[ewg] ***SPAM*** Re: [ofa-general] Forcing a DDR HCA to SDR speeds

[Hal Rosenstock]

On Tue, Sep 9, 2008 at 9:07 AM, Marty Schlining
<mschlining at datadirectnet.com> wrote:
> With OFED 1.3.1 or 1.4, is it possible to force the link speed of a DDR HCA
> port or the entire DDR HCA from a DDR link to strictly SDR? If so, how can
> it be done?  The HCAs in question is a Mellanox MT25208 dual port HCA, rev
> A3, firmware 4.8.2.

Yes.

For an individual port, look at the infiniband-diags ibportstate
command included in management:

ibportstate speed

There are ramifications on the SM to use this in that it must not
overwrite the speed (PortInfo:LinkSpeedEnabled). OpenSM has a
force_link_speed option for this which can be set to 0 for this type
of operation.

You will also need to reset the port to make it take effect as
renegotiation does not occur unless this is done.

ibportstate reset

The reset is only allowed on switch port so the peer port must be found.

If you want all ports to be SDR and are using OpenSM, you can just set
force_link_speed to SDR (1).

-- Hal

>
> Martin Schlining
>
> mschlining at datadirectnet.com
>
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