Cleaned up bs-start.s file

... thanks, AuroraWright!

source/abstraction/bs-start.s

@@ -5,103 +5,54 @@
 .extern main
 .align 4
 .arm
-
-#define SIZE_32KB  0b01110
-#define SIZE_128KB 0b10000
-#define SIZE_512KB 0b10010
-#define SIZE_2MB   0b10100
-#define SIZE_128MB 0b11010
-#define SIZE_256MB 0b11011
-#define SIZE_4GB   0b11111
-
-@ Makes a MPU partition value
-#define MAKE_PARTITION(offset, size_enum) \
-    (((offset) >> 12 << 12) | ((size_enum) << 1) | 1)
-
-
 _start:
-    b _init
-
-    @ required, don't move :)
-    @ will be set to FIRM ARM9 entry point by BRAHMA
-    arm9ep_backup:  .long 0xFFFF0000
-
-_mpu_partition_table:
-    .word MAKE_PARTITION(0x00000000, SIZE_4GB)   @ 0: Background region
-    .word MAKE_PARTITION(0x00000000, SIZE_128MB) @ 1: Instruction TCM (mirrored every 32KB)
-    .word MAKE_PARTITION(0x08000000, SIZE_2MB)   @ 2: ARM9 internal memory
-    .word MAKE_PARTITION(0x10000000, SIZE_128MB) @ 3: IO region
-    .word MAKE_PARTITION(0x18000000, SIZE_128MB) @ 4: external device memory
-    .word MAKE_PARTITION(0x1FF80000, SIZE_512KB) @ 5: AXI WRAM
-    .word MAKE_PARTITION(0x20000000, SIZE_256MB) @ 6: FCRAM
-    .word 0                                      @ 7: Unused
-
-_populate_mpu:
-    push {r4-r5, lr}
-    ldr r4, =_mpu_partition_table
-
-    ldr r5, [r4, #0x0]        @ mmu_partition_table[0] load
-    mcr p15, 0, r5, c6, c0, 0 @ mmu_partition_table[0] write
-    ldr r5, [r4, #0x4]
-    mcr p15, 0, r5, c6, c1, 0
-    ldr r5, [r4, #0x8]
-    mcr p15, 0, r5, c6, c2, 0
-    ldr r5, [r4, #0xC]
-    mcr p15, 0, r5, c6, c3, 0
-    ldr r5, [r4, #0x10]
-    mcr p15, 0, r5, c6, c4, 0
-    ldr r5, [r4, #0x14]
-    mcr p15, 0, r5, c6, c5, 0
-    ldr r5, [r4, #0x18]
-    mcr p15, 0, r5, c6, c6, 0
-    ldr r5, [r4, #0x1C]
-    mcr p15, 0, r5, c6, c7, 0
+    @ Change the stack pointer
+    mov sp, #0x27000000
     
     @ Give read/write access to all the memory regions
-    ldr r5, =0x03333333
-    mcr p15, 0, r5, c5, c0, 2 @ data access
-    ldr r5, =0x03300330
-    mcr p15, 0, r5, c5, c0, 3 @ instruction access
+    ldr r0, =0x33333333
+    mcr p15, 0, r0, c5, c0, 2 @ write data access
+    mcr p15, 0, r0, c5, c0, 3 @ write instruction access
 
-    mov r5, #0x66
-    mcr p15, 0, r5, c2, c0, 0  @ data cachable
-    mcr p15, 0, r5, c2, c0, 1  @ instruction cachable
+    @ Set MPU permissions and cache settings
+    ldr r0, =0xFFFF001D	@ ffff0000 32k
+    ldr r1, =0x01FF801D	@ 01ff8000 32k
+    ldr r2, =0x08000027	@ 08000000 1M
+    ldr r3, =0x10000021	@ 10000000 128k
+    ldr r4, =0x10100025	@ 10100000 512k
+    ldr r5, =0x20000035	@ 20000000 128M
+    ldr r6, =0x1FF00027	@ 1FF00000 1M
+    ldr r7, =0x1800002D	@ 18000000 8M
+    mcr p15, 0, r0, c6, c0, 0
+    mcr p15, 0, r1, c6, c1, 0
+    mcr p15, 0, r2, c6, c2, 0
+    mcr p15, 0, r3, c6, c3, 0
+    mcr p15, 0, r4, c6, c4, 0
+    mcr p15, 0, r5, c6, c5, 0
+    mcr p15, 0, r6, c6, c6, 0
+    mcr p15, 0, r7, c6, c7, 0
+    mov r0, #0x25
+    mcr p15, 0, r0, c2, c0, 0  @ data cacheable
+    mcr p15, 0, r0, c2, c0, 1  @ instruction cacheable
+    mcr p15, 0, r0, c3, c0, 0  @ data bufferable
  
-    mov r5, #0x10
-    mcr p15, 0, r5, c3, c0, 0  @ data bufferable
+    @ Enable caches
+    mrc p15, 0, r0, c1, c0, 0  @ read control register
+    orr r0, r0, #(1<<18)       @ - itcm enable
+    orr r0, r0, #(1<<12)       @ - instruction cache enable
+    orr r0, r0, #(1<<2)        @ - data cache enable
+    orr r0, r0, #(1<<0)        @ - mpu enable
+    mcr p15, 0, r0, c1, c0, 0  @ write control register
 
-    pop {r4-r5, pc}
+    @ Flush caches
+    mov r0, #0
+    mcr p15, 0, r0, c7, c5, 0  @ flush I-cache
+    mcr p15, 0, r0, c7, c6, 0  @ flush D-cache
+    mcr p15, 0, r0, c7, c10, 4 @ drain write buffer
 
-_enable_caches:
-    push {r4-r5, lr}
-
-    bl _populate_mpu
-    mov r5, #0
-    mcr p15, 0, r5, c7, c5, 0  @ flush I-cache
-    mcr p15, 0, r5, c7, c6, 0  @ flush D-cache
-
-    mrc p15, 0, r4, c1, c0, 0
-    orr r4, r4, #(1<<18)       @ itcm enable
-    orr r4, r4, #(1<<12)       @ instruction cache enable
-    orr r4, r4, #(1<<2)        @ data cache enable
-    orr r4, r4, #(1<<0)        @ mpu enable
-    mcr p15, 0, r4, c1, c0, 0
-
-    pop {r4-r5, pc}
-
-_init:
-    push {r0-r12, lr}
-
-    bl _enable_caches
     bl main
 
-    mrc p15, 0, r4, c1, c0, 0
-    bic r4, r4, #(1<<0)        @ mpu disable
-    mcr p15, 0, r4, c1, c0, 0
-
-    pop {r0-r12, lr}
-
-    @ return control to FIRM
-    ldr pc, arm9ep_backup
+.die:
+    b .die
 
 #endif // EXEC_BOOTSTRAP