nlnet_2019_coriolis2.mdwn

   1 # NL.net proposal
   2
   3 [[questions]]
   4
   5 ## Project name
   6
   7 The Libre-RISCV SoC, Coriolis2 ASIC Layout Collaboration
   8
   9 ## Website / wiki
  10
  11 <https://libre-riscv.org/nlnet_2019_coriolis2>
  12
  13 Please be short and to the point in your answers; focus primarily on
  14 the what and how, not so much on the why. Add longer descriptions as
  15 attachments (see below). If English isn't your first language, don't
  16 worry - our reviewers don't care about spelling errors, only about
  17 great ideas. We apologise for the inconvenience of having to submit in
  18 English. On the up side, you can be as technical as you need to be (but
  19 you don't have to). Do stay concrete. Use plain text in your reply only,
  20 if you need any HTML to make your point please include this as attachment.
  21
  22 ## Abstract: Can you explain the whole project and its expected outcome(s).
  23
  24 The Libre RISC-V SoC is being developed to provide a privacy-respecting
  25 modern processor, developed transparently and as libre to the bedrock
  26 as possible.  This means not just the software running on the processor:
  27 it means the actual hardware design and the hardware layout, right down
  28 to the transistor level.
  29
  30 It is necessary, therefore, to use libre-licensed VLSI Layout tools
  31 rather than pay for proprietary software that, apart from being incredibly
  32 expensive, could potentially compromise the integrity of the project.
  33
  34 We therefore intend to collaborate with engineers from LIP6, to use
  35 and improve their VLSI Layout tool, Coriolis2, in conjunction with
  36 Chips4Makers, to create the layout that Chips4Makers will then put into
  37 a 180nm 300mhz test chip.
  38
  39 # Have you been involved with projects or organisations relevant to this project before? And if so, can you tell us a bit about your contributions?
  40
  41 Luke Leighton is an ethical technology specialist who has a consistent
  42 24-year track record of developing code in a real-time transparent
  43 (fully libre) fashion, and in managing Software Libre teams.  He is the
  44 lead developer on the Libre RISC-V SoC.
  45
  46 Jean-Paul Chaput is the lead engineer on the Alliance and Coriolis2
  47 tools for VLSI backend layout, from LIP6.
  48
  49 # Requested Amount
  50
  51 EUR 50,000.
  52
  53 # Explain what the requested budget will be used for?
  54
  55 The key initial milestone for the 2018 NLNet Libre RISC-V SoC Project
  56 is the FPGA target: a working design that can run in an FPGA at approximately
  57 50Mhz.  The next logical step is to do the layout.
  58
  59 However, FPGA targets have some quirks which help accelerate FPGAs (not ASICs):
  60 an on-board DSP, specialist memory, and so on.  Without these "crutches"
  61 the design must be augmented and adapted to suit ASIC layout.
  62
  63 As we are using nmigen for the HDL front-end and yosys for the HDL
  64 back-end, we will need to work with the nmigen developers in order to
  65 augment nmigen to cope with the task of creating "netlists" suitable for
  66 ASICs.  Whilst yosys (the actual "netlist" generator) has been utilised
  67 for this task repeatedly and successfully, and whilst the prior version,
  68 "migen", was also used, nmigen has not yet been ASIC proven.
  69
  70 Once a "netlist" is available, the Coriolis2 VLSI tool will be used to
  71 actually create the layers of the chip.  Given the size and capabilities
  72 of the chip, we anticipate issues here, which we will need the support
  73 of LIP6's engineers to solve.
  74
  75 The layout itself is also dependent on what is called "Cell Libraries".
  76 One is "NSXLIB" which contains OR and AND gates to create MUXes and XORs.
  77 Another is an "SRAM" Library (memory), and another is a "GPIO" Cell
  78 Library.  Chips4Makers will be working on these low-level blocks for
  79 us (under a separate Programme), however we again anticipate issues -
  80 related to Foundry NDAs - which will hamper the communications process.
  81
  82 So therefore, the requested budget will be used for:
  83
  84 * Augmentation and adaptation of the Libre RISC-V SoC HDL to ASIC layout
  85 * Engineers to work on the layout using Alliance / Coriolos2 VLSI, from lip6
  86 * Engineers to bug-fix or augment Alliance / Coriolis2
  87 * Essential augmentations to nmigen to make it ASIC-layout-capable
  88
  89 All of these will be and are entirely libre-licensed software: there will
  90 be no proprietary software tools utilised in this process.
