[PATCH 18/18] drm/i915: Simplify calling engine->sync_to

Chris Wilson
2016-07-20T13:12:49Z

Since requests can no longer be generated as a side-effect of
intel_ring_begin(), we know that the seqno will be unchanged during
ring-emission. This predicatablity then means we do not have to check
for the seqno wrapping around whilst emitting the semaphore for
engine->sync_to().

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
drivers/gpu/drm/i915/i915_drv.h | 2 +-
drivers/gpu/drm/i915/i915_gem.c | 13 ++-----
drivers/gpu/drm/i915/i915_gem_request.c | 9 +----
drivers/gpu/drm/i915/intel_ringbuffer.c | 64 ++++++++++++---------------------
drivers/gpu/drm/i915/intel_ringbuffer.h | 5 ++-
5 files changed, 30 insertions(+), 63 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index f188c9a9b746..c374b8687d87 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -1757,7 +1757,7 @@ struct drm_i915_private {
struct i915_gem_context *kernel_context;
struct intel_engine_cs engine[I915_NUM_ENGINES];
struct drm_i915_gem_object *semaphore_obj;
- uint32_t last_seqno, next_seqno;
+ u32 next_seqno;

struct drm_dma_handle *status_page_dmah;
struct resource mch_res;
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 9fdecef34fa8..0b7a0e6f9dd1 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2864,22 +2864,15 @@ __i915_gem_object_sync(struct drm_i915_gem_object *obj,
i915_gem_object_retire_request(obj, from);
} else {
int idx = intel_engine_sync_index(from->engine, to->engine);
- u32 seqno = i915_gem_request_get_seqno(from);
-
- if (seqno <= from->engine->semaphore.sync_seqno[idx])
+ if (from->fence.seqno <= from->engine->semaphore.sync_seqno[idx])
return 0;

trace_i915_gem_ring_sync_to(to, from);
- ret = to->engine->semaphore.sync_to(to, from->engine, seqno);
+ ret = to->engine->semaphore.sync_to(to, from);
if (ret)
return ret;

- /* We use last_read_req because sync_to()
- * might have just caused seqno wrap under
- * the radar.
- */
- from->engine->semaphore.sync_seqno[idx] =
- i915_gem_request_get_seqno(obj->last_read_req[from->engine->id]);
+ from->engine->semaphore.sync_seqno[idx] = from->fence.seqno;
}

return 0;
diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
index 3e633b47213c..dfdb86c8a433 100644
--- a/drivers/gpu/drm/i915/i915_gem_request.c
+++ b/drivers/gpu/drm/i915/i915_gem_request.c
@@ -264,14 +264,7 @@ int i915_gem_set_seqno(struct drm_device *dev, u32 seqno)
if (ret)
return ret;

- /* Carefully set the last_seqno value so that wrap
- * detection still works
- */
dev_priv->next_seqno = seqno;
- dev_priv->last_seqno = seqno - 1;
- if (dev_priv->last_seqno == 0)
- dev_priv->last_seqno--;
-
return 0;
}

@@ -288,7 +281,7 @@ static int i915_gem_get_seqno(struct drm_i915_private *dev_priv, u32 *seqno)
dev_priv->next_seqno = 1;
}

- *seqno = dev_priv->last_seqno = dev_priv->next_seqno++;
+ *seqno = dev_priv->next_seqno++;
return 0;
}

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 8ae25bcc876e..bfeb16025327 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1494,12 +1494,6 @@ static int gen8_render_emit_request(struct drm_i915_gem_request *req)
return 0;
}

-static inline bool i915_gem_has_seqno_wrapped(struct drm_i915_private *dev_priv,
- u32 seqno)
-{
- return dev_priv->last_seqno < seqno;
-}
-
/**
* intel_ring_sync - sync the waiter to the signaller on seqno
*
@@ -1509,24 +1503,23 @@ static inline bool i915_gem_has_seqno_wrapped(struct drm_i915_private *dev_priv,
*/

static int
-gen8_ring_sync(struct drm_i915_gem_request *waiter_req,
- struct intel_engine_cs *signaller,
- u32 seqno)
+gen8_ring_sync(struct drm_i915_gem_request *wait,
+ struct drm_i915_gem_request *signal)
{
- struct intel_ring *waiter = waiter_req->ring;
- struct drm_i915_private *dev_priv = waiter_req->i915;
- u64 offset = GEN8_WAIT_OFFSET(waiter_req->engine, signaller->id);
+ struct intel_ring *waiter = wait->ring;
+ struct drm_i915_private *dev_priv = wait->i915;
+ u64 offset = GEN8_WAIT_OFFSET(wait->engine, signal->engine->id);
struct i915_hw_ppgtt *ppgtt;
int ret;

