernel.org
Acked-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20201015195023.32346-1-chris@chris-wilson.co.uk

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Revision tags: v5.8.13
# 5e39b4d9 30-Sep-2020 Chris Wilson <chris@chris-wilson.co.uk>

drm/i915/gt: Signal cancelled requests

After marking the requests on an engine as cancelled upon wedging, send
any signals for their completions.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.

drm/i915/gt: Signal cancelled requests

After marking the requests on an engine as cancelled upon wedging, send
any signals for their completions.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200930163253.2789-1-chris@chris-wilson.co.uk

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Revision tags: v5.8.12, v5.8.11, v5.8.10, v5.8.9, v5.8.8, v5.8.7, v5.8.6, v5.4.62, v5.8.5
# 29545e5c 26-Aug-2020 Chris Wilson <chris@chris-wilson.co.uk>

drm/i915/gt: Remove defunct intel_virtual_engine_get_sibling()

As the last user was eliminated in commit e21fecdcde40 ("drm/i915/gt:
Distinguish the virtual breadcrumbs from the irq breadcrumbs"), w

drm/i915/gt: Remove defunct intel_virtual_engine_get_sibling()

As the last user was eliminated in commit e21fecdcde40 ("drm/i915/gt:
Distinguish the virtual breadcrumbs from the irq breadcrumbs"), we can
remove the function. One less implementation detail creeping beyond its
scope.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200826132811.17577-16-chris@chris-wilson.co.uk

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# 4ff64bcf 15-Sep-2020 Chris Wilson <chris@chris-wilson.co.uk>

drm/i915/gt: Use a mmio read of the CSB in case of failure

If we find the GPU didn't update the CSB within 50us, we currently fail
and eventually reset the GPU. Lets report the value from the mmio s

drm/i915/gt: Use a mmio read of the CSB in case of failure

If we find the GPU didn't update the CSB within 50us, we currently fail
and eventually reset the GPU. Lets report the value from the mmio space
as a last resort, it may just stave off an unnecessary GPU reset.

References: HSDES#22011327657
Suggested-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200915134923.30088-4-chris@chris-wilson.co.uk

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# 884c4074 15-Sep-2020 Chris Wilson <chris@chris-wilson.co.uk>

drm/i915/gt: Apply the CSB w/a for all

Since we expect to inline the csb_parse() routines, the w/a for the
stale CSB data on Tigerlake will be pulled into process_csb(), and so we
might as well simp

drm/i915/gt: Apply the CSB w/a for all

Since we expect to inline the csb_parse() routines, the w/a for the
stale CSB data on Tigerlake will be pulled into process_csb(), and so we
might as well simply reuse the logic for all, and so will hopefully
avoid any strange behaviour on Icelake that was not covered by our
previous w/a.

References: d8f505311717 ("drm/i915/icl: Forcibly evict stale csb entries")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Bruce Chang <yu.bruce.chang@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200915134923.30088-3-chris@chris-wilson.co.uk

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# 233c1ae3 15-Sep-2020 Chris Wilson <chris@chris-wilson.co.uk>

drm/i915/gt: Wait for CSB entries on Tigerlake

On Tigerlake, we are seeing a repeat of commit d8f505311717 ("drm/i915/icl:
Forcibly evict stale csb entries") where, presumably, due to a missing
Glob

drm/i915/gt: Wait for CSB entries on Tigerlake

On Tigerlake, we are seeing a repeat of commit d8f505311717 ("drm/i915/icl:
Forcibly evict stale csb entries") where, presumably, due to a missing
Global Observation Point synchronisation, the write pointer of the CSB
ringbuffer is updated _prior_ to the contents of the ringbuffer. That is
we see the GPU report more context-switch entries for us to parse, but
those entries have not been written, leading us to process stale events,
and eventually report a hung GPU.

However, this effect appears to be much more severe than we previously
saw on Icelake (though it might be best if we try the same approach
there as well and measure), and Bruce suggested the good idea of resetting
the CSB entry after use so that we can detect when it has been updated by
the GPU. By instrumenting how long that may be, we can set a reliable
upper bound for how long we should wait for:

513 late, avg of 61 retries (590 ns), max of 1061 retries (10099 ns)

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2045
References: d8f505311717 ("drm/i915/icl: Forcibly evict stale csb entries")
References: HSDES#22011327657, HSDES#1508287568
Suggested-by: Bruce Chang <yu.bruce.chang@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Bruce Chang <yu.bruce.chang@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: stable@vger.kernel.org # v5.4
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200915134923.30088-2-chris@chris-wilson.co.uk

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# f24a44e5 15-Sep-2020 Chris Wilson <chris@chris-wilson.co.uk>

drm/i915/gt: Widen CSB pointer to u64 for the parsers

A CSB entry is 64b, and it is simpler for us to treat it as an array of
64b entries than as an array of pairs of 32b entries.

Signed-off-by: Ch

drm/i915/gt: Widen CSB pointer to u64 for the parsers

A CSB entry is 64b, and it is simpler for us to treat it as an array of
64b entries than as an array of pairs of 32b entries.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200915134923.30088-1-chris@chris-wilson.co.uk

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