AMDGPU VCE 1: some info needed

[Alexandre Demers]

Hi there,

Some of you may remember I was working on porting VCE 1 from Radeon to
AMDGPU a few years ago... about 3 and a half years. I hadn't had time
to work on it until last Holidays. But why do I persist in this work?
Because GCN 1st gen was still used in some GPU produced 4 years ago
(Radeon 520 and just before R5 and R7 in the entry level).

I'm pretty happy with where the code is sitting now, however I have
some questions.

1- should the firmware be validated like it was under Radeon and as it
is done for the newly ported UVD 3.1 code? This would mean having to
work with keyselect, isn't it?

2- last time I worked on VCE 1.0, Christian was saying that it was
possible a new VCE firmware could be provided for AMDGPU. Then, it
wasn't that clear, GCN 1.0 (SI) being in trouble and it was considered
to strip it from AMDGPU. And a few months ago, UVD and DC were added
for SI to AMDGPU and a new UVD firmware was released (yeah!). So, is
it possible to have a new VCE firmware? I produced an "updated" tahiti
VCE file where a header is added (script available on my account on
GitHub). Still, if this can be useful, I'd prefer an official
firmware.

3- is there any documentation about VCE 1.0 that would help me
complete this work?
3.1- Some variables that were previously defined are not available
under sid.c, vce_v1_0_d.h, vce_v1_0_sh_mask.h and others. Since the
new values (mostly in the range of 0x8xxx) are completely different
from the ones defined under Radeon (in the range of 0x2xxxx), I'd like
to be sure to use the good ones. I would assume the masks and shifts
are still valid though.

3.2- Some statuses are undefined, sometimes magic values appear here
and there without being ever defined or documented (status 0x337f
anyone?), even under CIK or they don't seem to be easily portable from
other VCE versions. Having a name for a value is really helpful
without an official documentation, when the code is supposed to be
self-documented. I've been able to identify some of them by looking at
variables used under Radeon or under AMDGPU's UVD 3.1. Interestingly,
some variables were previously defined under Radeon, but were left
aside in AMDGPU...

3.3- Being able to know how to properly set/reset which part, in what
order, etc.

4- Any input about 40 bit address limitation on VCE 1.0 and how to
handle it if it applies?

5- Any chance to have some code reviewed even if it still doesn't work
if I send it on this list?

6- I have some patches on the side to help document the code and
define variables (even for Radeon), a few typos fixed, etc. Should I
send them on this list?

Cheers

Alexandre Demers