Refactored platform code to use interfaces for patch code with a special feature and improved patch code file names

arm9/source/patches/platform/m3ds/M3DSReadSdSectorsPatchCode.s

@@ -0,0 +1,139 @@
+.cpu arm7tdmi
+.section "m3ds_readsdsectors", "ax"
+.syntax unified
+.thumb
+
+// r0 = src sector
+// r1 = dst
+// r2 = sector count
+.global m3ds_readSdSectors
+.type m3ds_readSdSectors, %function
+m3ds_readSdSectors:
+    push {r1,r2,r4-r7,lr}
+    ldr r4, =0x040001A0
+    movs r3, #0x80
+    strb r3, [r4,#1]
+
+    // construct first 4 bytes of the command
+    // given a sector address in r0: 0xaabbccdd
+    // first command word: B2 aa bb cc
+    // B2 is for requesting the next sequential read
+    adr r7, cmdWord0Tmp // write bytewise to this temp location
+    movs r3, #0xB2
+    strb r3, [r7,#0]
+    lsrs r3, r0, #24
+    strb r3, [r7,#1]
+    lsrs r3, r0, #16
+    strb r3, [r7,#2]
+    lsrs r3, r0, #8
+    strb r3, [r7,#3]
+    ldr r6, [r7] // read back as 32 bit value from the temp location
+    str r6, [r4,#8] // write to the actual command register
+
+    // construct second 4 bytes of the command
+    // second command word: dd 00 00 00
+    lsls r0, r0, #24
+    lsrs r7, r0, #24 // r7 = dd
+    str r7, [r4,#0xC] // storing as little-endian puts the bottom 8 bits as first byte
+
+    ldr r5, [sp,#4] // sector count
+    movs r3, #0xBD // command for single sector read request
+    cmp r5, #1
+    beq 1f
+    movs r3, #0xB1 // command for multi sector read request
+1:
+    strb r3, [r4,#8] // use the right command for the first sector
+
+    ldr r0, [sp,#0] // dst
+sector_loop:
+    ldr r3, m3ds_receiveSector_address
+    bl blx_r3
+    str r6, [r4,#8] // write the command for requesting the next sector
+    str r7, [r4,#0xC]
+    subs r5, #1
+    bne sector_loop
+    ldr r3, [sp,#4]
+    cmp r3, #1
+    bls read_sectors_end
+
+    // send command for ending multi-sector read
+    // B3 00 00 00 00 00 00 00
+    movs r2, #0xB3
+    str r2, [r4,#8] // B3 00 00 00
+    str r5, [r4,#0xC] // 00 00 00 00
+    ldr r3, =0xA0486100
+    str r3, [r4,#4] // start transfer
+
+    // wait for transfer to end
+3:
+    ldrb r1, [r4, #7]
+    lsrs r1, r1, #8
+    bcs 3b
+
+read_sectors_end:
+    pop {r1-r2,r4-r7,pc}
+
+blx_r3:
+    bx r3
+
+.balign 4
+
+.global m3ds_receiveSector_address
+m3ds_receiveSector_address:
+    .word 0
+
+cmdWord0Tmp:
+    .word 0
+
+.pool
+
+.section "m3ds_readsdsectors_receiveSector", "ax"
+.thumb
+.global m3ds_receiveSector
+.type m3ds_receiveSector, %function
+m3ds_receiveSector:
+    ldr r1, =0x04100010
+
+receiveSector_poll_loop:
+    ldr r3, =0xA7586000
+    str r3, [r4,#4]
+
+receiveSector_poll_transfer_loop:
+    ldrb r3, [r4,#6]
+    lsrs r3, r3, #8
+    bcc receiveSector_poll_check_transfer_end
+    ldr r2, [r1]
+
+receiveSector_poll_check_transfer_end:
+    ldrb r3, [r4,#7]
+    lsrs r3, r3, #8
+    bcs receiveSector_poll_transfer_loop
+
+    cmp r2, #0
+    bne receiveSector_poll_loop
+    movs r3, #0xBA
+    str r3, [r4,#8]
+    str r2, [r4,#0xC]
+    ldr r3, =0xA1586000
+    str r3, [r4,#4]
+
+receiveSector_data_loop:
+    ldrb r3, [r4,#6]
+    lsrs r3, r3, #8 // check if data is ready
+    bcc receiveSector_data_loop_check_transfer_end // if not skip reading
+    
+    ldr r3, [r1]
+    stmia r0!, {r3}
+
+receiveSector_data_loop_check_transfer_end:
+    ldrb r3, [r4,#7]
+    lsrs r3, r3, #8 // check if transfer is done
+    bcs receiveSector_data_loop
+
+    bx lr
+
+.balign 4
+
+.pool
+
+.end