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AM4378: Clarification on USB scanning messages during AM4378 boot sequence

Conor
Guru 13025 points
Part Number: AM4378


Hi,

When booting AM4378 with SYSBOOT[4:0] configured as 00110b (NAND boot), we observe the following messages in the console log:

starting USB...
scanning bus usb@483d0000 for devices...
0 Storage Device(s) found
Device 0: unknown device

Our current understanding is that these messages are not generated by the ROM code attempting a USB boot. Instead, after the ROM code successfully boots from NAND and loads U-Boot, U-Boot performs its standard peripheral scanning process, during which it scans the USB bus and reports no devices.

Specifically, we would like to confirm:

  • With SYSBOOT[4:0] = 00110b, the ROM code selects NAND as the primary boot source and does not use USB.

  • The USB-related messages observed are due to U-Boot’s standard device scanning, not part of the ROM boot process.

Could you please confirm whether this understanding is correct?

Thank you very much for your support.

Conor