[dpdk-dev] RFC: Kunpeng DMA driver API design decision

[Fengchengwen]

OK, I will send one, thanks


From:Jerin Jacob <jerinjacobk at gmail.com>
To:Thomas Monjalon <thomas at monjalon.net>
Cc:Fengchengwen <fengchengwen at huawei.com>;Ferruh Yigit <ferruh.yigit at intel.com>;dev <dev at dpdk.org>;Nipun Gupta <nipun.gupta at nxp.com>;Hemant Agrawal <hemant.agrawal at nxp.com>;Richardson, Bruce <bruce.richardson at intel.com>;Maxime Coquelin <maxime.coquelin at redhat.com>;Honnappa Nagarahalli <honnappa.nagarahalli at arm.com>;Jerin Jacob <jerinj at marvell.com>;David Marchand <david.marchand at redhat.com>
Date:2021-06-12 16:41:32
Subject:Re: [dpdk-dev] RFC: Kunpeng DMA driver API design decision

On Sat, Jun 12, 2021 at 2:01 PM Thomas Monjalon < thomas at monjalon.net<mailto:thomas at monjalon.net>> wrote:
>
> 12/06/2021 09:01, fengchengwen:
> > Hi all,
> >
> > We prepare support Kunpeng DMA engine under rawdev framework, and observed that
> > there are two different implementations of the data plane API:
> > 1. rte_rawdev_enqueue/dequeue_buffers which was implemented by dpaa2_qdma and
> >    octeontx2_dma driver.
> > 2. rte_ioat_enqueue_xxx/rte_ioat_completed_ops which was implemented by ioat
> >    driver.
> >
> > Due to following consideration (mainly performance), we plan to implement API
> > like ioat (not the same, have some differences) in data plane:
> > 1. The rte_rawdev_enqueue_buffers use opaque buffer reference which is vendor's
> >    specific, so it needs first to translate application parameters to opaque
> >    pointer, and then driver writes the opaque data onto hardware, this may lead
> >    to performance problem.
> > 2. rte_rawdev_xxx doesn't provide memory barrier API which may need to extend
> >    by opaque data (e.g. add flag to every request), this may introduce some
> >    complexity.
> >
> > Also the example/ioat was used to compare DMA and CPU-memcopy performance,
> > Could we generalized it so that it supports multiple-vendor ?
> >
> > I don't know if the community accepts this kind of implementation, so if you
> > have any comments, please provide feedback.
>
> I would love having a common generic API.
> I would prefer having drivers under drivers/dma/ directory,
> rather than rawdev.

+1 for rte_dmadev.

Now that we have multiple DMA drivers, it better to have a common
generic API for API.

@fengchengwen If you would like to pursue generic DMA API the please
propose an RFC for dmadev PUBLIC API before implementing it,
We can help you review the proposal of API.




>
>
>