iris: Add infrastructure to partition batch into sync boundaries.

This introduces some minimalistic infrastructure which will be used in
order to partition the batch into a series of sections, each one with
a unique, monotonically-increasing sequence number.  Section
boundaries will typically lie at points in the batch where the
execution and memory coherency status of some previous commands are
known, e.g. at batch buffer boundaries or PIPE_CONTROL commands.

Reviewed-by: Kenneth Graunke <[email protected]>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3875>

3 files changed, 61 insertions, 0 deletions

diff --git a/src/gallium/drivers/iris/iris_batch.c b/src/gallium/drivers/iris/iris_batch.c
index fabea867b48..e3be9c3df8a 100644
--- a/src/gallium/drivers/iris/iris_batch.c
+++ b/src/gallium/drivers/iris/iris_batch.c
@@ -398,6 +398,9 @@ iris_batch_reset(struct iris_batch *batch)
 
    iris_cache_sets_clear(batch);
 
+   assert(!batch->sync_region_depth);
+   iris_batch_sync_boundary(batch);
+
    /* Always add the workaround BO, it contains a driver identifier at the
     * beginning quite helpful to debug error states.
     */
diff --git a/src/gallium/drivers/iris/iris_batch.h b/src/gallium/drivers/iris/iris_batch.h
index c95fd23491f..50de99289cf 100644
--- a/src/gallium/drivers/iris/iris_batch.h
+++ b/src/gallium/drivers/iris/iris_batch.h
@@ -144,9 +144,21 @@ struct iris_batch {
    struct gen_batch_decode_ctx decoder;
    struct hash_table_u64 *state_sizes;
 
+   /**
+    * Sequence number used to track the completion of any subsequent memory
+    * operations in the batch until the next sync boundary.
+    */
+   uint64_t next_seqno;
+
    /** Have we emitted any draw calls to this batch? */
    bool contains_draw;
 
+   /**
+    * Number of times iris_batch_sync_region_start() has been called without a
+    * matching iris_batch_sync_region_end() on this batch.
+    */
+   uint32_t sync_region_depth;
+
    uint32_t last_aux_map_state;
 };
 
@@ -260,4 +272,41 @@ iris_record_state_size(struct hash_table_u64 *ht,
    }
 }
 
+/**
+ * Mark the start of a region in the batch with stable synchronization
+ * sequence number.  Any buffer object accessed by the batch buffer only needs
+ * to be marked once (e.g. via iris_bo_bump_seqno()) within a region delimited
+ * by iris_batch_sync_region_start() and iris_batch_sync_region_end().
+ */
+static inline void
+iris_batch_sync_region_start(struct iris_batch *batch)
+{
+   batch->sync_region_depth++;
+}
+
+/**
+ * Mark the end of a region in the batch with stable synchronization sequence
+ * number.  Should be called once after each call to
+ * iris_batch_sync_region_start().
+ */
+static inline void
+iris_batch_sync_region_end(struct iris_batch *batch)
+{
+   assert(batch->sync_region_depth);
+   batch->sync_region_depth--;
+}
+
+/**
+ * Start a new synchronization section at the current point of the batch,
+ * unless disallowed by a previous iris_batch_sync_region_start().
+ */
+static inline void
+iris_batch_sync_boundary(struct iris_batch *batch)
+{
+   if (!batch->sync_region_depth) {
+      batch->next_seqno = p_atomic_inc_return(&batch->screen->last_seqno);
+      assert(batch->next_seqno > 0);
+   }
+}
+
 #endif
diff --git a/src/gallium/drivers/iris/iris_screen.h b/src/gallium/drivers/iris/iris_screen.h
index bfc5284fc72..b536e10642b 100644
--- a/src/gallium/drivers/iris/iris_screen.h
+++ b/src/gallium/drivers/iris/iris_screen.h
@@ -182,6 +182,15 @@ struct iris_screen {
 
    uint64_t aperture_bytes;
 
+   /**
+    * Last sequence number allocated by the cache tracking mechanism.
+    *
+    * These are used for synchronization and are expected to identify a single
+    * section of a batch, so they should be monotonically increasing and
+    * unique across a single pipe_screen.
+    */
+   uint64_t last_seqno;
+
    struct gen_device_info devinfo;
    struct isl_device isl_dev;
    struct iris_bufmgr *bufmgr;