drm/i915: Track which ring a context ran on

Previously we dropped the association of a context to a ring. It is
however very important to know which ring a context ran on (we could
have reused the other member, but I was nitpicky).

This is very important when we switch address spaces, which unlike
context objects, do change per ring.

As an example, if we have:

        RCS   BCS
ctx            A
ctx      A
ctx      B
ctx            B

Without tracking the last ring B ran on, we wouldn't know to switch the
address space on BCS in the last row.

As a result, we no longer need to track which ring a context "belongs"
to, as it never really made much sense anyway.

Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 2c0115edc69ff250b8edcf49f0921f1eb947c765..2b16c29ea571d0604f685b42b5e97580c0fd7024 100644 (file)
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -696,7 +696,7 @@ struct i915_hw_context {
        bool is_initialized;
        uint8_t remap_slice;
        struct drm_i915_file_private *file_priv;
-       struct intel_ring_buffer *ring;
+       struct intel_ring_buffer *last_ring;
        struct drm_i915_gem_object *obj;
        struct i915_ctx_hang_stats hang_stats;
 

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 7a5311c3225af1eb5ba7144ccd25787c9cfe9816..5f8bc06e8594151cbe46ba316b2767f554b08a4d 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -176,11 +176,6 @@ create_hw_context(struct drm_device *dev,
                        goto err_out;
        }
 
-       /* The ring associated with the context object is handled by the normal
-        * object tracking code. We give an initial ring value simple to pass an
-        * assertion in the context switch code.
-        */
-       ctx->ring = &dev_priv->ring[RCS];
        list_add_tail(&ctx->link, &dev_priv->context_list);
 
        /* Default context will never have a file_priv */
@@ -208,7 +203,8 @@ err_out:
 
 static inline bool is_default_context(struct i915_hw_context *ctx)
 {
-       return (ctx == ctx->ring->default_context);
+       /* Cheap trick to determine default contexts */
+       return ctx->file_priv ? false : true;
 }
 
 /**
@@ -338,6 +334,7 @@ void i915_gem_context_fini(struct drm_device *dev)
                        i915_gem_context_unreference(ring->last_context);
 
                ring->default_context = NULL;
+               ring->last_context = NULL;
        }
 
        i915_gem_object_ggtt_unpin(dctx->obj);
@@ -467,7 +464,7 @@ static int do_switch(struct intel_ring_buffer *ring,
                BUG_ON(!i915_gem_obj_is_pinned(from->obj));
        }
 
-       if (from == to && !to->remap_slice)
+       if (from == to && from->last_ring == ring && !to->remap_slice)
                return 0;
 
        if (ring != &dev_priv->ring[RCS]) {
@@ -547,6 +544,7 @@ done:
        i915_gem_context_reference(to);
        ring->last_context = to;
        to->is_initialized = true;
+       to->last_ring = ring;
 
        return 0;
 }