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Re: Trouble with sound/mips/au1x00.c AC97 driver

To: Ralf Baechle <ralf@linux-mips.org>
Subject: Re: Trouble with sound/mips/au1x00.c AC97 driver
From: Andrew Dyer <adyer@righthandtech.com>
Date: Mon, 12 Mar 2007 20:00:58 -0500
Cc: Sergei Shtylyov <sshtylyov@ru.mvista.com>, Marco Braga <marco.braga@gmail.com>, Domen Puncer <domen.puncer@telargo.com>, linux-mips@linux-mips.org
In-reply-to: <20070313004315.GA26119@linux-mips.org>
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Ralf Baechle wrote:
For the general MIPS case (Alchemy may provide guarantees I don't know of)
a SYNC instruction is not sufficient to ensure that a write has actually
been reached by the device.  It may just like on PCI take a read from the
same device again:

I just looked it up.

Section 2.4.5 of the Alchemy Au1550 datasheet says that a SYNC is guaranteed to commit the write buffer to memory.

Whoever is looking at this should also pay attention to the CCA bits in the TLB mapping the registers (Section 2.3.6 of the manual) or the fixed regions (depending on the VA used) to make sure that merging and gathering are turned off.

--
Andrew Dyer <adyer@righthandtech.com>
Sr. Engineer
RightHand Technologies, Inc.
6545 N. Olmsted Ave.
Chicago, IL 60631
(773) 774-7600 x111


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