drm/i915: Switch back to an array of logical per-engine HW contexts

We switched to a tree of per-engine HW context to accommodate the
introduction of virtual engines. However, we plan to also support
multiple instances of the same engine within the GEM context, defeating
our use of the engine as a key to looking up the HW context. Just
allocate a logical per-engine instance and always use an index into the
ctx->engines[]. Later on, this ctx->engines[] may be replaced by a user
specified map.

v2: Add for_each_gem_engine() helper to iterator within the engines lock
v3: intel_context_create_request() helper
v4: s/unsigned long/unsigned int/ 4 billion engines is quite enough.
v5: Push iterator locking to caller

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190426163336.15906-7-chris@chris-wilson.co.uk

1 files changed, 58 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem_context.h b/drivers/gpu/drm/i915/i915_gem_context.h
index 5a8e080499fb..272e183ebc0c 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.h
+++ b/drivers/gpu/drm/i915/i915_gem_context.h
@@ -176,6 +176,64 @@ static inline void i915_gem_context_put(struct i915_gem_context *ctx)
 	kref_put(&ctx->ref, i915_gem_context_release);
 }
 
+static inline struct i915_gem_engines *
+i915_gem_context_engines(struct i915_gem_context *ctx)
+{
+	return rcu_dereference_protected(ctx->engines,
+					 lockdep_is_held(&ctx->engines_mutex));
+}
+
+static inline struct i915_gem_engines *
+i915_gem_context_lock_engines(struct i915_gem_context *ctx)
+	__acquires(&ctx->engines_mutex)
+{
+	mutex_lock(&ctx->engines_mutex);
+	return i915_gem_context_engines(ctx);
+}
+
+static inline void
+i915_gem_context_unlock_engines(struct i915_gem_context *ctx)
+	__releases(&ctx->engines_mutex)
+{
+	mutex_unlock(&ctx->engines_mutex);
+}
+
+static inline struct intel_context *
+i915_gem_context_lookup_engine(struct i915_gem_context *ctx, unsigned int idx)
+{
+	return i915_gem_context_engines(ctx)->engines[idx];
+}
+
+static inline struct intel_context *
+i915_gem_context_get_engine(struct i915_gem_context *ctx, unsigned int idx)
+{
+	struct intel_context *ce = ERR_PTR(-EINVAL);
+
+	rcu_read_lock(); {
+		struct i915_gem_engines *e = rcu_dereference(ctx->engines);
+		if (likely(idx < e->num_engines && e->engines[idx]))
+			ce = intel_context_get(e->engines[idx]);
+	} rcu_read_unlock();
+
+	return ce;
+}
+
+static inline void
+i915_gem_engines_iter_init(struct i915_gem_engines_iter *it,
+			   struct i915_gem_engines *engines)
+{
+	GEM_BUG_ON(!engines);
+	it->engines = engines;
+	it->idx = 0;
+}
+
+struct intel_context *
+i915_gem_engines_iter_next(struct i915_gem_engines_iter *it);
+
+#define for_each_gem_engine(ce, engines, it) \
+	for (i915_gem_engines_iter_init(&(it), (engines)); \
+	     ((ce) = i915_gem_engines_iter_next(&(it)));)
+
 struct i915_lut_handle *i915_lut_handle_alloc(void);
 void i915_lut_handle_free(struct i915_lut_handle *lut);