From f1a9f4d23705ec955d434a6519a54c7b017efc6f Mon Sep 17 00:00:00 2001
From: Luke Kenneth Casson Leighton <lkcl@lkcl.net>
Date: Sat, 13 Nov 2021 22:04:48 +0000
Subject: [PATCH] add first cut of jtag.py (from soc) to be cut down later

---
 src/spec/jtag.py | 143 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 143 insertions(+)
 create mode 100644 src/spec/jtag.py

diff --git a/src/spec/jtag.py b/src/spec/jtag.py
new file mode 100644
index 0000000..4b4f17a
--- /dev/null
+++ b/src/spec/jtag.py
@@ -0,0 +1,143 @@
+"""JTAG interface
+
+using Staf Verhaegen (Chips4Makers) wishbone TAP
+"""
+
+from collections import OrderedDict
+from nmigen import (Module, Signal, Elaboratable, Cat)
+from nmigen.cli import rtlil
+from c4m.nmigen.jtag.tap import IOType
+from soc.debug.dmi import  DMIInterface, DBGCore
+from soc.debug.dmi2jtag import DMITAP
+
+# map from pinmux to c4m jtag iotypes
+iotypes = {'-': IOType.In,
+           '+': IOType.Out,
+           '>': IOType.TriOut,
+           '*': IOType.InTriOut,
+        }
+
+scanlens = {IOType.In: 1,
+           IOType.Out: 1,
+           IOType.TriOut: 2,
+           IOType.InTriOut: 3,
+            }
+
+def dummy_pinset():
+    # sigh this needs to come from pinmux.
+    gpios = []
+    for i in range(16):
+        gpios.append("%d*" % i)
+    return {'uart': ['tx+', 'rx-'],
+             'gpio': gpios,
+             'i2c': ['sda*', 'scl+']}
+
+# TODO: move to suitable location
+class Pins:
+    """declare a list of pins, including name and direction.  grouped by fn
+    the pin dictionary needs to be in a reliable order so that the JTAG
+    Boundary Scan is also in a reliable order
+    """
+    def __init__(self, pindict):
+        self.io_names = OrderedDict()
+        if isinstance(pindict, OrderedDict):
+            self.io_names.update(pindict)
+        else:
+            keys = list(pindict.keys())
+            keys.sort()
+            for k in keys:
+                self.io_names[k] = pindict[k]
+
+    def __iter__(self):
+        # start parsing io_names and enumerate them to return pin specs
+        scan_idx = 0
+        for fn, pins in self.io_names.items():
+            for pin in pins:
+                # decode the pin name and determine the c4m jtag io type
+                name, pin_type = pin[:-1], pin[-1]
+                iotype = iotypes[pin_type]
+                pin_name = "%s_%s" % (fn, name)
+                yield (fn, name, iotype, pin_name, scan_idx)
+                scan_idx += scanlens[iotype] # inc boundary reg scan offset
+
+
+class JTAG(DMITAP, Pins):
+    # 32-bit data width here so that it matches with litex
+    def __init__(self, pinset, domain, wb_data_wid=32):
+        self.domain = domain
+        DMITAP.__init__(self, ir_width=4)
+        Pins.__init__(self, pinset)
+
+        # enumerate pin specs and create IOConn Records.
+        # we store the boundary scan register offset in the IOConn record
+        self.ios = [] # these are enumerated in external_ports
+        self.scan_len = 0
+        for fn, pin, iotype, pin_name, scan_idx in list(self):
+            io = self.add_io(iotype=iotype, name=pin_name)
+            io._scan_idx = scan_idx # hmm shouldn't really do this
+            self.scan_len += scan_idx # record full length of boundary scan
+            self.ios.append(io)
+
+        # this is redundant.  or maybe part of testing, i don't know.
+        self.sr = self.add_shiftreg(ircode=4, length=3,
+                                    domain=domain)
+
+        # create and connect wishbone
+        self.wb = self.add_wishbone(ircodes=[5, 6, 7], features={'err'},
+                                   address_width=30, data_width=wb_data_wid,
+                                   granularity=8, # 8-bit wide
+                                   name="jtag_wb",
+                                   domain=domain)
+
+        # create DMI2JTAG (goes through to dmi_sim())
+        self.dmi = self.add_dmi(ircodes=[8, 9, 10],
+                                    domain=domain)
+
+        # use this for enable/disable of parts of the ASIC.
+        # XXX make sure to add the _en sig to en_sigs list
+        self.wb_icache_en = Signal(reset=1)
+        self.wb_dcache_en = Signal(reset=1)
+        self.wb_sram_en = Signal(reset=1)
+        self.en_sigs = en_sigs = Cat(self.wb_icache_en, self.wb_dcache_en,
+                                     self.wb_sram_en)
+        self.sr_en = self.add_shiftreg(ircode=11, length=len(en_sigs),
+                                       domain=domain)
+
+    def elaborate(self, platform):
+        m = super().elaborate(platform)
+        m.d.comb += self.sr.i.eq(self.sr.o) # loopback as part of test?
+
+        # provide way to enable/disable wishbone caches and SRAM
+        # just in case of issues
+        # see https://bugs.libre-soc.org/show_bug.cgi?id=520
+        with m.If(self.sr_en.oe):
+            m.d.sync += self.en_sigs.eq(self.sr_en.o)
+        # also make it possible to read the enable/disable current state
+        with m.If(self.sr_en.ie):
+            m.d.comb += self.sr_en.i.eq(self.en_sigs)
+
+        # create a fake "stall"
+        #wb = self.wb
+        #m.d.comb += wb.stall.eq(wb.cyc & ~wb.ack) # No burst support
+
+        return m
+
+    def external_ports(self):
+        """create a list of ports that goes into the top level il (or verilog)
+        """
+        ports = super().external_ports()           # gets JTAG signal names
+        ports += list(self.wb.fields.values())     # wishbone signals
+        for io in self.ios:
+            ports += list(io.core.fields.values()) # io "core" signals
+            ports += list(io.pad.fields.values())  # io "pad" signals"
+        return ports
+
+
+if __name__ == '__main__':
+    pinset = dummy_pinset()
+    dut = JTAG(pinset)
+
+    vl = rtlil.convert(dut)
+    with open("test_jtag.il", "w") as f:
+        f.write(vl)
+
-- 
2.30.2