Small vc4 kms fixes and some questions.

[Eric Anholt]

Mario Kleiner <mario.kleiner.de at gmail.com> writes:

> Hi Eric and all,
>
> two small fixes against vc4 kms, built and tested agains the
> Raspberry Pi foundations 4.4.8 kernel tree on RPi2B.
>
> I'm tinkering with a Rpi 2B a bit to see if your vc4 work can
> already make the Pi useful as a device for some serious but low
> cost neuro-science applications.
>
> Eric:
>
> Is there any public documentation about the HVS hardware video scaler
> or the pixel valves? I could find other docs about Videocore's 3d
> part, but nothing about hvs or the pixel valves? Or are the register
> definitions inside the vc4 already all that exists in the hw?

Nope, docs for display never got released.  I've got docs internally,
and I'm happy to try to answer questions.

> Is the drm-next tree supposed to boot and work on the Pi already.
> To me it's a bit confusing against which tree i should actually
> work and test if i play with patches for vc4? drm-next, one of
> your many branches, RPi foundation? So far i was unsuccessful in
> booting kernels i built myself following tutorials. Building worked
> without error or warning, but booting never made it beyond the Pi's
> firmware startup splash.

drm-next won't have the devicetree necessary, but linux-next does.  I've
been doing a lot of my development off of linux-next these days.

I've been using u-boot with all of my upstream kernel development
(netbooting, since swapping SD cards around is awful).  Apparently for
non-uboot there was some weirdness with the firmware where you needed to
do non-standard things to the kernel image to get it to boot, which
u-boot's kernel included, and then u-boot could load a normal linux
kernel.  I think that's been changed in the firmware in the last couple
of weeks, though, so you might not need the weird scripting any more.
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