The Banana Pi R2 bootloader will load U-Boot from either the internal eMMC, or the external SD card if the latter is present.
If booted from the eMMC (and an SD card is subsequently inserted), both work from U-Boot. Both also work from Linux, whichever device is booted from.
If booted from SD, the internal eMMC cannot be accessed from U-Boot. This makes it slightly difficult for me to write a U-Boot script which installs OpenWRT from the SD card to the internal eMMC...
From SD:
U-Boot 2020.07-rc4-00057-gc622afb087 (Jun 16 2020 - 17:05:55 +0100)
CPU: MediaTek MT7623 E3 DRAM: 2 GiB WDT: Started with servicing (60s timeout) MMC: mmc@11230000: 0, mmc@11240000: 1 Loading Environment from FAT... ** No device specified ** ## Warning: Unknown environment variable type 'i' ## Warning: Unknown environment variable type 'i' ## Warning: Unknown environment variable type 'i' In: serial Out: serial Err: serial Hit any key to stop autoboot: 0 U-Boot> mmc list mmc@11230000: 0 mmc@11240000: 1 U-Boot> mmc dev 0 CMD_SEND:0 ARG 0x00000000 MMC_RSP_NONE CMD_SEND:8 ARG 0x000001aa RET -110 CMD_SEND:55 ARG 0x00000000 RET -110 CMD_SEND:0 ARG 0x00000000 MMC_RSP_NONE CMD_SEND:1 ARG 0x00000000 MMC_RSP_R3,4 0xffffffff CMD_SEND:2 ARG 0x00000000 RET -110 U-Boot> mmc dev 1 CMD_SEND:0 ARG 0x00000000 MMC_RSP_NONE CMD_SEND:8 ARG 0x000001aa MMC_RSP_R1,5,6,7 0x000001aa CMD_SEND:55 ARG 0x00000000 MMC_RSP_R1,5,6,7 0x00000120 CMD_SEND:41 ARG 0x40300000 MMC_RSP_R3,4 0x00ff8000 CMD_SEND:55 ARG 0x00000000 MMC_RSP_R1,5,6,7 0x00000120 CMD_SEND:41 ARG 0x40300000 MMC_RSP_R3,4 0x80ff8000 CMD_SEND:2 ARG 0x00000000 MMC_RSP_R2 0x744a6055 0x53442020 0x104059f3 0x34013be5
DUMPING DATA 000 - 74 4a 60 55 004 - 53 44 20 20 008 - 10 40 59 f3 012 - 34 01 3b e5 CMD_SEND:3 ARG 0x00000000 MMC_RSP_R1,5,6,7 0x59b40520 CMD_SEND:9 ARG 0x59b40000 MMC_RSP_R2 0x007f0032 0x5b5a83bd 0x6db7ff80 0x0a80008d
DUMPING DATA 000 - 00 7f 00 32 004 - 5b 5a 83 bd 008 - 6d b7 ff 80 012 - 0a 80 00 8d CMD_SEND:7 ARG 0x59b40000 MMC_RSP_R1,5,6,7 0x00000700 CMD_SEND:55 ARG 0x59b40000 MMC_RSP_R1,5,6,7 0x00000920 CMD_SEND:51 ARG 0x00000000 MMC_RSP_R1,5,6,7 0x00000920 CMD_SEND:6 ARG 0x00fffff1 MMC_RSP_R1,5,6,7 0x00000900 CMD_SEND:55 ARG 0x59b40000 MMC_RSP_R1,5,6,7 0x00000920 CMD_SEND:6 ARG 0x00000002 MMC_RSP_R1,5,6,7 0x00000920 CMD_SEND:6 ARG 0x80fffff1 MMC_RSP_R1,5,6,7 0x00000900 CMD_SEND:55 ARG 0x59b40000 MMC_RSP_R1,5,6,7 0x00000920 CMD_SEND:13 ARG 0x00000000 MMC_RSP_R1,5,6,7 0x00000920 CMD_SEND:16 ARG 0x00000200 MMC_RSP_R1,5,6,7 0x00000900 CMD_SEND:17 ARG 0x00000000 MMC_RSP_R1,5,6,7 0x00000900 switch to partitions #0, OK mmc1 is current device
From MMC:
U-Boot 2020.07-rc4-00057-gc622afb087 (Jun 16 2020 - 17:05:55 +0100)
CPU: MediaTek MT7623 E3 DRAM: 2 GiB WDT: Started with servicing (60s timeout) MMC: mmc@11230000: 0, mmc@11240000: 1 Loading Environment from FAT... ** No device specified ** ## Warning: Unknown environment variable type 'i' ## Warning: Unknown environment variable type 'i' ## Warning: Unknown environment variable type 'i' In: serial Out: serial Err: serial Hit any key to stop autoboot: 0 U-Boot> mmc list mmc@11230000: 0 mmc@11240000: 1 U-Boot> mmc dev 0 CMD_SEND:0 ARG 0x00000000 MMC_RSP_NONE CMD_SEND:8 ARG 0x000001aa RET -110 CMD_SEND:55 ARG 0x00000000 RET -110 CMD_SEND:0 ARG 0x00000000 MMC_RSP_NONE CMD_SEND:1 ARG 0x00000000 MMC_RSP_R3,4 0x40ff8080 CMD_SEND:1 ARG 0x40300000 MMC_RSP_R3,4 0x40ff8080 CMD_SEND:0 ARG 0x00000000 MMC_RSP_NONE CMD_SEND:1 ARG 0x40300000 MMC_RSP_R3,4 0x40ff8080 CMD_SEND:1 ARG 0x40300000 MMC_RSP_R3,4 0xc0ff8080 CMD_SEND:2 ARG 0x00000000 MMC_RSP_R2 0x15010038 0x47544634 0x5206071b 0x48de461d
