Re: [yocto] [meta-raspberrypi] Booting a Raspberry Pi 4 using PXE

["Manuel Wagesreither" <ManWag@FastMail.FM>]

Hello all,

to be able to diagnose my problem, I worked on enabling uart console access to my Raspberry Pi 4B.

It seems the Raspberry Pi puts `8250.nr_uarts=0` in the linux kernel cmdline whenever the Raspi is booting over the network. This is preventing me from getting console access. When I provide the exact same set of files on a USB drive, 8250.nr_uarts is `1`.

Here's my `cmdline.txt`:
`dwc_otg.lpm_enable=0 console=tty1 console=serial0,115200 root=/dev/sda2 rootfstype=ext4 rootwait 8250.nr_uarts=1`

When I boot over network, `/proc/cmdline` is:
```
coherent_pool=1M 8250.nr_uarts=0 snd_bcm2835.enable_compat_alsa=0 snd_bcm2835.enable_hdmi=1 snd_bcm2835.enable_headphones=1  smsc95xx.macaddr=DC:A6:32:B8:04:5C vc_mem.mem_base=0x3eb00000 vc_mem.mem_size=0x3ff00000  dwc_otg.lpm_enable=0 console=tty1 console=ttyS0,115200 root=/dev/sda2 rootfstype=ext4 rootwait 8250.nr_uarts=0
```
Note that both occurences of 8250.nr_uarts got set to 0. Even the one which I deliberatedly set to 1.

When I boot using usb disk:
```
coherent_pool=1M 8250.nr_uarts=1 snd_bcm2835.enable_compat_alsa=0 snd_bcm2835.enable_hdmi=1 snd_bcm2835.enable_headphones=1  smsc95xx.macaddr=DC:A6:32:B8:04:5C vc_mem.mem_base=0x3eb00000 vc_mem.mem_size=0x3ff00000  dwc_otg.lpm_enable=0 console=tty1 console=ttyS0,115200 root=/dev/sda2 rootfstype=ext4 rootwait 8250.nr_uarts=1
```

Has anyone any background info on that? I provide the exact same set of device tree overlays in both cases.

Thank you,
Regards,
Manuel


Am So, 2. Mai 2021, um 13:59, schrieb Manuel Wagesreither:
> Hello all!
> 
> Since a certain eeprom version, the Raspberry Pi 4 can directly boot from network. Has anyone experience on this?
> 
> I already managed to to have the Raspi to load the kernel and all the device tree stuff over network. I then exported `build/tmp/work/raspberrypi4_64-poky-linux/bora-image/1.0-r0/rootfs/` as via nfs and changed the linux kernel commandline so it would use this share as nfsroot. At boot many failing services get reported and and the boot progress stops somewhere along the way. It tells me the system is in emergency mode and asks me for the root password for maintenance. I have an empty root password. When I press Control-D to continue, the same prompt reappears. Same when I simply press enter.
> 
> Has onyone any input for me? I guess I'll need to monitor what gets written to the serial port.
> 
> Regards,
> Manuel
> 
> 
> 
> 
>