DSTT: Add DMA support and reduce code size (#162) Fixes #111

arm9/source/patches/platform/dstt/DsttReadSdHelperPatchCode.s

@@ -0,0 +1,103 @@
+.cpu arm7tdmi
+.section "dstt_readsd_helper", "ax"
+.syntax unified
+.thumb
+
+// r0 = src sector
+.global dstt_readSd_applySectorCommand
+.type dstt_readSd_applySectorCommand, %function
+dstt_readSd_applySectorCommand:
+    push {r5-r6,lr}
+
+.global dstt_readSd_sdsc_shift
+dstt_readSd_sdsc_shift:
+    lsls r6, r0, #9
+
+    // request sd read for sector 0xaabbccdd
+    // 54 aa bb cc dd 00 00 00
+    movs r5, #0x54
+    strb r5, [r4,#0x8]
+    lsrs r5, r6, #24
+    strb r5, [r4,#0x9]
+    lsrs r5, r6, #16
+    strb r5, [r4,#0xA]
+    lsrs r5, r6, #8
+    strb r5, [r4,#0xB]
+    // make sure the last 3 bytes are zero
+    movs r5, #0xFF
+    ands r6, r5
+    str r6, [r4,#0xC] // storing as little-endian puts the bottom 8 bits as first byte
+
+    pop {r5-r6,pc}
+
+.balign 4
+
+.global dstt_readSd_waitDataReady
+.type dstt_readSd_waitDataReady, %function
+dstt_readSd_waitDataReady:
+    push {r5-r7,lr}
+
+    movs r6, #0x41
+    lsls r6, r6, #20 // r6 = 0x04100000
+
+    // sd fifo full poll
+    // 80 xx xx xx xx xx xx xx
+    // xx bytes are leftover from previous command
+    movs r7, #0x80
+    strb r7, [r4,#0x8]
+
+    ldr r7, =0xA7180000
+cmd80_poll_loop:
+    str r7, [r4,#4]
+
+cmd80_wait_loop:
+    ldrb r5, [r4,#6]
+    lsrs r5, r5, #8
+    bcc cmd80_wait_loop
+    ldr r5, [r6, #0x10]
+    cmp r5, #0
+    bne cmd80_poll_loop
+
+    pop {r5-r7,pc}
+
+.balign 4
+
+// r1 = dst, will be incremented by 512
+.global dstt_readSd_transferData
+.type dstt_readSd_transferData, %function
+dstt_readSd_transferData:
+    push {r5-r7,lr}
+
+    ldr r5, =0xA7180000
+
+    movs r6, #0x41
+    lsls r6, r6, #20 // r6 = 0x04100000
+
+    // read sd fifo
+    // 81 xx xx xx xx xx xx xx
+    // xx bytes are leftover from previous command
+    movs r5, #0x81
+    strb r5, [r4,#0x8]
+    movs r5, #0xA1
+    strb r5, [r4,#7]
+
+cmd81_data_loop:
+    ldrb r5, [r4,#6]
+    lsrs r5, r5, #8 // check if data is ready
+    bcc cmd81_data_loop_check_transfer_end // if not skip reading
+
+    ldr r5, [r6, #0x10]
+    stmia r1!, {r5}
+
+cmd81_data_loop_check_transfer_end:
+    ldrb r5, [r4,#7]
+    lsrs r5, r5, #8 // check if transfer is done
+    bcs cmd81_data_loop
+
+    pop {r5-r7,pc}
+
+.balign 4
+
+.pool
+
+.end