External Debug Support
----------------------
Freescale's e500v1 and e500v2 cores (used in mpc85xx chips) have some
restrictions on external debugging (JTAG). In particular, for the debugger to
be able to receive control after a single step or breakpoint:
- MSR[DE] must be set
- A valid opcode must be fetchable, through the MMU, from the debug
exception vector (IVPR + IVOR15).
To maximize the time during which this requirement is met, U-Boot sets MSR[DE]
immediately on entry and keeps it set. It also uses a temporary TLB to keep a
mapping to a valid opcode at the debug exception vector, even if we normally
don't support exception vectors being used that early, and that's not the area
where U-Boot currently executes from.
Note that there may still be some small windows where debugging will not work,
such as in between updating IVPR and IVOR15.
Config Switches:
----------------
Please refer README section "MPC85xx External Debug Support"
Major Config Switches during various boot Modes
----------------------------------------------
NOR boot
!defined(CONFIG_SYS_RAMBOOT) && !defined(CONFIG_SPL)
NOR boot Secure
!defined(CONFIG_SYS_RAMBOOT) && defined(CONFIG_SECURE_BOOT)
RAMBOOT(SD, SPI & NAND boot)
defined(CONFIG_SYS_RAMBOOT)
RAMBOOT Secure (SD, SPI & NAND)
defined(CONFIG_SYS_RAMBOOT) && defined(CONFIG_SECURE_BOOT)
NAND SPL BOOT
defined(CONFIG_SYS_RAMBOOT) && defined(CONFIG_NAND_SPL)
TLB Entries during u-boot execution
-----------------------------------
Note: Sequence number is in order of execution
A) defined(CONFIG_SYS_RAMBOOT) i.e. SD, SPI, NAND RAMBOOT & NAND_SPL boot
1) TLB entry to overcome e500 v1/v2 debug restriction
Location : Label "_start_e500"
TLB Entry : CONFIG_SYS_PPC_E500_DEBUG_TLB
EPN -->RPN : CONFIG_SYS_MONITOR_BASE --> CONFIG_SYS_MONITOR_BASE
Properties : 256K, AS0, I, IPROT
2) TLB entry for working in AS1
Location : Label "create_init_ram_area"
TLB Entry : 15
EPN -->RPN : CONFIG_SYS_MONITOR_BASE --> CONFIG_SYS_MONITOR_BASE
Properties : 1M, AS1, I, G, IPROT
3) TLB entry for the stack during AS1
Location : Lable "create_init_ram_area"
TLB Entry : 14
EPN -->RPN : CONFIG_SYS_INIT_RAM_ADDR --> CONFIG_SYS_INIT_RAM_ADDR
Properties : 16K, AS1, IPROT
4) TLB entry for CCSRBAR during AS1 execution
Location : cpu_init_early_f
TLB Entry : 13
EPN -->RPN : CONFIG_SYS_CCSRBAR --> CONFIG_SYS_CCSRBAR
Properties : 1M, AS1, I, G
5) Invalidate unproctected TLB Entries
Location : cpu_init_early_f
Invalidated: 13
6) Create TLB entries as per boards/freescale/<board>/tlb.c
Location : cpu_init_early_f --> init_tlbs()
Properties : ..., AS0, ...
Please note It can overwrites previous TLB Entries.
7) Disable TLB Entries of AS1
Location : cpu_init_f --> disable_tlb()
Disable : 15, 14
8) Update Flash's TLB entry
Location : Board_init_r
TLB entry : Search from TLB entries
EPN -->RPN : CONFIG_SYS_FLASH_BASE --> CONFIG_SYS_FLASH_BASE_PHYS
Properties : Board specific size, AS0, I, G, IPROT
B) !defined(CONFIG_SYS_RAMBOOT) i.e. NOR boot
1) TLB entry to overcome e500 v1/v2 debug restriction
Location : Label "_start_e500"
TLB Entry : CONFIG_SYS_PPC_E500_DEBUG_TLB
#if defined(CONFIG_SECURE_BOOT)
EPN -->RPN : CONFIG_SYS_MONITOR_BASE --> CONFIG_SYS_PBI_FLASH_WINDOW
Properties : 1M, AS1, I, G, IPROT
#else
EPN -->RPN : CONFIG_SYS_MONITOR_BASE & 0xffc00000 --> 0xffc00000
Properties : 4M, AS0, I, G, IPROT
#endif
2) TLB entry for working in AS1
Location : Label "create_init_ram_area"
TLB Entry : 15
#if defined(CONFIG_SECURE_BOOT)
EPN -->RPN : CONFIG_SYS_MONITOR_BASE --> CONFIG_SYS_PBI_FLASH_WINDOW
Properties : 1M, AS1, I, G, IPROT
#else
EPN -->RPN : CONFIG_SYS_MONITOR_BASE & 0xffc00000 --> 0xffc00000
Properties : 4M, AS1, I, G, IPROT
#endif
3) TLB entry for the stack during AS1
Location : Lable "create_init_ram_area"
TLB Entry : 14
EPN -->RPN : CONFIG_SYS_INIT_RAM_ADDR --> CONFIG_SYS_INIT_RAM_ADDR
Properties : 16K, AS1, IPROT
4) TLB entry for CCSRBAR during AS1 execution
Location : cpu_init_early_f
TLB Entry : 13
EPN -->RPN : CONFIG_SYS_CCSRBAR --> CONFIG_SYS_CCSRBAR
Properties : 1M, AS1, I, G
5) TLB entry for Errata workaround CONFIG_SYS_FSL_ERRATUM_IFC_A003399
Location : cpu_init_early_f
TLB Entry : 9
EPN -->RPN : SRAM_BASE_ADDR --> SRAM_BASE_ADDR
Properties : 1M, AS1, I
6) CONFIG_SYS_FSL_ERRATUM_IFC_A003399 Adjust flash's phys addr
Location : cpu_init_early_f --> setup_ifc
TLB Entry : Get Flash TLB
EPN -->RPN : Adjusted flash_phys --> Adjusted flash_phys
Properties : 4M, AS1, I, G, IPROT
7) CONFIG_SYS_FSL_ERRATUM_IFC_A003399: E500 v1,v2 debug restriction
Location : cpu_init_early_f --> setup_ifc
TLB Entry : CONFIG_SYS_PPC_E500_DEBUG_TLB
EPN -->RPN : Adjusted flash_phys --> Adjusted flash_phys
Properties : 4M, AS0, I, G, IPROT
8) Invalidate unproctected TLB Entries
Location : cpu_init_early_f
Invalidated: 13, 9
9) Create TLB entries as per boards/freescale/<board>/tlb.c
Location : cpu_init_early_f --> init_tlbs()
Properties : ..., AS0, ...
Note: It can overwrites previous TLB Entries
10) Disable TLB Entries of AS1
Location : cpu_init_f --> disable_tlb()
Disable : 15, 14
11) Create DDR's TLB entriy
Location : Board_init_f -> dram_init
TLB entry : Search free TLB entry
12) Update Flash's TLB entry
Location : Board_init_r
TLB entry : Search from TLB entries
EPN -->RPN : CONFIG_SYS_FLASH_BASE --> CONFIG_SYS_FLASH_BASE_PHYS
Properties : Board specific size, AS0, I, G, IPROT