[RFC 1/2] drm/i915: Select engines via class and instance in execbuffer2

* [RFC 1/2] drm/i915: Select engines via class and instance in execbuffer2
@ 2017-06-21  9:13 Tvrtko Ursulin
  2017-06-21  9:13 ` [RFC 2/2] drm/i915: Engine capabilities uAPI Tvrtko Ursulin
  2017-06-21 10:20 ` ✓ Fi.CI.BAT: success for series starting with [RFC,1/2] drm/i915: Select engines via class and instance in execbuffer2 Patchwork
  0 siblings, 2 replies; 6+ messages in thread
From: Tvrtko Ursulin @ 2017-06-21  9:13 UTC (permalink / raw)
  To: Intel-gfx; +Cc: Ben Widawsky, intel-vaapi-media, Daniel Vetter

From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>

Building on top of the previous patch which exported the concept
of engine classes and instances, we can also use this instead of
the current awkward engine selection uAPI.

This is primarily interesting for the VCS engine selection which
is a) currently done via disjoint set of flags, and b) the
current I915_EXEC_BSD flags has different semantics depending on
the underlying hardware which is bad.

Proposed idea here is to reserve 8-bits of flags, to pass in the
engine instance, re-use the existing engine selection bits for
the class selection, and a new flag named
I915_EXEC_CLASS_INSTANCE to tell the kernel this new engine
selection API is in use.

The new uAPI also removes access to the weak VCS engine
balancing as currently existing in the driver.

Example usage to send a command to VCS0:

  eb.flags = i915_execbuffer2_engine(I915_ENGINE_CLASS_VIDEO_DECODE, 0);

Or to send a command to VCS1:

  eb.flags = i915_execbuffer2_engine(I915_ENGINE_CLASS_VIDEO_DECODE, 1);

v2:
 * Fix unknown flags mask.
 * Use I915_EXEC_RING_MASK for class. (Chris Wilson)

v3:
 * Add a map for fast class-instance engine lookup. (Chris Wilson)

v4:
 * Update commit to reflect v3.
 * Export intel_engine_lookup for other users. (Chris Wilson)
 * Split out some warns. (Chris Wilson)

v5:
 * Fixed shift and mask logic.
 * Rebased to be standalone.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Ben Widawsky <ben@bwidawsk.net>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Jon Bloomfield <jon.bloomfield@intel.com>
Cc: "Rogozhkin, Dmitry V" <dmitry.v.rogozhkin@intel.com>
Cc: Oscar Mateo <oscar.mateo@intel.com>
Cc: "Gong, Zhipeng" <zhipeng.gong@intel.com>
Cc: intel-vaapi-media@lists.01.org
---
 drivers/gpu/drm/i915/i915_drv.h            |  1 +
 drivers/gpu/drm/i915/i915_gem_execbuffer.c | 27 +++++++++++++++++++++++++++
 drivers/gpu/drm/i915/i915_reg.h            |  3 +++
 drivers/gpu/drm/i915/intel_engine_cs.c     | 20 ++++++++++++++++++++
 drivers/gpu/drm/i915/intel_ringbuffer.h    |  3 +++
 include/uapi/drm/i915_drm.h                | 22 +++++++++++++++++++++-
 6 files changed, 75 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 30e89456fc61..325e1f325f60 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2137,6 +2137,7 @@ struct drm_i915_private {
 	struct pci_dev *bridge_dev;
 	struct i915_gem_context *kernel_context;
 	struct intel_engine_cs *engine[I915_NUM_ENGINES];
+	struct intel_engine_cs *engine_class[MAX_ENGINE_CLASS + 1][MAX_ENGINE_INSTANCE + 1];
 	struct i915_vma *semaphore;
 
 	struct drm_dma_handle *status_page_dmah;
diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index b2457556591c..00c363a801cb 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -2049,6 +2049,30 @@ gen8_dispatch_bsd_engine(struct drm_i915_private *dev_priv,
 	return file_priv->bsd_engine;
 }
 
+static u8 user_class_map[I915_ENGINE_CLASS_MAX] = {
+	[I915_ENGINE_CLASS_OTHER] = OTHER_CLASS,
+	[I915_ENGINE_CLASS_RENDER] = RENDER_CLASS,
+	[I915_ENGINE_CLASS_COPY] = COPY_ENGINE_CLASS,
+	[I915_ENGINE_CLASS_VIDEO] = VIDEO_DECODE_CLASS,
+	[I915_ENGINE_CLASS_VIDEO_ENHANCE] = VIDEO_ENHANCEMENT_CLASS,
+};
+
+static struct intel_engine_cs *
+eb_select_engine_class_instance(struct drm_i915_private *i915,
+				struct drm_i915_gem_execbuffer2 *args)
+{
+	u8 class = args->flags & I915_EXEC_RING_MASK;
+	u8 instance;
+
+	if (class >= ARRAY_SIZE(user_class_map))
+		return NULL;
+
+	instance = (args->flags & I915_EXEC_INSTANCE_MASK) >>
+		   I915_EXEC_INSTANCE_SHIFT;
+
+	return intel_engine_lookup(i915, user_class_map[class], instance);
+}
+
 #define I915_USER_RINGS (4)
 
 static const enum intel_engine_id user_ring_map[I915_USER_RINGS + 1] = {
@@ -2067,6 +2091,9 @@ eb_select_engine(struct drm_i915_private *dev_priv,
 	unsigned int user_ring_id = args->flags & I915_EXEC_RING_MASK;
 	struct intel_engine_cs *engine;
 
