Serial console unavailable when booting Raspberry Pi 4B over network #1575
Comments
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The netboot firmware seems to take Here's a config.txt which boots the device but will result in When you remove any character before the |
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The is a difference in the two lines. The top one (broken) is Looks like there is a typo, but it probably should be able to handle if the line is >_ 0x1000 |
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@adudek16 The |
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I had the exact same problem with RaspberryPI3 booting over PXE and your issue saved my time. I confirm that if we remove all of the comments in config.txt file, it works fine. Did someone know where is the limit of 0x1000 exactly ? Raspberry PI bootcode ? |
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IIRC its somewhere deep down in the file handling code in the bootloader, which we haven't touched in ten years, so people are reluctant to make changes to it. Could be wrong, sure someone will correct me if so! |
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Thank you for posting this issue - it's a couple years later, but the same/similar issue still appears to be present with the serial console during a PXE boot, and shortening the config.txt resolved it for me as well, so this report was a real lifesaver. Your attention and diligent work tracking this down saved me a bunch of time, so again, thank you very much! |
Problem description
When booting my Raspberry Pi 4B using a USB drive, I receive diagnostic information via UART while booting and can login through said UART afterwards. When netbooting the device and providing the exact same set of boot files (verified with
md5sum) through TFTP, the device stops to send data through UART early during boot.It seems to me, some part of the firmware forces the kernel parameter
8250.nr_uartsto0when netbooting. Even when I set8250.nr_uarts=1incmdline.txt, I get8250.nr_uarts=0in/proc/cmdlineof the netbooted system. This is not the case when usb booting the device.Expected behaviour
While netbooting, the kernel sends diagnostic information over serial. After boot, it provides a console interface over serial interface.
Actual behaviour
Kernel neither sends diagnostic information, nor does it provide a console interface over UART when netboot is used.
How to reproduce
/proc/cmdlineand notice that8250.nr_uarts=1./proc/cmdlineand notice that8250.nr_uarts=0.System information
vcgencmd version:Feb 25 2021 12:10:40 version 564e5f9b852b23a330b1764bcf0b2d022a20afd0 (clean) (release) (start)Linux raspberrypi4-64 5.4.59-v8 #1 SMP PREEMPT Fri Aug 28 21:04:05 UTC 2020 aarch64 GNU/LinuxConfiguration
cmdline.txt:dwc_otg.lpm_enable=0 console=tty1 console=serial0,115200 root=/dev/sda2 rootfstype=ext4 rootwait 8250.nr_uarts=1config.txt:Logs
/proc/cmdlineof netbooted device:/proc/cmdlineof usb booted device:Serial mappings on both the netbooted and usb booted system
/proc/device-tree/aliases/serial0:/soc/serial@7e215040pi/proc/device-tree/aliases/serial1:/soc/serial@7e201000Received UART data when netbooting:
For comparison, received UART data when usb booting:
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