Difference between revisions of "Fuses"
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| Line 161: | Line 161: | ||
| 0x7000F924 | | 0x7000F924 | ||
|- | |- | ||
| − | | FUSE_OPT_FT_REV | + | | [[#FUSE_OPT_FT_REV|FUSE_OPT_FT_REV]] |
| 0x7000F928 | | 0x7000F928 | ||
|- | |- | ||
| Line 239: | Line 239: | ||
| 0x7000F98C | | 0x7000F98C | ||
|- | |- | ||
| − | | FUSE_OPT_CP_REV | + | | [[#FUSE_OPT_CP_REV|FUSE_OPT_CP_REV]] |
| 0x7000F990 | | 0x7000F990 | ||
|- | |- | ||
| Line 644: | Line 644: | ||
==== FUSE_SKU_INFO ==== | ==== FUSE_SKU_INFO ==== | ||
Stores the SKU ID (must be 0x83). | Stores the SKU ID (must be 0x83). | ||
| + | |||
| + | ==== FUSE_OPT_FT_REV ==== | ||
| + | Stores the FT (Final Test) revision. | ||
| + | |||
| + | Original launch units have this value set to 0xA0 (revision 5.0). The first batch of patched units have this value set to 0xC0 (revision 6.0). | ||
==== FUSE_FA ==== | ==== FUSE_FA ==== | ||
| Line 652: | Line 657: | ||
==== FUSE_RESERVED_ODM0 ==== | ==== FUSE_RESERVED_ODM0 ==== | ||
| − | This | + | This stores an hardware ID. |
==== FUSE_RESERVED_ODM1 ==== | ==== FUSE_RESERVED_ODM1 ==== | ||
| − | This | + | This stores an hardware ID. |
==== FUSE_RESERVED_ODM2 ==== | ==== FUSE_RESERVED_ODM2 ==== | ||
| Line 663: | Line 668: | ||
|- | |- | ||
| 0-4 | | 0-4 | ||
| − | | [5.0.0+] Used as key generation | + | | [5.0.0+] Used as key generation (patched units only) |
|} | |} | ||
| − | This | + | This stores an hardware ID in original launch units, but in patched units it stores a single value (key generation). |
==== FUSE_RESERVED_ODM3 ==== | ==== FUSE_RESERVED_ODM3 ==== | ||
| − | This | + | This stores an hardware ID in original launch units, but in patched units it's empty. |
==== FUSE_RESERVED_ODM4 ==== | ==== FUSE_RESERVED_ODM4 ==== | ||
| Line 684: | Line 689: | ||
| [1.0.0-3.0.2] 3-5 | | [1.0.0-3.0.2] 3-5 | ||
[4.0.0+] 3-7 | [4.0.0+] 3-7 | ||
| − | | DRAM | + | | DRAM ID |
|- | |- | ||
| 8 | | 8 | ||
| Line 696: | Line 701: | ||
|- | |- | ||
| 11 | | 11 | ||
| − | | [5.0.0+] | + | | [5.0.0+] Unit patch flag (0 = unpatched; 1 = patched) |
|- | |- | ||
| 16-19 | | 16-19 | ||
| Line 710: | Line 715: | ||
This register returns the value programmed into index 0x3C of the fuse array. | This register returns the value programmed into index 0x3C of the fuse array. | ||
| − | ==== | + | ==== FUSE_PUBLIC_KEY ==== |
| − | + | This stores the SHA256 hash of the 2048-bit RSA key expected at BCT+0x210. | |
| − | ==== | + | ==== FUSE_OPT_CP_REV ==== |
| − | Stores | + | Stores the CP (Chip Probing) revision. |
| − | + | Original launch units have this value set to 0xA0 (revision 5.0). The first batch of patched units have this value set to 0x103 (revision 8.3). | |
| − | |||
| − | |||
| − | |||
| − | |||
| − | |||
==== FUSE_PRIVATE_KEY ==== | ==== FUSE_PRIVATE_KEY ==== | ||
This stores the 160-bit private key (128 bit SBK + 32-bit device key). | This stores the 160-bit private key (128 bit SBK + 32-bit device key). | ||
Reads to these registers after the SBK is locked out produce all-FF output. | Reads to these registers after the SBK is locked out produce all-FF output. | ||
| − | |||
| − | |||
| − | |||
==== FUSE_RESERVED_SW ==== | ==== FUSE_RESERVED_SW ==== | ||
| Line 755: | Line 752: | ||
This caches the value of the sw_reserved fuse from the hardware array. | This caches the value of the sw_reserved fuse from the hardware array. | ||
| + | |||
| + | Original launch units have the RCM USB controller mode set to USB 2.0, while the first batch of patched units have the RCM USB controller mode set to XUSB. | ||
==== FUSE_PKC_DISABLE ==== | ==== FUSE_PKC_DISABLE ==== | ||
This caches the value of the pkc_disable fuse from the hardware array. | This caches the value of the pkc_disable fuse from the hardware array. | ||
| + | |||
| + | ==== FUSE_SPARE_BIT_2 ==== | ||
| + | Stores part of the speedo fusing revision. | ||
| + | |||
| + | ==== FUSE_SPARE_BIT_3 ==== | ||
| + | Stores part of the speedo fusing revision. | ||
| + | |||
| + | ==== FUSE_SPARE_BIT_4 ==== | ||
| + | Stores part of the speedo fusing revision. | ||
| + | |||
| + | ==== FUSE_SPARE_BIT_5 ==== | ||
| + | Must be non-zero on retail units, otherwise the first bootloader panics. | ||
| + | On debug units it can be zero, which tells the bootloader to choose from two debug master key seeds. If set to non-zero on a debug unit, it tells the bootloader to choose from two master key seeds (with the second one being the retail master key seed). | ||
| + | |||
| + | [4.0.0+] This value is no longer used during boot. | ||
== eFuses == | == eFuses == | ||
| Line 836: | Line 850: | ||
=== bootrom_ipatch === | === bootrom_ipatch === | ||
| − | Tegra210 based hardware such as the Switch provides support for bootrom patches. The patch data is burned to the hardware fuse array using a specific format (see [https://gist.github.com/shuffle2/f8728159da100e9df2606d43925de0af shuffle2's ipatch decoder]). The bootrom reads these fuses in order to initialize the IPATCH hardware, which allows overriding data returned for code and data fetches done by BPMP | + | Tegra210 based hardware such as the Switch provides support for bootrom patches. The patch data is burned to the hardware fuse array using a specific format (see [https://gist.github.com/shuffle2/f8728159da100e9df2606d43925de0af shuffle2's ipatch decoder]). The bootrom reads these fuses in order to initialize the IPATCH hardware, which allows overriding data returned for code and data fetches done by BPMP. |
The following represents the patch data dumped from a Switch console: | The following represents the patch data dumped from a Switch console: | ||
Revision as of 17:51, 17 April 2019
The Nintendo Switch makes use of Tegra's fuse driver for a number of operations. This driver is mapped to physical address 0x7000F800 with a total size of 0x400 bytes and exposes several registers for fuse programming.
