From 15fe3d93d8dab95d19cc1ca7903da1d24a286344 Mon Sep 17 00:00:00 2001
From: Florent Kermarrec <florent@enjoy-digital.fr>
Date: Thu, 22 Aug 2024 09:12:34 +0200
Subject: [PATCH] litedram/frontend/wishbone: Add initial
 LiteDRAMNative2Wishbone.

---
 litedram/frontend/wishbone.py | 61 +++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)

diff --git a/litedram/frontend/wishbone.py b/litedram/frontend/wishbone.py
index df4930f..76cc57a 100644
--- a/litedram/frontend/wishbone.py
+++ b/litedram/frontend/wishbone.py
@@ -26,6 +26,8 @@ class LiteDRAMWishbone2Native(LiteXModule):
         port_data_width     = 2**int(log2(len(port.wdata.data))) # Round to lowest power 2
         ratio               = wishbone_data_width/port_data_width
 
+        assert wishbone.addressing == "byte"
+
         if wishbone_data_width != port_data_width:
             if wishbone_data_width > port_data_width:
                 addr_shift = -log2_int(wishbone_data_width//port_data_width)
@@ -79,3 +81,62 @@ class LiteDRAMWishbone2Native(LiteXModule):
                 NextState("CMD")
             )
         )
+
+# LiteDRAMNative2Wishbone --------------------------------------------------------------------------
+
+class LiteDRAMNative2Wishbone(LiteXModule):
+    def __init__(self, port, wishbone, base_address=0x00000000):
+        wishbone_data_width = len(wishbone.dat_w)
+        port_data_width     = 2**int(log2(len(port.wdata.data))) # Round to lowest power 2
+        ratio               = wishbone_data_width/port_data_width
+
+        assert ratio == 1
+
+        # # #
+
+        # Signals.
+        adr = Signal(32)
+
+        # FSM.
+        self.fsm = fsm = FSM(reset_state="CMD")
+        fsm.act("CMD",
+            If(port.cmd.valid,
+                port.cmd.ready.eq(1),
+                If(wishbone.addressing == "byte",
+                    NextValue(adr, port.cmd.addr*int(port_data_width//8) + base_address),
+                ).Else(
+                    NextValue(adr, port.cmd.addr + base_address//int(port_data_width//8)),
+                ),
+                If(port.cmd.we,
+                    NextState("WRITE")
+                ).Else(
+                    NextState("READ")
+                )
+            )
+        )
+        fsm.act("WRITE",
+            If(port.wdata.valid,
+                wishbone.stb.eq(1),
+                wishbone.cyc.eq(1),
+                wishbone.we.eq(1),
+                wishbone.adr.eq(adr),
+                wishbone.sel.eq(port.wdata.we),
+                wishbone.dat_w.eq(port.wdata.data),
+                If(wishbone.ack,
+                    port.wdata.ready.eq(1),
+                    NextState("CMD")
+                )
+            )
+        )
+        fsm.act("READ",
+            wishbone.stb.eq(1),
+            wishbone.cyc.eq(1),
+            wishbone.adr.eq(adr),
+            wishbone.sel.eq(2**len(wishbone.sel) - 1),
+            If(wishbone.ack,
+                # Assume port.rdata.ready always 1.
+                port.rdata.valid.eq(1),
+                port.rdata.data.eq(wishbone.dat_r),
+                NextState("CMD"),
+            )
+        )