[PATCH v2 2/2] accel: Add Arm Ethos-U NPU driver

[Rob Herring]

On Tue, Aug 12, 2025 at 6:01 AM Thomas Zimmermann <tzimmermann at suse.de> wrote:
>
> Hi
>
> Am 11.08.25 um 23:05 schrieb Rob Herring (Arm):
> > Add a driver for Arm Ethos-U65/U85 NPUs. The Ethos-U NPU has a
> > relatively simple interface with single command stream to describe
> > buffers, operation settings, and network operations. It supports up to 8
> > memory regions (though no h/w bounds on a region). The Ethos NPUs
> > are designed to use an SRAM for scratch memory. Region 2 is reserved
> > for SRAM (like the downstream driver stack and compiler). Userspace
> > doesn't need access to the SRAM.
> >
> > The h/w has no MMU nor external IOMMU and is a DMA engine which can
> > read and write anywhere in memory without h/w bounds checks. The user
> > submitted command streams must be validated against the bounds of the
> > GEM BOs. This is similar to the VC4 design which validates shaders.
> >
> > The job submit is based on the rocket driver for the Rockchip NPU
> > utilizing the GPU scheduler. It is simpler as there's only 1 core rather
> > than 3.
> >
> > Tested on i.MX93 platform (U65) with WIP Mesa Teflon support.
> >
> > Signed-off-by: Rob Herring (Arm) <robh at kernel.org>
>
> I've looked over this patch and it looks good to me. There's a
> dev_info() in ethos_init() of which I think it should become drm_dbg().
> Anyway

I prefer to print out what h/w we've discovered. That's a fairly
common pattern for drivers (and more useful than announcing drivers
that only loaded).

> Acked-by: Thomas Zimmermann <tzimmermann at suse.de>

Thanks!

> Side note: I noticed that there's buffer-allocation code here that
> reinvents dumb buffers. We've ocationally talked about creating a better
> dumb-buffers ioctl interface and this drivers could be another use case.

Yeah. In the past I got told don't use dumb buffers APIs for anything
but dumb scanout buffers. I guess with enough copies opinions
change...

Rob