[RFC 2/5] drm/i915: Engine capabilities uAPI

[Tvrtko Ursulin <tursulin@ursulin.net>]

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

To add the knowledge that VCS1 engine does not support HEVC,
we introduce the concept of engine capabilities. These are
flags defined in per-engine class space which can be passed
in during execbuf time. The driver is then able to fail the
execbuf in case of mismatch between the requested capabilities
and the selected target engine.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
---
 drivers/gpu/drm/i915/i915_gem_execbuffer.c | 19 +++++++++++++++----
 drivers/gpu/drm/i915/intel_engine_cs.c     |  3 +++
 drivers/gpu/drm/i915/intel_ringbuffer.h    |  2 ++
 include/uapi/drm/i915_drm.h                | 17 ++++++++++++++++-
 4 files changed, 36 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 2e7ddd197cc4..f7aabea601b0 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -56,9 +56,10 @@ enum {
 #define __EXEC_OBJECT_INTERNAL_FLAGS	(~0u << 27) /* all of the above */
 #define __EXEC_OBJECT_RESERVED (__EXEC_OBJECT_HAS_PIN | __EXEC_OBJECT_HAS_FENCE)
 
-#define __EXEC_HAS_RELOC	BIT(31)
-#define __EXEC_VALIDATED	BIT(30)
-#define __EXEC_INTERNAL_FLAGS	(~0u << 30)
+#define __EXEC_HAS_RELOC	BIT(63)
+#define __EXEC_VALIDATED	BIT(62)
+#define __EXEC_INTERNAL_FLAGS	(~0ULL << 62)
+
 #define UPDATE			PIN_OFFSET_FIXED
 
 #define BATCH_OFFSET_BIAS (256*1024)
@@ -2010,8 +2011,16 @@ eb_select_engine_class_instance(struct drm_i915_private *i915, u64 eb_flags)
 	u8 class = eb_flags & I915_EXEC_RING_MASK;
 	u8 instance = (eb_flags & I915_EXEC_INSTANCE_MASK) >>
 		      I915_EXEC_INSTANCE_SHIFT;
+	u8 caps = (eb_flags & I915_EXEC_ENGINE_CAP_MASK) >>
+		  I915_EXEC_ENGINE_CAP_SHIFT;
+	struct intel_engine_cs *engine;
 
-	return intel_engine_lookup_user(i915, class, instance);
+	engine = intel_engine_lookup_user(i915, class, instance);
+
+	if (engine && ((caps & engine->caps) != caps))
+		return NULL;
+
+	return engine;
 }
 
 #define I915_USER_RINGS (4)
@@ -2217,6 +2226,8 @@ i915_gem_do_execbuffer(struct drm_device *dev,
 	BUILD_BUG_ON(__EXEC_OBJECT_INTERNAL_FLAGS &
 		     ~__EXEC_OBJECT_UNKNOWN_FLAGS);
 
+	BUILD_BUG_ON(__EXEC_INTERNAL_FLAGS & ~__I915_EXEC_UNKNOWN_FLAGS);
+
 	eb.i915 = to_i915(dev);
 	eb.file = file;
 	eb.args = args;
diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
index 7f4d60fed46f..c75bd2c9d797 100644
--- a/drivers/gpu/drm/i915/intel_engine_cs.c
+++ b/drivers/gpu/drm/i915/intel_engine_cs.c
@@ -233,6 +233,9 @@ intel_engine_setup(struct drm_i915_private *dev_priv,
 	engine->irq_shift = info->irq_shift;
 	engine->class = info->class;
 	engine->instance = info->instance;
+	if (INTEL_GEN(dev_priv) >= 8 && engine->class == VIDEO_DECODE_CLASS &&
+	    engine->instance == 0)
+		engine->caps = I915_BSD_CAP_HEVC;
 
 	engine->uabi_id = info->uabi_id;
 	engine->uabi_class = class_info->uabi_class;
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 4660c6f920e5..a84749bcad33 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -300,6 +300,8 @@ struct intel_engine_cs {
 
 	u8 class;
 	u8 instance;
+	u8 caps;
+
 	u32 context_size;
 	u32 mmio_base;
 	unsigned int irq_shift;
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index 9ed351f4a304..ad5fa26fc9e7 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -1056,7 +1056,18 @@ struct drm_i915_gem_execbuffer2 {
 #define I915_EXEC_INSTANCE_SHIFT	(21)
 #define I915_EXEC_INSTANCE_MASK		(0xff << I915_EXEC_INSTANCE_SHIFT)
 
-#define __I915_EXEC_UNKNOWN_FLAGS (-((1 << 29) << 1))
+/*
+ * Inform the kernel of what engine capabilities this batch buffer
+ * requires. For example only the first VCS engine has the HEVC block.
+ *
+ * We reserve four bits for the capabilities where each can be shared
+ * between different engines. Eg. first bit can mean one feature for
+ * one engine and something else for the other.
+ */
+#define I915_EXEC_ENGINE_CAP_SHIFT	(29)
+#define I915_EXEC_ENGINE_CAP_MASK	(0xf << I915_EXEC_ENGINE_CAP_SHIFT)
+
+#define __I915_EXEC_UNKNOWN_FLAGS (-((1ULL << 33) << 1))
 
 #define I915_EXEC_CONTEXT_ID_MASK	(0xffffffff)
 #define i915_execbuffer2_set_context_id(eb2, context) \
@@ -1069,6 +1080,10 @@ struct drm_i915_gem_execbuffer2 {
 	(class) | \
 	((instance) << I915_EXEC_INSTANCE_SHIFT))
 
+#define I915_BSD_CAP_HEVC	(1 << 0)
+
+#define I915_ENGINE_CAP_FLAG(v)	((v) << I915_EXEC_ENGINE_CAP_SHIFT)
+
 struct drm_i915_gem_pin {
 	/** Handle of the buffer to be pinned. */
 	__u32 handle;
-- 
2.14.1

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