[PATCH v3 00/17] Imagination Technologies PowerVR DRM driver

[Frank Binns]

Hi Linus,

On Fri, 2023-06-16 at 14:29 +0200, Linus Walleij wrote:
> Hi Sarah,
> 
> thanks for starting this long awaited work!
> 
> On Tue, Jun 13, 2023 at 5:20 PM Sarah Walker <sarah.walker at imgtec.com> wrote:
> 
> > This patch series adds the initial DRM driver for Imagination Technologies PowerVR
> > GPUs, starting with those based on our Rogue architecture. It's worth pointing
> > out that this is a new driver, written from the ground up, rather than a
> > refactored version of our existing downstream driver (pvrsrvkm).
> 
> This seems to be a fairly good starting point, a bit of trade-off
> between latest-and-greatest
> and recent enough devices that need aftermarket support.
> 
> I assume you are aware of the community existing around Series 5
> (should be the immediate
> predecessor to Rogue?):
> https://github.com/openpvrsgx-devgroup/linux_openpvrsgx

Actually we were unaware of this community, so thank you for pointing it out.

> 
> I don't know how active those people are these days, but I can see that a branch
> was updated for v6.4-rc3 just three weeks ago.
> https://github.com/openpvrsgx-devgroup/linux_openpvrsgx/tree/pvrsrvkm-6.4-rc3
> 
> I think it would be good for community building to make sure that you get these
> people involved in reviewing, especially neutral stuff like device tree bindings
> but also to make sure no architectural choices are done that will make it hard
> to retrofit a proper driver for the older engines if this community
> decide to work
> on it.

On the face of it, I'd imagine that it will make more sense for SGX to have its
own driver, just because it's different enough to require a different
design. For example, Series6 onwards uses a completely different firmware to
SGX/Series5. Another possible approach might be to share code between this
driver and a future SGX driver by extracting code out into a library. Of course,
we won't know what code to extract, if any, until someone starts working on
upstream SGX support.

> 
> Specifically I would ask that the DT bindings include all old and new PowerVR
> hardware in one go, unless they have very specific hardware definition needs,
> which I doubt.

I'll comment about this on the other thread.

> 
> Also I think they could use your help to get the proper firmware for the older
> hardware licensed properly from Imagination and included into linux-firmware
> so they do not need to ship files on the side.

Sure, we can do this. I've already got approval for the existing SGX firmware to
use the same license as the Rogue firmware, which can be found here:
https://gitlab.freedesktop.org/frankbinns/linux-firmware/-/blob/powervr/LICENSE.powervr

I'll speak to Nikolaus about next steps.

Thanks
Frank

> 
> Yours,
> Linus Walleij