Imagination Releases Full ISA Documentation For PowerVR Rogue GPUs

[alexvoica]

Developer feedback.

Suggested reading from well-known developers that perhaps addresses some of your comments:

http://www.joshbarczak.com/blog/?p=467

https://twitter.com/aras_p/status/524206976293945344

https://twitter.com/TimothyLottes/status/524257668832432128

Regards,
Alex.

[caligula]

PowerVR hardware can be still considered a cancer. Don't buy from them. Boycott their products until they become as open as Intel.

[chithanh]

PowerVR hardware can be still considered a cancer. Don't buy from them. Boycott their products until they become as open as Intel.

That statement is quite ironic given that Intel uses PowerVR graphics in some of their Atom chips, especially in the mobile ones.

[caligula]

That statement is quite ironic given that Intel uses PowerVR graphics in some of their Atom chips, especially in the mobile ones.

I knew that, but I didn't mean the policy they have with chipsets using 3rd party GPUs. The HD graphics also has closed source firmware, but it's much much better for free use than any other commercial GPU stack. AFAIK Intel also provides HD graphics for some mobile products, but PowerVR for some lower end stuff.

[robclark]

That statement is quite ironic given that Intel uses PowerVR graphics in some of their Atom chips, especially in the mobile ones.

which, at least for linux support, intel would rather pretend didn't exist ;-)

[Philip]

Since pvr does so much in the shader (including the micro-kernel / firmware, which is a big part of what makes it's architecture such a convoluted mess), it is actually a pretty useful step. *Assuming* it doesn't require a click through agreement that would prevent r/e or working on an open src driver (and I have heard this is not the case).

The newly released documentation is only for PVR Series6, not for Series5 (which still requires an NDA), and apparently Series6 was a significant redesign of the shader ISA. Series5 does run the microkernel on its shader engines (with the microkernel being written directly as shader assembly, which sounds like great fun), but Series6 has a separate microcontroller for that (source) which is still undocumented. So the documentation won't help with understanding the microkernel on either generation.

And as far as I can tell from having installed the SDK, the ISA documentation is basically just a list of the assembly syntax and a description of each instruction - it doesn't even describe the instruction encoding. (The SDK does include Series6/6XT shader compiler+disassembler tools though, under a license that doesn't look too restrictive on use, which I guess would be helpful when reverse engineering.)

[chithanh]

That Intel uses 3rd party IP in their products does not absolve them from providing proper drivers or documentation.

AFAIK Intel also provides HD graphics for some mobile products, but PowerVR for some lower end stuff.

The current SoCs for mobile (Merrifield/Moorefield) use PowerVR Series 6 graphics.

Unless of course you count tablets and notebooks as mobile devices, but that is not the industry consensus.

[robclark]

The newly released documentation is only for PVR Series6, not for Series5 (which still requires an NDA), and apparently Series6 was a significant redesign of the shader ISA. Series5 does run the microkernel on its shader engines (with the microkernel being written directly as shader assembly, which sounds like great fun), but Series6 has a separate microcontroller for that (source) which is still undocumented. So the documentation won't help with understanding the microkernel on either generation.

ahh, I did not realize that.. all my experience w/ pvr was sgx, not rgx..

[robclark]

That Intel uses 3rd party IP in their products does not absolve them from providing proper drivers or documentation.

Except intel does not have the rights to release docs about the IMG cores. Which is probably why all the intel OSTC folks would rather pretend that these parts didn't exist ;-)

[Philip]

Series6 has a separate microcontroller for [the microkernel] (source) which is still undocumented

(Hmm, I was annoyed yesterday at not knowing exactly what kind of microcontroller, but found out now that it's a META (source; and there's ton of META references in the rgx kernel driver (e.g. in the kernel for Kindle Fire HD 6/7 (based on MT8135))). But I don't see any detailed public documentation of META, so it's yet another black box to reverse-engineer.)