  91
  92
  93 # Does the project have other funding sources, both past and present?
  94
  95 The overall project has sponsorship from Purism as well as a prior grant
  96 from NLNet.  However that is for specifically covering the development
  97 of the RTL (the hardware source code).
  98
  99 There is no source of funds for the work on the *next* stage: the actual
 100 VLSI ASIC Layout.  Chips4Makers is however putting in an *additional*
 101 (and separate) funding application for the stage after *this*: the
 102 creation of the Cell Libraries that will be used in the VLSI ASIC Layout.
 103
 104 All these three projects are separate and distinct (despite being related
 105 to the same CPU), and funding may not cross over from one project to
 106 the other.
 107
 108 # Compare your own project with existing or historical efforts.
 109
 110 There are several Open VLSI Tool suites:
 111
 112 * GNU Electric: https://www.gnu.org/software/electric/
 113 * MAGIC: http://opencircuitdesign.com/magic/
 114 * The OpenROAD Project: https://theopenroadproject.org/ (using MAGIC)
 115 * QFlow: http://opencircuitdesign.com/qflow/
 116 * Toped: http://www.toped.org.uk/
 117
 118 and a few more.  We choose Coriolis2 because of its python interface.
 119 The VLSI Layout is actually done as a *python* program.  With nmigen
 120 (the HDL) being in python, we anticipate the same OO benefits to be
 121 achievable in coriolis2 as well.
 122
 123 The case for the Libre RISC-V SoC itself was made already in the initial
 124 2018.02 proposal.  That has not changed: there are no Libre / Open Projects
 125 approaching anything like the complexity and product market opportunities
 126 of the Libre RISC-V SoC, which is being designed to be a quad-core 800mhz
 127 multi-issue out-of-order design.  All other Libre / Open processors such
 128 as Raven, and many more, have a goal set in advance not to exceed around
 129 the 350mhz mark, and are single-core.
 130
 131 Other projects which are "open", such as the Ariane Processor, are
 132 developed by universities, and in the case of Ariane were *SPECIFICALLY*
 133 designed by and for the use of proprietary toolchains, such as those from
 134 Cadence, Synopsys and Mentor Graphics.  Despite the source code being
 135 "open", there was absolutely no expectation that the processor of the
 136 same capability as the Libre RISC-V SoC would use Libre / Open tools.
 137
 138 Although our first ASIC (thanks to Chips4Makers) will be only 180nm,
 139 single-core and a maximum of around 350mhz, this is just the first
 140 stepping stone to a much larger processor.
 141
 142 ## What are significant technical challenges you expect to solve during the project, if any?
 143
 144 Some of these have been mentioned above:
 145
 146 * NDAs by Foundries may interfere with the ability for Chips4Makers to
 147   communicate with LIP6 regarding the necessary changes to NSXLIB which
 148   meet the TSMC Foundry "Design Rule Checks" (DRCs).
 149 * Bugs or missing features in nmigen, yosys, coriolis2, NSXLIB, OpenRAM,
 150   and the knock-on implications throughout the chain, right the way up
 151   to the *actual* Libre RISC-V SoC's HDL source code itself, all need to
 152   be dealt with.
 153 * Circuit simulation and unit testing is going to be a major factor, and
 154   a huge utilisation of Computing power.  Machines with "only" 16 GB of RAM
 155   and high-end quad-core processors are going to be hopelessly inadequate.
 156
 157 ## Describe the ecosystem of the project, and how you will engage with relevant actors and promote the outcomes?
 158
 159 LIP6 have their own mailing list for the (transparent) discussion of
 160 issues related to coriolis2: <alliance-users@asim.lip6.fr>.  The Libre RISC-V
 161 SoC has a full set of resources for Libre Project Management and development:
 162 mailing list, bugtracker, git repository and wiki - all listed here:
 163 <https://libre-riscv.org/>
 164
 165 In addition, we have a Crowdsupply page
 166 <https://www.crowdsupply.com/libre-risc-v/m-class> which provides a public
 167 gateway, and heise.de, reddit, phoronix, slashdot and other locations have
 168 all picked up the story.  The list is updated and maintained here:
 169 <https://libre-riscv.org/3d_gpu/>
 170
 171 # Extra info to be submitted
 172
 173 * <http://libre-riscv.org/3d_gpu/>
 174 * <https://www-soc.lip6.fr/equipe-cian/logiciels/coriolis/>
 175 * <https://nlnet.nl/project/Libre-RISCV/>
 176 * <https://chips4makers.io/blog/>
 177