panfrost: Add a batch fence

So we can implement fine-grained dependency tracking between batches.

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>

src/gallium/drivers/panfrost/pan_job.c

@@ -36,6 +36,45 @@
 #include "pan_util.h"
 #include "pandecode/decode.h"
 
+static struct panfrost_batch_fence *
+panfrost_create_batch_fence(struct panfrost_batch *batch)
+{
+        struct panfrost_batch_fence *fence;
+        ASSERTED int ret;
+
+        fence = rzalloc(NULL, struct panfrost_batch_fence);
+        assert(fence);
+        pipe_reference_init(&fence->reference, 1);
+        fence->ctx = batch->ctx;
+        fence->batch = batch;
+        ret = drmSyncobjCreate(pan_screen(batch->ctx->base.screen)->fd, 0,
+                               &fence->syncobj);
+        assert(!ret);
+
+        return fence;
+}
+
+static void
+panfrost_free_batch_fence(struct panfrost_batch_fence *fence)
+{
+        drmSyncobjDestroy(pan_screen(fence->ctx->base.screen)->fd,
+                          fence->syncobj);
+        ralloc_free(fence);
+}
+
+void
+panfrost_batch_fence_unreference(struct panfrost_batch_fence *fence)
+{
+        if (pipe_reference(&fence->reference, NULL))
+                 panfrost_free_batch_fence(fence);
+}
+
+void
+panfrost_batch_fence_reference(struct panfrost_batch_fence *fence)
+{
+        pipe_reference(NULL, &fence->reference);
+}
+
 static struct panfrost_batch *
 panfrost_create_batch(struct panfrost_context *ctx,
                       const struct pipe_framebuffer_state *key)
@@ -53,6 +92,7 @@ panfrost_create_batch(struct panfrost_context *ctx,
 
         util_dynarray_init(&batch->headers, batch);
         util_dynarray_init(&batch->gpu_headers, batch);
+        batch->out_sync = panfrost_create_batch_fence(batch);
         util_copy_framebuffer_state(&batch->key, key);
 
         return batch;
@@ -74,6 +114,15 @@ panfrost_free_batch(struct panfrost_batch *batch)
         if (ctx->batch == batch)
                 ctx->batch = NULL;
 
+        /* The out_sync fence lifetime is different from the the batch one
+         * since other batches might want to wait on a fence of already
+         * submitted/signaled batch. All we need to do here is make sure the
+         * fence does not point to an invalid batch, which the core will
+         * interpret as 'batch is already submitted'.
+         */
+        batch->out_sync->batch = NULL;
+        panfrost_batch_fence_unreference(batch->out_sync);
+
         util_unreference_framebuffer_state(&batch->key);
         ralloc_free(batch);
 }
@@ -441,8 +490,13 @@ panfrost_batch_submit(struct panfrost_batch *batch)
         int ret;
 
         /* Nothing to do! */
-        if (!batch->last_job.gpu && !batch->clear)
+        if (!batch->last_job.gpu && !batch->clear) {
+                /* Mark the fence as signaled so the fence logic does not try
+                 * to wait on it.
+                 */
+                batch->out_sync->signaled = true;
                 goto out;
+        }
 
         if (!batch->clear && batch->last_tiler.gpu)
                 panfrost_batch_draw_wallpaper(batch);

src/gallium/drivers/panfrost/pan_job.h

@@ -31,6 +31,36 @@
 #include "pan_allocate.h"
 #include "pan_resource.h"
 
+/* panfrost_batch_fence is the out fence of a batch that users or other batches
+ * might want to wait on. The batch fence lifetime is different from the batch
+ * one as want will certainly want to wait upon the fence after the batch has
+ * been submitted (which is when panfrost_batch objects are freed).
+ */
+struct panfrost_batch_fence {
+        /* Refcounting object for the fence. */
+        struct pipe_reference reference;
+
+        /* Batch that created this fence object. Will become NULL at batch
+         * submission time. This field is mainly here to know whether the
+         * batch has been flushed or not.
+         */
+        struct panfrost_batch *batch;
+
+        /* Context this fence is attached to. We need both ctx and batch, as
+         * the batch will go away after it's been submitted, but the fence
+         * will stay a bit longer.
+         */
+        struct panfrost_context *ctx;
+
+        /* Sync object backing this fence. */
+        uint32_t syncobj;
+
+        /* Cached value of the signaled state to avoid calling WAIT_SYNCOBJs
+         * when we know the fence has already been signaled.
+         */
+        bool signaled;
+};
+
 #define PAN_REQ_MSAA            (1 << 0)
 #define PAN_REQ_DEPTH_WRITE     (1 << 1)
 
@@ -120,10 +150,19 @@ struct panfrost_batch {
 
         /* Framebuffer descriptor. */
         mali_ptr framebuffer;
+
+        /* Output sync object. Only valid when submitted is true. */
+        struct panfrost_batch_fence *out_sync;
 };
 
 /* Functions for managing the above */
 
+void
+panfrost_batch_fence_unreference(struct panfrost_batch_fence *fence);
+
+void
+panfrost_batch_fence_reference(struct panfrost_batch_fence *batch);
+
 struct panfrost_batch *
 panfrost_get_batch_for_fbo(struct panfrost_context *ctx);