[Intel-gfx] [PATCH 1/2] drm/i915: Specify bsd rings through exec flag

[Zhipeng Gong]

On Broadwell GT3 we have 2 Video Command Streamers (VCS), but userspace
has no control when using VCS1 or VCS2. This patch introduces a mechanism
to avoid the default ping-pong mode and use one specific ring through
execution flag.

Signed-off-by: Zhipeng Gong <zhipeng.gong at intel.com>
---
 drivers/gpu/drm/i915/i915_gem_execbuffer.c | 19 +++++++++++++++++--
 include/uapi/drm/i915_drm.h                |  8 +++++++-
 2 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
index 60998fc..f9ed8e0 100644
--- a/drivers/gpu/drm/i915/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/i915_gem_execbuffer.c
@@ -1279,8 +1279,23 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 	else if ((args->flags & I915_EXEC_RING_MASK) == I915_EXEC_BSD) {
 		if (HAS_BSD2(dev)) {
 			int ring_id;
-			ring_id = gen8_dispatch_bsd_ring(dev, file);
-			ring = &dev_priv->ring[ring_id];
+
+			switch (args->flags & I915_EXEC_BSD_MASK) {
+			case I915_EXEC_BSD_DEFAULT:
+				ring_id = gen8_dispatch_bsd_ring(dev, file);
+				ring = &dev_priv->ring[ring_id];
+				break;
+			case I915_EXEC_BSD_RING1:
+				ring = &dev_priv->ring[VCS];
+				break;
+			case I915_EXEC_BSD_RING2:
+				ring = &dev_priv->ring[VCS2];
+				break;
+			default:
+				DRM_DEBUG("execbuf with unknown bsd ring: %d\n",
+ 					  (int)(args->flags & I915_EXEC_BSD_MASK));
+				return -EINVAL;
+			}
 		} else
 			ring = &dev_priv->ring[VCS];
 	} else
diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
index ff57f07..421420a 100644
--- a/include/uapi/drm/i915_drm.h
+++ b/include/uapi/drm/i915_drm.h
@@ -736,7 +736,13 @@ struct drm_i915_gem_execbuffer2 {
  */
 #define I915_EXEC_HANDLE_LUT		(1<<12)
 
-#define __I915_EXEC_UNKNOWN_FLAGS -(I915_EXEC_HANDLE_LUT<<1)
+/** Used for switching BSD rings on the platforms with two BSD rings */
+#define I915_EXEC_BSD_MASK		(3<<13)
+#define I915_EXEC_BSD_DEFAULT		(0<<13) /* default ping-pong mode */
+#define I915_EXEC_BSD_RING1		(1<<13)
+#define I915_EXEC_BSD_RING2		(2<<13)
+
+#define __I915_EXEC_UNKNOWN_FLAGS -(1<<15)
 
 #define I915_EXEC_CONTEXT_ID_MASK	(0xffffffff)
 #define i915_execbuffer2_set_context_id(eb2, context) \
-- 
2.0.3