Subject: Re: kern/19435 and uncached memory
To: TAMURA Kent <>
From: Frank van der Linden <>
List: tech-kern
Date: 01/17/2003 12:33:05
On Wed, Jan 15, 2003 at 11:45:55AM +0900, TAMURA Kent wrote:
> The PR kern/19435 "auich(4) hangs after few hours of playing" is
> caused by a hardware erratum of 440MX.  The erratum is decribed
> in [1] as "AC97 Soft Audio and Soft Modem Master Abort Errata."
> A workaround described in [1] is to disable cache of buffers.
> Do we have a standard way to allocate uncached memory on NetBSD?

If we're talking about DMA buffers, what would be needed is a new
flag to the bus_dma(9) interfaces, BUS_DMA_NOCACHE. It's trivial
to implement on i386, I don't know about other platforms. If
specified as a hint (i.e. a platform may ignore the flag),
it's easy to add.

Overloading _COHERENT to do this would lead to some problems.

- Frank

Frank van der Linden                          
Quality NetBSD Development, Support & Service.