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

Arnd Bergmann
2013-01-30T10:08:30Z

On Wednesday 30 January 2013, Viresh Kumar wrote:
> On Wed, Jan 30, 2013 at 3:11 PM, Arnd Bergmann <arnd@arndb.de> wrote:
> > On Wednesday 30 January 2013, Viresh Kumar wrote:
> >> I knew you will come to this :)
> >> So, the hardware is like: there are 16 request line slots per master, a
> >> platform can choose to connect same or separate devices to these.
> >>
> >> So, these are really 16 per master.
> >
> > Ok, I see. Do you know how these are numbered in the data sheet?
> >
> > If the convention is to have subsequent numbers for these in the
> > hardware description, we should probably just have that single
> > request number in the binding, too, and calculate the master number
> > from that. If it lists pairs of request/master number, we should
> > use pairs in the binding as well, in the same order.
>
> Actually what would be better to have is:
> - have this range from 0-15 only
> - together with the master we want to use for peripheral
>
> this should be enough.

Ok.

> Datasheet of dw_dmac doesn't tell much about it.. just four bits for programming
> it and so values are from 0-15 :)

I meant the spear13xx data sheet, which has to list the request lines
for its integrated components. There may be other SoCs using the
same dw_dmac, but this is the main one that is upstream now, and it's
probably as good as any other one. I just wouldn't want to establish
a binding that doesn't match any of the known implementations in the
way it expresses request lines.

Arnd