Describe CVA6 for write-through and write-back cache versions

[MikeOpenHWGroup]

In #602, there was a conversation like this:

Is the list of files in the manifest complete?

Looks okay for the write-through cache version. Of course, the write-back cache needs different files.

AFAICT, the ability to compile CVA6 for either write-through and write-back cache versions is not described in the User Manual. The User Manual should be updated to explain:

1. How to compile the CVA6 for write-through and write-back cache versions.
2. Theory of operation for the write-through cache controller.
3. Theory of operation for the write-back cache controller.

[j-silv]

1. How to compile the CVA6 for write-through and write-back cache versions.

For an FPGA emulation (say for example, using the Genesys 2 board) can we enable the write-back cache by simply commenting out the `define WT_DCACHE line in the genesysii.svh file?

It seems as though the WB_DCACHE define is not mentioned anywhere else in the source code, so I'm assuming we don't need to uncomment that line.

[suppamax]

@j-silv yes, by default the write-back cache is selected; you have compile the design with WT_DCACHE defined if you want to use a write-through cache

[suppamax]

We've just published our notes about the WB cache.
And here's an interesting paper about the WT cache.

Hope it helps

[MikeOpenHWGroup]

Hi @JeanRochCoulon, this is an old issue with new information. Let's get this into the User Manual.

[JeanRochCoulon]

I agree. The cache type should be addded in the CVA6 parameter chapter of user manual. I take the point !

[JeanRochCoulon]

Hi, I have just merged the #1127 to replace the define by a localparam into the config pkg. On my side, the issue is solved. Mike, up to you to take the decidsion to close the issue.

[MikeOpenHWGroup]

Thanks everyone! Closing.