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

[Hal Rosenstock]

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.

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

-- Hal