From cbcb7010c6409104e59d52162eb8ad5779bbac9f Mon Sep 17 00:00:00 2001
From: pjht <terppa05@gmail.com>
Date: Mon, 21 Nov 2022 10:39:29 -0600
Subject: [PATCH] Switch to use DMA and clean up boot code

---
 boot/boot.68k |  32 ++++++++++----------------------
 rom.bin       | Bin 188 -> 180 bytes
 2 files changed, 10 insertions(+), 22 deletions(-)

diff --git a/boot/boot.68k b/boot/boot.68k
index 6f70b58..0c257b2 100644
--- a/boot/boot.68k
+++ b/boot/boot.68k
@@ -22,21 +22,20 @@ phead_loop:
 move.l (a0), d1 | If the type of the program header isn't 1 (LOAD), skip the header
 cmpi.l #0x1, d1
 bne.b next_seg
-| Zero the destination memory of the program header
-move.l (20, a0), d1 | Put the memory size of the program header - 1 in d1
+| Zero the destination memory
+move.l (20, a0), d1 | Put the memory size - 1 in d1
 subq.l #0x1, d1
-move.l (8, a0), a1 | Put the starting memory address of the program header in a1
+move.l (8, a0), a1 | Put the starting memory address in a1
 zero_loop:
 move.b #0, (a1)+ | Zero a byte of the destination memory
 dbra d1, zero_loop | Loop back if there is more to zero
-| Copy the data of the program header from the loaded file into position
-move.l (16, a0), d1 | Put the file size of the program header - 1 in d1
+| Copy the data from the loaded file into position
+move.l (16, a0), d1 | Put the file size - 1 in d1
+beq.b next_seg | If the file size is 0, skip the copy (ex, .bss section)
 subq.l #0x1, d1
-cmpi.l #0xFFFFFFFF, d1 | If the file size is 0, skip the copy (ex, .bss section)
-beq.b next_seg
-move.l (4, a0), a1 | Put the address of the start of the loaded program header's data in a1
+move.l (4, a0), a1 | Put the address of the loaded data in a1
 adda.l #0xA000, a1
-move.l (8, a0), a2 | Put the starting memory address of the program header in a2
+move.l (8, a0), a2 | Put the starting memory address in a2
 load_loop:
 move.b (a1)+, (a2)+ | Copy a byte of data into position
 dbra d1, load_loop | Loop back if there is more to copy
@@ -68,22 +67,11 @@ ffc_done:
 | Destination in a1
 | Start sector in d0.l
 | Sector count in d1.l
-| Clobbers a1, d1
 read_sectors:
 move.l d0, (a0) | Set the sector number
 move.l d1, (4, a0) | Set the sector count
-move.w #0x0, (8, a0) | Issue a read command
-| Transfer 0x200 (512) * sector_count bytes from the storage card's data register to (a1)
-lsl.l #8, d1 | d0 = d0 * 256 to compute the number of words to transfer
-subq.l #0x1, d1 | Subtract 1 from the word count to account for the extra loop done by dbra
-bra.b rs_loop
-rs_loop_swap:
-swap.w d1
-rs_loop:
-move.w (0xA, a0), (a1)+ | Transfer a word of sector data to the destination
-dbra.w d1, rs_loop 
-swap.w d1
-dbra.w d1, rs_loop_swap
+move.l a1, (0xC, a0) | Set the destination address
+move.w #0x1, (8, a0) | Issue a DMA read command
 rts
 
 .if . != 512
diff --git a/rom.bin b/rom.bin
index f8b80044bec89b43a99d58d34672fc4755a7990b..3fdcdec42158ae4b58c3e143dbfdeecf36b664e4 100644
GIT binary patch
delta 64
zcmdnPxP?)Tfq`KI5OWCFFfb;>>3I0RWB8Dmr{$r?02E<K^wIDzuwgKosHVrKSp!tZ
Qz`$c!!@$VEF)=F$0KgaxCIA2c

delta 72
zcmdnOxQ9`Vfq`KM5OWCFFfb;h>3I0RWB8C*rsbi>02E<K4AJl~uwk&8sHP`oSp!mM
V1SEkX|Bc=-a0Q<D|7&7W5CB#p67K*2