This page explains how to manually update OTP with the U-Boot fuse command.
1. The fuse command[edit source]
The fuse command allows you to update the OTP words in U-Boot:
- sense/program to directly access the OTP value (for a permanent update)
- read/overidde to access only the shadow cache value (for a temporary update).
help fuse fuse - Fuse sub-system Usage: fuse read <bank> <word> [<cnt>] - read 1 or 'cnt' fuse words, starting at 'word' fuse sense <bank> <word> [<cnt>] - sense 1 or 'cnt' fuse words, starting at 'word' fuse prog [-y] <bank> <word> <hexval> [<hexval>...] - program 1 or several fuse words, starting at 'word' (PERMANENT) fuse override <bank> <word> <hexval> [<hexval>...] - override 1 or several fuse words, starting at 'word'.
See doc/README.fuse for details.
2. STM32MP15x support[edit source]
The STM32MP15x lines 
support is implemented in drivers/misc/stm32mp_fuse.c with 2 banks:
- <bank> = SOC OTP: 0 #STM32MP15x OTP
- <bank> = PMIC NVM : 1 #STPMIC1 NVM.
2.1. STM32MP15x OTP[edit source]
<bank> = 0 provides access to the 96 STM32MP15x OTP words with the BSEC driver: arch/arm/mach-stm32mp/bsec.c .
Refer to the STM32MP15 reference manuals for the OTP layout.
The OTP<index> words value and lock status (0=unlocked, 1=locked) are available with <index> = 0 to 95 :
- for value: <word> = <index>
- for lock status: <word> = 0x10000000 + <index>
not shadowed, only support operation 'sense' and 'program'.
2.1.1. Simple OTP examples[edit source]
1) Read OTP value for OTP57 and 58 (2 OTP words)
fuse sense 0 57 2 Sensing bank 0: Word 0x00000039: 42e18000 0000e448
2) Check lock status of OTP 57 - 60 (4 words at index 57 = 0x39)
fuse sense 0 0x10000039 4 Sensing bank 0: Word 0x10000039: 00000001 00000001 00000001 00000000
3) Display shadow values for all OTPs
fuse read 0 0 96 Reading bank 0: Word 0x00000000: 00000017 00008000 00000000 00000000 Word 0x00000004: 00000000 00000000 00000000 00000000 Word 0x00000008: 00000000 00000000 00000000 00000000 Word 0x0000000c: 7cf5f0f9 00410032 33385116 34383330 Word 0x00000010: 129675aa 2931215e 7a550000 069013ec Word 0x00000014: 5e360042 00000000 00000000 40133023 Word 0x00000018: 00000000 00000000 00000000 00000000 Word 0x0000001c: 00000000 00000000 00000000 00000000 Word 0x00000020: 00000000 00000000 00000000 00000000 Word 0x00000024: 00000000 00000000 00000000 00000000 Word 0x00000028: aa333e40 b5e90dda f15f4678 8ab41400 Word 0x0000002c: b74efe3a f0a03b1b 01e016b3 d06a79dd Word 0x00000030: 48b96fbe 20fbd352 6732dbf4 edc395f9 Word 0x00000034: cdf15575 418fd3d0 0bb7d994 8dc929d0 Word 0x00000038: 00000000 42e18000 0000e448 12722301 Word 0x0000003c: 00000000 00000000 00000000 00000000 Word 0x00000040: 00000000 00000000 00000000 00000000 Word 0x00000044: 00000000 00000000 00000000 00000000 Word 0x00000048: 00000000 00000000 00000000 00000000 Word 0x0000004c: 00000000 00000000 00000000 00000000 Word 0x00000050: 00000000 00000000 00000000 00000000 Word 0x00000054: 00000000 00000000 00000000 00000000 Word 0x00000058: 00000000 00000000 00000000 00000000 Word 0x0000005c: 00000000 00000000 00000000 00000000
4) Override value for one OTP
fuse override 0 0x0000005c 1 Overriding bank 0 word 0x0000005c with 0x00000001...
fuse read 0 0x0000005c Reading bank 0: Word 0x0000005c: 00000001 fuse sense 0 0x0000005c Sensing bank 0: Word 0x0000005c: 00000000
2.1.2. MAC address example[edit source]
For STM32MP15_boards, the MAC address[1] is retrieved in the 2 OTP words:
- OTP_57[31:0] = MAC_ADDR[31:0]
- OTP_58[15:0] = MAC_ADDR[47:32]
To program a MAC address on virgin OTP words above, you can use the fuse command on bank 0 to access internal OTP words and lock them:
Prerequisite: check if a MAC address isn't yet programmed in OTP.
1) Check OTPs: their value must be equal to 0:
fuse sense 0 57 2 Sensing bank 0: Word 0x00000039: 00000000 00000000
2) Check environment variable:
env print ethaddr ## Error: "ethaddr" not defined
3) Check lock status of OTP 57 & 58 (at 0x39, 0=unlocked, 1=locked):
fuse sense 0 0x10000039 2
Sensing bank 0:
Word 0x10000039: 00000000 00000000
Example to set MAC address "12:34:56:78:9a:bc"
1) Write OTP:
fuse prog -y 0 57 0x78563412 0x0000bc9a
2) Read OTP:
fuse sense 0 57 2 Sensing bank 0: Word 0x00000039: 78563412 0000bc9a
3) Lock OTP:
fuse prog 0 0x10000039 1 1
fuse sense 0 0x10000039 2
Sensing bank 0:
Word 0x10000039: 00000001 00000001
4) OTP is used after REBOOT, in the trace:
### Setting environment from OTP MAC address = "12:34:56:78:9a:bc"
5) Check env update:
env print ethaddr ethaddr=12:34:56:78:9a:bc
2.2. STPMIC1 NVM[edit source]
<bank> = 1 provides access to the non-volatile memory (NVM) of the PMIC on the board.
For STPMIC1, the NVM has 8 bytes as defined in datasheet: DS12792, with <word> = <0xf8> to <0xff>.
1) Read the values of the 8 NVM
fuse read 1 0xf8 8 Reading bank 1: Word 0x000000f8: 000000ee 00000092 000000c0 00000002 Word 0x000000fc: 000000f2 00000080 00000002 00000033
2) Read 2 NVM shadow values
fuse sense 1 0xf9 2 Sensing bank 1: Word 0x000000f9: 00000092 000000c0
3) Update the NVM at index 0xfc with value 0xf2
fuse prog 1 0xfc 0xf2 Programming bank 1 word 0x000000fc to 0x000000f2... Warning: Programming fuses is an irreversible operation! This may brick your system. Use this command only if you are sure of what you are doing! Really perform this fuse programming? <y/N> y
3. References[edit source]