Re: [PATCH v3 2/2] DMAEngine: Add DMAEngine driver based on old MSMDMA APIs

From: David Brown
Date: Tue Mar 13 2012 - 15:34:37 EST


On Tue, Mar 13, 2012 at 04:27:37PM +0530, Shantanu Gupta wrote:

> Any info available(publicly) on so as to what all chipsets have this capability
> ?

The ADM hardware is in every currently available MSM that can run
Linux. It is being phased out, to be replaced by a new DMA system
(SPS/BAM). Fortunately, there are some chips (MSM8960) that have both
ADM and SPS/BAM so there should be time to get those drivers in.

At least as my memory serves me:

7201 - ADM
8250 - ADM
8660 - 2 ADMs, SPS/BAM
8960 - 1 ADM, SPS/BAM

The ADM is mostly a regular DMA-type device. Each channel can be
associated with a rate-control channel, which is needed for some
devices. It also has a mode called "box mode", which works kind of
like a self-repeating scatter list. This mode is needed for some of
the peripherals also on the MSM.

David

> On Tue, Mar 13, 2012 at 1:44 AM, Daniel Walker <dwalker@xxxxxxxxxx> wrote:
>
> On Mon, Mar 12, 2012 at 04:02:44PM +0530, Ravi Kumar V wrote:
> > Add DMAEngine based driver using the old MSM DMA APIs internally.
>
> What do you mean by this?
>
> > The benefit of this approach is that not all the drivers
> > have to get converted to DMAEngine APIs simultaneosly while
> > both the drivers can stay enabled in the kernel. The client
> > drivers using the old MSM APIs directly can now convert to
> > DMAEngine one by one.
>
> Which drivers?
>
> Daniel
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