drm/i915: Emphasize that ctx->obj & ctx->is_initialized refer to the legacy rcs ctx

We have already advanced that Logical Ring Contexts have their own kind
of backing objects, but everything will be better explained in the Execlists
series. For now, suffice it to say that the current backing object is only
ever used with the render ring, so we're making this fact more explicit
(which is a good reason on its own).

As for the is_initialized flag, we only use to signify that the render state
has been initialized (a.k.a. golden context, a.k.a. null context). It doesn't
mean anything for the other engines, so make that distinction obvious.

Done with the following Coccinelle patch (plus manual frobbing of the struct):

    @@
    struct intel_context c;
    @@
    - (c).obj
    + c.legacy_hw_ctx.rcs_state

    @@
    struct intel_context *c;
    @@
    - (c)->obj
    + c->legacy_hw_ctx.rcs_state

    @@
    struct intel_context c;
    @@
    - (c).is_initialized
    + c.legacy_hw_ctx.initialized

    @@
    struct intel_context *c;
    @@
    - (c)->is_initialized
    + c->legacy_hw_ctx.initialized

This Execlists prep-work patch has been suggested by Chris Wilson and Daniel
Vetter separately.

Initially, it was two separate patches:
drm/i915: Rename ctx->obj to ctx->rcs_state
drm/i915: Make it obvious that ctx->id is merely a user handle
Signed-off-by: Oscar Mateo <oscar.mateo@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
[danvet: s/id/is_initialized/ to fix the subject and resolve a
conflict in i915_gem_context_reset. Also introduce a new lctx local
variable to avoid overtly long lines.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_debugfs.c

@@ -176,7 +176,7 @@ describe_obj(struct seq_file *m, struct drm_i915_gem_object *obj)
 
 static void describe_ctx(struct seq_file *m, struct intel_context *ctx)
 {
-	seq_putc(m, ctx->is_initialized ? 'I' : 'i');
+	seq_putc(m, ctx->legacy_hw_ctx.initialized ? 'I' : 'i');
 	seq_putc(m, ctx->remap_slice ? 'R' : 'r');
 	seq_putc(m, ' ');
 }
@@ -1753,7 +1753,7 @@ static int i915_context_status(struct seq_file *m, void *unused)
 	}
 
 	list_for_each_entry(ctx, &dev_priv->context_list, link) {
-		if (ctx->obj == NULL)
+		if (ctx->legacy_hw_ctx.rcs_state == NULL)
 			continue;
 
 		seq_puts(m, "HW context ");
@@ -1762,7 +1762,7 @@ static int i915_context_status(struct seq_file *m, void *unused)
 			if (ring->default_context == ctx)
 				seq_printf(m, "(default context %s) ", ring->name);
 
-		describe_obj(m, ctx->obj);
+		describe_obj(m, ctx->legacy_hw_ctx.rcs_state);
 		seq_putc(m, '\n');
 	}
 

drivers/gpu/drm/i915/i915_drv.h

@@ -589,13 +589,16 @@ struct i915_ctx_hang_stats {
 struct intel_context {
 	struct kref ref;
 	int id;
-	bool is_initialized;
 	uint8_t remap_slice;
 	struct drm_i915_file_private *file_priv;
-	struct drm_i915_gem_object *obj;
 	struct i915_ctx_hang_stats hang_stats;
 	struct i915_address_space *vm;
 
+	struct {
+		struct drm_i915_gem_object *rcs_state;
+		bool initialized;
+	} legacy_hw_ctx;
+
 	struct list_head link;
 };
 

drivers/gpu/drm/i915/i915_gem_context.c

@@ -182,14 +182,14 @@ void i915_gem_context_free(struct kref *ctx_ref)
 						   typeof(*ctx), ref);
 	struct i915_hw_ppgtt *ppgtt = NULL;
 
-	if (ctx->obj) {
+	if (ctx->legacy_hw_ctx.rcs_state) {
 		/* We refcount even the aliasing PPGTT to keep the code symmetric */
-		if (USES_PPGTT(ctx->obj->base.dev))
+		if (USES_PPGTT(ctx->legacy_hw_ctx.rcs_state->base.dev))
 			ppgtt = ctx_to_ppgtt(ctx);
 
 		/* XXX: Free up the object before tearing down the address space, in
 		 * case we're bound in the PPGTT */
-		drm_gem_object_unreference(&ctx->obj->base);
+		drm_gem_object_unreference(&ctx->legacy_hw_ctx.rcs_state->base);
 	}
 
 	if (ppgtt)
@@ -270,7 +270,7 @@ __create_hw_context(struct drm_device *dev,
 			ret = PTR_ERR(obj);
 			goto err_out;
 		}
-		ctx->obj = obj;
+		ctx->legacy_hw_ctx.rcs_state = obj;
 	}
 
 	/* Default context will never have a file_priv */
@@ -317,7 +317,7 @@ i915_gem_create_context(struct drm_device *dev,
 	if (IS_ERR(ctx))
 		return ctx;
 
