Re: Doing DMA from peripheral to userland memory

["François Legal" <devel@thom.fr.eu.org>]

Le Vendredi, Août 27, 2021 15:01 CEST, Philippe Gerum <rpm@xenomai.org> a écrit:

>
> François Legal via Xenomai <xenomai@xenomai.org> writes:
>
> > Hello,
> >
> > working on a zynq7000 target (arm cortex a9), we have a peripheral that generates loads of data (many kbytes per ms).
> >
> > We would like to move that data, directly from the peripheral memory (the OCM of the SoC) directly to our RT application user memory using DMA.
> >
> > For one part of the data, we would like the DMA to de interlace that data while moving it. We figured out, the PL330 peripheral on the SoC should be able to do it, however, we would like, as much as possible, to retain the use of one or two channels of the PL330 to plain linux non RT use (via dmaengine).
> >
> > My first attempt would be to enhance the dmaengine API to add RT API, then implement the RT API calls in the PL330 driver.
> >
> > What do you think of this approach, and is it achievable at all (DMA directly to user land memory and/or having DMA channels exploited by xenomai and other by linux) ?
> >
> > Thanks in advance
> >
> > François
>
> As a starting point, you may want to have a look at this document:
> https://evlproject.org/core/oob-drivers/dma/
>
> This is part of the EVL core documentation, but this is actually a
> Dovetail feature.
>

Well, that's quite what I want to do, so this is very good news that it is already available in the future. However, I need it through the ipipe right now, but I guess the process stays the same (through patching the dmaengine API and the DMA engine driver).

I would guess the modifications to the DMA engine driver would be then easily ported to dovetail ?

François

> --
> Philippe.