Implement the note indicated in the bspec.
Signed-off-by: Ben Widawsky <ben@xxxxxxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem_context.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index e08acab..a14a3b3 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -446,6 +446,15 @@ static int do_switch(struct i915_hw_context *to)
if (!to->is_initialized || is_default_context(to))
hw_flags |= MI_RESTORE_INHIBIT;
+ /* When SW intends to use semaphore signaling between Command streamers,
+ * it must avoid lite restores in HW by programming "Force Restore" bit
+ * to ‘1’ in context descriptor during context submission
+ *
+ * XXX: is this really needed for ringbuffer mode?
+ */
+ if (IS_GEN8(ring->dev) && i915_semaphore_is_enabled(ring->dev))
+ hw_flags |= MI_FORCE_RESTORE;
+
ret = mi_set_context(ring, to, hw_flags);
if (ret) {
i915_gem_object_unpin(to->obj);
--
1.8.5.1
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