Small vc4 kms fixes and some questions.

[Mario Kleiner]

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?

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.

What worked in the end was using Adafruits kernel-o-matic to build
the 4.4.8 kernel, using their "automated building a kernel for dummies"
method. Their 4.8 kernel however locked up after boot as soon as kms
started.

thanks,
-mario