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From: David Brownell <david-b@pacbell.net>
To: "Lev A. Melnikovsky" <melnikovsky@mail.ru>
Subject: Re: ehci-hcd affects hda speed
Date: Mon, 17 Mar 2008 13:06:52 -0800
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Cc: Alessandro Suardi <alessandro.suardi@gmail.com>,
       Rene Herman <rene.herman@keyaccess.nl>, linux-kernel@vger.kernel.org
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On Saturday 15 March 2008, Lev A. Melnikovsky wrote:
>  	Particularly, what does "MAC turn around 
> time" stand for with respect to EHCI? I would appreciate some reference, 
> thanks.

Blame VIA for that one.  Notice how their descriptions of the
fields in that register don't even mention a MAC.  :)

But the relevant bit is the "sleep time" and that's described
in the EHCI specification.  It basically means how long it waits,
after noticing a "no work for me" async schedule ring, before
scanning that schedule again.  It seems your system had that
set to just 1 usec, meaning it would hardly give anything else
a chance to get onto the PCI bus.  That's probably why the EHCI
spec uses a value of 10 usec:  basic fairness.

- Dave


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