+	if (args->flags & I915_EXEC_CLASS_INSTANCE)
+		return eb_select_engine_class_instance(dev_priv, args);
+
 	if (user_ring_id > I915_USER_RINGS) {
 		DRM_DEBUG("execbuf with unknown ring: %u\n", user_ring_id);
 		return NULL;
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
index c8647cfa81ba..834673c9ee6b 100644
--- a/drivers/gpu/drm/i915/i915_reg.h
+++ b/drivers/gpu/drm/i915/i915_reg.h
@@ -95,6 +95,9 @@ static inline bool i915_mmio_reg_valid(i915_reg_t reg)
 #define VIDEO_ENHANCEMENT_CLASS	2
 #define COPY_ENGINE_CLASS	3
 #define OTHER_CLASS		4
+#define MAX_ENGINE_CLASS	4
+
+#define MAX_ENGINE_INSTANCE	1
 
 /* PCI config space */
 
diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index 3b46c1f7b88b..93466761ebd6 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -197,6 +197,15 @@ intel_engine_setup(struct drm_i915_private *dev_priv,
 	GEM_BUG_ON(info->class >= ARRAY_SIZE(intel_engine_classes));
 	class_info = &intel_engine_classes[info->class];
 
+	if (GEM_WARN_ON(info->class > MAX_ENGINE_CLASS))
+		return -EINVAL;
+
+	if (GEM_WARN_ON(info->instance > MAX_ENGINE_INSTANCE))
+		return -EINVAL;
+
+	if (GEM_WARN_ON(dev_priv->engine_class[info->class][info->instance]))
+		return -EINVAL;
+
 	GEM_BUG_ON(dev_priv->engine[id]);
 	engine = kzalloc(sizeof(*engine), GFP_KERNEL);
 	if (!engine)
@@ -224,7 +233,9 @@ intel_engine_setup(struct drm_i915_private *dev_priv,
 
 	ATOMIC_INIT_NOTIFIER_HEAD(&engine->context_status_notifier);
 
+	dev_priv->engine_class[info->class][info->instance] = engine;
 	dev_priv->engine[id] = engine;
+
 	return 0;
 }
 
@@ -1332,6 +1343,15 @@ void intel_engines_mark_idle(struct drm_i915_private *i915)
 	}
 }
 
+struct intel_engine_cs *
+intel_engine_lookup(struct drm_i915_private *i915, u8 class, u8 instance)
+{
+	if (class > MAX_ENGINE_CLASS || instance > MAX_ENGINE_INSTANCE)
+		return NULL;
+
+	return i915->engine_class[class][instance];
+}
+
 #if IS_ENABLED(CONFIG_DRM_I915_SELFTEST)
 #include "selftests/mock_engine.c"
 #endif
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index d33c93444c0d..c408d3d5cc80 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -735,4 +735,7 @@ bool intel_engines_are_idle(struct drm_i915_private *dev_priv);
 void intel_engines_mark_idle(struct drm_i915_private *i915);
 void intel_engines_reset_default_submission(struct drm_i915_private *i915);
 
+struct intel_engine_cs *
+intel_engine_lookup(struct drm_i915_private *i915, u8 class, u8 instance);
+
 #endif /* _INTEL_RINGBUFFER_H_ */
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 7ccbd6a2bbe0..30fec2c8fc95 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -927,7 +927,13 @@ struct drm_i915_gem_execbuffer2 {
  * element).
  */
 #define I915_EXEC_BATCH_FIRST		(1<<18)
-#define __I915_EXEC_UNKNOWN_FLAGS (-(I915_EXEC_BATCH_FIRST<<1))
+
+#define I915_EXEC_CLASS_INSTANCE	(1<<19)
+
+#define I915_EXEC_INSTANCE_SHIFT	(20)
+#define I915_EXEC_INSTANCE_MASK		(0xff << I915_EXEC_INSTANCE_SHIFT)
+
+#define __I915_EXEC_UNKNOWN_FLAGS (-((1 << 27) << 1))
 
 #define I915_EXEC_CONTEXT_ID_MASK	(0xffffffff)
 #define i915_execbuffer2_set_context_id(eb2, context) \
@@ -935,6 +941,20 @@ struct drm_i915_gem_execbuffer2 {
 #define i915_execbuffer2_get_context_id(eb2) \
 	((eb2).rsvd1 & I915_EXEC_CONTEXT_ID_MASK)
 
+enum drm_i915_gem_engine_class {
+	I915_ENGINE_CLASS_OTHER = 0,
+	I915_ENGINE_CLASS_RENDER = 1,
+	I915_ENGINE_CLASS_COPY = 2,
+	I915_ENGINE_CLASS_VIDEO = 3,
+	I915_ENGINE_CLASS_VIDEO_ENHANCE = 4,
+	I915_ENGINE_CLASS_MAX /* non-ABI */
+};
+
+#define i915_execbuffer2_engine(class, instance) \
+	(I915_EXEC_CLASS_INSTANCE | \
+	(class) | \
+	((instance) << I915_EXEC_INSTANCE_SHIFT))
+
 struct drm_i915_gem_pin {
 	/** Handle of the buffer to be pinned. */
 	__u32 handle;
-- 
2.9.4

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