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authorMichel Thierry <michel.thierry@intel.com>2015-04-15 17:11:33 (GMT)
committerJani Nikula <jani.nikula@intel.com>2015-04-23 20:56:52 (GMT)
commit53292cdb066950611e5bc2e0eb109c7edb42af78 (patch)
tree2c2b0ed161701386dfff4000b084d9289c8eca97 /drivers
parent9535c4757b881e06fae72a857485ad57c422b8d2 (diff)
downloadlinux-53292cdb066950611e5bc2e0eb109c7edb42af78.tar.xz
drm/i915: Workaround to avoid lite restore with HEAD==TAIL
WaIdleLiteRestore is an execlists-only workaround, and requires the driver to ensure that any context always has HEAD!=TAIL when attempting lite restore. Add two extra MI_NOOP instructions at the end of each request, but keep the requests tail pointing before the MI_NOOPs. We may not need to executed them, and this is why request->tail is sampled before adding these extra instructions. If we submit a context to the ELSP which has previously been submitted, move the tail pointer past the MI_NOOPs. This ensures HEAD!=TAIL. v2: Move overallocation to gen8_emit_request, and added note about sampling request->tail in commit message (Chris). v3: Remove redundant request->tail assignment in __i915_add_request, in lrc mode this is already set in execlists_context_queue. Do not add wa implementation details inside gem (Chris). v4: Apply the wa whenever the req has been resubmitted and update comment (Chris). Cc: Chris Wilson <chris@chris-wilson.co.uk> Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk> Signed-off-by: Thomas Daniel <thomas.daniel@intel.com> Signed-off-by: Michel Thierry <michel.thierry@intel.com> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/gpu/drm/i915/i915_gem.c3
-rw-r--r--drivers/gpu/drm/i915/intel_lrc.c35
2 files changed, 36 insertions, 2 deletions
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index d07c0b1..53394f9 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2377,10 +2377,11 @@ int __i915_add_request(struct intel_engine_cs *ring,
ret = ring->add_request(ring);
if (ret)
return ret;
+
+ request->tail = intel_ring_get_tail(ringbuf);
}
request->head = request_start;
- request->tail = intel_ring_get_tail(ringbuf);
/* Whilst this request exists, batch_obj will be on the
* active_list, and so will hold the active reference. Only when this
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index fcb074b..09df74b 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -393,6 +393,26 @@ static void execlists_context_unqueue(struct intel_engine_cs *ring)
}
}
+ if (IS_GEN8(ring->dev) || IS_GEN9(ring->dev)) {
+ /*
+ * WaIdleLiteRestore: make sure we never cause a lite
+ * restore with HEAD==TAIL
+ */
+ if (req0 && req0->elsp_submitted) {
+ /*
+ * Apply the wa NOOPS to prevent ring:HEAD == req:TAIL
+ * as we resubmit the request. See gen8_emit_request()
+ * for where we prepare the padding after the end of the
+ * request.
+ */
+ struct intel_ringbuffer *ringbuf;
+
+ ringbuf = req0->ctx->engine[ring->id].ringbuf;
+ req0->tail += 8;
+ req0->tail &= ringbuf->size - 1;
+ }
+ }
+
WARN_ON(req1 && req1->elsp_submitted);
execlists_submit_contexts(ring, req0->ctx, req0->tail,
@@ -1315,7 +1335,12 @@ static int gen8_emit_request(struct intel_ringbuffer *ringbuf,
u32 cmd;
int ret;
- ret = intel_logical_ring_begin(ringbuf, request->ctx, 6);
+ /*
+ * Reserve space for 2 NOOPs at the end of each request to be
+ * used as a workaround for not being allowed to do lite
+ * restore with HEAD==TAIL (WaIdleLiteRestore).
+ */
+ ret = intel_logical_ring_begin(ringbuf, request->ctx, 8);
if (ret)
return ret;
@@ -1333,6 +1358,14 @@ static int gen8_emit_request(struct intel_ringbuffer *ringbuf,
intel_logical_ring_emit(ringbuf, MI_NOOP);
intel_logical_ring_advance_and_submit(ringbuf, request->ctx, request);
+ /*
+ * Here we add two extra NOOPs as padding to avoid
+ * lite restore of a context with HEAD==TAIL.
+ */
+ intel_logical_ring_emit(ringbuf, MI_NOOP);
+ intel_logical_ring_emit(ringbuf, MI_NOOP);
+ intel_logical_ring_advance(ringbuf);
+
return 0;
}