-	if (is_global_default_ctx && ctx->obj) {
+	if (is_global_default_ctx && ctx->legacy_hw_ctx.rcs_state) {
 		/* We may need to do things with the shrinker which
 		 * require us to immediately switch back to the default
 		 * context. This can cause a problem as pinning the
@@ -325,7 +325,7 @@ i915_gem_create_context(struct drm_device *dev,
 		 * be available. To avoid this we always pin the default
 		 * context.
 		 */
-		ret = i915_gem_obj_ggtt_pin(ctx->obj,
+		ret = i915_gem_obj_ggtt_pin(ctx->legacy_hw_ctx.rcs_state,
 					    get_context_alignment(dev), 0);
 		if (ret) {
 			DRM_DEBUG_DRIVER("Couldn't pin %d\n", ret);
@@ -365,8 +365,8 @@ i915_gem_create_context(struct drm_device *dev,
 	return ctx;
 
 err_unpin:
-	if (is_global_default_ctx && ctx->obj)
-		i915_gem_object_ggtt_unpin(ctx->obj);
+	if (is_global_default_ctx && ctx->legacy_hw_ctx.rcs_state)
+		i915_gem_object_ggtt_unpin(ctx->legacy_hw_ctx.rcs_state);
 err_destroy:
 	i915_gem_context_unreference(ctx);
 	return ERR_PTR(ret);
@@ -382,26 +382,27 @@ void i915_gem_context_reset(struct drm_device *dev)
 	for (i = 0; i < I915_NUM_RINGS; i++) {
 		struct intel_engine_cs *ring = &dev_priv->ring[i];
 		struct intel_context *dctx = ring->default_context;
+		struct intel_context *lctx = ring->last_context;
 
 		/* Do a fake switch to the default context */
-		if (ring->last_context == dctx)
+		if (lctx == dctx)
 			continue;
 
-		if (!ring->last_context)
+		if (!lctx)
 			continue;
 
-		if (dctx->obj && i == RCS) {
-			WARN_ON(i915_gem_obj_ggtt_pin(dctx->obj,
+		if (dctx->legacy_hw_ctx.rcs_state && i == RCS) {
+			WARN_ON(i915_gem_obj_ggtt_pin(dctx->legacy_hw_ctx.rcs_state,
 						      get_context_alignment(dev), 0));
 			/* Fake a finish/inactive */
-			dctx->obj->base.write_domain = 0;
-			dctx->obj->active = 0;
+			dctx->legacy_hw_ctx.rcs_state->base.write_domain = 0;
+			dctx->legacy_hw_ctx.rcs_state->active = 0;
 		}
 
-		if (ring->last_context->obj && i == RCS)
-			i915_gem_object_ggtt_unpin(ring->last_context->obj);
+		if (lctx->legacy_hw_ctx.rcs_state && i == RCS)
+			i915_gem_object_ggtt_unpin(lctx->legacy_hw_ctx.rcs_state);
 
-		i915_gem_context_unreference(ring->last_context);
+		i915_gem_context_unreference(lctx);
 		i915_gem_context_reference(dctx);
 		ring->last_context = dctx;
 	}
@@ -448,7 +449,7 @@ void i915_gem_context_fini(struct drm_device *dev)
 	struct intel_context *dctx = dev_priv->ring[RCS].default_context;
 	int i;
 
-	if (dctx->obj) {
+	if (dctx->legacy_hw_ctx.rcs_state) {
 		/* The only known way to stop the gpu from accessing the hw context is
 		 * to reset it. Do this as the very last operation to avoid confusing
 		 * other code, leading to spurious errors. */
@@ -463,13 +464,13 @@ void i915_gem_context_fini(struct drm_device *dev)
 		WARN_ON(!dev_priv->ring[RCS].last_context);
 		if (dev_priv->ring[RCS].last_context == dctx) {
 			/* Fake switch to NULL context */
-			WARN_ON(dctx->obj->active);
-			i915_gem_object_ggtt_unpin(dctx->obj);
+			WARN_ON(dctx->legacy_hw_ctx.rcs_state->active);
+			i915_gem_object_ggtt_unpin(dctx->legacy_hw_ctx.rcs_state);
 			i915_gem_context_unreference(dctx);
 			dev_priv->ring[RCS].last_context = NULL;
 		}
 
-		i915_gem_object_ggtt_unpin(dctx->obj);
+		i915_gem_object_ggtt_unpin(dctx->legacy_hw_ctx.rcs_state);
 	}
 
 	for (i = 0; i < I915_NUM_RINGS; i++) {
@@ -589,7 +590,7 @@ mi_set_context(struct intel_engine_cs *ring,
 
 	intel_ring_emit(ring, MI_NOOP);
 	intel_ring_emit(ring, MI_SET_CONTEXT);
-	intel_ring_emit(ring, i915_gem_obj_ggtt_offset(new_context->obj) |
+	intel_ring_emit(ring, i915_gem_obj_ggtt_offset(new_context->legacy_hw_ctx.rcs_state) |
 			MI_MM_SPACE_GTT |
 			MI_SAVE_EXT_STATE_EN |
 			MI_RESTORE_EXT_STATE_EN |
@@ -621,8 +622,8 @@ static int do_switch(struct intel_engine_cs *ring,
 	int ret, i;
 
 	if (from != NULL && ring == &dev_priv->ring[RCS]) {
-		BUG_ON(from->obj == NULL);
-		BUG_ON(!i915_gem_obj_is_pinned(from->obj));
+		BUG_ON(from->legacy_hw_ctx.rcs_state == NULL);
+		BUG_ON(!i915_gem_obj_is_pinned(from->legacy_hw_ctx.rcs_state));
 	}
 
 	if (from == to && !to->remap_slice)
@@ -630,7 +631,7 @@ static int do_switch(struct intel_engine_cs *ring,
 