Registers from 0x7000F800 to 0x7000F800 + 0xFF can be used to directly program the hardware fuse array, while registers from 0x7000F800 + 0x100 (FUSE_CHIP_REG_START_OFFSET) to 0x7000F800 + 0x3FC (FUSE_CHIP_REG_END_OFFSET) represent cached values read from certain fuses.
Registers
Below is a list of fuse driver registers used by the Switch's bootloaders.
Driver registers
| Name | Address |
|---|---|
| FUSE_CTRL | 0x7000F800 |
| FUSE_REG_ADDR | 0x7000F804 |
| FUSE_REG_READ | 0x7000F808 |
| FUSE_REG_WRITE | 0x7000F80C |
| FUSE_TIME_RD1 | 0x7000F810 |
| FUSE_TIME_RD2 | 0x7000F814 |
| FUSE_TIME_PGM1 | 0x7000F818 |
| FUSE_TIME_PGM2 | 0x7000F81C |
| FUSE_PRIV2INTFC | 0x7000F820 |
| FUSE_FUSEBYPASS | 0x7000F824 |
| FUSE_PRIVATEKEYDISABLE | 0x7000F828 |
| FUSE_DIS_PGM | 0x7000F82C |
| FUSE_WRITE_ACCESS | 0x7000F830 |
| FUSE_PWR_GOOD_SW | 0x7000F834 |
| FUSE_PRIV2RESHIFT | 0x7000F83C |
| FUSE_TIME_RD3 | 0x7000F84C |
| FUSE_PRIVATE_KEY0_NONZERO | 0x7000F880 |
| FUSE_PRIVATE_KEY1_NONZERO | 0x7000F884 |
| FUSE_PRIVATE_KEY2_NONZERO | 0x7000F888 |
| FUSE_PRIVATE_KEY3_NONZERO | 0x7000F88C |
| FUSE_PRIVATE_KEY4_NONZERO | 0x7000F890 |
FUSE_CTRL
| Bits | Description |
|---|---|
| 0-1 | Fuse command (1 = FUSE_READ; 2 = FUSE_WRITE; 3 = FUSE_SENSE) |
| 16-20 | Fuse state (4 = STATE_IDLE) |
| 26 | Fuse power down mode flag (FUSE_CTRL_PD) |
| 30 | Fuse sense status (FUSE_CTRL_SENSE_DONE) |
Before fuse reading/writing the power down mode must be disabled. FUSE_SENSE mode flushes programmed values into the cache registers.
FUSE_REG_ADDR
This register takes the address of the fuse to be read/written/sensed.
FUSE_REG_READ
This register receives the value read from the fuse.
FUSE_REG_WRITE
This register takes the value to be written to the fuse.
FUSE_TIME_PGM2
This register takes the fuse programming pulse (0xC0 == 19200 kHz).
FUSE_PRIV2INTFC
| Bits | Description |
|---|---|
| 0 | FUSE_PRIV2INTFC_SDATA |
| 1 | FUSE_PRIV2INTFC_SKIP_RECORDS |
FUSE_DIS_PGM
If set to 0x01, this register disables fuse programming.
FUSE_WRITE_ACCESS
If set to 0x01, this register disables software writes to the fuse driver registers.
Cache registers
| Name | Address |
|---|---|
| FUSE_PRODUCTION_MODE | 0x7000F900 |
| FUSE_JTAG_SECUREID_VALID | 0x7000F904 |
| FUSE_ODM_LOCK | 0x7000F908 |
| FUSE_OPT_OPENGL_EN | 0x7000F90C |
| FUSE_SKU_INFO | 0x7000F910 |
| FUSE_CPU_SPEEDO_0_CALIB | 0x7000F914 |
| FUSE_CPU_IDDQ_CALIB | 0x7000F918 |
| FUSE_DAC_CRT_CALIB | 0x7000F91C |
| FUSE_DAC_HDTV_CALIB | 0x7000F920 |
| FUSE_DAC_SDTV_CALIB | 0x7000F924 |
| FUSE_OPT_FT_REV | 0x7000F928 |
| FUSE_CPU_SPEEDO_1_CALIB | 0x7000F92C |
| FUSE_CPU_SPEEDO_2_CALIB | 0x7000F930 |
| FUSE_SOC_SPEEDO_0_CALIB | 0x7000F934 |
| FUSE_SOC_SPEEDO_1_CALIB | 0x7000F938 |
| FUSE_SOC_SPEEDO_2_CALIB | 0x7000F93C |
| FUSE_SOC_IDDQ_CALIB | 0x7000F940 |
| FUSE_RESERVED_PRODUCTION_WP | 0x7000F944 |
| FUSE_FA | 0x7000F948 |
| FUSE_RESERVED_PRODUCTION | 0x7000F94C |
| FUSE_HDMI_LANE0_CALIB | 0x7000F950 |
| FUSE_HDMI_LANE1_CALIB | 0x7000F954 |
| FUSE_HDMI_LANE2_CALIB | 0x7000F958 |
| FUSE_HDMI_LANE3_CALIB | 0x7000F95C |
| FUSE_ENCRYPTION_RATE | 0x7000F960 |
| FUSE_PUBLIC_KEY0 | 0x7000F964 |
| FUSE_PUBLIC_KEY1 | 0x7000F968 |
| FUSE_PUBLIC_KEY2 | 0x7000F96C |
| FUSE_PUBLIC_KEY3 | 0x7000F970 |
| FUSE_PUBLIC_KEY4 | 0x7000F974 |
| FUSE_PUBLIC_KEY5 | 0x7000F978 |
| FUSE_PUBLIC_KEY6 | 0x7000F97C |
| FUSE_PUBLIC_KEY7 | 0x7000F980 |
| FUSE_TSENSOR1_CALIB | 0x7000F984 |
| FUSE_TSENSOR2_CALIB | 0x7000F988 |
| FUSE_VSENSOR_CALIB | 0x7000F98C |
| FUSE_OPT_CP_REV | 0x7000F990 |
| FUSE_OPT_PFG | 0x7000F994 |
| FUSE_TSENSOR0_CALIB | 0x7000F998 |
