linux-kernel - Re: [PATCH] drm/etnaviv: Create an accel device node if compute-only

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Date: Fri, 28 Jun 2024 10:54:20 +0100
From: Daniel Stone <daniel@...ishbar.org>
To: Tomeu Vizoso <tomeu@...euvizoso.net>
Cc: Lucas Stach <l.stach@...gutronix.de>, linux-kernel@...r.kernel.org, 
	Oded Gabbay <ogabbay@...nel.org>, Russell King <linux+etnaviv@...linux.org.uk>, 
	Christian Gmeiner <christian.gmeiner@...il.com>, David Airlie <airlied@...il.com>, 
	etnaviv@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org, 
	Daniel Stone <daniels@...labora.com>, Daniel Vetter <daniel@...ll.ch>
Subject: Re: [PATCH] drm/etnaviv: Create an accel device node if compute-only

Hi,

On Fri, 28 Jun 2024 at 10:43, Tomeu Vizoso <tomeu@...euvizoso.net> wrote:
> On Wed, Jun 26, 2024 at 9:26 PM Daniel Stone <daniel@...ishbar.org> wrote:
> > It's not just etnaviv, it's literally every Mesa driver which works
> > with decoupled render/display. So that would be etnaviv-v2,
> > panfrost-v2, panthor-v2, v3d-v2, powervr-v2, ... albeit those don't
> > tend to have multiple instances.
>
> TBH, I think VeriSilicon is the only IP vendor that has recycled a
> render-only IP into a compute-only IP.
>
> That is why I liked the approach of conditionally creating an accel
> node, as it neatly reflects that reality.
>
> > Anyway, I'm still leaning towards the answer being: this is not an
> > etnaviv regression caused by NPU, it's a longstanding generic Mesa
> > issue for which the answer is to fix the known fragility.
>
> My understanding of the consensus so far is that Mesa should be fixed
> so that Gallium drivers can fail at screen init if the device doesn't
> support some new usage flags that we would be adding.
>
> If for some reason that doesn't work, we would be looking at having
> etnaviv use a different kind of driver name, such as etnaviv-npu or
> etnaviv-compute.
>
> Did I get it right?

Yep, wfm. :)

Cheers,
Daniel