microblaze: Support little-endian microblaze target

[platform/kernel/u-boot.git] / arch / microblaze / cpu / start.S

diff --git a/arch/microblaze/cpu/start.S b/arch/microblaze/cpu/start.S
index 2e9a08d..7f60434 100644 (file)
--- 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