vdp: add support for targets that don't sufficiently waitstate the TM…

…S I/O

Based on all the work from wigglethemouse and productiondave's testing
on the Z80 Retro discord

What seems to happen is that the Z80 at 10MHz without waitstates is enough
that
         out (c),l
         out (c),h

sometimes loses stuff and it needs a nop in the middle. We don't see this on
slower systems or on other fast ports as the other fast ports wait state the
TMS9918A so meet the timings.

Kernel/dev/vdp1.s

@@ -170,6 +170,7 @@ _vdp_load_font:
 	    ld bc,(_vdpport)
 	    ld de,#0x7C00
 	    out (c),e			; set write and font area
+	    VDP_DELAY3
 	    out (c),d
 	    ld hl,#_fontdata_6x8
 	    ld b,e
@@ -202,18 +203,22 @@ _vdp_restore_font:
 	    in a,(c)
 fontnext:
 	    out (c),e
+	    VDP_DELAY3
 	    out (c),d
 	    VDP_DELAY2
 	    dec c
 	    in a,(c)
 	    inc c
+	    VDP_DELAY3		; shouldn't need a normal delay here
 	    out (c),e
+	    VDP_DELAY3
 	    out (c),h
 	    dec c
 	    out (c),a
 	    VDP_DELAY
 	    inc c
 	    out (c),e
+	    VDP_DELAY3
 	    out (c),l
 	    cpl
 	    dec c
@@ -234,6 +239,7 @@ _vdp_wipe_consoles:
 	    ld b,#0
 	    ld a,#0x40
 	    out (c),b			; 0x0000 for writing
+ 	    VDP_DELAY3
 	    out (c),a
 	    dec c
 	    ld a,#32
@@ -251,6 +257,7 @@ _vdp_setcolour:
 	    ld b,#0
 	    ld a,#0x60			; 0x2000 in the VDP, for write
 	    out (c),b
+	    VDP_DELAY3
 	    out (c),a
 	    dec c
 	    ld b,#32
@@ -270,6 +277,7 @@ _vdp_set:
 	    ex de, hl
 vdpout:	    ld bc, (_vdpport)
 	    out (c), e			; Write the data
+	    VDP_DELAY3
 	    out (c), d			; and then the register | 0x80
 	    ret
 
@@ -335,6 +343,7 @@ plotit:
 plotit2:
 	    ld bc, (_vdpport)
 	    out (c), l			; address
+	    VDP_DELAY3
 	    out (c), h			; address | 0x40
 	    dec c
 	    out (c), a			; character
@@ -380,6 +389,7 @@ upline:
 	    ld bc, (_vdpport)	; vdpport + 1 always holds #80
 	    ld hl, #scrollbuf
 	    out (c), e		; our position
+	    VDP_DELAY3
 	    out (c), d
 	    dec c
 down_0:
@@ -390,8 +400,8 @@ down_0:
 	    ld hl, (_scrolld_s1); go down one line and into write mode
 	    add hl, de		; relative to our position
 	    out (c), l
+	    VDP_DELAY3
 	    out (c), h
-	; FIME - from vdpport - and into other copies
 	    ld b, #40
 	    ld hl, #scrollbuf
 	    dec c
@@ -430,6 +440,7 @@ downline:   push bc
 	    ld bc, (_vdpport)
 	    ld hl, #scrollbuf
 	    out (c), e
+	    VDP_DELAY3
 	    out (c), d
 	    dec c
 up_0:
@@ -442,6 +453,7 @@ up_0:
 				; nybble)
 	    add hl, de
 	    out (c), l
+	    VDP_DELAY3
 	    out (c), h
 	    dec c
 	    ld hl, #scrollbuf
@@ -479,6 +491,7 @@ clear_lines:
 	    ld e, c
 	    ld bc, (_vdpport)
 	    out (c), l
+	    VDP_DELAY3
 	    out (c), h
 				; Safe on MSX 2 to loop the data with IRQ on
 				; but *not* on MSX 1
@@ -516,6 +529,7 @@ clear_across:
 	    ld a, c
 	    ld bc, (_vdpport)
 	    out (c), l
+	    VDP_DELAY3
 	    out (c), h
 	    ld b, a
             ld a, #' '
@@ -550,6 +564,7 @@ cursor_on:
 	    ld a, c
 	    ld bc, (_vdpport)
 	    out (c), l			; address
+	    VDP_DELAY3
 	    out (c), h			; address
 	    dec c
 	    VDP_DELAY2
@@ -627,6 +642,7 @@ _vdp_rop:
 	    ld d, #0
 	    ld bc, (_vdpport)
 	    out (c), l
+	    VDP_DELAY3
 	    out (c), h		; Set starting pointer
 	    exx
 	    ld l, (ix)		; User pointer
@@ -648,6 +664,7 @@ ropc:
 	    cp h		; just 3F
 	    jr c, bounds
 	    out (c), l		; next line
+	    VDP_DELAY3
 	    out (c), h
 	    exx
 	    dec e
@@ -675,6 +692,7 @@ _vdp_wop:
 	    ld e, 6(ix)		; Stride
 	    ld d, #0
 	    out (c),l
+	    VDP_DELAY3
 	    out (c),h		; Set starting pointer
 	    exx
 	    ld l,(ix)		; User pointer

