panfrost: Use the per-batch fences to wait on the last submitted batch

We just replace the per-context out_sync object by a pointer to the
the fence of the last last submitted batch. Pipelining of batches will
come later.

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

src/gallium/drivers/panfrost/pan_context.c

@@ -2696,12 +2696,6 @@ panfrost_create_context(struct pipe_screen *screen, void *priv, unsigned flags)
         panfrost_blend_context_init(gallium);
         panfrost_compute_context_init(gallium);
 
-        ASSERTED int ret;
-
-        ret = drmSyncobjCreate(pscreen->fd, DRM_SYNCOBJ_CREATE_SIGNALED,
-                               &ctx->out_sync);
-        assert(!ret);
-
         /* XXX: leaks */
         gallium->stream_uploader = u_upload_create_default(gallium);
         gallium->const_uploader = gallium->stream_uploader;

src/gallium/drivers/panfrost/pan_context.h

@@ -191,7 +191,8 @@ struct panfrost_context {
         /* True for t6XX, false for t8xx. */
         bool is_t6xx;
 
-        uint32_t out_sync;
+        /* The out sync fence of the last submitted batch. */
+        struct panfrost_batch_fence *last_out_sync;
 };
 
 /* Corresponds to the CSO */

src/gallium/drivers/panfrost/pan_job.c

@@ -425,11 +425,13 @@ panfrost_batch_submit_ioctl(struct panfrost_batch *batch,
         uint32_t *bo_handles;
         int ret;
 
-        submit.in_syncs = (u64) (uintptr_t) &ctx->out_sync;
-        submit.in_sync_count = 1;
 
-        submit.out_sync = ctx->out_sync;
+        if (ctx->last_out_sync) {
+                submit.in_sync_count = 1;
+                submit.in_syncs = (uintptr_t)&ctx->last_out_sync->syncobj;
+        }
 
+        submit.out_sync = batch->out_sync->syncobj;
         submit.jc = first_job_desc;
         submit.requirements = reqs;
 
@@ -445,6 +447,14 @@ panfrost_batch_submit_ioctl(struct panfrost_batch *batch,
         submit.bo_handles = (u64) (uintptr_t) bo_handles;
         ret = drmIoctl(screen->fd, DRM_IOCTL_PANFROST_SUBMIT, &submit);
         free(bo_handles);
+
+        /* Release the last batch fence if any, and retain the new one */
+        if (ctx->last_out_sync)
+                panfrost_batch_fence_unreference(ctx->last_out_sync);
+
+        panfrost_batch_fence_reference(batch->out_sync);
+        ctx->last_out_sync = batch->out_sync;
+
         if (ret) {
                 fprintf(stderr, "Error submitting: %m\n");
                 return errno;
@@ -453,7 +463,8 @@ panfrost_batch_submit_ioctl(struct panfrost_batch *batch,
         /* Trace the job if we're doing that */
         if (pan_debug & PAN_DBG_TRACE) {
                 /* Wait so we can get errors reported back */
-                drmSyncobjWait(screen->fd, &ctx->out_sync, 1, INT64_MAX, 0, NULL);
+                drmSyncobjWait(screen->fd, &batch->out_sync->syncobj, 1,
+                               INT64_MAX, 0, NULL);
                 pandecode_jc(submit.jc, FALSE);
         }
 
@@ -495,6 +506,15 @@ panfrost_batch_submit(struct panfrost_batch *batch)
                  * to wait on it.
                  */
                 batch->out_sync->signaled = true;
+
+                /* Release the last batch fence if any, and set ->last_out_sync
+                 * to NULL
+                 */
+                if (ctx->last_out_sync) {
+                        panfrost_batch_fence_unreference(ctx->last_out_sync);
+                        ctx->last_out_sync = NULL;
+                }
+
                 goto out;
         }
 
@@ -527,8 +547,11 @@ out:
          * rendering is quite broken right now (to be fixed by the panfrost_job
          * refactor, just take the perf hit for correctness)
          */
-        drmSyncobjWait(pan_screen(ctx->base.screen)->fd, &ctx->out_sync, 1,
-                       INT64_MAX, 0, NULL);
+        if (!batch->out_sync->signaled)
+                drmSyncobjWait(pan_screen(ctx->base.screen)->fd,
+                               &batch->out_sync->syncobj, 1, INT64_MAX, 0,
+                               NULL);
+
         panfrost_free_batch(batch);
 }
 

src/gallium/drivers/panfrost/pan_screen.c

@@ -590,8 +590,12 @@ panfrost_fence_finish(struct pipe_screen *pscreen,
         struct panfrost_screen *screen = pan_screen(pscreen);
         struct panfrost_fence *f = (struct panfrost_fence *)fence;
         int ret;
-
         unsigned syncobj;
+
+        /* The fence was already signaled */
+        if (f->fd == -1)
+                return true;
+
         ret = drmSyncobjCreate(screen->fd, 0, &syncobj);
         if (ret) {
                 fprintf(stderr, "Failed to create syncobj to wait on: %m\n");
@@ -623,18 +627,28 @@ panfrost_fence_create(struct panfrost_context *ctx)
         if (!f)
                 return NULL;
 
+        f->fd = -1;
+
+        /* There was no job flushed yet or the batch fence was already
+         * signaled, let's return a dummy fence object that returns true
+         * directly when ->fence_finish() is called.
+         */
+        if (!ctx->last_out_sync || ctx->last_out_sync->signaled)
+                goto out;
+
         /* Snapshot the last Panfrost's rendering's out fence.  We'd rather have
          * another syncobj instead of a sync file, but this is all we get.
          * (HandleToFD/FDToHandle just gives you another syncobj ID for the
          * same syncobj).
          */
-        drmSyncobjExportSyncFile(screen->fd, ctx->out_sync, &f->fd);
+        drmSyncobjExportSyncFile(screen->fd, ctx->last_out_sync->syncobj, &f->fd);
         if (f->fd == -1) {
                 fprintf(stderr, "export failed: %m\n");
                 free(f);
                 return NULL;
         }
 
+out:
         pipe_reference_init(&f->reference, 1);
 
         return f;