[openib-general] MT25218 (aka Arbel memfree) support

[Michael S. Tsirkin]

Hello!
Quoting r. Hal Rosenstock (halr at voltaire.com) "Re: [openib-general] MT25218 (aka Arbel memfree) support":
> Hi,
> 
> On Wed, 2004-12-15 at 07:58, Michael S. Tsirkin wrote:
> > Hello!
> > I'd like to start working on MT25218 (aka Arbel memfree, aka native mode)
> > support for openib gen2.
> > 
> > There are many similiarities with MT25208, but there are also
> > major differences, and a lot of extra setup to be done
> > to compensate for the absence of on-board memory,
> > which unfortunately affects not only the set-up
> > commands but also performance-critical data path verbs
> > (e.g. posting WQEs, CQ polling).
> > 
> > What would be the best way to organise this code?
> > I guess could be two thinkable ways to do this:
> > 
> > 1. Add the functionality to the mthca module,
> >    use a run-time flag to describe hardware differences.
> >    Thus, the same module will handle devices of all
> >    types.
> > 
> > 2. Create a sibling or a child directory to mthca,
> >    and export common functions from mthca.
> >    In this case we will have two kernel modules,
> >    sharing some common files.
> > 
> > I am leaning towards option 2 for both the performance
> > reasons and for better separation between drivers.
> > 
> > 
> > Therefore, I propose adding a directory memfree under
> > 
> > https://openib.org/svn/gen2/trunk/src/linux-kernel/infiniband/hw/mthca/memfree
> > 
> > and all memfree specific code will go there.
> 
> There already is some Arbel native code in mthca. I believe the path
> being taken is more in lines with approach 1. As Roland is the
> maintainer of this, you would need to coordinate with him. I would
> expect we can utilize your offer to accelerate Arbel native support,
> which a number of people have asked about.

OK.

> Also, with this work, would Tavor also be made to work with DDR hidden ?
> 
> -- Hal
>

Thats an unrelated issue.

With DDR hidden AFAIK the only difference is
that FMRs dont work since you have to use a command to access the
internal DDR.

Do you know of any issues with that?

MST