[Intel-gfx] [PATCH] drm/i915: Generalise BSD default selection

[Chris Wilson]

For the default I915_EXEC_BSD round robin selector, it may select any
available VCS engine. Make it so.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin at intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
index 7fdb2ec94aff..7784a314f5c2 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
@@ -2102,6 +2102,13 @@ static int eb_submit(struct i915_execbuffer *eb)
 	return 0;
 }
 
+static int num_vcs_engines(const struct drm_i915_private *i915)
+{
+	BUILD_BUG_ON(I915_MAX_VCS > 8); /* using hweight8() */
+	return hweight8(INTEL_INFO(i915)->engine_mask >> VCS0 &
+			(I915_MAX_VCS - 1));
+}
+
 /*
  * Find one BSD ring to dispatch the corresponding BSD command.
  * The engine index is returned.
@@ -2114,7 +2121,8 @@ gen8_dispatch_bsd_engine(struct drm_i915_private *dev_priv,
 
 	/* Check whether the file_priv has already selected one ring. */
 	if ((int)file_priv->bsd_engine < 0)
-		file_priv->bsd_engine = get_random_int() & 1;
+		file_priv->bsd_engine =
+			get_random_int() % num_vcs_engines(dev_priv);
 
 	return file_priv->bsd_engine;
 }
-- 
2.23.0.rc1