[Arm-netbook] moved to taiwan, started passthrough card

[Luke Kenneth Casson Leighton]

ok so much of this is in the upcoming update, we made a snap decision
to go to taiwan because of the 30 limit on the china dual-entry visas.
i'm staying with a friend who has a stack of equipment including IR
oven, small pick-and-place machine, scope etc. so it's a much easier
arrangement, i'm helping him out as well.

the rk3288 board is going to first prototyping, we're getting
quotations from PCB manufacturers. that leaves me free to move to the
next PCB design, and i picked the passthrough card... which turns out
to be much more complicated than i was expecting. i _could_ do a
simple version (just a TFP401a) but it would have to have 2 USB ports
and a break-out arrangement for the remaining pins.... i decided
instead to wire them all to a STM32F072.

now, the idea here is to pre-load a userspace USB-based DFU bootloader
into the NAND flash, and to require firmware to be uploaded after it
reports the contents of the EOMA68 EEPROM ID. the TFP401a's I2C will
be connected to the STM32F072, it can emulate an EEPROM and can load
EDID data which tells the TFP401a what the LCD's resolution is.

normally the LCD resolution would be fixed... but here it is not
possible to know what the LCD resolution is going to be.... also we
have no idea in advance what the various functions are of the EOMA68
pins: maybe the SD/MMC pins are used for an SD card (in which case the
STM32F072 can be programmed to be a USB mass-storage device), but
maybe they are used as GPIO, or maybe they are used for a WIFI SIP
module: we just don't know. hence the need to be flexible and for
firmware to be uploaded on a per-boot basis.

i would _like_ to use a more powerful EC but i haven't the time to
learn a new EC... so the STM32F072 it is.

l.

---
crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68

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[FaTony]

Hi. I have a CRT monitor from 2002 and it is my only monitor. Are these
monitors supported by EOMA68-A20?

If you remember CRT monitors, they physically update the screen and 60
hz refresh rate is extremely harmful to the eyes because you see
flicker. My monitor runs at 85hz refresh rate. The problem is that most
today's monitors are pretty much hardcoded to 60 hz and it's not easy to
change it.

I connect 2 desktops to this monitor. 1st one has GeForce 4 Ti GPU
(2005) and 2nd one has Radeon HD 5850 (2011). Both computers report that
there's no EDID. However, GeForce card correctly finds the maximum
resolution (***@60hz) and uses it in GRUB, Radeon uses ***@60hz.

I was able to make a script that sets my preferred resolution
(***@85hz):

xrandr --newmode "1024x768_85.00" 94.50 1024 1096 1200 1376 768 771
775 809 -hsync +vsync
xrandr --verbose --addmode DVI-1 "1024x768_85.00"
xrandr --output DVI-1 --mode "1024x768_85.00"

However, it only works with Geforce and the only way to make it work
with Radeon is to install proprietary firmware and free driver.
Proprietary driver or no firmware don't work.

I wonder, does EOMA68-A20 support these commands, especially without
proprietary firmware for it's Mali GPU?

[Luke Kenneth Casson Leighton]

---
crowd-funded eco-conscious hardware: https://www.crowdsupply.com/eoma68

Post by FaTony
I wonder, does EOMA68-A20 support these commands, especially without
proprietary firmware for it's Mali GPU?

for its MALI GPU, not "for it is MALI GPU".

basically: i don't know, but it's easy for you to find out. it's an
A20 processor. if you can find the answer on the general internet
about any device with an A20 processor, then that's the answer.
there's nothing special about the EOMA68-A20 Card's A20 processor, nor
anything else additional, specific or restrictive or different in any
way compared to any other device using the A20.

so, you could ask on the linux-sunxi forums for example.

l.

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[Stefan Monnier]

Post by FaTony
I wonder, does EOMA68-A20 support these commands, especially without
proprietary firmware for it's Mali GPU?

This has nothing to do with MALI: a GPU is a (co)processor which lets
you do computations often useful for graphics (but nowadays also used
for other things), so it is usually wired such that it can write
directly onto the framebuffer memory.

But the GPU itself sees the framebuffer as some chunk of memory, writes
to it, and that's it. It has nothing to do with bringing this chunk of
memory to an LCD or some other display, which is instead done by some
other circuitry (called the "display engine" (DE) on the A20).
The same goes for the video-decode accelerator (aka VPU), which
is usually also a completely independent piece of hardware, BTW, which
also just writes to the framebuffer.

In the x86 world, since the graphics cards include both the GPU, the
VPU, and the "display engine", those notions are usually conflated,
but technically, they are independent, and in the ARM world they tend to
be clearly separate.

So, the question in your case is if the DE can handle your timings and
if the `xrandr` thingy will be able to properly configure the hardware.
AFAIK the A20's hardware should have no trouble with a 1600x1200x85Hz
timing, so the question is more on the software side.

For the "vanilla" kernels, I know there's some "sunxi-drm" module
available (tho AFAIK it still hasn't been merged into Linus's tree), so
some of the infrastructure is available but you still need an Xorg server
on top (presumably the `modesetting` driver might do the trick).


Stefan


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[Luke Kenneth Casson Leighton]

http://rhombus-tech.net/community_ideas/passthrough_card/

quick update of the passthrough card page, revision 0.10 layout is
almost done and will be sent off for PCB (4 layer) manufacturing soon.

l.

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