From 182dd322a5502a2fbdad11e90340bf1c45a64a47 Mon Sep 17 00:00:00 2001
From: Wayne Warthen <wwarthen@gmail.com>
Date: Fri, 8 May 2020 15:46:30 -0700
Subject: [PATCH] Disk I/O Cleanup

---
 Source/CBIOS/cbios.asm | 36 +++++++++++++-------
 Source/CPM3/diskio.z80 | 77 ++++++++++++++++++++++++------------------
 Source/ver.inc         |  2 +-
 Source/ver.lib         |  2 +-
 4 files changed, 69 insertions(+), 48 deletions(-)

diff --git a/Source/CBIOS/cbios.asm b/Source/CBIOS/cbios.asm
index 9940be25..4482cf6e 100644
--- a/Source/CBIOS/cbios.asm
+++ b/Source/CBIOS/cbios.asm
@@ -1247,7 +1247,7 @@ DSK_SELECT1:
 	BIT	7,B		; TEST RAM DRIVE BIT
 	LD	A,MID_MDROM	; ASSUME ROM
 	JR	Z,DSK_SELECT1A	; IS ROM, DONE
-	LD	A,MID_MDRAM	; MSUT BE RAM
+	LD	A,MID_MDRAM	; MUST BE RAM
 ;
 DSK_SELECT1A:
 	LD	(MEDID),A
@@ -1269,10 +1269,28 @@ DSK_SELECT1A:
 #ENDIF
 ;
 	; CLEAR LBA OFFSET (DWORD)
+	; SET HI BIT FOR LBA ACCESS FOR NOW
 	LD	HL,0		; ZERO
 	LD	(SEKLBA),HL	; CLEAR FIRST WORD
+	SET	7,H		; ASSUME LBA ACCESS FOR NOW
 	LD	(SEKLBA+2),HL	; CLEAR SECOND WORD
 ;
+#IFDEF PLTWBW
+;
+	LD	A,(SEKUNIT)	; GET UNIT
+	LD	C,A		; STORE IN C
+	LD	B,BF_DIODEVICE	; HBIOS FUNC: REPORT DEVICE INFO
+	RST	08		; GET UNIT INFO, DEVICE TYPE IN D
+	LD	A,D		; DEVICE TYPE -> A
+	AND	$F0		; ISOLATE HIGH BITS
+	CP	DIODEV_FD	; FLOPPY?
+	JR	NZ,DSK_SELECT1B	; IF NOT, DO LBA IO
+	LD	HL,SEKLBA+3	; POINT TO HIGH ORDER BYTE
+	RES	7,(HL)		; SWITCH FROM LBA -> CHS
+;
+#ENDIF
+;
+DSK_SELECT1B:
 	; SET LEGACY SECTORS PER SLICE
 	LD	HL,16640	; LEGACY SECTORS PER SLICE
 	LD	(SPS),HL	; SAVE IT
@@ -1452,6 +1470,7 @@ DSK_MBR7:
 	DEC	A			; DEC LOOP DOWNCOUNTER
 	JR	DSK_MBR6		; AND LOOP
 DSK_MBR8:
+	SET	7,D		; SET LBA ACCESS FLAG
 	; RESAVE IT
 	LD	(SEKLBA),HL	; LOWORD
 	LD	(SEKLBA+2),DE	; HIWORD
@@ -1498,15 +1517,9 @@ DSK_IO:
 	LD	C,A			; UNIT -> C
 ;
 #IFDEF PLTWBW
-;	
-	PUSH	BC			; SAVE FUNC/UNIT
-	LD	B,BF_DIODEVICE		; HBIOS FUNC: REPORT DEVICE INFO
-	RST	08			; GET UNIT INFO, DEVICE TYPE IN D
-	POP	BC			; GET FUNC/UNIT BACK TO BC
-	LD	A,D			; DEVICE TYPE -> A
-	AND	$F0			; ISOLATE HIGH BITS
-	CP	DIODEV_FD		; FLOPPY?
-	JR	NZ,LBA_IO		; IF NOT, DO LBA IO
+	LD	A,(HSTLBA+3)		; GET HIGH ORDER BYTE
+	BIT	7,A			; LBA ACCESS?
+	JR	NZ,LBA_IO		; IF SET, GO TO LBA I/O
 ;
 ; FLOPPY SPECIFIC TRANSLATION ASSUMES FLOPPY IS DOUBLE-SIDED AND
 ; USES LOW ORDER BIT OF TRACK AS HEAD VALUE
@@ -1540,9 +1553,6 @@ LBA_IO:
 	LD	BC,(HSTLBA+2)		; LBA OFFSET HIWORD
 	ADC	HL,BC
 	EX	DE,HL
-#IFDEF PLTWBW
-	SET	7,D			; MAKE SURE LBA ACCESS BIT SET
-#ENDIF
 	POP	BC			; RESTORE FUNC/UNIT
 	;JR	DSK_IO2			; DO THE DISK I/O (FALL THRU)
 ;
diff --git a/Source/CPM3/diskio.z80 b/Source/CPM3/diskio.z80
index 8ba7574d..3e52d60a 100644
--- a/Source/CPM3/diskio.z80
+++ b/Source/CPM3/diskio.z80
@@ -421,7 +421,7 @@ media:
 	ld	(retry$adr),hl
 	