DUMPING DATA 000 - 15 01 00 38 004 - 47 54 46 34 008 - 52 06 07 1b 012 - 48 de 46 1d CMD_SEND:3 ARG 0x00010000 MMC_RSP_R1,5,6,7 0x00000500 CMD_SEND:9 ARG 0x00010000 MMC_RSP_R2 0xd0270132 0x0f5903ff 0xf6dbffef 0x8e40400d
DUMPING DATA 000 - d0 27 01 32 004 - 0f 59 03 ff 008 - f6 db ff ef 012 - 8e 40 40 0d CMD_SEND:7 ARG 0x00010000 MMC_RSP_R1,5,6,7 0x00000700 CMD_SEND:8 ARG 0x00000000 MMC_RSP_R1,5,6,7 0x00000900 CMD_SEND:6 ARG 0x03b70200 MMC_RSP_R1b 0x00000900 CMD_SEND:13 ARG 0x00010000 MMC_RSP_R1,5,6,7 0x00000900 CURR STATE:4 CMD_SEND:6 ARG 0x03b90100 MMC_RSP_R1b 0x00000900 CMD_SEND:13 ARG 0x00010000 MMC_RSP_R1,5,6,7 0x00000900 CURR STATE:4 CMD_SEND:8 ARG 0x00000000 MMC_RSP_R1,5,6,7 0x00000900 CMD_SEND:8 ARG 0x00000000 MMC_RSP_R1,5,6,7 0x00000900 CMD_SEND:16 ARG 0x00000200 MMC_RSP_R1,5,6,7 0x00000900 CMD_SEND:17 ARG 0x00000000 MMC_RSP_R1,5,6,7 0x00000900 switch to partitions #0, OK mmc0(part 0) is current device U-Boot> mmc dev 1 CMD_SEND:0 ARG 0x00000000 MMC_RSP_NONE CMD_SEND:8 ARG 0x000001aa MMC_RSP_R1,5,6,7 0x000001aa CMD_SEND:55 ARG 0x00000000 MMC_RSP_R1,5,6,7 0x00000120 CMD_SEND:41 ARG 0x40300000 MMC_RSP_R3,4 0x00ff8000 CMD_SEND:55 ARG 0x00000000 MMC_RSP_R1,5,6,7 0x00000120 CMD_SEND:41 ARG 0x40300000 MMC_RSP_R3,4 0x00ff8000 CMD_SEND:55 ARG 0x00000000 MMC_RSP_R1,5,6,7 0x00000120 CMD_SEND:41 ARG 0x40300000 MMC_RSP_R3,4 0x00ff8000 CMD_SEND:55 ARG 0x00000000 MMC_RSP_R1,5,6,7 0x00000120 CMD_SEND:41 ARG 0x40300000 MMC_RSP_R3,4 0x00ff8000 CMD_SEND:55 ARG 0x00000000 MMC_RSP_R1,5,6,7 0x00000120 CMD_SEND:41 ARG 0x40300000 MMC_RSP_R3,4 0x00ff8000 CMD_SEND:55 ARG 0x00000000 MMC_RSP_R1,5,6,7 0x00000120 CMD_SEND:41 ARG 0x40300000 MMC_RSP_R3,4 0x80ff8000 CMD_SEND:2 ARG 0x00000000 MMC_RSP_R2 0x744a6055 0x53442020 0x104059f3 0x34013be5
DUMPING DATA 000 - 74 4a 60 55 004 - 53 44 20 20 008 - 10 40 59 f3 012 - 34 01 3b e5 CMD_SEND:3 ARG 0x00000000 MMC_RSP_R1,5,6,7 0x59b40520 CMD_SEND:9 ARG 0x59b40000 MMC_RSP_R2 0x007f0032 0x5b5a83bd 0x6db7ff80 0x0a80008d
DUMPING DATA 000 - 00 7f 00 32 004 - 5b 5a 83 bd 008 - 6d b7 ff 80 012 - 0a 80 00 8d CMD_SEND:7 ARG 0x59b40000 MMC_RSP_R1,5,6,7 0x00000700 CMD_SEND:55 ARG 0x59b40000 MMC_RSP_R1,5,6,7 0x00000920 CMD_SEND:51 ARG 0x00000000 MMC_RSP_R1,5,6,7 0x00000920 CMD_SEND:6 ARG 0x00fffff1 MMC_RSP_R1,5,6,7 0x00000900 CMD_SEND:55 ARG 0x59b40000 MMC_RSP_R1,5,6,7 0x00000920 CMD_SEND:6 ARG 0x00000002 MMC_RSP_R1,5,6,7 0x00000920 CMD_SEND:6 ARG 0x80fffff1 MMC_RSP_R1,5,6,7 0x00000900 CMD_SEND:55 ARG 0x59b40000 MMC_RSP_R1,5,6,7 0x00000920 CMD_SEND:13 ARG 0x00000000 MMC_RSP_R1,5,6,7 0x00000920 CMD_SEND:16 ARG 0x00000200 MMC_RSP_R1,5,6,7 0x00000900 CMD_SEND:17 ARG 0x00000000 MMC_RSP_R1,5,6,7 0x00000900 switch to partitions #0, OK mmc1 is current device U-Boot>