[prim/fifo_async] Disallow non-power-of-two depths
If the depth is not a power of two, the transitions will not be
gray-coded when the pointers wrap.
Signed-off-by: Tom Roberts <tomroberts@lowrisc.org>
diff --git a/util/tlgen/xbar.rtl.sv.tpl b/util/tlgen/xbar.rtl.sv.tpl
index 5dce4df..cf1e2be 100644
--- a/util/tlgen/xbar.rtl.sv.tpl
+++ b/util/tlgen/xbar.rtl.sv.tpl
@@ -198,8 +198,8 @@
% for block in xbar.nodes:
% if block.node_type.name == "ASYNC_FIFO":
tlul_fifo_async #(
- .ReqDepth (3),// At least 3 to make async work
- .RspDepth (3) // At least 3 to make async work
+ .ReqDepth (4),// At least 4 to make async work
+ .RspDepth (4) // At least 4 to make async work
) u_${block.name} (
.clk_h_i (${block.clocks[0]}),
.rst_h_ni (${block.resets[0]}),
