[PATCH 1/5] dmaengine: dw_dmac: move to generic DMA binding

Viresh Kumar
2013-01-29T15:17:13Z

On 29 January 2013 19:01, Arnd Bergmann <arnd@arndb.de> wrote:
> Ah, good. So I guess the "dma-requests" property should actually
> be "16" then.

yes, even i was checking on that separately :)

> Does this mean that an implicit zero request line means memory?

No. 0 is also request line for a peripheral and numbers are from 0 to 15.
memcpy are identified by setting type of transfer as memcpy.

> Could we have device-to-device DMAs with this controller, and if
> we can, should we have both 'src' and 'dst' fields? Are the
> two number ranges sharing the same address space, i.e. is
> request '7' as the destination guaranteed to be the same device
> as request '7' in the source?

Request lines are per master... So, for a master single request line
is independent of direction. Many DMA controllers have capability of
doing dev-to-dev transfers but DMAENGINE doesn't have any support
for it, even we don't have a usecase too :)

> If we need two lines, we could interleave them with the bus
> master numbers:

not required.

> In theory, we could use bit-stuffing to put them all into
> a single 32 bit word I guess, but generally people don't
> seem to like that for new bindings.

:)

--
viresh