Subject: Re: BUS_DMA_CONTROLDATA flag for bus_dma(9)
To: None <cgd@broadcom.com>
From: Richard Earnshaw <rearnsha@buzzard.freeserve.co.uk>
List: tech-kern
Date: 08/15/2003 23:36:59 
> Actually, BUS_DMA_COHERENT involves memory as seen by CPU and devices.
> 
> With BUS_DMA_COHERENT, devices and the CPU must have a coherent view
> of memory.

Which implies that coherrency is impossible if bounce buffers are needed.

R.