Using IDMA1 ( or IDMA2 ) on 860

Dan Malek dan at
Mon Aug 20 06:41:38 EST 2001

John Francis wrote:

> May be I should have been more specific, yes I have
> setup the PC15 pin to have correct direction.

Well, your description indicated you were expecting the
transition of DREQ to generate an interrupt.  This isn't
the case.  Have you connected a logic analyzer to the bus
and determined the DMA is working correctly?

> /* version2 of GetChipAddress this WORKS why? */

Because you can't directly access physical bus addresses from
the kernel.  They have to be mapped to some virtual address.
The IMMR is mapped to a well known address that can generally
be used anywhere in the kernel.  Anything else must be mapped,
as your example shows.  Just make sure you do this _once_,
don't keep calling ioremap() over and over or you will exhaust
the VM space and get a different address every time.

	-- Dan

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