| FUSE_FIRST_BOOTROM_PATCH_SIZE | 0x7000F99C |
| FUSE_SECURITY_MODE | 0x7000F9A0 |
| FUSE_PRIVATE_KEY0 | 0x7000F9A4 |
| FUSE_PRIVATE_KEY1 | 0x7000F9A8 |
| FUSE_PRIVATE_KEY2 | 0x7000F9AC |
| FUSE_PRIVATE_KEY3 | 0x7000F9B0 |
| FUSE_PRIVATE_KEY4 | 0x7000F9B4 |
| FUSE_ARM_JTAG_DIS | 0x7000F9B8 |
| FUSE_BOOT_DEVICE_INFO | 0x7000F9BC |
| FUSE_RESERVED_SW | 0x7000F9C0 |
| FUSE_OPT_VP9_DISABLE | 0x7000F9C4 |
| FUSE_RESERVED_ODM0 | 0x7000F9C8 |
| FUSE_RESERVED_ODM1 | 0x7000F9CC |
| FUSE_RESERVED_ODM2 | 0x7000F9D0 |
| FUSE_RESERVED_ODM3 | 0x7000F9D4 |
| FUSE_RESERVED_ODM4 | 0x7000F9D8 |
| FUSE_RESERVED_ODM5 | 0x7000F9DC |
| FUSE_RESERVED_ODM6 | 0x7000F9E0 |
| FUSE_RESERVED_ODM7 | 0x7000F9E4 |
| FUSE_OBS_DIS | 0x7000F9E8 |
| FUSE_NOR_INFO | 0x7000F9EC |
| FUSE_USB_CALIB | 0x7000F9F0 |
| FUSE_SKU_DIRECT_CONFIG | 0x7000F9F4 |
| FUSE_KFUSE_PRIVKEY_CTRL | 0x7000F9F8 |
| FUSE_PACKAGE_INFO | 0x7000F9FC |
| FUSE_OPT_VENDOR_CODE | 0x7000FA00 |
| FUSE_OPT_FAB_CODE | 0x7000FA04 |
| FUSE_OPT_LOT_CODE_0 | 0x7000FA08 |
| FUSE_OPT_LOT_CODE_1 | 0x7000FA0C |
| FUSE_OPT_WAFER_ID | 0x7000FA10 |
| FUSE_OPT_X_COORDINATE | 0x7000FA14 |
| FUSE_OPT_Y_COORDINATE | 0x7000FA18 |
| FUSE_OPT_SEC_DEBUG_EN | 0x7000FA1C |
| FUSE_OPT_OPS_RESERVED | 0x7000FA20 |
| FUSE_SATA_CALIB | 0x7000FA24 |
| FUSE_GPU_IDDQ_CALIB | 0x7000FA28 |
| FUSE_TSENSOR3_CALIB | 0x7000FA2C |
| FUSE_SKU_BOND_OUT_L | 0x7000FA30 |
| FUSE_SKU_BOND_OUT_H | 0x7000FA34 |
| FUSE_SKU_BOND_OUT_U | 0x7000FA38 |
| FUSE_SKU_BOND_OUT_V | 0x7000FA3C |
| FUSE_SKU_BOND_OUT_W | 0x7000FA40 |
| FUSE_OPT_SAMPLE_TYPE | 0x7000FA44 |
| FUSE_OPT_SUBREVISION | 0x7000FA48 |
| FUSE_OPT_SW_RESERVED_0 | 0x7000FA4C |
| FUSE_OPT_SW_RESERVED_1 | 0x7000FA50 |
| FUSE_TSENSOR4_CALIB | 0x7000FA54 |
| FUSE_TSENSOR5_CALIB | 0x7000FA58 |
| FUSE_TSENSOR6_CALIB | 0x7000FA5C |
| FUSE_TSENSOR7_CALIB | 0x7000FA60 |
| FUSE_OPT_PRIV_SEC_EN | 0x7000FA64 |
| FUSE_PKC_DISABLE | 0x7000FA68 |
| FUSE_FUSE2TSEC_DEBUG_DISABLE | 0x7000FA7C |
| FUSE_TSENSOR_COMMON | 0x7000FA80 |
| FUSE_OPT_CP_BIN | 0x7000FA84 |
| FUSE_OPT_GPU_DISABLE | 0x7000FA88 |
| FUSE_OPT_FT_BIN | 0x7000FA8C |
| FUSE_OPT_DONE_MAP | 0x7000FA90 |
| FUSE_APB2JTAG_DISABLE | 0x7000FA98 |
| FUSE_ODM_INFO | 0x7000FA9C |
| FUSE_ARM_CRYPT_DE_FEATURE | 0x7000FAA8 |
| FUSE_WOA_SKU_FLAG | 0x7000FAC0 |
| FUSE_ECO_RESERVE_1 | 0x7000FAC4 |
| FUSE_GCPLEX_CONFIG_FUSE | 0x7000FAC8 |
| FUSE_PRODUCTION_MONTH | 0x7000FACC |
| FUSE_RAM_REPAIR_INDICATOR | 0x7000FAD0 |
| FUSE_TSENSOR9_CALIB | 0x7000FAD4 |
| FUSE_VMIN_CALIBRATION | 0x7000FADC |
| FUSE_AGING_SENSOR_CALIBRATION | 0x7000FAE0 |
| FUSE_DEBUG_AUTHENTICATION | 0x7000FAE4 |
| FUSE_SECURE_PROVISION_INDEX | 0x7000FAE8 |
| FUSE_SECURE_PROVISION_INFO | 0x7000FAEC |
| FUSE_OPT_GPU_DISABLE_CP1 | 0x7000FAF0 |
| FUSE_SPARE_ENDIS | 0x7000FAF4 |
| FUSE_ECO_RESERVE_0 | 0x7000FAF8 |
| FUSE_SPARE_REALIGNMENT_REG_OLD | 0x7000FAFC |
| FUSE_RESERVED_CALIB0 | 0x7000FB04 |
| FUSE_RESERVED_CALIB1 | 0x7000FB08 |
| FUSE_OPT_GPU_TPC0_DISABLE | 0x7000FB0C |
| FUSE_OPT_GPU_TPC0_DISABLE_CP1 | 0x7000FB10 |
| FUSE_OPT_CPU_DISABLE | 0x7000FB14 |
| FUSE_OPT_CPU_DISABLE_CP1 | 0x7000FB18 |
| FUSE_TSENSOR10_CALIB | 0x7000FB1C |
| FUSE_TSENSOR10_CALIB_AUX | 0x7000FB20 |
| FUSE_OPT_RAM_SVOP_DP | 0x7000FB24 |
| FUSE_OPT_RAM_SVOP_PDP | 0x7000FB28 |
| FUSE_OPT_RAM_SVOP_REG | 0x7000FB2C |
| FUSE_OPT_RAM_SVOP_SP | 0x7000FB30 |
| FUSE_OPT_RAM_SVOP_SMPDP | 0x7000FB34 |
| FUSE_OPT_GPU_TPC0_DISABLE_CP2 | 0x7000FB38 |
| FUSE_OPT_GPU_TPC1_DISABLE | 0x7000FB3C |
| FUSE_OPT_GPU_TPC1_DISABLE_CP1 | 0x7000FB40 |
| FUSE_OPT_GPU_TPC1_DISABLE_CP2 | 0x7000FB44 |
| FUSE_OPT_CPU_DISABLE_CP2 | 0x7000FB48 |
