[Libre-soc-dev] HDMI, DVI, DisplayPort on SBC (like Raspberry Pi) and on BMC

[Jacob Lifshay]

We should seriously consider using DisplayPort instead of HDMI, it supports
nearly all the same features, can be implemented without requiring
closed-source firmware since HDCP is optional, and supports higher
resolutions and other more modern stuff than DVI.

HDMI:
* extra cost for patent licensing
* requires closed-source firmware for HDCP
* supports >4K, high refresh rate, variable refresh rate (important for
power-saving and games), high bit-depth (HDR and better color gamut than
sRGB).
* supports audio output
* backward compatible with DVI (can be adapted to DVI-D using wires-only
cheap adaptor)
* the modern standard for TVs

DVI:
* simple/cheap
* patent licensing is free
* max resolution is 1920x1200 at 60Hz, 1080p60 is supported
* no audio
* no variable refresh rate (though we might be able to get it to work by
breaking the spec).
* no high bit-depth
* forward compatible with HDMI (can run over same HDMI physical connector,
you can get wires-only cheap (~$5) adaptors to physical DVI-D connector for
old monitors).

DisplayPort:
* HDCP optional
* patent licensing is free
* supports >4K, high refresh rate, variable refresh rate (important for
power-saving and games), high bit-depth (HDR and better color gamut than
sRGB).
* supports audio output
* works over USB type-C
* the modern standard for computer monitors


So, I think we should have 1 DisplayPort output (perhaps shared with USB
type-C) if we're licensing someone elses design, as well as 1 DVI-D over a
HDMI connector for physical compatibility with TVs that only support HDMI
and older monitors that only support DVI.

Jacob