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diff --git a/doc/board/nxp/psb.rst b/doc/board/nxp/psb.rst new file mode 100644 index 00000000000..2eccdcfccd9 --- /dev/null +++ b/doc/board/nxp/psb.rst @@ -0,0 +1,176 @@ +i.MX7D/i.MX8MM SRC_GPR10 PERSIST_SECONDARY_BOOT for bootloader A/B switching +============================================================================ + +Introduction +------------ +Since at least iMX53 until iMX8MM, it is possible to have two copies of +bootloader in SD/eMMC and switch between them. The switch is triggered +either by the BootROM in case the bootloader image is faulty OR can be +enforced by the user. + +Operation +--------- + #. Upon Power-On Reset (POR) + + - SRC_GPR10 bit PERSIST_SECONDARY_BOOT is set to 0 + - BootROM attempts to start bootloader A-copy + + - if A-copy valid + + - BootROM starts A-copy + - END + + - if A-copy NOT valid + + - BootROM sets SRC_GPR10 bit PERSIST_SECONDARY_BOOT to 1 + - BootROM triggers WARM reset, GOTO 1) + - END + + #. Upon COLD Reset + + - GOTO 1) + - END + + #. Upon WARM Reset + + - SRC_GPR10 bit PERSIST_SECONDARY_BOOT is retained + + - if SRC_GPR10 bit PERSIST_SECONDARY_BOOT is 0 + + - BootROM attempts to start bootloader A-copy + + - if A-copy valid + + - BootROM starts A-copy + - END + + - if A-copy NOT valid + + - BootROM sets SRC_GPR10 bit PERSIST_SECONDARY_BOOT to 1 + - BootROM triggers WARM reset. GOTO 1.3) + - END + + - if SRC_GPR10 bit PERSIST_SECONDARY_BOOT is 1 + + - BootROM attempts to start bootloader B-copy + + - if B-copy valid + + - BootROM starts B-copy + - END + + - if B-copy NOT valid + - System hangs + - END + +Setup +----- +The bootloader A-copy must be placed at predetermined offset in SD/eMMC. The +bootloader B-copy area offset is determined by an offset stored in Secondary +Image Table (SIT). The SIT must be placed at predetermined offset in SD/eMMC. + +The following table contains offset of SIT, bootloader A-copy and recommended +bootloader B-copy offset. The offsets are in 512 Byte sector units (that is +offset 0x1 means 512 Bytes from the start of SD/eMMC card data partition). +For details on the addition of two numbers in recommended B-copy offset, see +SIT format below. + ++----------+-----------------------------+--------------------+-----------------------+-----------------------------+ +| SoC | Boot Device Type | SIT offset (fixed) | A-copy offset (fixed) | B-copy offset (recommended) | ++----------+-----------------------------+--------------------+-----------------------+-----------------------------+ +| iMX7D | | 0x1 | 0x2 | 0x800+0x2 | ++----------+-----------------------------+--------------------+-----------------------+-----------------------------+ +| iMX8MM | SD/eSD/MMC/eMMC normal boot | 0x41 | 0x42 | 0x1000+0x42 | ++----------+-----------------------------+--------------------+-----------------------+-----------------------------+ +| iMX8MM | eMMC Fast boot fuse blown | 0x1 | 0x2 | 0x1000+0x2 | ++----------+-----------------------------+--------------------+-----------------------+-----------------------------+ + +SIT format +~~~~~~~~~~ +SIT is a 20 byte long structure containing of 5 32-bit words. Those encode +bootloader B-copy area offset (called "firstSectorNumber"), magic value +(called "tag") that is always 0x00112233, and three unused words set to 0. +SIT is documented in [1]_ and [2]_. Example SIT are below:: + + $ hexdump -vC sit-mx7d.bin + 00000000 00 00 00 00 + 00000004 00 00 00 00 + 00000008 33 22 11 00 <--- This is the "tag" + 0000000c 00 08 00 00 <--- This is the "firstSectorNumber" + 00000010 00 00 00 00 + + $ hexdump -vC sit-mx8mm.bin + 00000000 00 00 00 00 + 00000004 00 00 00 00 + 00000008 33 22 11 00 <--- This is the "tag" + 0000000c 00 10 00 00 <--- This is the "firstSectorNumber" + 00000010 00 00 00 00 + +B-copy area offset ("firstSectorNumber") is offset, in units of 512 Byte +sectors, that is added to the start of boot media when switching between +A-copy and B-copy. For A-copy, this offset is 0x0. For B-copy, this offset +is determined by SIT (e.g. if firstSectorNumber is 0x1000 as it is above +in sit-mx8mm.bin, then the B-copy offset is 0x1000 sectors = 2 MiB). + +Bootloader A-copy (e.g. u-boot.imx or flash.bin) is placed at fixed offset +from A-copy area offset (e.g. 0x2 sectors from sector 0x0 for iMX7D, which +means u-boot.imx A-copy must be written to sector 0x2). + +The same applies to bootloader B-copy, which is placed at fixed offset from +B-copy area offset determined by SIT (e.g. 0x2 sectors from sector 0x800 [see +sit-mx7d.bin example above, this can be changed in SIT firstSectorNumber] for +iMX7D, which means u-boot.imx B-copy must be written to sector 0x802) + +**WARNING:** +B-copy area offset ("firstSectorNumber") is NOT equal to bootloader +(image, which is u-boot.imx or flash.bin) B-copy offset. + +To generate SIT, use for example the following bourne shell printf command:: + +$ printf '\x0\x0\x0\x0\x0\x0\x0\x0\x33\x22\x11\x00\x00\x08\x00\x00\x0\x0\x0\x0' > sit-mx7d.bin +$ printf '\x0\x0\x0\x0\x0\x0\x0\x0\x33\x22\x11\x00\x00\x10\x00\x00\x0\x0\x0\x0' > sit-mx8mm.bin + +Write bootloader A/B copy and SIT to SD/eMMC +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Examples of writing SIT and two copies of bootloader to SD or eMMC: + +- iMX8MM, SD card at /dev/sdX, Linux command line + :: + + $ dd if=sit-mx8mm.bin of=/dev/sdX bs=512 seek=65 + $ dd if=flash.bin of=/dev/sdX bs=512 seek=66 + $ dd if=flash.bin of=/dev/sdX bs=512 seek=4162 + +- iMX8MM, eMMC 1 data partition, U-Boot command line + :: + + => mmc partconf 1 0 0 0 + + => dhcp ${loadaddr} sit-mx8mm.bin + => mmc dev 1 + => mmc write ${loadaddr} 0x41 0x1 + + => dhcp ${loadaddr} flash.bin + => setexpr blkcnt ${filesize} + 0x1ff && setexpr blkcnt ${blkcnt} / 0x200 + => mmc dev 1 + => mmc write ${loadaddr} 0x42 ${blkcnt} + => mmc write ${loadaddr} 0x1042 ${blkcnt} + +WARM reset into B-copy using WDT +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +To perform a reboot into B-copy, the PERSIST_SECONDARY_BOOT must be set +in SRC_GPR10 register. Example on iMX8MM:: + + => mw 0x30390098 0x40000000 + +A WARM reset can be triggered using WDT as follows:: + + => mw.w 0x30280000 0x25 + +References +---------- + +.. [1] i.MX 7Dual Applications Processor Reference Manual, Rev. 1, 01/2018 ; section 6.6.5.3.5 Redundant boot support for expansion device +.. [2] i.MX 8M Mini Applications Processor Reference Manual, Rev. 3, 11/2020 ; section 6.1.5.4.5 Redundant boot support for expansion device |