diff options
Diffstat (limited to 'arch/microblaze/cpu')
| -rw-r--r-- | arch/microblaze/cpu/start.S | 60 |
1 files changed, 51 insertions, 9 deletions
diff --git a/arch/microblaze/cpu/start.S b/arch/microblaze/cpu/start.S index 2e9a08d..7f60434 100644 --- a/arch/microblaze/cpu/start.S +++ b/arch/microblaze/cpu/start.S @@ -32,6 +32,22 @@ _start: mts rmsr, r0 /* disable cache */ addi r1, r0, CONFIG_SYS_INIT_SP_OFFSET addi r1, r1, -4 /* Decrement SP to top of memory */ + + /* Find-out if u-boot is running on BIG/LITTLE endian platform + * There are some steps which is necessary to keep in mind: + * 1. Setup offset value to r6 + * 2. Store word offset value to address 0x0 + * 3. Load just byte from address 0x0 + * 4a) LITTLE endian - r10 contains 0x2 because it is the smallest + * value that's why is on address 0x0 + * 4b) BIG endian - r10 contains 0x0 because 0x2 offset is on addr 0x3 + */ + addik r6, r0, 0x2 /* BIG/LITTLE endian offset */ + swi r6, r0, 0 + lbui r10, r0, 0 + swi r6, r0, 0x40 + swi r10, r0, 0x50 + /* add opcode instruction for 32bit jump - 2 instruction imm & brai*/ addi r6, r0, 0xb0000000 /* hex b000 opcode imm */ swi r6, r0, 0x0 /* reset address */ @@ -75,26 +91,52 @@ _start: /* user_vector_exception */ addik r6, r0, _exception_handler sw r6, r1, r0 - lhu r7, r1, r0 - shi r7, r0, 0xa - shi r6, r0, 0xe + /* + * BIG ENDIAN memory map for user exception + * 0x8: 0xB000XXXX + * 0xC: 0xB808XXXX + * + * then it is necessary to count address for storing the most significant + * 16bits from _exception_handler address and copy it to + * 0xa address. Big endian use offset in r10=0 that's why is it just + * 0xa address. The same is done for the least significant 16 bits + * for 0xe address. + * + * LITTLE ENDIAN memory map for user exception + * 0x8: 0xXXXX00B0 + * 0xC: 0xXXXX08B8 + * + * Offset is for little endian setup to 0x2. rsubi instruction decrease + * address value to ensure that points to proper place which is + * 0x8 for the most significant 16 bits and + * 0xC for the least significant 16 bits + */ + lhu r7, r1, r10 + rsubi r8, r10, 0xa + sh r7, r0, r8 + rsubi r8, r10, 0xe + sh r6, r0, r8 #endif #ifdef CONFIG_SYS_INTC_0 /* interrupt_handler */ addik r6, r0, _interrupt_handler sw r6, r1, r0 - lhu r7, r1, r0 - shi r7, r0, 0x12 - shi r6, r0, 0x16 + lhu r7, r1, r10 + rsubi r8, r10, 0x12 + sh r7, r0, r8 + rsubi r8, r10, 0x16 + sh r6, r0, r8 #endif /* hardware exception */ addik r6, r0, _hw_exception_handler sw r6, r1, r0 - lhu r7, r1, r0 - shi r7, r0, 0x22 - shi r6, r0, 0x26 + lhu r7, r1, r10 + rsubi r8, r10, 0x22 + sh r7, r0, r8 + rsubi r8, r10, 0x26 + sh r6, r0, r8 /* enable instruction and data cache */ mfs r12, rmsr |