[Tinkerphones] Librem 5

Paul Boddie paul at boddie.org.uk
Sat Oct 28 15:45:47 CEST 2017


On Saturday 28. October 2017 14.14.26 rhn wrote:
> On Sat, 28 Oct 2017 13:33:17 +0200 "H. Nikolaus Schaller"
> <hns at goldelico.com> wrote:
> > 
> > But I just found this morning:
> > 	https://community.imgtec.com/developers/powervr/documentation/
> > 
> > This looks to be very important (dated 07 Apr 2017):
> > 	http://cdn.imgtec.com/sdk-documentation/PowerVR+Instruction+Set+Referenc
> > 	e.pdf
> > 
> > I haven't spent time to look through the other material, but it looks as
> > if IMG has become much more open!

I think expectations are so low with Imagination Technologies and openness of 
PowerVR that any new public documentation (if it is new) could easily pass by 
unnoticed. I wonder if policies will change under their new ownership (subject 
to approval of the acquisition).

> > Maybe this material is already sufficient to write an open source
> > firmware for the PVR and assembler/compiler for shaders but this is
> > something for 3D/GPU experts (you know I am hardware expert and still
> > struggle with Linux kernels :).
> 
> this is a nice find! Quite a few documents there indeed.
> 
> As you have said, shaders got suddenly much easier. Still, there's a long
> way to go from there, as shader ISA is only part of the equation. I had
> just a skim, but I couldn't immediately find the two other important
> pieces: communication protocol and, if it's relevant for this GPU,
> initialization and power features.

I also saw this:

"Refer to the main PowerVR ISR document (NDA required) for precise information 
regarding feature availability."

I don't see any opcode or instruction format details, so perhaps this is also 
an obstacle.

[...]

> Depending on the level of control that firmware has on PVR, replacing it
> may be necessary. With new NVIDIA cards, nouveau is stuck with power
> issues: clock speeds can only be altered by signed firmware they have no
> access to. I haven't seen anything about firmware among the PVR docs.

This kind of thing was already worrying me, and now you have confirmed that it 
is actually done, which is very troubling indeed.

Paul



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