drm2/i915/i915_gem_context.c

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39  * context's state is never restored to help prevent programming errors. This
41  * The default context only exists to give the GPU some offset to load as the
42  * current to invoke a save of the context we actually care about. In fact, the
43  * code could likely be constructed, albeit in a more complicated fashion, to
44  * never use the default context, though that limits the driver's ability to
48  * store GPU state, and thus allow GPU clients to not re-emit state (and
78  *  offset, but it will on the next context switch. The only way to avoid this
79  *  is to do a GPU reset.
82  *  on the active list waiting for the next context switch to occur. Until this
84  *  possible to destroy a context, but it is still active.
96  * I've seen in a spec to date, and that was a workaround for a non-shipping
97  * part. It should be safe to decrease this, but it's more future proof as is.
103 static int do_switch(struct i915_hw_context *to);
176 	 * object tracking code. We give an initial ring value simple to pass an
214  * The default context needs to exist per ring that uses contexts. It stores the
229 	/* We may need to do things with the shrinker which require us to
230 	 * immediately switch back to the default context. This can cause a
293 	/* The only known way to stop the gpu from accessing the hw context is
294 	 * to reset it. Do this as the very last operation to avoid confusing
295 	 * other code, leading to spurious errors. */
300 	/* When default context is created and switched to, base object refcount
303 	 * to default context. So we need to unreference the base object once
304 	 * to offset the do_switch part, so that i915_gem_context_unreference()
346 	 * invalidation prior to MI_SET_CONTEXT. On GEN6 we don't set the value
385 static int do_switch(struct i915_hw_context *to)
387 	struct intel_ring_buffer *ring = to->ring;
395 	if (from_obj == to->obj)
398 	ret = i915_gem_object_pin(to->obj, CONTEXT_ALIGN, false, false);
403 	 * that thanks to write = false in this call and us not setting any gpu
406 	 * XXX: We need a real interface to do this instead of trickery. */
407 	ret = i915_gem_object_set_to_gtt_domain(to->obj, false);
409 		i915_gem_object_unpin(to->obj);
413 	if (!to->obj->has_global_gtt_mapping)
414 		i915_gem_gtt_bind_object(to->obj, to->obj->cache_level);
416 	if (!to->is_initialized || is_default_context(to))
418 	else if (from_obj == to->obj) /* not yet expected */
421 	ret = mi_set_context(ring, to, hw_flags);
423 		i915_gem_object_unpin(to->obj);
427 	/* The backing object for the context is done after switching to the
437 		 * whole damn pipeline, we don't need to explicitly mark the
440 		 * able to defer doing this until we know the object would be
441 		 * swapped, but there is no way to do that yet.
450 	drm_gem_object_reference(&to->obj->base);
451 	ring->last_context_obj = to->obj;
452 	to->is_initialized = true;
462  * @seqno: sequence number by which the new context will be switched to
467  * it will have a refoucnt > 1. This allows us to destroy the context abstract
475 	struct i915_hw_context *to;
484 		to = ring->default_context;
489 		to = i915_gem_context_get(file->driver_priv, to_id);
490 		if (to == NULL)
494 	return do_switch(to);