[lowrisc-dev] Porting TileLink2 to LowRISC

Sean Halle seanhalle at intensivate.com
Sun Jun 25 11:03:28 BST 2017

I think the crux of this is whether the idea of merging Berkeley code into
LowRISC is realistic or not..  it seems like a very large amount of work?
Do I have that right?  For example, might it even be easier be to simply
restart with the current Rocket repo and redo the integration work, rather
then trying to weed through all the merge conflicts..?  Or, do I
misunderstand the effort involved?

If that is the case, that the effort of a merge is prohibitive, and as a
result LowRISC never actually merge Berkeley code back in, then we would be
fine..  we port TL2 once, and then mainstream it into LowRISC, and there's
no more effort after that.  At least as long as that version is good
enough, then there is no strong reason to update it.

Has there been any discussion about the likelihood and timing of updating
LowRISC to the new Berkeley style of things?  We have some evidence that
the new Berkeley style is less modular, and has a steeper learning curve
than the July 2016 version of the code.  We chose LowRISC in part for this
reason -- the older style is simpler, easier for us to get up and running.



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On Sun, Jun 25, 2017 at 2:44 AM, Stefan Wallentowitz <stefan at wallentowitz.de
> wrote:

> Hi Sean,
> I don't speak for the project.
> On 24.06.2017 22:16, Sean Halle wrote:
> >    The issue is that we are based on LowRISC and plan to continue with
> the
> > LowRISC distribution to the end.
> That is great to hear and exactly what I understand lowRISC is intended
> for.
> >    So, as a compromise they are proposing to port TileLink2 to LowRISC.
> > The question we have for the list is what do people think about the
> porting
> > and then upstreaming?  If we resolve the Chisel2 vs Chisel3 part, then
> > would it be a viable option for them to send a pull request and have the
> > port become a permanent part of the LowRISC distro?
> TL2 is not in lowRISC because it is an old version of Rocket, right?
> Aside the issues some people see with the Rocket code base, wouldn't it
> be desirable to catch up with upstream instead of diverging permanently?
> The current lowRISC rocket still is on privilege spec 1.9, too.
> Maintaining a lowRISC specific application core that entirely diverged
> from the upstream rocket can become a massive workload, I think.
> Cheers,
> Stefan

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