| FUSE_OPT_GPU_DISABLE_CP2 | 0x7000FB4C |
| FUSE_USB_CALIB_EXT | 0x7000FB50 |
| FUSE_RESERVED_FIELD | 0x7000FB54 |
| FUSE_OPT_ECC_EN | 0x7000FB58 |
| FUSE_SPARE_REALIGNMENT_REG | 0x7000FB7C |
| FUSE_SPARE_BIT_0 | 0x7000FB80 |
| FUSE_SPARE_BIT_1 | 0x7000FB84 |
| FUSE_SPARE_BIT_2 | 0x7000FB88 |
| FUSE_SPARE_BIT_3 | 0x7000FB8C |
| FUSE_SPARE_BIT_4 | 0x7000FB90 |
| FUSE_SPARE_BIT_5 | 0x7000FB94 |
| FUSE_SPARE_BIT_6 | 0x7000FB98 |
| FUSE_SPARE_BIT_7 | 0x7000FB9C |
| FUSE_SPARE_BIT_8 | 0x7000FBA0 |
| FUSE_SPARE_BIT_9 | 0x7000FBA4 |
| FUSE_SPARE_BIT_10 | 0x7000FBA8 |
| FUSE_SPARE_BIT_11 | 0x7000FBAC |
| FUSE_SPARE_BIT_12 | 0x7000FBB0 |
| FUSE_SPARE_BIT_13 | 0x7000FBB4 |
| FUSE_SPARE_BIT_14 | 0x7000FBB8 |
| FUSE_SPARE_BIT_15 | 0x7000FBBC |
| FUSE_SPARE_BIT_16 | 0x7000FBC0 |
| FUSE_SPARE_BIT_17 | 0x7000FBC4 |
| FUSE_SPARE_BIT_18 | 0x7000FBC8 |
| FUSE_SPARE_BIT_19 | 0x7000FBCC |
| FUSE_SPARE_BIT_20 | 0x7000FBD0 |
| FUSE_SPARE_BIT_21 | 0x7000FBD4 |
| FUSE_SPARE_BIT_22 | 0x7000FBD8 |
| FUSE_SPARE_BIT_23 | 0x7000FBDC |
| FUSE_SPARE_BIT_24 | 0x7000FBE0 |
| FUSE_SPARE_BIT_25 | 0x7000FBE4 |
| FUSE_SPARE_BIT_26 | 0x7000FBE8 |
| FUSE_SPARE_BIT_27 | 0x7000FBEC |
| FUSE_SPARE_BIT_28 | 0x7000FBF0 |
| FUSE_SPARE_BIT_29 | 0x7000FBF4 |
| FUSE_SPARE_BIT_30 | 0x7000FBF8 |
| FUSE_SPARE_BIT_31 | 0x7000FBFC |
FUSE_SKU_INFO
Stores the SKU ID (must be 0x83).
FUSE_OPT_FT_REV
Stores the FT (Final Test) revision.
Original launch units have this value set to 0xA0 (revision 5.0). The first batch of patched units have this value set to 0xC0 (revision 6.0).
FUSE_FA
Stores failure analysis mode.
FUSE_SOC_SPEEDO_1_CALIB
Stores the bootrom patch version.
FUSE_RESERVED_ODM0
This stores an hardware ID.
FUSE_RESERVED_ODM1
This stores an hardware ID.
FUSE_RESERVED_ODM2
| Bits | Description |
|---|---|
| 0-4 | [5.0.0+] Used as key generation (patched units only) |
This stores an hardware ID in original launch units, but in patched units it stores a single value (key generation).
FUSE_RESERVED_ODM3
This stores an hardware ID in original launch units, but in patched units it's empty.
FUSE_RESERVED_ODM4
| Bits | Description |
|---|---|
| 0-1 | Unit type (3 = debug; 0 = retail) |
| 2 | Unknown config (must be 1 on retail) |
| [1.0.0-3.0.2] 3-5
[4.0.0+] 3-7 |
DRAM ID |
| 8 | Unknown config mask (must be 0 on retail) |
| 9 | Unit type mask (0 = debug; 1 = retail) |
| 10 | [3.0.0+] Kiosk mode (0 = retail; 1 = kiosk) |
| 11 | [5.0.0+] Unit patch flag (0 = unpatched; 1 = patched) |
| 16-19 | [4.0.0+] New unit type |
This stores some device configuration parameters.
FUSE_RESERVED_ODM6
This register returns the value programmed into index 0x3A of the fuse array.
FUSE_RESERVED_ODM7
This register returns the value programmed into index 0x3C of the fuse array.
FUSE_PUBLIC_KEY
This stores the SHA256 hash of the 2048-bit RSA key expected at BCT+0x210.
FUSE_OPT_CP_REV
Stores the CP (Chip Probing) revision.
Original launch units have this value set to 0xA0 (revision 5.0). The first batch of patched units have this value set to 0x103 (revision 8.3).
FUSE_PRIVATE_KEY
This stores the 160-bit private key (128 bit SBK + 32-bit device key). Reads to these registers after the SBK is locked out produce all-FF output.
FUSE_RESERVED_SW
| Bits | Description |
|---|---|
| 0-2 | Boot device |
| 3 | Skip device selection straps (0 = don't skip; 1 = skip) |
| 4 | ENABLE_CHARGER_DETECT |
| 5 | ENABLE_WATCHDOG |
| 6 | Forced RCM two button mode (0 = Only VOLUME_UP; 1 = VOLUME_UP + HOME) |
| 7 | RCM USB controller mode (0 = USB 2.0; 1 = XUSB) |
This caches the value of the sw_reserved fuse from the hardware array.
