Date:   Tue, 6 Jul 2021 13:29:53 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Daniel Vetter <daniel.vetter@...ll.ch>
Cc:     Oded Gabbay <oded.gabbay@...il.com>,
        Oded Gabbay <ogabbay@...nel.org>,
        "Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        Christian König <christian.koenig@....com>,
        Gal Pressman <galpress@...zon.com>, sleybo@...zon.com,
        Maling list - DRI developers 
        <dri-devel@...ts.freedesktop.org>,
        linux-rdma <linux-rdma@...r.kernel.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        Doug Ledford <dledford@...hat.com>,
        Dave Airlie <airlied@...il.com>,
        Alex Deucher <alexander.deucher@....com>,
        Leon Romanovsky <leonro@...dia.com>,
        Christoph Hellwig <hch@....de>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        "moderated list:DMA BUFFER SHARING FRAMEWORK" 
        <linaro-mm-sig@...ts.linaro.org>
Subject: Re: [PATCH v4 0/2] Add p2p via dmabuf to habanalabs

On Tue, Jul 06, 2021 at 05:49:01PM +0200, Daniel Vetter wrote:

> The other thing to keep in mind is that one of these drivers supports
> 25 years of product generations, and the other one doesn't. 

Sure, but that is the point, isn't it? To have an actually useful
thing you need all of this mess

> > My argument is that an in-tree open kernel driver is a big help to
> > reverse engineering an open userspace. Having the vendors
> > collaboration to build that monstrous thing can only help the end goal
> > of an end to end open stack.
> 
> Not sure where this got lost, but we're totally fine with vendors
> using the upstream driver together with their closed stack. And most
> of the drivers we do have in upstream are actually, at least in parts,
> supported by the vendor. E.g. if you'd have looked the drm/arm driver
> you picked is actually 100% written by ARM engineers. So kinda
> unfitting example.

So the argument with Habana really boils down to how much do they need
to show in the open source space to get a kernel driver? You want to
see the ISA or compiler at least?

That at least doesn't seem "extreme" to me.

> > For instance a vendor with an in-tree driver has a strong incentive to
> > sort out their FW licensing issues so it can be redistributed.
> 
> Nvidia has been claiming to try and sort out the FW problem for years.
> They even managed to release a few things, but I think the last one is
> 2-3 years late now. Partially the reason is that there don't have a
> stable api between the firmware and driver, it's all internal from the
> same source tree, and they don't really want to change that.

Right, companies have no incentive to work in a sane way if they have
their own parallel world. I think drawing them part by part into the
standard open workflows and expectations is actually helpful to
everyone.

> > > I don't think the facts on the ground support your claim here, aside
> > > from the practical problem that nvidia is unwilling to even create an
> > > open driver to begin with. So there isn't anything to merge.
> >
> > The internet tells me there is nvgpu, it doesn't seem to have helped.
> 
> Not sure which one you mean, but every once in a while they open up a
> few headers, or a few programming specs, or a small driver somewhere
> for a very specific thing, and then it dies again or gets obfuscated
> for the next platform, or just never updated. I've never seen anything
> that comes remotely to something complete, aside from tegra socs,
> which are fully supported in upstream afaik.

I understand nvgpu is the tegra driver that people actualy
use. nouveau may have good tegra support but is it used in any actual
commercial product?

Jason

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