[Intel-gfx] [PATCH 11/18] drm/i915: Record space required for request emission

[Chris Wilson]

On Wed, Sep 14, 2016 at 02:30:20PM +0100, Tvrtko Ursulin wrote:
> 
> On 14/09/2016 07:52, Chris Wilson wrote:
> >In the next patch, we will use deferred request emission. That requires
> >reserving sufficient space in the ringbuffer to emit the request, which
> >first requires us to know how large the request is.
> >
> >Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> >---
> >  drivers/gpu/drm/i915/i915_gem_request.c |  1 +
> >  drivers/gpu/drm/i915/intel_lrc.c        |  6 ++++++
> >  drivers/gpu/drm/i915/intel_ringbuffer.c | 29 +++++++++++++++++++++++++++--
> >  drivers/gpu/drm/i915/intel_ringbuffer.h |  1 +
> >  4 files changed, 35 insertions(+), 2 deletions(-)
> >
> >diff --git a/drivers/gpu/drm/i915/i915_gem_request.c b/drivers/gpu/drm/i915/i915_gem_request.c
> >index ebc2feba3e50..9a735e2d5aea 100644
> >--- a/drivers/gpu/drm/i915/i915_gem_request.c
> >+++ b/drivers/gpu/drm/i915/i915_gem_request.c
> >@@ -425,6 +425,7 @@ i915_gem_request_alloc(struct intel_engine_cs *engine,
> >  	 * away, e.g. because a GPU scheduler has deferred it.
> >  	 */
> >  	req->reserved_space = MIN_SPACE_FOR_ADD_REQUEST;
> >+	GEM_BUG_ON(req->reserved_space < engine->emit_request_sz);
> >  	if (i915.enable_execlists)
> >  		ret = intel_logical_ring_alloc_request_extras(req);
> >diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> >index 00fcf36ba919..7e944a0acc10 100644
> >--- a/drivers/gpu/drm/i915/intel_lrc.c
> >+++ b/drivers/gpu/drm/i915/intel_lrc.c
> >@@ -1572,6 +1572,8 @@ static int gen8_emit_request(struct drm_i915_gem_request *request)
> >  	return intel_logical_ring_advance(request);
> >  }
> >+static const int gen8_emit_request_sz = 6 + WA_TAIL_DWORDS;
> >+
> >  static int gen8_emit_request_render(struct drm_i915_gem_request *request)
> >  {
> >  	struct intel_ring *ring = request->ring;
> >@@ -1603,6 +1605,8 @@ static int gen8_emit_request_render(struct drm_i915_gem_request *request)
> >  	return intel_logical_ring_advance(request);
> >  }
> >+static const int gen8_emit_request_render_sz = 8 + WA_TAIL_DWORDS;
> >+
> >  static int gen8_init_rcs_context(struct drm_i915_gem_request *req)
> >  {
> >  	int ret;
> >@@ -1677,6 +1681,7 @@ logical_ring_default_vfuncs(struct intel_engine_cs *engine)
> >  	engine->reset_hw = reset_common_ring;
> >  	engine->emit_flush = gen8_emit_flush;
> >  	engine->emit_request = gen8_emit_request;
> >+	engine->emit_request_sz = gen8_emit_request_sz;
> >  	engine->submit_request = execlists_submit_request;
> >  	engine->irq_enable = gen8_logical_ring_enable_irq;
> >@@ -1799,6 +1804,7 @@ int logical_render_ring_init(struct intel_engine_cs *engine)
> >  	engine->init_context = gen8_init_rcs_context;
> >  	engine->emit_flush = gen8_emit_flush_render;
> >  	engine->emit_request = gen8_emit_request_render;
> >+	engine->emit_request_sz = gen8_emit_request_render_sz;
> >  	ret = intel_engine_create_scratch(engine, 4096);
> >  	if (ret)
> >diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> >index 597e35c9b699..c8c9ad40fd93 100644
> >--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> >+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> >@@ -1405,6 +1405,8 @@ static int i9xx_emit_request(struct drm_i915_gem_request *req)
> >  	return 0;
> >  }
> >+static const int i9xx_emit_request_sz = 4;
> >+
> >  /**
> >   * gen6_sema_emit_request - Update the semaphore mailbox registers
> >   *
> >@@ -1458,6 +1460,8 @@ static int gen8_render_emit_request(struct drm_i915_gem_request *req)
> >  	return 0;
> >  }
> >+static const int gen8_render_emit_request_sz = 8;
> >+
> >  /**
> >   * intel_ring_sync - sync the waiter to the signaller on seqno
> >   *
> >@@ -2677,8 +2681,21 @@ static void intel_ring_default_vfuncs(struct drm_i915_private *dev_priv,
> >  	engine->reset_hw = reset_ring_common;
> >  	engine->emit_request = i9xx_emit_request;
> >-	if (i915.semaphores)
> >+	engine->emit_request_sz = i9xx_emit_request_sz;
> >+	if (i915.semaphores) {
> >+		int num_rings;
> >+
> >  		engine->emit_request = gen6_sema_emit_request;
> >+
> >+		num_rings = hweight32(INTEL_INFO(dev_priv)->ring_mask) - 1;
> 
> You can use INTEL_INFO(dev_priv)->num_rings instead of hweight32.

I thought info->num_rings was set afterwards? (And num_rings may be an
overestimate here :(
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre