[openib-general] [PATCH] Add support for querying port width/ speed

[Diego Crupnicoff]

I think the choice of IPD is beyond the scope of the IB spec. The spec
provides a mechanism to regulate the injection rate but does not mandate its
use. Your assumption below (rounding up) makes perfect sense. Rounding down
would defeat the entire purpose of the IPD mechanism.

Diego

> -----Original Message-----
> From: Roland Dreier [mailto:roland at topspin.com] 
> Sent: Tuesday, December 28, 2004 3:11 AM
> To: openib-general at openib.org
> Subject: Re: [openib-general] [PATCH] Add support for 
> querying port width/speed
> 
> 
> By, the way does anyone know what IPD is supposed to be used 
> when the injection port's rate is not a multiple of the rate 
> for the path?  For example, suppose an 8X DDR port is sending 
> to a 12X path -- 12 doesn't divide 16 evenly.
> 
> I would guess that the correct thing to do is round up, so 8X DDR
> -> 12X uses an IPD of 1, 8X QDR -> 12X uses an IPD of 2, etc.
> 
>  - R.
> 
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