Original launch units have the RCM USB controller mode set to USB 2.0, while the first batch of patched units have the RCM USB controller mode set to XUSB.
FUSE_PKC_DISABLE
This caches the value of the pkc_disable fuse from the hardware array.
FUSE_SPARE_BIT_2
Stores part of the speedo fusing revision.
FUSE_SPARE_BIT_3
Stores part of the speedo fusing revision.
FUSE_SPARE_BIT_4
Stores part of the speedo fusing revision.
FUSE_SPARE_BIT_5
Must be non-zero on retail units, otherwise the first bootloader panics. On debug units it can be zero, which tells the bootloader to choose from two debug master key seeds. If set to non-zero on a debug unit, it tells the bootloader to choose from two master key seeds (with the second one being the retail master key seed).
[4.0.0+] This value is no longer used during boot.
eFuses
The actual hardware fuses can be programmed through the fuse driver after enabling fuse programming.
Below is a list of common fuse indexes used by Tegra devices (and applicable to the Switch). Note that the indexes are relative to the start of the fuse array and each element is a 4 byte word. A single fuse write operation always writes the same word at both fuse_array + 0 (PRIMARY_ALIAS) and fuse_array + 1 (REDUNDANT_ALIAS).
| Name | Index | Bits |
|---|---|---|
| jtag_disable | 0x00 | 1 |
| odm_production_mode | 0x00 | 1 |
| odm_lock | 0x00 | 4 |
| public_key | 0x0C | 256 |
| secure_boot_key | 0x22 | 128 |
| device_key | 0x2A | 32 |
| sec_boot_dev_cfg | 0x2C | 16 |
| sec_boot_dev_sel | 0x2C | 3 |
| sw_reserved | 0x2E | 12 |
| ignore_dev_sel_straps | 0x2E | 1 |
| odm_reserved | 0x2E | 256 |
| pkc_disable | 0x52 | 1 |
| debug_authentication | 0x5A | 5 |
| aid | 0x67 | 32 |
| bootrom_ipatch | 0x72 | 624 |
odm_reserved
The first bootloader only burns fuses in this region. Both fuse indexes 0x3A (odm_reserved + 0x0C) and 0x3C (odm_reserved + 0x0E) are used for anti-downgrade control. These fuses will have their values cached into FUSE_RESERVED_ODM6 and FUSE_RESERVED_ODM7.
bootrom_ipatch
Tegra210 based hardware such as the Switch provides support for bootrom patches. The patch data is burned to the hardware fuse array using a specific format (see shuffle2's ipatch decoder). The bootrom reads these fuses in order to initialize the IPATCH hardware, which allows overriding data returned for code and data fetches done by BPMP.
The following represents the patch data dumped from a Switch console:
RAM:00000000 ; =============== S U B R O U T I N E =======================================
RAM:00000000
RAM:00000000
RAM:00000000 irom_svc_dispatch
RAM:00000000 STMFD SP!, {R0-R2} ; ipatches:
RAM:00000000 ; 0 b57df00 16ae df00 : svc #0x00 (offset 0x48)
RAM:00000000 ; 1 1820df22 3040 df22 : svc #0x22 (offset 0x8c)
RAM:00000000 ; 2 3797df26 6f2e df26 : svc #0x26 (offset 0x94)
RAM:00000000 ; 3 7d9e2000 fb3c 2000 : movs r0, #0x00
RAM:00000000 ; 4 42bdf2c 856 df2c : svc #0x2c (offset 0xa0)
RAM:00000000 ; 5 37aadf42 6f54 df42 : svc #0x42 (offset 0xcc)
RAM:00000000 ; 6 972df4b 12e4 df4b : svc #0x4b (offset 0xde)
RAM:00000000 ; 7 2293df54 4526 df54 : svc #0x54 (offset 0xf0)
RAM:00000000 ; 8 21fadf5d 43f4 df5d : svc #0x5d (offset 0x102)
RAM:00000000 ; 9 bba2ac57 17744 ac57 : data
RAM:00000000 ; 10 bbac3d19 17758 3d19 : data
RAM:00000000 ; 11 1e952001 3d2a 2001 : movs r0, #0x01
RAM:00000004 MOV R2, LR
RAM:00000008 SUB R2, R2, #2
RAM:0000000C LDR R2, [R2]
RAM:00000010 AND R2, R2, #0xFF
RAM:00000014 MOV R2, R2,LSL#1
RAM:00000018 LDR R0, =0x1007B0
RAM:0000001C LDR R1, =0x1007F8
RAM:00000020 SUB R1, R1, R0
RAM:00000024 LDR R0, =0x40004C30
RAM:00000028 ADD R0, R0, R1
RAM:0000002C ADD R2, R2, R0
RAM:00000030 ORR R2, R2, #1
RAM:00000034 LDMFD SP!, {R0,R1}
RAM:00000038 BX R2
RAM:00000038 ; End of function irom_svc_dispatch
RAM:00000038
RAM:00000038 ; ---------------------------------------------------------------------------
RAM:0000003C dword_3C DCD 0x1007B0 ; DATA XREF: irom_svc_dispatch+18↑r
RAM:00000040 dword_40 DCD 0x1007F8 ; DATA XREF: irom_svc_dispatch+1C↑r
RAM:00000044 dword_44 DCD 0x40004C30 ; DATA XREF: irom_svc_dispatch+24↑r
RAM:00000048 CODE16
RAM:00000048
