freedreno: allow ctx->batch to be NULL

This was mostly true already, now that we use `fd_context_batch()` for
first access to batch in draw/clear/grid paths.  So we can drop the old
code in `batch_flush()` that tried to prevent `ctx->batch` from being
NULL.

Fixes a crash with a large number of tabs in chromium.

Cc: "20.0" mesa-stable@lists.freedesktop.org
Signed-off-by: Rob Clark <robdclark@chromium.org>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3700>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3700>

src/gallium/drivers/freedreno/freedreno_batch.c

@@ -321,7 +321,6 @@ void
 fd_batch_flush(struct fd_batch *batch)
 {
 	struct fd_batch *tmp = NULL;
-	bool newbatch = false;
 
 	/* NOTE: we need to hold an extra ref across the body of flush,
 	 * since the last ref to this batch could be dropped when cleaning
@@ -329,30 +328,10 @@ fd_batch_flush(struct fd_batch *batch)
 	 */
 	fd_batch_reference(&tmp, batch);
 
-	if (batch == batch->ctx->batch) {
-		batch->ctx->batch = NULL;
-		newbatch = true;
-	}
-
 	batch_flush(tmp);
 
-	if (newbatch) {
+	if (batch == batch->ctx->batch) {
-		struct fd_context *ctx = batch->ctx;
+		fd_batch_reference(&batch->ctx->batch, NULL);
-		struct fd_batch *new_batch;
-
-		if (ctx->screen->reorder) {
-			/* defer allocating new batch until one is needed for rendering
-			 * to avoid unused batches for apps that create many contexts
-			 */
-			new_batch = NULL;
-		} else {
-			new_batch = fd_bc_alloc_batch(&ctx->screen->batch_cache, ctx, false);
-			util_copy_framebuffer_state(&new_batch->framebuffer, &batch->framebuffer);
-		}
-
-		fd_batch_reference(&batch, NULL);
-		ctx->batch = new_batch;
-		fd_context_all_dirty(ctx);
 	}
 
 	fd_batch_reference(&tmp, NULL);

src/gallium/drivers/freedreno/freedreno_batch_cache.c

@@ -295,9 +295,6 @@ fd_bc_alloc_batch(struct fd_batch_cache *cache, struct fd_context *ctx, bool non
 		 */
 		struct fd_batch *flush_batch = NULL;
 		for (unsigned i = 0; i < ARRAY_SIZE(cache->batches); i++) {
-			if ((cache->batches[i] == ctx->batch) ||
-					!cache->batches[i]->needs_flush)
-				continue;
 			if (!flush_batch || (cache->batches[i]->seqno < flush_batch->seqno))
 				fd_batch_reference_locked(&flush_batch, cache->batches[i]);
 		}

src/gallium/drivers/freedreno/freedreno_context.c

@@ -385,9 +385,6 @@ fd_context_init(struct fd_context *ctx, struct pipe_screen *pscreen,
 		goto fail;
 	pctx->const_uploader = pctx->stream_uploader;
 
-	if (!ctx->screen->reorder)
-		ctx->batch = fd_bc_alloc_batch(&screen->batch_cache, ctx, false);
-
 	slab_create_child(&ctx->transfer_pool, &screen->transfer_pool);
 
 	fd_draw_init(pctx);

src/gallium/drivers/freedreno/freedreno_state.c

@@ -256,7 +256,6 @@ fd_set_framebuffer_state(struct pipe_context *pctx,
 		DBG("%d: cbufs[0]=%p, zsbuf=%p", ctx->batch->needs_flush,
 				framebuffer->cbufs[0], framebuffer->zsbuf);
 		fd_batch_flush(ctx->batch);
-		util_copy_framebuffer_state(&ctx->batch->framebuffer, cso);
 	}
 
 	ctx->dirty |= FD_DIRTY_FRAMEBUFFER;