The SD/USB first booting only exists when the uboot on the emmc is intact. The. SoCs boot order is emmc, then SD.
The easiest way to recover (if you don't have the USB-emmc adapter) would be to remove the bottom panel from the PBP (with the lid open to avoid flexing/breaking the plastics,) insert a bootable SD, boot from it, flip the emmc switch to enabled, and rebind the emmc:
Now the emmc should appear as a storage device to your OS, booted from SD. Write your desired image to the emmc now. (Don't use an 'emmc installer' image. They typically are meant to be booted from SD to write to the emmc.)
If you have the USB-emmc adapter, just take out the emmc, pop it onto the adapter, plug it into your PC, and write your image.
The easiest way to recover (if you don't have the USB-emmc adapter) would be to remove the bottom panel from the PBP (with the lid open to avoid flexing/breaking the plastics,) insert a bootable SD, boot from it, flip the emmc switch to enabled, and rebind the emmc:
Code:
echo fe330000.sdhci >/sys/bus/platform/drivers/sdhci-arasan/unbind
echo fe330000.sdhci >/sys/bus/platform/drivers/sdhci-arasan/bind
Now the emmc should appear as a storage device to your OS, booted from SD. Write your desired image to the emmc now. (Don't use an 'emmc installer' image. They typically are meant to be booted from SD to write to the emmc.)
If you have the USB-emmc adapter, just take out the emmc, pop it onto the adapter, plug it into your PC, and write your image.