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Re: [PATCH, RESEND] Add MWI workaround for Tulip DC21143

To: Martin Michlmayr <tbm@cyrius.com>
Subject: Re: [PATCH, RESEND] Add MWI workaround for Tulip DC21143
From: Peter Horton <phorton@bitbox.co.uk>
Date: Mon, 27 Mar 2006 13:39:00 +0100
Cc: "P. Horton" <pdh@colonel-panic.org>, Geert Uytterhoeven <geert@linux-m68k.org>, netdev@vger.kernel.org, Linux/MIPS Development <linux-mips@linux-mips.org>, Francois Romieu <romieu@fr.zoreil.com>
In-reply-to: <20060327070112.GA10906@deprecation.cyrius.com>
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References: <20060129230816.GD4094@colonel-panic.org> <20060218220851.GA1601@colonel-panic.org> <20060306225131.GA23327@unjust.cyrius.com> <20060306231530.GB16082@electric-eye.fr.zoreil.com> <20060307035824.GA24018@linux-mips.org> <Pine.LNX.4.62.0603071031520.5292@pademelon.sonytel.be> <20060308224139.GA7536@electric-eye.fr.zoreil.com> <Pine.LNX.4.62.0603091032490.9741@pademelon.sonytel.be> <20060309224456.GB9103@electric-eye.fr.zoreil.com> <20060327070112.GA10906@deprecation.cyrius.com>
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Martin Michlmayr wrote:
* Francois Romieu <romieu@fr.zoreil.com> [2006-03-09 23:44]:
So when compiling for Cobalt, we work around the hardware bug, while for other
platforms, we just disable MWI?

Wouldn't it be possible to always (I mean, when a rev 65 chip is detected)
work around the bug?
Of course it is possible but it is not the same semantic as the initial
patch (not that I know if it is right or not).

So:
- does the issue exist beyond Cobalt hosts ?
- is the fix Cobalt-only ?

I don't think anyone has replied to this message yet.  My
understanding is that it's not Cobalt only but a problem in a specific
revision of the chip, which the Cobalt happens to use.  However, I'd
be glad if somone else could comment.  Peter, you read the errata
right?

According to the errata it applies to all DEC 21143-PD and 21143-TD which are the chips with the revision code 0x41 (65). The errata states the receive buffers should not end on a cache aligned boundary when using MWI otherwise the receiver will not close the last descriptor.

P.

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