 	; Sense media to determine media format
-	ld	a,(unit)		; Get disk unit
+	ld	a,(unit)		; get disk unit
 	ld	c,a			; put in C
 	ld	b,18h			; HBIOS Media function
 	ld	e,1			; Enable media check/discovery
@@ -435,7 +435,22 @@ media:
 	; Initialize slice start LBA & sectors per slice
 	ld	hl,0			; assume slice starts
 	ld	(lba),hl		; ... at LBA offset
-	ld	(lba+2),hl		; ... of zero
+	set	7,h			; ... of zero
+	ld	(lba+2),hl		; ... w/ LBA access
+
+	; Check device type
+	ld	a,(unit)		; get disk unit
+	ld	c,a			; put in C
+	ld	b,17h			; HBIOS func: report device info
+	call	0FFF0h			; get unit info, device type in D
+	ld	a,d			; device type -> A
+	and	0F0h			; isolate high bits
+	cp	10h			; floppy?
+	jr	nz,media1		; if not, do LBA I/O
+	ld	hl,lba+3		; point to high order byte
+	res	7,(hl)			; switch from LBA -> CHS
+
+media1:
 	ld	hl,16640		; assume legacy value for
 	ld	(sps),hl		; ... sectors per slice
 
@@ -472,7 +487,7 @@ media:
 media3:
 	ld	a,(hl)			; get part type
 	cp	2Eh			; CP/M partition?
-	jr	z,media4			; cool, grab the LBA offset
+	jr	z,media4		; cool, grab the LBA offset
 	ld	de,16			; part table entry size
 	add	hl,de			; bump to next part type
 	djnz	media3			; loop thru table
@@ -536,9 +551,10 @@ boot7:
 	dec	a			; dec loop downcounter
 	jr	boot6			; and loop
 boot8:
+	set	7,d			; set LBA access flag
 	ld	(lba),hl		; save new lba, low word
 	ld	(lba+2),de		; save new lba, high word
-	
+
 media9:
 	; Locate DPB corresponding to media id
 	ld	hl,dpb$start - dpb$sz
@@ -599,23 +615,31 @@ dsk$rw:
 	; Common disk read/write routine
 	; Assumes func is set to HBIOS read or write
 	
-	; Save XDPH address
-	ld	(curdph),de		; save to curdph
-
 	; Set retry address
-	ld	hl,dsk$rw
+	ld	hl,dsk$rw$retry
 	ld	(retry$adr),hl
 	
-	; Check device type
-	ld	a,(@rdrv)		; get unit
-	ld	c,a			; BIOS Disk Unit in C
-	ld	b,17h			; HBIOS DEVICE function
-	call	0FFF0h			; do it, D=device type
-	ld	a,d			; put in accum
-	and	0F0h			; isolate high bits
-	cp	10h			; floppy?
-	jr	nz,dsk$rw2		; if not, do LBA i/o
-	
+	; Save XDPH address
+	ld	(curdph),de		; save to curdph
+
+dsk$rw$retry:
+	; Get LBA offset from DPH to DE:HL
+	ld	hl,(curdph)		; HL := DPH adr
+	ld	de,25			; LBA value adr
+	add	hl,de			; HL := LBA offset
+	ld	e,(hl)			; lobyte of loword
+	inc	hl			; bump
+	ld	d,(hl)			; hibyte of loword
+	inc	hl			; bump
+	push	de			; save loword
+	ld	e,(hl)			; lobyte of hiword
+	inc	hl			; bump
+	ld	d,(hl)			; hibyte of hiword
+	pop	hl			; recover loword
+
+	bit	7,d			; LBA access bit set?
+	jr	nz,dsk$rw2		; if so, go to LBA I/O
+
 	; Floppy I/O
 	ld	de,(@sect)		; sector -> de, head(d) becomes zero
 	ld	hl,(@trk)		; track -> hl (low bit has head)
@@ -625,20 +649,8 @@ dsk$rw:
 	jr	dsk$rw9			; do the disk I/O
 	
 dsk$rw2:
-	; LBA IO: Get LBA offset from DPH
-	ld	hl,(curdph)		; HL := DPH adr
-	ld	de,25+3			; LBA value + 3
-	add	hl,de			; HL := LBA offset (last byte!)
-	ld	b,(hl)			; hibyte of hiword
-	dec	hl			; bump
-	ld	c,(hl)			; lobyte of hiword
-	dec	hl			; bump
-	push	bc			; save hiword
-	ld	b,(hl)			; hibyte of loword
-	dec	hl			; bump
-	ld	c,(hl)			; lobyte of loword
-	dec	hl			; bump
-	push	bc			; save loword
+	push	de			; save hiword of LBA
+	push	hl			; save loword of LBA
 	
 	; Get track and shift into correct bits
 	ld	hl,(@trk)		; get track
@@ -658,7 +670,6 @@ dsk$rw2:
 	pop	bc			; lba offset hiword
 	adc	hl,bc			; add w/ carry to cur hiword
 	ex	de,hl			; swap back
-	set	7,d			; set lba access bit
 	
 dsk$rw9:
 	; DE:HL has sector address to read (LBA or CHS)
diff --git a/Source/ver.inc b/Source/ver.inc
index dea2c716..3cb3dc77 100644
--- a/Source/ver.inc
+++ b/Source/ver.inc
@@ -2,4 +2,4 @@
 #DEFINE	RMN	1
 #DEFINE	RUP	1
 #DEFINE	RTP	0
-#DEFINE BIOSVER	"3.1.1-pre.2"
+#DEFINE BIOSVER	"3.1.1-pre.3"
diff --git a/Source/ver.lib b/Source/ver.lib
index cff1d4a5..3c226412 100644
--- a/Source/ver.lib
+++ b/Source/ver.lib
@@ -3,5 +3,5 @@ rmn	equ	1
 rup	equ	1
 rtp	equ	0
 biosver	macro
-	db	"3.1.1-pre.2"
+	db	"3.1.1-pre.3"
 	endm