Fuses
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_CTRL
| Bits | Description |
|---|---|
| 0-1 | Fuse command (1 = FUSE_READ; 2 = FUSE_WRITE; 3 = FUSE_SENSE) |
| 26 | Fuse power down mode flag (FUSE_CTRL_PD) |
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_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_SKU_INFO | 0x7000F910 |
| FUSE_CPU_SPEEDO_0 | 0x7000F914 |
| FUSE_CPU_IDDQ | 0x7000F918 |
| FUSE_FT_REV | 0x7000F928 |
| FUSE_CPU_SPEEDO_1 | 0x7000F92C |
| FUSE_CPU_SPEEDO_2 | 0x7000F930 |
| FUSE_SOC_SPEEDO_0 | 0x7000F934 |
| FUSE_SOC_SPEEDO_1 | 0x7000F938 |
| FUSE_SOC_SPEEDO_2 | 0x7000F93C |
| FUSE_SOC_IDDQ | 0x7000F940 |
| FUSE_FA | 0x7000F948 |
| 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_TSENSOR_1 | 0x7000F984 |
| FUSE_TSENSOR_2 | 0x7000F988 |
| FUSE_CP_REV | 0x7000F990 |
| FUSE_TSENSOR_0 | 0x7000F998 |
| FUSE_FIRST_BOOTROM_PATCH_SIZE_REG | 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_BOOT_DEVICE_INFO | 0x7000F9BC |
| FUSE_RESERVED_SW | 0x7000F9C0 |
| FUSE_VP8_ENABLE | 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_SKU_USB_CALIB | 0x7000F9F0 |
| FUSE_SKU_DIRECT_CONFIG | 0x7000F9F4 |
| FUSE_VENDOR_CODE | 0x7000FA00 |
| FUSE_FAB_CODE | 0x7000FA04 |
| FUSE_LOT_CODE_0 | 0x7000FA08 |
| FUSE_LOT_CODE_1 | 0x7000FA0C |
| FUSE_WAFER_ID | 0x7000FA10 |
| FUSE_X_COORDINATE | 0x7000FA14 |
| FUSE_Y_COORDINATE | 0x7000FA18 |
| FUSE_SATA_CALIB | 0x7000FA24 |
| FUSE_GPU_IDDQ | 0x7000FA28 |
| FUSE_TSENSOR_3 | 0x7000FA2C |
| FUSE_OPT_SUBREVISION | 0x7000FA48 |
| FUSE_TSENSOR_4 | 0x7000FA54 |
| FUSE_TSENSOR_5 | 0x7000FA58 |
| FUSE_TSENSOR_6 | 0x7000FA5C |
| FUSE_TSENSOR_7 | 0x7000FA60 |
| FUSE_OPT_PRIV_SEC_DIS | 0x7000FA64 |
| FUSE_PKC_DISABLE | 0x7000FA68 |
| FUSE_TSENSOR_COMMON | 0x7000FA80 |
| FUSE_DEBUG_AUTH_OVERRIDE | 0x7000FA9C |
| FUSE_TSENSOR_8 | 0x7000FAD4 |
| FUSE_SECURE_PROVISION_INDEX | 0x7000FAE8 |
| FUSE_RESERVED_CALIB | 0x7000FB04 |
| FUSE_TSENSOR_9 | 0x7000FB1C |
| FUSE_USB_CALIB_EXT | 0x7000FB50 |
| 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_FA
Stores failure analysis mode.
FUSE_SOC_SPEEDO_1
Stores the bootrom patch version.
FUSE_RESERVED_ODM0
This appears to store an hardware ID.
FUSE_RESERVED_ODM1
This appears to store an hardware ID.
FUSE_RESERVED_ODM2
| Bits | Description |
|---|---|
| 0-4 | [5.0.0+] Used as key generation |
This appears to store an hardware ID.
FUSE_RESERVED_ODM3
This appears to store an hardware ID.
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 | [4.0.0+] Kiosk mode (0 = retail; 1 = kiosk) |
| 11 | [5.0.0+] SoC variant (0 = T210; 1 = T214) |
| 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_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 retail master key seeds (only the last one matches the retail master key seed).
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_PUBLIC_KEY
This stores the SHA256 hash of the 2048-bit RSA key expected at BCT+0x210.
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.
FUSE_PKC_DISABLE
This caches the value of the pkc_disable fuse from the hardware array.
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 |
| 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 revision stored in FUSE_CP_REV indicates the unique set of values stored in ipatch fuses.
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.
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 | 6 | 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.