烧录完boot_linux.img，打印有missing environment variable: pxeuuid

[16:22:26]U-Boot 2017.09-g22af63b-dirty (Sep 28 2020 - 15:00:58 +0800)
[16:22:26]
[16:22:26]Model: Rockchip RK3399 Evaluation Board
[16:22:26]PreSerial: 2
[16:22:26]DRAM:  2 GiB
[16:22:26]Sysmem: init
[16:22:26]Relocation Offset is: 7dbd1000
[16:22:26]Using default environment
[16:22:26]
[16:22:26]dwmmc@fe320000: 1, sdhci@fe330000: 0
[16:22:28]Bootdev(atags): mmc 0
[16:22:28]MMC0: HS400, 150Mhz
[16:22:28]PartType: EFI
[16:22:28]rockchip_get_boot_mode: Could not found misc partition
[16:22:28]boot mode: None
[16:22:28]init_resource_list: failed to get boot part, ret=-1
[16:22:28]init_resource_list: failed to get resource part, ret=-1
[16:22:28]Distro DTB: /extlinux/toybrick.dtb
[16:22:28]** File not found /extlinux/toybrick.dtb **
[16:22:28]Read kernel dtb failed, ret=-5
[16:22:28]Model: Rockchip RK3399 Evaluation Board
[16:22:28]toybrick_SnMacAc_check other type
[16:22:28]CLK: (uboot. arml: enter 816000 KHz, init 816000 KHz, kernel 0N/A)
[16:22:28]CLK: (uboot. armb: enter 24000 KHz, init 24000 KHz, kernel 0N/A)
[16:22:28]  aplll 816000 KHz
[16:22:28]  apllb 24000 KHz
[16:22:28]  dpll 856000 KHz
[16:22:28]  cpll 24000 KHz
[16:22:28]  gpll 800000 KHz
[16:22:28]  npll 600000 KHz
[16:22:28]  vpll 24000 KHz
[16:22:28]  aclk_perihp 133333 KHz
[16:22:28]  hclk_perihp 66666 KHz
[16:22:28]  pclk_perihp 33333 KHz
[16:22:28]  aclk_perilp0 266666 KHz
[16:22:28]  hclk_perilp0 88888 KHz
[16:22:28]  pclk_perilp0 44444 KHz
[16:22:28]  hclk_perilp1 100000 KHz
[16:22:28]  pclk_perilp1 50000 KHz
[16:22:28]Net:   No ethernet found.
[16:22:28]Hit key to stop autoboot('CTRL+C'):  0
[16:22:28]Could not find misc partition
[16:22:28]ANDROID: reboot reason: "(none)"
[16:22:28]Not AVB images, AVB skip
[16:22:28]load_android_image: Can't find part: boot
[16:22:28]Android image load failed
[16:22:28]Android boot failed, error -1.
[16:22:28]do_boot_rockchip: Could not find misc partition
[16:22:28]do_boot_rockchip: Could not find rootfs part
[16:22:28]Card did not respond to voltage select!
[16:22:28]mmc_init: -95, time 9
[16:22:28]switch to partitions #0, OK
[16:22:28]mmc0(part 0) is current device
[16:22:28]Scanning mmc 0:3...
[16:22:28]starting USB...
[16:22:28]USB0:   Register 2000140 NbrPorts 2
[16:22:28]Starting the controller
[16:22:28]USB XHCI 1.10
[16:22:28]USB1:   Register 2000140 NbrPorts 2
[16:22:28]Starting the controller
[16:22:28]USB XHCI 1.10
[16:22:28]scanning bus 0 for devices... 1 USB Device(s) found
[16:22:29]scanning bus 1 for devices... 1 USB Device(s) found
[16:22:29]       scanning usb for storage devices... 0 Storage Device(s) found
[16:22:29]
[16:22:29]Device 0: unknown device
[16:22:29]No ethernet found.
[16:22:29]missing environment variable: pxeuuid
[16:22:29]missing environment variable: bootfile
[16:22:29]Retrieving file: pxelinux.cfg/00000000
[16:22:29]No ethernet found.
[16:22:29]missing environment variable: bootfile
[16:22:29]Retrieving file: pxelinux.cfg/0000000
[16:22:29]No ethernet found.
[16:22:29]missing environment variable: bootfile
[16:22:29]Retrieving file: pxelinux.cfg/000000
[16:22:29]No ethernet found.
[16:22:29]missing environment variable: bootfile
[16:22:29]Retrieving file: pxelinux.cfg/00000
[16:22:29]No ethernet found.

请问有谁知道是怎么回事？怎么解决？求指教