Re: Using loader to switch kernel and root device on Pi2

On Thu, Apr 03, 2025 at 10:26:11AM -0700, Mark Millard wrote:
> 
> 
> So CONFIG_IS_ENABLED(ENV_SUPPORT) is required to be able to
> override the default value involved. I've not checked if the
> FreeBSD U-Boot ports are enabling that or not.
> 

Some experiments suggest it is not enabled. I've tinkered
with config.txt and don't see corresponding changes in 
output from printenv at the u-boot prompt.

But, this touches on my longstanding point of confusion:
Is config.txt read by u-boot, or by bootcode.bin with
the values passed to u-boot? Or maybe both?

The Raspberry Pi docs mention quite a few time delay variables:
https://www.raspberrypi.com/documentation/computers/raspberry-pi.html

USB_MSD_DISCOVER_TIMEOUT
USB_MSD_LUN_TIMEOUT
USB_MSD_STARTUP_DELAY

Increasing those values to
USB_MSD_DISCOVER_TIMEOUT=20000
USB_MSD_LUN_TIMEOUT=2000
USB_MSD_STARTUP_DELAY=5000
does seem to slow down the boot process. Alas, it does not seem
to improve disk detection reliability on a warm boot.

Thanks for writing,

bob prohaska