[Nix-dev] Raspberry-Pi NixOS

[Lluís Batlle i Rossell]

On Tue, Jul 19, 2016 at 11:53:59PM +0200, Tomas Hlavaty wrote:
> Lluís Batlle i Rossell <viric at viric.name> writes:
> > The device tree blob should be built by the kernel, like with pi and pi2,
> > isn't it?
> 
> This is the kernel which works for me and is taken from
> raspberry-firmware/boot:
> 
> Linux version 4.4.13-v7+ (dc4 at dc4-XPS13-9333) (gcc version 4.9.3
> (crosstool-NG crosstool-ng-1.22.0-88-g8460611) ) #894 SMP Mon Jun 13
> 13:13:27 BST 2016
> 
> and the corresponding device tree is bcm2710-rpi-3-b.dtb.
> 
> This looks like the same kernel version in
> pkgs/os-specific/linux/kernel/linux-rpi.nix (modDirVersion = "4.4.13";
> tag = "1.20160620-1")
> 
> Are you saying that this is not good enough?
> 
> What works: If I copy files from raspberry-firmware/boot to /boot, rpi3
> starts fine.  These are the files I have in /boot:
> 
> $ ls -al /boot
> -rwxr-xr-x  1 root root   13221 Jun 18 22:31 bcm2708-rpi-b.dtb
> -rwxr-xr-x  1 root root   13484 Jun 18 22:31 bcm2708-rpi-b-plus.dtb
> -rwxr-xr-x  1 root root   13257 Jun 18 22:31 bcm2708-rpi-cm.dtb
> -rwxr-xr-x  1 root root   14567 Jun 18 22:31 bcm2709-rpi-2-b.dtb
> -rwxr-xr-x  1 root root   15237 Jun 18 22:31 bcm2710-rpi-3-b.dtb
> -rwxr-xr-x  1 root root   17932 Jun 18 22:31 bootcode.bin
> -rwxr-xr-x  1 root root     165 Jul 19 22:46 cmdline.txt
> -rwxr-xr-x  1 root root    1369 Jan 11  2016 config.txt
> -rwxr-xr-x  1 root root    2504 Jun 23 20:42 fixup_cd.dat
> -rwxr-xr-x  1 root root    6482 Jun 23 20:42 fixup.dat
> -rwxr-xr-x  1 root root    9717 Jun 23 20:42 fixup_db.dat
> -rwxr-xr-x  1 root root    9717 Jun 23 20:42 fixup_x.dat
> -rwxr-xr-x  1 root root 4224232 Jun 18 22:31 kernel7.img
> drwxr-xr-x  2 root root    8192 Jun 18 22:31 overlays
> -rwxr-xr-x  1 root root  617432 Jun 23 20:42 start_cd.elf
> -rwxr-xr-x  1 root root 4926264 Jun 23 20:42 start_db.elf
> -rwxr-xr-x  1 root root 2746552 Jun 23 20:42 start.elf
> -rwxr-xr-x  1 root root 3877720 Jun 23 20:42 start_x.elf
> 
> I don't see, why raspberrypi/builder.sh creates defaultgeneration,
> initrd and nixos-init files in /boot.  It actually seems to me, that
> initrd should not be there at all for the boot to work.
> 
> raspberrypi/builder.sh doesn't create fixup_x.dat, which is in the list
> above; but I haven't tried booting without it.
> 
> Although pkgs/os-specific/linux/kernel/linux-rpi.nix copies DTB files,
> it renames them to something that looks wrong and also it does not copy
> them to /boot at all:
> 
>     # I am not sure if all of these are correct...
>     copyDTB bcm2708-rpi-b.dtb bcm2835-rpi-a.dtb
>     copyDTB bcm2708-rpi-b.dtb bcm2835-rpi-b.dtb
>     copyDTB bcm2708-rpi-b.dtb bcm2835-rpi-b-rev2.dtb
>     copyDTB bcm2708-rpi-b-plus.dtb bcm2835-rpi-a-plus.dtb
>     copyDTB bcm2708-rpi-b-plus.dtb bcm2835-rpi-b-plus.dtb
>     copyDTB bcm2708-rpi-b-plus.dtb bcm2835-rpi-zero.dtb
>     copyDTB bcm2708-rpi-cm.dtb bcm2835-rpi-cm.dtb
>     copyDTB bcm2709-rpi-2-b.dtb bcm2836-rpi-2-b.dtb
>     copyDTB bcm2710-rpi-3-b.dtb bcm2837-rpi-3-b.dtb
> 
> I looks like the files in raspberry-firmware/boot should work on any rpi
> version so we should probably immitate that somehow in nixos and at
> least get it to work out of the box even if we just take the precompiled
> files from raspberrypi-firmware/boot and improve that later.

I don't remember any of the details. I'm using it in rpi2 just fine. I
could forget some file, and I may have written code that is fit just for a
very specific kernel version. Maybe it has all changed in 4.4.

The relevant detail that I remember is that the kernel recipe is told to
build the DTB, so I think that you should not need any dtb from the
firmwarefiles/boot.

Regards,
Lluís.

-- 
(Escriu-me xifrat si saps PGP / Write ciphered if you know PGP)
PGP key D4831A8A - https://emailselfdefense.fsf.org/