Re: Guix on Mobile (Was: Interest check: U-Boot bootloader support)

[Danny Milosavljevic <dannym@scratchpost.org>]

Hi,

On Tue, 23 Feb 2016 06:19:27 +1100
Jookia <166291@gmail.com> wrote:

> Basically the bootloader would just be Linux to do some hardware init (touch screen, etc)

Actually, on ARM you usually have to do basic hardware init before Linux runs. 
Linux doesn't do it all. Often, booting Linux without U-Boot doesn't work.

On linux-sunxi, U-Boot initializes some clocks, memory, important regulators, USB, MMC and the framebuffer (I'm sure I forgot some). 

U-Boot started out as just a tiny copy of Linux, but it has diverged a bit since.

There are also weird things like you aren't allowed to turn stuff you need later off (in, say, U-Boot), because once it's off, you can't turn it on again (because it's off, duh) without rebooting. So kexeced Linux can find itself in a world of hurt. 

(There's a special data-passing mechanism between U-Boot and Linux in order to mitigate that problem - but does it work between Linux and kexec-Linux?)

> systems with GRUB and U-Boot as Linux tends to initialize hardware better than
> them (neither U-Boot nor Libreboot like either of the EDID values of my screen!)
> and would probably allow faster bootup given you're not initializing the
> hardware twice.

I also have a screen with wrong EDID. I have a DVI<->HDMI adapter by ATI which contains an EDID chip in order to fake the data in order to get it to work. How insane is that?

That said, on the general interest: guix is already slooow on a fairly modern X200. If that ran on an armv7, it would probably be much slower. Not fun. 

But might be worth a try. Did someone try the non-GuixSD armv7 thing? Is the speed acceptable?