UBoot vs. BeagleBone on-board eMMC?

["John D. Baker" <jdbaker%consolidated.net@localhost>]

When I updated UBoot on my BeagleBone Green, I noticed that it prefers to
load UBoot from the on-board eMMC device.  (I had only updated it on the
uSD card at that point and when I reset the board it loaded the old UBoot.)

I then updated UBoot on the on-board eMMC device and when rebooted was
running the new UBoot.  At first, it showed:


U-Boot SPL 2018.11 (Dec 02 2019 - 14:36:08 -0600)
Trying to boot from MMC2
Loading Environment from FAT... *** Warning - bad CRC, using default environment
Loading Environment from MMC... *** Warning - bad CRC, using default environment



U-Boot 2018.11nb4 (Dec 02 2019 - 14:36:08 -0600)

CPU  : AM335X-GP rev 2.1
I2C:   ready
DRAM:  512 MiB
No match for driver 'omap_hsmmc'
No match for driver 'omap_hsmmc'
Some drivers were not found
MMC:   OMAP SD/MMC: 0, OMAP SD/MMC: 1
Loading Environment from FAT... *** Warning - bad CRC, using default environment
Loading Environment from MMC... *** Warning - bad CRC, using default environment

<ethaddr> not set. Validating first E-fuse MAC
Net:   cpsw, usb_ether
Press SPACE to abort autoboot in 2 seconds
=> 


Which was undestandable as the old UBoot I'd been running treated 'env
save' as a no-op and I had to patch in my preferences with a hex editor.

With the new UBoot, I issued an 'env save' command and upon the next
boot the warning messages were gone.


At the time, there were problems with sdhc driver stability in GENERIC,
so I removed the uSD card from the BBG and put it in uSD-USB adapter.

The next boot showed:


U-Boot SPL 2018.11 (Dec 02 2019 - 14:36:08 -0600)
Trying to boot from MMC2
Loading Environment from FAT... Card did not respond to voltage select!
Loading Environment from MMC... *** Warning - bad CRC, using default environment



U-Boot 2018.11nb4 (Dec 02 2019 - 14:36:08 -0600)

CPU  : AM335X-GP rev 2.1
I2C:   ready
DRAM:  512 MiB
No match for driver 'omap_hsmmc'
No match for driver 'omap_hsmmc'
Some drivers were not found
MMC:   OMAP SD/MMC: 0, OMAP SD/MMC: 1
Loading Environment from FAT... Card did not respond to voltage select!
Loading Environment from MMC... *** Warning - bad CRC, using default environment

<ethaddr> not set. Validating first E-fuse MAC
Net:   cpsw, usb_ether
Press SPACE to abort autoboot in 2 seconds
=> 


Which wasn't much of a surprise as the uSD had been removed.  It appears,
however, that the uSD card is the only location considered for saving
the environment to FAT, ignoring the FAT partition on the on-board eMMC:


=> env save
Saving Environment to FAT... Card did not respond to voltage select!
Failed (1)


I've tried explicitly setting MMC 1 as the default device, but that has
no effect.  I'm also puzzled about what it's checking on the eMMC when
it fails to load the environment, but subsequently refuses to save the
environment to the eMMC.  (I suppose if it would, the "bad CRC" message
would go away.)

With the uSD in the USB adapter and issuing 'usb start', one can operate
from the USB device, but it is still not a candidate for loading/saving
the environment from/to the FAT partition on the uSD card (in the adapter).


Any clues on how to get UBoot to save its environment on the on-board
eMMC (presumedly the FAT partition on the eMMC or ???)?

Thanks.

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