[RFC] Inter-processor Mailboxes Drivers

[Hiroshi DOYU]

From: Hiroshi DOYU <Hiroshi.DOYU at nokia.com>
Subject: Re: [RFC] Inter-processor Mailboxes Drivers
Date: Mon, 14 Feb 2011 10:55:53 +0200 (EET)

> From: ext Linus Walleij <linus.walleij at linaro.org>
> Subject: Re: [RFC] Inter-processor Mailboxes Drivers
> Date: Mon, 14 Feb 2011 09:39:32 +0100
> 
>> On Mon, Feb 14, 2011 at 8:32 AM, Hiroshi DOYU <Hiroshi.DOYU at nokia.com> wrote:
>> 
>>> OMAP mailbox is the interrupt driven 32bit unit H/W FIFO to other
>>> cores.
>> 
>> How is it used? Is it a low-traffic (like single 32bit words etc) signal
>> control-path link while the actual high-throughput data-path is done
>> with shared memory? (That is how the db5500 mbox works anyways.)
> 
> Yes, maybe quite similar.
> 
> maibox is not single 32 bit but is 32 bit x 4(or 8?) slots fifo, IIRC,
> and mainly it is used as notification between cores. And big amount of
> data is transftered with sahred memory, which has been mapped onto the
> virtual address space of the other side of core, in advance.
> 
> For example, typical usage of DSP, mp3 decoding,
> 
> 1, ARM maps 2 shared memory area(input/output) onto DSP virtual
>    address space.
> 2, ARM fills mp3 data in input buffer.
> 3, ARM notifies DSP that data is ready in input buffer.
> 4, DSP decodes input data and put output data on output buffer.
> 5, DSP notifies that output buffer is ready.
> 
> Roughly something like the above. DSP S/W is multi-tasking, though.

Here, ARM side process talks to DSP site process in their own way, and
also there are another cores, talking with their own protocols. So I
think that at least, protocol part should be pluggable anyway although
it doesn't have to be always in userland.