Kernel/platform/platform-2063/vdp.s

@@ -27,23 +27,24 @@ VDP_ROP		.equ	1
 ;	We need 2us between the last control write and a data read. We might
 ;	be running at 10MHz or faster so use long delays
 ;
-;
-;	These are 38 cycles a pair so 72 cycles all in. That should be
-;	good for 10MHz and a fair bit more. We could tune the delays down
-;	a bit if we were sure nobody went over 10MHz.
+;	These will only work on the TMS9918A text mode but fail on the
+;	later chips. There is no 9938/58 for the 2063 however
 ;
 .macro VDP_DELAY
-	ex (sp),hl
-	ex (sp),hl
-	ex (sp),hl
-	ex (sp),hl
+	nop
+	nop
+	nop
 .endm
 
 .macro VDP_DELAY2
-	ex (sp),hl
-	ex (sp),hl
-	ex (sp),hl
-	ex (sp),hl
+	nop
+	nop
+	nop
+.endm
+
+; The 2063 doesn't waitstate the I/O so back to back outs go funny
+.macro VDP_DELAY3
+	nop
 .endm
 
 	    .include "../../dev/vdp1.s"

Kernel/platform/platform-msx1/vdp.s

@@ -35,6 +35,8 @@ VDP_ROP		.equ	1
 .endm
 .macro VDP_DELAY2
 	    nop
+.endm
+.macro VDP_DELAY3
 .endm
 	    .include "../../dev/vdp1.s"
 

Kernel/platform/platform-mtx/vdp.s

@@ -24,14 +24,16 @@ VDP_IRQ	     .equ	0	; leave the vdp irq off
 VDP_ROP      .equ	1
 
 ;
-;	On an MSX at 4Mhz our loop worst case is 26 clocks so for
+;	On an MTX at 4Mhz our loop worst case is 26 clocks so for
 ;	graphics one we need a nop
 ;
 .macro VDP_DELAY
 	    nop
 .endm
 .macro VDP_DELAY2
 	    nop
+.endm
+.macro VDP_DELAY2
 .endm
 
 	    .area _COMMONMEM

Kernel/platform/platform-n8/vdp.s

@@ -44,6 +44,10 @@ VDP_ROP		.equ	1
 		call twiddle_thumbs
 .endm
 
+; This is covered by the I/O wait states
+.macro VDP_DELAY3
+.endm
+
 twiddle_thumbs:			; Burn 125 clocks including the call return
 		; We spend 27 getting here and going back
 		ex (sp),ix	; 19