Initial commit

arm9/source/patches/platform/r4/r4WriteSdAsm.s

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+.cpu arm7tdmi
+.section "r4_writesd", "ax"
+.syntax unified
+.thumb
+
+// r0 = dst sector
+// r1 = src
+// r2 = sector count
+.global r4_writeSd
+.type r4_writeSd, %function
+r4_writeSd:
+    push {r4-r7,lr}
+
+    ldr r4, =0x040001A0
+    movs r3, #0x80
+    strb r3, [r4,#1]
+
+sector_loop:
+    // write at sd byte address 0xaabbccdd
+    // BB aa bb cc dd 00 00 00
+    lsls r7, r0, #9 // sd sector to sd byte address
+    movs r3, #0xBB
+    strb r3, [r4,#0x8]
+    lsrs r3, r7, #24
+    strb r3, [r4,#0x9]
+    lsrs r3, r7, #16
+    strb r3, [r4,#0xA]
+    lsrs r3, r7, #8
+    strb r3, [r4,#0xB]
+    lsls r3, r7, #24
+    lsrs r3, r3, #24 // r7 = dd
+    str r3, [r4,#0xC] // storing as little-endian puts the bottom 8 bits as first byte
+
+    ldr r6, =0x04100010
+
+    ldr r3, =0xE1586000
+    str r3, [r4,#4]
+
+BB_data_loop:
+    ldrb r3, [r4,#6]
+    lsrs r3, r3, #8 // check if ready to write
+    bcc BB_data_loop_check_transfer_end // if not skip reading
+
+    ldmia r1!, {r3}
+    str r3, [r6]
+
+BB_data_loop_check_transfer_end:
+    ldrb r3, [r4,#7]
+    lsrs r3, r3, #8 // check if transfer is done
+    bcs BB_data_loop
+
+    movs r3, #0xBC
+    strb r3, [r4,#0x8]
+
+BC_poll_loop:
+    ldr r3, =0xA7586000
+    str r3, [r4,#4]
+
+BC_poll_transfer_loop:
+    ldrb r3, [r4,#6]
+    lsrs r3, r3, #8
+    bcc BC_poll_check_transfer_end
+    ldr r5, [r6]
+
+BC_poll_check_transfer_end:
+    ldrb r3, [r4,#7]
+    lsrs r3, r3, #8
+    bcs BC_poll_transfer_loop
+
+    cmp r5, #0
+    bne BC_poll_loop
+
+    adds r0, #1
+    subs r2, #1
+    bne sector_loop
+
+    pop {r4-r7,pc}
+
+.balign 4
+
+.pool
+
+.end