drm/i915/gt: Use the kernel_context to measure the breadcrumb size

We set up a dummy ring in order to measure the size we require for our
breadcrumb emission, so that we don't have to manually count dwords! We
can pass in the kernel_context to use for this so that if required it is
known for the breadcrumb emitter, and we can reuse some details from the
kernel_context to reduce the number of temporaries we have to mock.

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/20200207125827.2787472-1-chris@chris-wilson.co.uk

diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
index b1c7b1e..f6f5e1e 100644 (file)
--- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c
@@ -631,13 +631,13 @@ static int engine_setup_common(struct intel_engine_cs *engine)
 
 struct measure_breadcrumb {
        struct i915_request rq;
-       struct intel_timeline timeline;
        struct intel_ring ring;
        u32 cs[1024];
 };
 
-static int measure_breadcrumb_dw(struct intel_engine_cs *engine)
+static int measure_breadcrumb_dw(struct intel_context *ce)
 {
+       struct intel_engine_cs *engine = ce->engine;
        struct measure_breadcrumb *frame;
        int dw = -ENOMEM;
 
@@ -647,39 +647,27 @@ static int measure_breadcrumb_dw(struct intel_engine_cs *engine)
        if (!frame)
                return -ENOMEM;
 
-       if (intel_timeline_init(&frame->timeline,
-                               engine->gt,
-                               engine->status_page.vma))
-               goto out_frame;
-
-       mutex_lock(&frame->timeline.mutex);
+       frame->rq.i915 = engine->i915;
+       frame->rq.engine = engine;
+       frame->rq.context = ce;
+       rcu_assign_pointer(frame->rq.timeline, ce->timeline);
 
        frame->ring.vaddr = frame->cs;
        frame->ring.size = sizeof(frame->cs);
        frame->ring.effective_size = frame->ring.size;
        intel_ring_update_space(&frame->ring);
-
-       frame->rq.i915 = engine->i915;
-       frame->rq.engine = engine;
        frame->rq.ring = &frame->ring;
-       rcu_assign_pointer(frame->rq.timeline, &frame->timeline);
-
-       dw = intel_timeline_pin(&frame->timeline);
-       if (dw < 0)
-               goto out_timeline;
 
+       mutex_lock(&ce->timeline->mutex);
        spin_lock_irq(&engine->active.lock);
+
        dw = engine->emit_fini_breadcrumb(&frame->rq, frame->cs) - frame->cs;
+
        spin_unlock_irq(&engine->active.lock);
+       mutex_unlock(&ce->timeline->mutex);
 
        GEM_BUG_ON(dw & 1); /* RING_TAIL must be qword aligned */
 
-       intel_timeline_unpin(&frame->timeline);
-
-out_timeline:
-       mutex_unlock(&frame->timeline.mutex);
-       intel_timeline_fini(&frame->timeline);
-out_frame:
        kfree(frame);
        return dw;
 }
@@ -754,12 +742,6 @@ static int engine_init_common(struct intel_engine_cs *engine)
 
        engine->set_default_submission(engine);
 
-       ret = measure_breadcrumb_dw(engine);
-       if (ret < 0)
-               return ret;
-
-       engine->emit_fini_breadcrumb_dw = ret;
-
        /*
         * We may need to do things with the shrinker which
         * require us to immediately switch back to the default
@@ -772,9 +754,18 @@ static int engine_init_common(struct intel_engine_cs *engine)
        if (IS_ERR(ce))
                return PTR_ERR(ce);
 
+       ret = measure_breadcrumb_dw(ce);
+       if (ret < 0)
+               goto err_context;
+
+       engine->emit_fini_breadcrumb_dw = ret;
        engine->kernel_context = ce;
 
        return 0;
+
+err_context:
+       intel_context_put(ce);
+       return ret;
 }
 
 int intel_engines_init(struct intel_gt *gt)