什么情况下会出现“boot from FEL”的启动信息？

[abcdef]

u-boot启动信息中有"boot from FEL"或”boot from MMC1",象下面2段u-boot启动信息：

U-Boot SPL 2018.01-05679-g013ca457fd (Apr 29 2022 - 07:58:42)
DRAM: 32 MiB
Trying to boot from FEL

U-Boot SPL 2018.01-05679-g013ca457fsd (Apr 29 2022 - 07:58:42)
DRAM: 32 MiB
Trying to boot from MMC1
Card did not respond to voltage select!
mmc_init: -95, time 22
spl: mmc init failed with error: -95
Trying to boot from sunxi SPI

请问，什么情况下会出现“boot from FEL”的启动信息呢？谢谢

[WhycanService]

烧录的时候会boot from FEL