Add AXI4

[martijnbastiaan]

TODO:

• Convenience functions defined for DfLike should be exposed for the various AXI channels. This should be pretty straight-forward. It'd basically be the same as Df.
• I think I made a mistake defining the Payloads (see review comments)
• It would still needs some examples (like a FIFO) on how to use it. clash-protocols is (for good reasons) a maze of type families unfortunately.
• Build an interconnect component.
• Build data generators and verifiers for functional verification.

[jeehoonkang]

@martijnbastiaan Hi Martijn! Thank you for working on this wonderful project. I wonder if this PR is going to be merged. I really wish to use Clash for a project with AXI4 and AXI4-Stream.

(Unrelatedly, I also wonder if there is any documentation for this project. It seems the link in the README.md is broken.)

[martijnbastiaan]

After working some more with AXI, I don't think exposing userType as the payload is a good idea. Perhaps we should define the address as the payload, so functions like map operate on that instead.

[martijnbastiaan]

Same comments as for ReadAddress. dataType probably makes more sense.

[martijnbastiaan]

Hi @jeehoonkang, thanks for the kind words :).

There's still some things missing in this PR:

• Convenience functions defined for DfLike should be exposed for the various Axi channels. This should be pretty straight-forward. It'd basically be the same as Df:

clash-protocols/src/Protocols/Df.hs

Lines 199 to 201 in 9795f14

	-- | Like 'P.map', but over payload (/a/) of a Df stream.
	map :: (a -> b) -> Circuit (Df dom a) (Df dom b)
	map = DfLike.map Proxy Proxy

• I think I made a mistake defining the Payloads (see review comments)
• It would still needs some examples on how to use it. clash-protocols is (for good reasons) a maze of type families unfortunately.

[martijnbastiaan]

(Unrelatedly, I also wonder if there is any documentation for this project. It seems the link in the README.md is broken.)

I haven't uploaded the package to Hackage yet as I feel it isn't ready yet. The documentation is built on CI though, but it takes a bit of clicking (click green tick next to commit => details => haddock => browse job artifacts => docs => index.html). The rendered documentation for this PR can be found here.

[martijnbastiaan]

Also, AXI-Stream and AXI-Lite should definitely be added! Full-blown AXI is almost always overkill! :)

I'm on another project that's draining all my energy for the next couple of months, so I doubt I'm going to have the energy to finish the PR :(. If you'd like to help finish this PR I'd be more than happy to help!

[PietPtr]

Convenience functions have only been defined for the read data channel, as that is the only channel for which a field of kind Type is available (other channels do have the field userType, but the specification actively discourages using that field).

Designing the FIFO is left as issue #23.

Designing the interconnect is left as issue #24.

[martijnbastiaan]

Thanks @PietPtr !