Message-ID: <491873FE.2030408@zytor.com>
Date: Mon, 10 Nov 2008 09:48:46 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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CC: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: EHCI "on the go"
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Miguel Ángel Álvarez wrote:
> Hi.
> 
> Due to some problems with the EHCI in an IXP465, I have found that
> this micro has an "on the go" feature. One of its features seems to be
> an "Embedded Transaction Translator", that seems to be quite
> "propietary".
> 
> I see in ehci.h, that using CONFIG_USB_EHCI_ROOT_HUB_TT, a function
> called "ehci_port_speed" has been added, and the comments suggest to
> implement the particularities of each controller with other functions.
> 
> The question is:
> - Are there many different implementations (it seems there are not,
> because I cannot see code for each of them... unless they are so
> particular that they do not even use the general interface)?
> - Is there any place comparing the similarities / differences between them?
> 

I only know of one interface for this, which is based on hardware IP I
believe is currently owned by ChipIdea.  It's pretty straightforward; it
functionally does the same translation for the root port as a separate
hub would do for a full speed/low speed downstream port.

	-hpa
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