- ret = intel_ring_begin(waiter_req, 4);
+ ret = intel_ring_begin(wait, 4);
if (ret)
return ret;

intel_ring_emit(waiter, MI_SEMAPHORE_WAIT |
MI_SEMAPHORE_GLOBAL_GTT |
MI_SEMAPHORE_SAD_GTE_SDD);
- intel_ring_emit(waiter, seqno);
+ intel_ring_emit(waiter, signal->fence.seqno);
intel_ring_emit(waiter, lower_32_bits(offset));
intel_ring_emit(waiter, upper_32_bits(offset));
intel_ring_advance(waiter);
@@ -1536,48 +1529,37 @@ gen8_ring_sync(struct drm_i915_gem_request *waiter_req,
* We do this on the i915_switch_context() following the wait and
* before the dispatch.
*/
- ppgtt = waiter_req->ctx->ppgtt;
- if (ppgtt && waiter_req->engine->id != RCS)
- ppgtt->pd_dirty_rings |= intel_engine_flag(waiter_req->engine);
+ ppgtt = wait->ctx->ppgtt;
+ if (ppgtt && wait->engine->id != RCS)
+ ppgtt->pd_dirty_rings |= intel_engine_flag(wait->engine);
return 0;
}

static int
-gen6_ring_sync(struct drm_i915_gem_request *waiter_req,
- struct intel_engine_cs *signaller,
- u32 seqno)
+gen6_ring_sync(struct drm_i915_gem_request *wait,
+ struct drm_i915_gem_request *signal)
{
- struct intel_ring *waiter = waiter_req->ring;
+ struct intel_ring *waiter = wait->ring;
u32 dw1 = MI_SEMAPHORE_MBOX |
MI_SEMAPHORE_COMPARE |
MI_SEMAPHORE_REGISTER;
- u32 wait_mbox = signaller->semaphore.mbox.wait[waiter_req->engine->id];
+ u32 wait_mbox = signal->engine->semaphore.mbox.wait[wait->engine->id];
int ret;

- /* Throughout all of the GEM code, seqno passed implies our current
- * seqno is >= the last seqno executed. However for hardware the
- * comparison is strictly greater than.
- */
- seqno -= 1;
-
WARN_ON(wait_mbox == MI_SEMAPHORE_SYNC_INVALID);

- ret = intel_ring_begin(waiter_req, 4);
+ ret = intel_ring_begin(wait, 4);
if (ret)
return ret;

- /* If seqno wrap happened, omit the wait with no-ops */
- if (likely(!i915_gem_has_seqno_wrapped(waiter_req->i915, seqno))) {
- intel_ring_emit(waiter, dw1 | wait_mbox);
- intel_ring_emit(waiter, seqno);
- intel_ring_emit(waiter, 0);
- intel_ring_emit(waiter, MI_NOOP);
- } else {
- intel_ring_emit(waiter, MI_NOOP);
- intel_ring_emit(waiter, MI_NOOP);
- intel_ring_emit(waiter, MI_NOOP);
- intel_ring_emit(waiter, MI_NOOP);
- }
+ intel_ring_emit(waiter, dw1 | wait_mbox);
+ /* Throughout all of the GEM code, seqno passed implies our current
+ * seqno is >= the last seqno executed. However for hardware the
+ * comparison is strictly greater than.
+ */
+ intel_ring_emit(waiter, signal->fence.seqno - 1);
+ intel_ring_emit(waiter, 0);
+ intel_ring_emit(waiter, MI_NOOP);
intel_ring_advance(waiter);

return 0;
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 08e86204a3d5..65cb6adf26ca 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -275,9 +275,8 @@ struct intel_engine_cs {
};

/* AKA wait() */
- int (*sync_to)(struct drm_i915_gem_request *to_req,
- struct intel_engine_cs *from,
- u32 seqno);
+ int (*sync_to)(struct drm_i915_gem_request *to,
+ struct drm_i915_gem_request *from);
int (*signal)(struct drm_i915_gem_request *signaller_req);
} semaphore;

--
2.8.1