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 > > > > >
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