RAM:00000048 ; =============== S U B R O U T I N E =======================================
RAM:00000048
RAM:00000048
RAM:00000048 sub_48
RAM:00000048 MOVS R2, #0 ; 0 b57df00 16ae df00 : svc #0x00 (offset 0x48)
RAM:0000004A MVNS R2, R2
RAM:0000004C LDR R1, =0x60006410
RAM:0000004E STR R2, [R1,#0x30]
RAM:00000050 STR R2, [R1,#0x38]
RAM:00000052 LDR R1, =0x600060F8
RAM:00000054 STR R2, [R1]
RAM:00000056 STR R2, [R1,#4]
RAM:00000058 LDR R1, =0x60006284
RAM:0000005A STR R2, [R1]
RAM:0000005C STR R2, [R1,#0x18]
RAM:0000005E ADDS R1, #0x80
RAM:00000060 ADDS R1, #0x1C
RAM:00000062 STR R2, [R1]
RAM:00000064 STR R2, [R1,#8]
RAM:00000066 STR R2, [R1,#0x10]
RAM:00000068 ADDS R1, #0x80
RAM:0000006A STR R2, [R1]
RAM:0000006C STR R2, [R1,#4]
RAM:0000006E LDR R1, =0x60006554
RAM:00000070 STR R2, [R1]
RAM:00000072 MOVS R2, #0xA0000000
RAM:00000076 LDR R1, =0x60006148
RAM:00000078 STR R2, [R1]
RAM:0000007A ADDS R1, #0x38 ; '8'
RAM:0000007C STR R2, [R1]
RAM:0000007E MOVS R2, #0xE0000000
RAM:00000082 LDR R1, =0x600066A0
RAM:00000084 STR R2, [R1]
RAM:00000086 MOVS R1, #0
RAM:00000088 MOVS R0, #0xE
RAM:0000008A B pop_r2_mov_pc_lr
RAM:0000008A ; End of function sub_48
RAM:0000008A
RAM:0000008C
RAM:0000008C ; =============== S U B R O U T I N E =======================================
RAM:0000008C
RAM:0000008C
RAM:0000008C sub_8C
RAM:0000008C LDR R0, [R1,#0x18] ; 1 1820df22 3040 df22 : svc #0x22 (offset 0x8c)
RAM:0000008E MOVS R2, #1
RAM:00000090 ORRS R0, R2
RAM:00000092 B pop_r2_mov_pc_lr
RAM:00000092 ; End of function sub_8C
RAM:00000092
RAM:00000094
RAM:00000094 ; =============== S U B R O U T I N E =======================================
RAM:00000094
RAM:00000094
RAM:00000094 sub_94
RAM:00000094 LDR R2, [R4,#0x50] ; 2 3797df26 6f2e df26 : svc #0x26 (offset 0x94)
RAM:00000096 ADDS R2, R2, #2
RAM:00000098 STR R2, [R4,#0x50]
RAM:0000009A SUBS R1, #0x80
RAM:0000009C STR R1, [R4,#0x34]
RAM:0000009E B pop_r2_mov_pc_lr
RAM:0000009E ; End of function sub_94
RAM:0000009E
RAM:000000A0
RAM:000000A0 ; =============== S U B R O U T I N E =======================================
RAM:000000A0
RAM:000000A0
RAM:000000A0 sub_A0
RAM:000000A0
RAM:000000A0 ; FUNCTION CHUNK AT RAM:00000148 SIZE 00000004 BYTES
RAM:000000A0
RAM:000000A0 MOVS R0, #0x70000000 ; 4 42bdf2c 856 df2c : svc #0x2c (offset 0xa0)
RAM:000000A4 LDR R6, =dword_7000EF14
RAM:000000A6 LDR R2, =dword_7000E5B4
RAM:000000A8 LDR R2, [R2]
RAM:000000AA CMP R2, #0
RAM:000000AC BEQ loc_B4
RAM:000000AE LDR R2, [R6]
RAM:000000B0 STR R2, [R0,#8]
RAM:000000B2 B loc_BC
RAM:000000B4 ; ---------------------------------------------------------------------------
RAM:000000B4
RAM:000000B4 loc_B4 ; CODE XREF: sub_A0+C↑j
RAM:000000B4 LDR R2, [R0,#8]
RAM:000000B6 LSRS R0, R0, #0x12
RAM:000000B8 ORRS R2, R0
RAM:000000BA STR R2, [R6]
RAM:000000BC
RAM:000000BC loc_BC ; CODE XREF: sub_A0+12↑j
RAM:000000BC LDR R6, =dword_7000E9C0
RAM:000000BE LDR R0, [R6]
RAM:000000C0 MOVS R2, #0x4000
RAM:000000C4 ORRS R2, R0
RAM:000000C6 STR R2, [R6]
RAM:000000C8 LDR R0, [R5,#0x10]
RAM:000000CA B pop_r2_mov_pc_lr
RAM:000000CA ; End of function sub_A0
RAM:000000CA
RAM:000000CC
RAM:000000CC ; =============== S U B R O U T I N E =======================================
RAM:000000CC
RAM:000000CC
RAM:000000CC sub_CC
RAM:000000CC MOVS R2, #0xF000000 ; 5 37aadf42 6f54 df42 : svc #0x42 (offset 0xcc)
RAM:000000D0 BICS R1, R2
RAM:000000D2 STR R1, [R4,#0x10]
RAM:000000D4 LDR R1, [R4,#0x50]
RAM:000000D6 MOVS R2, #7
RAM:000000D8 BICS R1, R2
RAM:000000DA STR R1, [R4,#0x50]
RAM:000000DC B pop_r2_mov_pc_lr
RAM:000000DC ; End of function sub_CC
RAM:000000DC
RAM:000000DE
RAM:000000DE ; =============== S U B R O U T I N E =======================================
RAM:000000DE
RAM:000000DE
RAM:000000DE sub_DE
RAM:000000DE LDR R2, =dword_7000FA9C ; 6 972df4b 12e4 df4b : svc #0x4b (offset 0xde)
RAM:000000E0 LDR R2, [R2]
RAM:000000E2 LSRS R2, R2, #8
RAM:000000E4 LSLS R2, R2, #1
RAM:000000E6 LDR R1, [R4]
RAM:000000E8 BICS R1, R2
RAM:000000EA STR R1, [R4]
RAM:000000EC CMP R0, #0
RAM:000000EE B pop_r2_mov_pc_lr
RAM:000000EE ; End of function sub_DE
RAM:000000EE
RAM:000000F0
