msx2: fix rom bootstrap

Kernel/platform-msx2/Makefile

@@ -14,7 +14,7 @@ JUNK = $(CSRCS:.c=.lst) $(CSRCS:.c=.asm) $(CSRCS:.c=.sym) $(ASRCS:.s=.lst) $(ASR
 all:	$(OBJS)
 
 $(COBJS): %.rel: %.c
-	$(CROSS_CC) $(CROSS_CCOPTS) -c $<
+	$(CROSS_CC) $(CROSS_CCOPTS) --codeseg CODE2 -c $<
 
 $(AOBJS): %.rel: %.s
 	$(CROSS_AS) $(ASOPTS) $<
@@ -24,4 +24,4 @@ clean:
 
 image:
 	dd if=../fuzix.bin of=../fuzix.com bs=256 skip=1
-	dd if=../fuzix.bin of=../fuzix.cart bs=16384 conv=sync
+	dd if=../fuzix.bin of=../fuzix.rom bs=16384 conv=sync

Kernel/platform-msx2/bootrom.s

@@ -1,94 +1,239 @@
-		.area _CODE
+		.area _BOOT
 
 		.db 'A'
 		.db 'B'
-		.dw wtfami + 0x4000
+		.dw bootstrap
 		.dw 0,0,0,0,0,0
 
-;
-;	Entered at 0x4000 but linked at 0x0000 so be careful
-;
-wtfami:		di
-
-		ld a, #0x23		; Debug port
-		out (0x2e), a
-		ld a, #':'
-		out (0x2f), a
-
-		in a, (0xA8)
-		ld d, a
-		and #0x0C		; bits for 0x4000
-		ld b, a
-		rla
-		rla			; to 0x8000
-		or b			; and 0x4000
-		rla
-		rla			; to 0xC000/8000
-		or b			; and 0x4000
-		ld b, a			; B is now the bits for
-					; putting 48K of cartridge
-					; in place
-		out (0xA8), a		; Map cartridge
+		.globl enaslt
+		.globl slotrom
+		.globl slotram
+		.globl find_ram
+
+		; At this point the BIOS has detected the cartridge AB signature and
+		; jumped here; we have the rom bios in bank 0, ram in bank 3, and rom
+		; in bank 1 (this code).
+bootstrap:
+		di
+		ld sp,#0xf340       ; temporary stack
+
+		; FIXME: init vdp using bios so that font is in place after vdpinit
+		ld a,#0x50
+		ld (0xf3ae),a
+		ld ix,#0x00d5
+		call #0x015f
+
+		call find_ram
+		ld (slotram),a
+		call find_rom
+		ld (slotrom),a
+
+		; set cartridge rom in bank 0 and ram in bank 2
+		ld hl,#0
+		call enaslt
+		ld a,(slotram)
+		ld hl,#0x8000
+		call enaslt
 		ld a, #3
-		out (0xFC), a		; Begin mapping RAM
-		ld a, #'1'
-		out (0x2f), a
-		exx
-		ld hl, #0x4000		; Cartridge 0x4000 -> RAM 0
-		ld de, #0x0
+		out (0xFE),a
+
+		; copy kernel page 3 to ram
+		ld hl, #0x0
+		ld de, #0x8000
 		ld bc, #0x4000
 		ldir
-		dec a
-		out (0xFC), a
-		ld de, #0		; 0x8000 -> RAM 0x4000
+
+		; set ram in bank 0 and cartridge rom in bank 2
+		ld a,(slotram)
+		ld hl,#0
+		call enaslt
+		ld a,(slotrom)
+		ld hl,#0x8000
+		call enaslt
+
+		; copy kernel pages 2 and 1 to ram
+		ld a, #2
+		out (0xFC),a
+		ld hl, #0x4000
+		ld de, #0x0
 		ld bc, #0x4000
 		ldir
-		dec a
-		out (0xFC), a
-		ld de, #0		; 0xC000 -> RAM 0x8000
+		ld a, #1
+		out (0xFC),a
+		ld hl, #0x8000
+		ld de, #0x0
 		ld bc, #0x4000
 		ldir
-		exx	
-		ld a, #3		; put the maps right
+
+		; prepare mapped ram pages for all-ram
+		ld a, #3
 		out (0xFC), a
 		ld a, #2
 		out (0xFD), a
 		ld a, #1
 		out (0xFE), a
-		xor a
-		out (0xFF), a
-		ld a, #'G'
-		out (0x2f), a
-		ld a, d
-		and #0xC0		; RAM in 0xC000 slot bits
-		ld e, a			
-		rra			; Propogate into other banks
-		rra
-		or e
-		rra
-		rra
-		or e
-		rra
-		rra
-		or e
-		ld e, a			; E is now "all RAM"
-		and #0xF3
-		ld c, a
-		ld a, d			; Get original status
-		and #0x0c		; bits for 0x4000 as cartridge
-		or c			; bits for the RAM
-		out (0xA8), a
-		ld a, #'O'
-		out (0x2f), a
-		;
-		;	We now have RAM where we need it
-		;
-		jp ramgo
-ramgo:		ld a, #'!'
-		out (0x2f), a
-		ld a, e
-		out (0xA8), a		; Now go all ram
+
+		; set bank 2 to ram
+		ld a,(slotram)
+		ld hl,#0x8000
+		call enaslt
+
+		; jump to start while keeping rom in page 1 (we are running from it)
+		; will switch to all-ram in there
 		jp 0x100
 
