Re: IDE DMA on AXP & barriers

[Ivan Kokshaysky]

On Thu, Dec 06, 2001 at 06:13:15AM +0100, Kurt Garloff wrote:
> I would imagine that the following barriers are nacessary:
> * After setting up the IDE DMA tables (PRD) and having the data there,
>   we need to have a barrier before telling the controller to do DMA.

Actually, we have more than one - the memory barriers are hidden in outX()
macros.

> * After the controller is done with it, we need to make sure the
>   data is in mem before we use it (i.e. we need some mb() equiv on the
>   controller)

Sure, otherwise the controller just wouldn't work, and not only on alpha.
I never had any problems with IDE DMA on lx164 (which has exactly the same
IDE chip), but it was back in 2.3 or 2.4-test times...
Maybe something got broken since then - I could check this (if I find
a spare IDE drive).

Ivan.