RAM:000000F0 ; =============== S U B R O U T I N E =======================================
RAM:000000F0
RAM:000000F0
RAM:000000F0 sub_F0
RAM:000000F0
RAM:000000F0 arg_0= 0
RAM:000000F0
RAM:000000F0 LDR R0, =0x400049F0 ; 7 2293df54 4526 df54 : svc #0x54 (offset 0xf0)
RAM:000000F2 LDR R2, [R0]
RAM:000000F4 STR R2, [SP,#arg_0]
RAM:000000F6 LDR R0, =0x40010000
RAM:000000F8 LSRS R2, R2, #17
RAM:000000FA BEQ pop_r2_mov_pc_lr ; if ([0x400049F0] >> 17) == 0) {
RAM:000000FA ; r2 = [0x400049F0];
RAM:000000FA ; } else {
RAM:000000FC LDR R0, =APBDEV_PMC_CNTRL_0
RAM:000000FE STR R4, [R0] ; write APBDEV_PMC_CNTRL
RAM:00000100
RAM:00000100 loc_100 ; CODE XREF: sub_F0:loc_100↓j
RAM:00000100 B loc_100 ; hang
RAM:00000100 ; End of function sub_F0 ; }
RAM:00000100
RAM:00000102
RAM:00000102 ; =============== S U B R O U T I N E =======================================
RAM:00000102
RAM:00000102
RAM:00000102 sub_102
RAM:00000102
RAM:00000102 arg_0= 0
RAM:00000102
RAM:00000102 LDR R2, =0x40010220 ; 8 21fadf5d 43f4 df5d : svc #0x5d (offset 0x102)
RAM:00000104 STR R2, [SP,#arg_0] ; set r2 retval = [0x40010220]
RAM:00000106 LDR R2, [R2,#0x18]
RAM:00000108 ADDS R0, #0xFC
RAM:0000010A STR R2, [R0,#0x1C] ; [r0+0x118] = [0x40010220 + 0x18]
RAM:0000010C B pop_r2_mov_pc_lr
RAM:0000010C ; End of function sub_102
RAM:0000010C
RAM:0000010C ; ---------------------------------------------------------------------------
RAM:0000010E DCB 0
RAM:0000010F DCB 0
RAM:00000110 off_110 DCD 0x60006410 ; DATA XREF: sub_48+4↑r
RAM:00000114 off_114 DCD 0x600060F8 ; DATA XREF: sub_48+A↑r
RAM:00000118 off_118 DCD 0x60006284 ; DATA XREF: sub_48+10↑r
RAM:0000011C off_11C DCD 0x60006554 ; DATA XREF: sub_48+26↑r
RAM:00000120 off_120 DCD 0x60006148 ; DATA XREF: sub_48+2E↑r
RAM:00000124 off_124 DCD 0x600066A0 ; DATA XREF: sub_48+3A↑r
RAM:00000128 off_128 DCD dword_7000EF14 ; DATA XREF: sub_A0+4↑r
RAM:0000012C off_12C DCD dword_7000E5B4 ; DATA XREF: sub_A0+6↑r
RAM:00000130 off_130 DCD dword_7000E9C0 ; DATA XREF: sub_A0:loc_BC↑r
RAM:00000134 off_134 DCD dword_7000FA9C ; DATA XREF: sub_DE↑r
RAM:00000138 off_138 DCD 0x400049F0 ; DATA XREF: sub_F0↑r
RAM:0000013C dword_13C DCD 0x40010000 ; DATA XREF: sub_F0+6↑r
RAM:00000140 off_140 DCD APBDEV_PMC_CNTRL_0 ; DATA XREF: sub_F0+C↑r
RAM:00000144 off_144 DCD 0x40010220 ; DATA XREF: sub_102↑r
RAM:00000148 ; ---------------------------------------------------------------------------
RAM:00000148 ; START OF FUNCTION CHUNK FOR sub_A0
RAM:00000148
RAM:00000148 pop_r2_mov_pc_lr ; CODE XREF: sub_48+42↑j
RAM:00000148 ; sub_8C+6↑j ...
RAM:00000148 POP {R2}
RAM:0000014A MOV PC, LR
RAM:0000014A ; END OF FUNCTION CHUNK FOR sub_A0The last 4 patches are exclusive to the Switch, while the remaining ones are often included in most Tegra210 based devices.
ipatch 0
This patch configures clock enables and clock gate overrides for new hardware.
u32 CLK_ENB_H_SET = 0x60006328;
u32 CLK_ENB_L_SET = 0x60006320;
u32 CLK_ENB_U_SET = 0x60006330;
u32 CLK_ENB_V_SET = 0x60006440;
u32 CLK_ENB_W_SET = 0x60006448;
u32 CLK_ENB_X_SET = 0x60006284;
u32 CLK_ENB_Y_SET = 0x6000629C;
u32 LVL2_CLK_GATE_OVRA = 0x600060F8;
u32 LVL2_CLK_GATE_OVRB = 0x600060FC;
u32 LVL2_CLK_GATE_OVRC = 0x600063A0;
u32 LVL2_CLK_GATE_OVRD = 0x600063A4;
u32 LVL2_CLK_GATE_OVRE = 0x60006554;
u32 CLK_SOURCE_VI = 0x60006148;
u32 CLK_SOURCE_HOST1X = 0x60006180;
u32 CLK_SOURCE_NVENC = 0x600066A0;
// Set all clock enables and overrides
*(u32 *)CLK_ENB_V_SET = 0xFFFFFFFF;
*(u32 *)CLK_ENB_W_SET = 0xFFFFFFFF;
*(u32 *)LVL2_CLK_GATE_OVRA = 0xFFFFFFFF;
*(u32 *)LVL2_CLK_GATE_OVRB = 0xFFFFFFFF;
*(u32 *)CLK_ENB_X_SET = 0xFFFFFFFF;
*(u32 *)CLK_ENB_Y_SET = 0xFFFFFFFF;
*(u32 *)CLK_ENB_L_SET = 0xFFFFFFFF;
*(u32 *)CLK_ENB_H_SET = 0xFFFFFFFF;
*(u32 *)CLK_ENB_U_SET = 0xFFFFFFFF;
*(u32 *)LVL2_CLK_GATE_OVRC = 0xFFFFFFFF;
*(u32 *)LVL2_CLK_GATE_OVRD = 0xFFFFFFFF;
*(u32 *)LVL2_CLK_GATE_OVRE = 0xFFFFFFFF;
// Set VI, HOST1X and NVENC clock sources to CLK_M
*(u32 *)CLK_SOURCE_VI = 0xA0000000;
*(u32 *)CLK_SOURCE_HOST1X = 0xA0000000;
*(u32 *)CLK_SOURCE_NVENC = 0xE0000000;
/*
Untranslated instructions:
MOVS R1, #0
MOVS R0, #0xE
*/
return;ipatch 1
This patch is a bugfix.
