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Random ideas and interesting ideas for things we hope to eventually do.
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Merge different approaches to generate devicetree (Linux-on-LiteX-Vexriscv and litex-devicetree) #2

Open mithro opened 5 years ago

mithro commented 5 years ago

It would be good for LiteX to generate suitable device tree for Linux / Zephyr (potentially micropython in future).

I started (but never finished) a tool to take a csr.cvs file and generate a Linux Device Tree file - see https://github.com/mithro/litex-devicetree

It was targeting producing suitable dts for or1k as part of the LCA2018 Miniconf tutorial (see https://github.com/timvideos/litex-buildenv/wiki/HowTo-LCA2018-FPGA-Miniconf). It seems to be used here;

https://github.com/timvideos/litex-buildenv/blob/005f7463bd5e022ee3e3d8cc90efde57e8465b86/scripts/build-linux.sh#L97-L131

A much better solution would be to allow modules to provide devicetree fragments in the same way that they can provide CSRs and stuff.

enjoy-digital commented 5 years ago

Thanks, i also want to go in that direction. I'll experiment with your previous work.

mithro commented 5 years ago

FYI - There are some useful links at https://github.com/timvideos/litex-buildenv/wiki/DeviceTree

Some links to devicetree fragments which might be useful in this old Google Doc too.

futaris commented 5 years ago

https://github.com/riscv/meta-riscv/issues/143

Looks like DTS is changing in Linux 5.2 and 5.3

gsomlo commented 5 years ago

Just to thrown in my $0.02, from the 64bit RocketChip perspective: I'm starting with the Chisel-generated dts file (see e.g., https://github.com/enjoy-digital/rocket-litex-verilog/blob/master/generated-src/freechips.rocketchip.system.LitexFullConfig.dts) which for now needs to have cpu@0's timebase-frequency moved one level up under cpus, and then throw out mmio-port-axi4 and adjust memory accordingly, then paste in the various LiteX devices as appropriate (uart0 and mac0 for now).

Not sure how I/we could automate the hand-editing of this file from the LiteX builder. Maybe the 32-bit CPU options are less complex as far as DTS is concerned?

enjoy-digital commented 5 years ago

With https://github.com/enjoy-digital/litex/commit/2899928aba932d5fa93902d9a2ef6a169f1c76b7 and https://github.com/litex-hub/linux-on-litex-vexriscv/commit/acffa47e621e11f8eed9eefea950323755838198 dts files are not auto-generated. A json file is exported with LiteX and then used by the json2dts.py script. We could improve that in the future but at least it's already enough for linux-on-litex-vexriscv.

mithro commented 5 years ago

We also had https://github.com/litex-hub/litex-devicetree

Would be good to merge these two approaches...

enjoy-digital commented 5 years ago

I agree, let's track this in https://github.com/litex-hub/litex-devicetree (i just transfered the issue), once we'll have something more generic than the actual json2dts.py of linux-on-litex-vexriscv, we could also use it there.