Subject: Re: bus_dmamap_sync not enough ?
To: Stephan Uphoff <>
From: Jason R Thorpe <>
List: tech-kern
Date: 02/10/2003 22:59:31
On Tue, Feb 11, 2003 at 12:54:03AM -0500, Stephan Uphoff wrote:

 > bus_dmamap_sync not enough for some devices ?

bus_dmamap_sync is supposed to also provide any necessary memory barriers.
From the bus_dma(9) manual page:

	On platforms which implement reordered stores, bus_dmamap_sync()
	will always cause the store buffer to be flushed.

The wording might not be the best, there, but I think the intent is clear
(particularly because of the use of the word "reordered").

        -- Jason R. Thorpe <>