From 18a1d74cf63178b3bcba129374f0fd5be8478709 Mon Sep 17 00:00:00 2001
From: Ilia Sergachev <ilia.sergachev@protonmail.ch>
Date: Wed, 8 Dec 2021 23:08:45 +0100
Subject: [PATCH] soc/interconnect: add basic ahb support

---
 litex/soc/interconnect/ahb.py | 67 +++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)
 create mode 100644 litex/soc/interconnect/ahb.py

diff --git a/litex/soc/interconnect/ahb.py b/litex/soc/interconnect/ahb.py
new file mode 100644
index 000000000..d791d2958
--- /dev/null
+++ b/litex/soc/interconnect/ahb.py
@@ -0,0 +1,67 @@
+from enum import IntEnum
+from migen import *
+
+
+class TransferType(IntEnum):
+    IDLE = 0
+    BUSY = 1
+    NONSEQUENTIAL = 2
+    SEQUENTIAL = 3
+
+
+class Interface(Record):
+    adr_width = 32
+    data_width = 32
+
+    master_signals = [
+        ('addr', adr_width),
+        ('burst', 3),
+        ('mastlock', 1),
+        ('prot', 4),
+        ('size', 3),
+        ('trans', 2),
+        ('wdata', data_width),
+        ('write', 1),
+        ('sel', 1),
+    ]
+
+    slave_signals = [
+        ('rdata', data_width),
+        ('readyout', 1),
+        ('resp', 1),
+    ]
+
+    def __init__(self):
+        Record.__init__(self, set_layout_parameters(self.master_signals + self.slave_signals))
+
+
+class AHB2Wishbone(Module):
+    def __init__(self, ahb, wishbone):
+        wb = wishbone
+        wishbone_adr_shift = log2_int(ahb.data_width // 8)
+        assert ahb.data_width == wb.data_width
+        assert ahb.adr_width == wb.adr_width + wishbone_adr_shift
+
+        self.comb += [
+            ahb.resp.eq(wb.err),
+        ]
+
+        self.submodules.fsm = fsm = FSM()
+        fsm.act("IDLE",
+            ahb.readyout.eq(1),
+            If(ahb.sel & (ahb.size == wishbone_adr_shift) & (ahb.trans == TransferType.NONSEQUENTIAL),
+               NextValue(wb.adr, ahb.addr[2:]),
+               NextValue(wb.dat_w, ahb.wdata),
+               NextValue(wb.we, ahb.write),
+               NextValue(wb.sel, 2 ** len(wb.sel) - 1),
+               NextState('ACT'),
+            )
+        )
+        fsm.act("ACT",
+            wb.stb.eq(1),
+            wb.cyc.eq(1),
+            If(wb.ack,
+               If(~wb.we, NextValue(ahb.rdata, wb.dat_r)),
+               NextState("IDLE")
+            )
+        )