LP0 resume code expects APBDEV_PMC_SCRATCH190_0 to be set to 0x01, but the bootrom didn't set it.
u32 APBDEV_PMC_SCRATCH190_0 = 0x7000EC18;
u32 pmc_scratch190_val = *(u32 *)APBDEV_PMC_SCRATCH190_0;
return (pmc_scratch190_val | 0x01);ipatch 2
This patch adjusts USB configurations.
u32 USB1_UTMIP_SPARE_CFG0_0 = 0x7D000834;
u32 USB1_UTMIP_BIAS_CFG2_0 = 0x7D000850;
// Increase UTMIP_HSSQUELCH_LEVEL_NEW by 0x02
*(u32 *)USB1_UTMIP_BIAS_CFG2_0 += 0x02;
// Clear FUSE_HS_IREF_CAP_CFG
*(u32 *)USB1_UTMIP_SPARE_CFG0_0 = ((*(u32 *)USB1_UTMIP_SPARE_CFG0_0 & ~(0x118)) - 0x80);
return;ipatch 3
This patch ensures that waiting on PRC_PENDING from the XUSB_DEV register T_XUSB_DEV_XHCI_PORTSC never fails.
ipatch 4
This patch allows backing up and restoring strapping options for warmboot.
u32 APBDEV_PMC_SCRATCH0_0 = 0x7000E450;
u32 APBDEV_PMC_RST_STATUS_0 = 0x7000E5B4;
u32 APBDEV_PMC_SEC_DISABLE8_0 = 0x7000E9C0;
u32 APBDEV_PMC_SECURE_SCRATCH111_0 = 0x7000EF14;
u32 APB_MISC_PP_STRAPPING_OPT_A_0 = 0x70000008;
u32 reset_status = *(u32 *)APBDEV_PMC_RST_STATUS_0;
// Check for regular power on
if (reset_status == 0)
{
// Set all buttons in RCM_STRAPS and backup to PMC scratch
*(u32 *)APBDEV_PMC_SECURE_SCRATCH111_0 = (*(u32 *)APB_MISC_PP_STRAPPING_OPT_A_0 | 0x1C00);
}
else
{
// Restore strapping options from PMC scratch
*(u32 *)APB_MISC_PP_STRAPPING_OPT_A_0 = *(u32 *)APBDEV_PMC_SECURE_SCRATCH111_0;
}
// Disable write access to APBDEV_PMC_SECURE_SCRATCH111_0
*(u32 *)APBDEV_PMC_SEC_DISABLE8_0 |= 0x4000;
return *(u32 *)APBDEV_PMC_SCRATCH0_0;ipatch 5
This patch adjusts USB configurations.
u32 USB1_UTMIP_HSRX_CFG0_0 = 0x7D000810;
u32 USB1_UTMIP_BIAS_CFG2_0 = 0x7D000850;
// Clear UTMIP_IDLE_WAIT, UTMIP_ELASTIC_LIMIT and UTMIP_PCOUNT_UPDN_DIV,
// and set UTMIP_IDLE_WAIT to 0x11 and UTMIP_ELASTIC_LIMIT to 0x10
*(u32 *)USB1_UTMIP_HSRX_CFG0_0 = ((*(u32 *)USB1_UTMIP_HSRX_CFG0_0 & ~(0xF8000) + 0x88000 & ~(0x7C00) + 0x4000) & ~(0xF000000));
// Clear UTMIP_HSSQUELCH_LEVEL_NEW
*(u32 *)USB1_UTMIP_BIAS_CFG2_0 &= ~(0x07);
return;ipatch 6
This patch is a factory backdoor.
It allows controlling the debug authentication configuration using a fuse.
u32 FUSE_ODM_INFO = 0x7000FA9C;
u32 odm_info = *(u32 *)FUSE_ODM_INFO;
debug_auth_override_val = ((odm_info >> 0x08) << 0x01);
// Override debug authentication value stored in IRAM
*(u32 *)0x400028E4 &= ~(debug_auth_override_val);
/*
Untranslated instructions:
CMP R0, #0
*/
return;ipatch 7
This patch is a bugfix.
It prevents overflowing IRAM (0x40010000) when copying the warmboot binary from DRAM.
u32 APBDEV_PMC_CNTRL_0 = 0x7000E400;
u32 warmboot_header_addr = 0x400049F0;
u32 warmboot_bin_size = *(u32 *)warmboot_bin_header_addr;
// Invalid warmboot binary size
if (warmboot_size >> 0x11)
{
// Assert MAIN_RST
// 0x40004BF0 comes from R4 and the bootrom doesn't bother to change it
*(u32 *)APBDEV_PMC_CNTRL_0 = 0x40004BF0;
// Deadlock
while(1);
}
/*
Untranslated instructions:
LDR R0, =0x40010000
LDR R2, [warmboot_bin_header_addr]
*/
return;ipatch 8
This patch is a bugfix.
It sets the correct warmboot binary entrypoint address for RSA signature verification, which would be done in DRAM instead of IRAM without this patch.
u32 warmboot_addr_ptr = 0x40010238;
u32 warmboot_entry_addr_ptr = 0x40004C28;
*(u32 *)warmboot_entry_addr_ptr = *(u32 *)warmboot_addr_ptr;
/*
Untranslated instructions:
LDR R2, [warmboot_addr_ptr]
*/
return;ipatches 9 and 10
These patches modify the 256-bit Secure Provisioning AES key with index 0x3A.
ipatch 11
This patch forces the value of SE_TZRAM_SECURITY to be 0x01 instead of restoring it from the saved SE context.
Anti-downgrade
The first bootloader verifies FUSE_RESERVED_ODM7 to prevent downgrading. How many fuses are expected to be burnt depends the device's unit type as below.
| System version | Expected number of burnt fuses (retail) | Expected number of burnt fuses (non-retail) |
|---|---|---|
| 1.0.0 | 1 | 0 |
| 2.0.0-2.3.0 | 2 | 0 |
| 3.0.0 | 3 | 1 |
| 3.0.1-3.0.2 | 4 | 1 |
| 4.0.0-4.1.0 | 5 | 1 |
| 5.0.0-5.1.0 | 6 | 1 |
| 6.0.0-6.1.0 | 7 | 1 |
| 6.2.0 | 8 | 1 |
| 7.0.0-7.0.1 | 9 | 1 |
If too many fuses are burnt the bootloader will panic immediately.
If too few are burnt, the bootloader will enable fuse programming and write the expected value to fuse indexes 0x3A and 0x3C. Afterwards, fuse programming is disabled and the panic value 0x21 is written to PMC_SCRATCH200 register (0x7000EC40). Finally, the watchdog timer is initialized and programmed to force a reset.
On a subsequent boot, after the anti-downgrade fuses are checked again, the PMC_RST_STATUS register (0x7000E5B4) is checked and if set to 0x01 (watchdog reset) the PMC_SCRATCH200 register (0x7000EC40) will be checked for the panic value 0x21. PMC_RST_STATUS will only be set back to 0 (power on reset) if the fuse count matches the new expected value, otherwise the system will panic.