-# TODO
-
-* use chroot
-* run all nmigen and yosys dev-scripts hdl-dev-repos hdl-tools-yosys
- install-hdl-apt-reqs
-* run nextpnr-xilinx dev-script and nextpnr-ecp5-install
-* run hdl-dev-ls2 dev-script
-* git clone microwatt as well
-* make hello_world.bin in microwatt and copy it to ls2
-* "make microwatt_external_core" in soc and copy external_core_top.v to ls2
-* plug in FPGA board (Arty A7-100t, VERSA_ECP5, other)
-* run in 2nd terminal "minicom -D /dev/ttyUSB1"
-* python3 src/ls2.py arty_a7 hello_world.bin (for an Arty A7-100t)
-* OR python3 src/ls2.py versa_ecp5 hello_world.bin (for a VERSA_ECP5)
+# Steps for Hello World Microwatt ls2 for fpga/boards
+
+* Currently works for Arty A7-100t, VERSA_ECP5 and in future others
+* Bugzilla page <https://bugs.libre-soc.org/show_bug.cgi?id=802>
+* NGI POINTER <https://bugs.libre-soc.org/show_bug.cgi?id=818>
+* [Bug #1127 - Generating core with SVP64](https://bugs.libre-soc.org/show_bug.cgi?id=1127)
+
+# Install Instructions
+
+ # devscripts
+ git clone https://git.libre-soc.org/git/dev-env-setup.git
+ cd dev-env-setup
+ sudo bash
+ ./mk-deb-chroot ls2-hello-world
+ ./cp-scripts-to-chroot ls2-hello-world
+ exit # back to user
+
+ schroot -c ls2-hello-world
+ sudo bash # helps define SUDO_USER in new chroot
+ cd ~/dev-env-setup
+
+ # install dependencies in new chroot
+ ./install-hdl-apt-reqs
+ ./hdl-dev-repos
+ ./hdl-tools-yosys
+ ./nextpnr-xilinx-install
+ ./hdl-dev-ls2
+
+ # if you intend to upload fpga bitstreams in the same chroot, also need
+ # the fpga utilities
+ ./fpga-boot-load-prog-install
+
+ cd ~/src
+
+ # make hello_world.bin from microwatt
+ cd tercel-qspi/
+ cd hello_world/
+ make
+ cp hello_world.bin ../../ls2
+ cd ../..
+
+ # make the Libre-SOC core (for external use)
+ cd soc
+ make microwatt_external_core
+ cp external_core_top.v ../ls2
+
+ # check out ls2 peripheral framework
+ cd ../ls2
+ git checkout 426e2d9585cd4b1fb96a38987f97878285ee5ba7
+
+ export PATH=/usr/local/nextpnr-xilinx/bin:$PATH
+ export XRAY_DIR=/usr/local/nextpnr-xilinx
+
+ # plug in FPGA board (Arty A7-100t, VERSA_ECP5, other)
+ # run in 2nd terminal "minicom -D /dev/ttyUSB1"
+
+ python3 src/ls2.py arty_a7 hello_world.bin # for Arty A7-100t
+ python3 src/ls2.py versa_ecp5 hello_world.bin # (for a VERSA_ECP5)
+
+This directly programs a tmp bitstream using xc3sprog to nexys4 board.
+If needed modify sources to produce a fixed file bitstream and
+
+ copy build/top.bit to board/server (scp, rsync)
+ minicom -D /dev/ttyUSB1
+ xc3sprog -c nexys4 top.bit
+
+If there are multiple Arty-A7-100t boards connected you need to know
+the serial number (lsusb | grep Serial)
+
+ xc3sprog -c nexys4 -s {insert_full_serial_number} top.bit
+
+# Using ls2 with microwatt
+
+This is doable but tricky. An older version is required at present.
+
+ git clone https://git.libre-soc.org/git/microwatt.git
+ git checkout microwatt_verilator
+ make microwatt.v
+
+From there, some hand-editing is required. search for core_NNNNNNN_XXX_YYY
+and rename it to external_core_top. Save the file as external_core_top.v
+and it can be used in place of the Libre-SOC Core, above.
+
+In fact any core can be used with ls, as long as it is compliant with
+the interfaces. Both Wishbone Interfaces must be WB4 Pipeline
+compliant (proper stall handling) or the stall signal faked externally
+with a wrapper: `stall=stb&~ack`
+
+# Using ls2 with verilator
+
+first you need to build hello_world (or any other firmware) to start at
+0xff000000. Then you can run build ls.v using that firmware:
+
+ python3 src/ls2.py sim /tmp/ff000000_hw.bin
+
+The output of that command is:
+
+ platform sim /tmp/ff000000_hw.bin None
+ fpga sim firmware /tmp/ff000000_hw.bin
+ ddr pins None
+ spiflash pins None
+ ethmac pins None
+ hyperram pins [<lambdasoc.periph.hyperram.HyperRAMPads object at 0x735e9940dd30>]
+ fw at address ff000000
+ SRAM 0x8000 at address 0x0
+
+To use verilator, make sure to run the devscript:
+
+ ./verilator-install
+
+And set the GHDLSYNTH and update PATH:
+
+ export PATH=/usr/local/verilator/bin:$PATH
+ export GHDLSYNTH=ghdl
+
+After that you can compile microwatt-verilator:
+
+ export FPGA_TARGET=verilator
+ make microwatt-verilator
+
+# Estimating transistor count using yosys
+
+Use yosys to run synthesis and using `stat` to view gate/transistor count:
+
+ cd src/ls2/
+ yosys
+ yosys> read_verilog ls2.v external_core_top.v ../uart16550/rtl/verilog/*.v
+ yosys> synth
+ yosys> tee -a stat_cmos.log stat -tech cmos
+
+Then you can view the resulting log file afterwards. Bare in mind `synth` will probably take a while. **TODO: Find multi-threaded option**