Pine64+ HDMI output note

[Milan Obuch]

On Tue, 25 Jun 2019 08:32:49 +0200
Emmanuel Vadot <manu at bidouilliste.com> wrote:

> On Sun, 16 Jun 2019 09:34:39 +0200
> Milan Obuch <freebsd-arm at dino.sk> wrote:

[ snip ]

> > which makes me think, together with presence of getty processes
> > attached to /dev/ttyvN devices, that all what's missing is just
> > physical video output signal, and this is most probably caused by
> > output buffer being shut down. So I googled a bit and found a hint,
> > tried it - I put line
> > 
> > hw.regulator.disable_unused=0
> > 
> > into /boot/loader.conf file and it works. I think it just uses HDMI
> > output engine configured by u-boot instead of configuring it
> > itself, as we have no driver for hdmi and hdmi-phy devices on A64
> > SoCs.  
> 
>  With this you are using efifb.
>  The reason for the tunable is that since there is no node in the dtb
> related to efifb the kernel will shutdown every regulator that isn't
> referenced, this is 1) to save power 2) to do the same thing as the
> Linux kernel as at one point I commited some bad DTS into Linux where
> almost every regulator got shutdown after a while.
>

Thanks for explanation.

> > Maybe this is just as simple as adding appropriate compatible string
> > into arm/allwinner/a10_hdmi.c file, but I do not know if A20 and A64
> > cores are compatible in this area... and workaround found is just OK
> > for me.  
> 
>  No, A64 uses the version 2 of the Allwinner display engine, I have a
> DRM driver working for it (but still have some work to do on it).
> https://github.com/evadot/freebsd/tree/drm_aw_de2
>

OK. Maybe I'll try it, but I have no immediate need for it... good to
know I can expect it in some future, far or near :)

> > Next step would be to try X on Pine64+... Any hint on this? I am
> > going to try scfb video driver for this, as noted on
> > FreeBSD/arm/Allwinner wiki page. As for this wiki page - maybe it
> > could be updated in 'supported devices' table, in column A64 - I
> > think framebuffer works and HDMI video too, kind of, leaving it in
> > pre-initialised state with above mentioned workaround.  
> 
>  SCFB driver will work correctly with efifb.
> 

Confirmed. I checked it on my Pine64-LTS acquired recently as well. Now
I am trying various ports/applications on it when time permits...

Regards,
Milan