-		; Hack Hack FIXME
-		.ds 0x73
+
+		; find slot currently set in page 1
+		; returns slot in reg a using FxxxSSPP format (see enaslt)
+find_rom:
+		in a,(0xa8)
+		rrca
+		rrca
+		and #3
+		ld c,a
+		ld b,#0
+		ld hl,#0xfcc1       ; system variables containing slot and sub-slot data
+                            ; set up by bios on boot
+		add hl,bc
+		ld a,(hl)
+		and #0x80
+		jr z,find_rom0
+		or c
+		ld c,a
+		inc hl
+		inc hl
+		inc hl
+		inc hl
+		ld a,(hl)
+		and #0x0C
+find_rom0:
+		or c
+		ret
+
+		; find slot currently set in page 3
+		; returns slot in reg a using FxxxSSPP format (see enaslt)
+find_ram:
+		in a,(0xa8)
+		rlca
+		rlca
+		and #3
+		ld c,a
+		ld b,#0
+		ld hl,#0xfcc1       ; system variables containing slot and sub-slot data
+                            ; set up by bios on boot
+		add hl,bc
+		ld a,(hl)
+		and #0x80
+		jr z,find_ram0
+		or c
+		ld c,a
+		inc hl
+		inc hl
+		inc hl
+		inc hl
+		ld a,(hl)
+		rlca
+		rlca
+		rlca
+		rlca
+		and #0x0C
+find_ram0:
+		or c
+		ret
+
+		; set slot and subslot at target address
+		; (from msx bios listing)
+		; hl - target address
+		; a  - slot : FxxxSSPP
+		;             F  : expanded slot flag (if F=0, SS is ignored)
+		;             SS : expanded subslot
+		;             PP : primary slot
+enaslt:
+		call selprm         ; calculate bit pattern and mask code
+		jp m, eneslt        ; if expanded set secondary first
+		in a,(0xa8)
+		and c
+		or b
+		out (0xa8),a        ; set primary slot
+		ret
+eneslt:
+		push hl
+		call selexp         ; set secondary slot
+		pop hl
+		jr enaslt
+
+		; calculate bit pattern and mask
+selprm:
+		di
+		push af
+		ld a,h
+		rlca
+		rlca
+		and #3
+		ld e,a              ; bank number
+		ld a,#0xC0
+selprm1:
+		rlca
+		rlca
+		dec e
+		jp p, selprm1
+		ld e,a              ; mask pattern
+		cpl
+		ld c,a              ; inverted mask pattern
+		pop af
+		push af
+		and #3              ; extract xxxxxxPP
+		inc a
+		ld b,a
+		ld a,#0xAB
+selprm2:
+		add a,#0x55
+		djnz selprm2
+		ld d,a              ; primary slot bit pattern
+		and e
+		ld b,a
+		pop af
+		and a               ; if expanded slot set sign flag
+		ret
+
+		; set secondary slot
+selexp:
+		push af
+		ld a,d
+		and #0xC0          ; get slot number for bank 3
+		ld c,a
+		pop af
+		push af
+		ld d,a
+		in a,(0xa8)
+		ld b,a
+		and #0x3F
+		or c
+		out (0xa8),a        ; set bank 3 to target slot
+		ld a,d
+		rrca
+		rrca
+		and #3
+		ld d,a
+		ld a,#0xAB          ; secondary slot to bit pattern
+selexp1:
+		add a,#0x55
+		dec d
+		jp p,selexp1
+		and e
+		ld d,a
+		ld a,e
+		cpl
+		ld h,a
+		ld a,(0xffff)       ; read and update secondary slot register
+		cpl
+		ld l,a
+		and h               ; strip off old bits
+		or d                ; add new bits
+		ld (0xffff),a
+		ld a,b
+		out (0xa8),a        ; restore status
+		pop af
+		and #3
+		ret
+

Kernel/platform-msx2/crt0.s

@@ -35,6 +35,9 @@
 
 		; Just for the benefit of the map file
 		.globl start
+		.globl enaslt
+		.globl slotram
+		.globl find_ram
 
 	        ; startup code @0x100
 	        .area _CODE
@@ -45,26 +48,39 @@
 ; We assume here that the kernel packs below 48K for now we've got a few
 ; KBytes free but revisit as needed
 ;
-start:		di
-	        ld a, #4		; 0 holds 8K of stuff we might want
-                out (0xff), a		; if we go the OS route, so use 4
-					; plus "0" is magic so this saves
-					; shifting them all by one.
+		.ds 0x100
+start:
+		di
 		; Debug port
 		ld a, #0x23
-	        out (0x2e), a
+		out (0x2e), a
 		ld a, #'@'
 		out (0x2f), a
+
+		; read slot before switching ram page
+		ld a,(slotram)
+		ld hl,#0x4000
+		call enaslt
+
+		ld a, #4            ; 0 holds 8K of stuff we might want
+		out (0xff), a       ; if we go the OS route, so use 4
+		                    ; plus "0" is magic so this saves
+                            ; shifting them all by one.
+
+
 		ld sp, #kstack_top
+
 		; move the common memory where it belongs
 		ld hl, #s__INITIALIZER
 		ld de, #s__COMMONMEM
 		ld bc, #l__COMMONMEM
 		ldir
+
 		; move the discardable memory where it belongs    
 		ld de, #s__DISCARD
 		ld bc, #l__DISCARD
 		ldir
+
 		; then zero the data area
 		ld hl, #s__DATA
 		ld de, #s__DATA + 1
@@ -76,6 +92,6 @@ start:		di
 		call init_hardware
 		call _fuzix_main
 		di
-stop:		halt
+stop:	halt
 		jr stop