 	/* Trying to pin first makes error handling easier. */
 	if (ring == &dev_priv->ring[RCS]) {
-		ret = i915_gem_obj_ggtt_pin(to->obj,
+		ret = i915_gem_obj_ggtt_pin(to->legacy_hw_ctx.rcs_state,
 					    get_context_alignment(ring->dev), 0);
 		if (ret)
 			return ret;
@@ -663,17 +664,17 @@ static int do_switch(struct intel_engine_cs *ring,
 	 *
 	 * XXX: We need a real interface to do this instead of trickery.
 	 */
-	ret = i915_gem_object_set_to_gtt_domain(to->obj, false);
+	ret = i915_gem_object_set_to_gtt_domain(to->legacy_hw_ctx.rcs_state, false);
 	if (ret)
 		goto unpin_out;
 
-	if (!to->obj->has_global_gtt_mapping) {
-		struct i915_vma *vma = i915_gem_obj_to_vma(to->obj,
+	if (!to->legacy_hw_ctx.rcs_state->has_global_gtt_mapping) {
+		struct i915_vma *vma = i915_gem_obj_to_vma(to->legacy_hw_ctx.rcs_state,
 							   &dev_priv->gtt.base);
-		vma->bind_vma(vma, to->obj->cache_level, GLOBAL_BIND);
+		vma->bind_vma(vma, to->legacy_hw_ctx.rcs_state->cache_level, GLOBAL_BIND);
 	}
 
-	if (!to->is_initialized || i915_gem_context_is_default(to))
+	if (!to->legacy_hw_ctx.initialized || i915_gem_context_is_default(to))
 		hw_flags |= MI_RESTORE_INHIBIT;
 
 	ret = mi_set_context(ring, to, hw_flags);
@@ -699,8 +700,8 @@ static int do_switch(struct intel_engine_cs *ring,
 	 * MI_SET_CONTEXT instead of when the next seqno has completed.
 	 */
 	if (from != NULL) {
-		from->obj->base.read_domains = I915_GEM_DOMAIN_INSTRUCTION;
-		i915_vma_move_to_active(i915_gem_obj_to_ggtt(from->obj), ring);
+		from->legacy_hw_ctx.rcs_state->base.read_domains = I915_GEM_DOMAIN_INSTRUCTION;
+		i915_vma_move_to_active(i915_gem_obj_to_ggtt(from->legacy_hw_ctx.rcs_state), ring);
 		/* As long as MI_SET_CONTEXT is serializing, ie. it flushes the
 		 * whole damn pipeline, we don't need to explicitly mark the
 		 * object dirty. The only exception is that the context must be
@@ -708,16 +709,16 @@ static int do_switch(struct intel_engine_cs *ring,
 		 * able to defer doing this until we know the object would be
 		 * swapped, but there is no way to do that yet.
 		 */
-		from->obj->dirty = 1;
-		BUG_ON(from->obj->ring != ring);
+		from->legacy_hw_ctx.rcs_state->dirty = 1;
+		BUG_ON(from->legacy_hw_ctx.rcs_state->ring != ring);
 
 		/* obj is kept alive until the next request by its active ref */
-		i915_gem_object_ggtt_unpin(from->obj);
+		i915_gem_object_ggtt_unpin(from->legacy_hw_ctx.rcs_state);
 		i915_gem_context_unreference(from);
 	}
 
-	uninitialized = !to->is_initialized && from == NULL;
-	to->is_initialized = true;
+	uninitialized = !to->legacy_hw_ctx.initialized && from == NULL;
+	to->legacy_hw_ctx.initialized = true;
 
 done:
 	i915_gem_context_reference(to);
@@ -733,7 +734,7 @@ static int do_switch(struct intel_engine_cs *ring,
 
 unpin_out:
 	if (ring->id == RCS)
-		i915_gem_object_ggtt_unpin(to->obj);
+		i915_gem_object_ggtt_unpin(to->legacy_hw_ctx.rcs_state);
 	return ret;
 }
 
@@ -754,7 +755,7 @@ int i915_switch_context(struct intel_engine_cs *ring,
 
 	WARN_ON(!mutex_is_locked(&dev_priv->dev->struct_mutex));
 
-	if (to->obj == NULL) { /* We have the fake context */
+	if (to->legacy_hw_ctx.rcs_state == NULL) { /* We have the fake context */
 		if (to != ring->last_context) {
 			i915_gem_context_reference(to);
 			if (ring->last_context)