From: Alan Cox <alan@linux.intel.com>
Date: Sun, 19 Aug 2018 20:12:14 +0000 (+0100)
Subject: sam: video and stub fixes
X-Git-Url: https://git.ndcode.org/public/gitweb.cgi?a=commitdiff_plain;h=e4f6584e77daf6c3e507ccdd09dfab00e5d7574f;p=FUZIX.git

sam: video and stub fixes

Rearrange our logic a bit so we can copy the stubs where we need them
Copy stubs into the top of the video 32K so we can in theory at some point
re-arrange the video logic and maps to keep interrupts on by using a private
low stack and high mapping video.
Fix the last character on a line being corrupted
Add initial (not used) colour support for the console
---

diff --git a/Kernel/platform-sam/boot.s b/Kernel/platform-sam/boot.s
index fefb1dc5..872e395e 100644
--- a/Kernel/platform-sam/boot.s
+++ b/Kernel/platform-sam/boot.s
@@ -1,5 +1,8 @@
 ;
 ;	Boot block, loaded at 0x8000 in the top bank that is free (varies)
+;	but this works so long as we are above bank 7. If that becomes
+;	an issue then instead of flipping banks we can always ldir ourself
+;	into bank 0 and run from there.
 ;
 ;	The boot block is trivial but it gets a bit fun once we've loaded
 ;	our 14 tracks
@@ -15,7 +18,6 @@
 ;	We then run from 0x8000 in bank 6, which will untangle everything
 ;	for us shuffling the kernel so that 0/1 is the low kernel in RAM
 ;	2/3 is the high kernel in RAM and 4/5 is the video
-;	(or maybe it'll be saner to use 4/5 for kernel 2/3 video..)
 ;
 	.area BOOT(ABS)
 	.org 0x0000
diff --git a/Kernel/platform-sam/sam.s b/Kernel/platform-sam/sam.s
index dcc538c0..e5fb77dc 100644
--- a/Kernel/platform-sam/sam.s
+++ b/Kernel/platform-sam/sam.s
@@ -67,7 +67,8 @@ _platform_reboot:
 	    rst 0			; bang
 
 ; -----------------------------------------------------------------------------
-; KERNEL MEMORY BANK (below common, only accessible when the kernel is mapped)
+;	We have discard mapped high up so we can map stuff under it
+;	during setup. All of discard gets reclaimed when init is run
 ; -----------------------------------------------------------------------------
             .area _DISCARD
 
@@ -91,11 +92,47 @@ init_early:
 
 init_hardware:
             ; set system RAM size (FIXME - check for 512/1M)
+	    ld a,#0x10			; Upper 256K
+	    call map_page_low
+	    ld hl,#0x0000
+	    ld (hl),#0xff
+	    ld a,(hl)
+	    inc a
+	    jr nz, is256k
+	    ld (hl),a
+	    ld a,(hl)
+	    or a
+	    ld hl,#512
+	    jr z, is512k
+is256k:	    
             ld hl, #256
+is512k:
             ld (_ramsize), hl
-            ld hl, #(256-96)		; 64K for kernel, 32K for video/font/etc
+	    ld de,#96			; 64K for kernel, 32K for video etc
+	    sbc hl,de			; C is always clear here
             ld (_procmem), hl
 
+	    ld a,#VIDEO_LOW
+	    call map_page_low		; Map the video in the low 32K
+
+	    ; Place a copy of the high stubs into the video bank so that we
+	    ; can in future field interrupts with video mapped. Quite a bit
+	    ; of other work is needed for this due to the stack situation.
+	    ld hl,#0xFF00
+	    ld de,#0x7F00
+	    ld bc,#0x100
+	    ldir
+
+	    call map_kernel_low
+
+	    ; Make a copy of the low page somewhere accessible. This may
+	    ; change if we decide to make the kernel low page different - eg
+	    ; to fast path interrupts in kernel mode. FIXME
+	    ld hl,#0x0000
+	    ld de,#lowstubs
+	    ld bc,#0x0068
+	    ldir
+
             im 1 ; set CPU interrupt mode
 
 	    ; interrupt mask
@@ -159,11 +196,9 @@ _program_vectors:
 
 	    exx
 	    ; Copy the stub page into place
-	    ; FIXME: doesn't work because our stubs are at 0000. Maybe put
-	    ; a copy somewhere else ?
-            ld hl, #stub_page_1 - 1
+            ld hl, #lowstubs
             ld de, #0x0000
-            ld bc, #0x0100
+            ld bc, #0x0068
             ldir
 	    exx
 
@@ -422,3 +457,7 @@ syscall_sighelp:
 	    pop hl
 	    ld h,#0		; clear signal bit
 	    ret
+
+	    .area _DATA
+lowstubs:
+	    .ds 0x68
diff --git a/Kernel/platform-sam/sam_vt.s b/Kernel/platform-sam/sam_vt.s
index 334852b2..6eb46f32 100644
--- a/Kernel/platform-sam/sam_vt.s
+++ b/Kernel/platform-sam/sam_vt.s
@@ -109,22 +109,67 @@ _plot_char:
 	call map_video
 	ld bc,#0x04FF		; it gets decremented by DJNZ while the FF
 				; ensures the ldi never decrements B
+;
+;	Need to add a slow path version that does colour and effects. Colour
+;	is a matter of masking with FF, CC, 33 or 00.
+;
 plot_loop:
-	; FIXME: this trick doesn't work on the last row - need a better way
 	ldi			; copy expanded char
-	ldi
-	dec e
+	ld a,(hl)
+	ld (de),a
+	inc hl
 	dec e
 	set 7,e			; de += 126
 	ldi			; copy second char row
-	ldi
-	dec e			; Similar idea
+	ld a,(hl)
+	ld (de),a
+	inc hl
 	dec e			; toggle the bit back and gives us
 	res 7,e
 	inc d			; de += 126
 	djnz plot_loop
 	jr pop_unmap
 
+;
+;	We will need this once we wire in colour support
+;
+plot_slow:
+	ld a,#4
+	exx
+	ld de,(colours)
+	exx
+plot_loop_slow:
+	ex af,af'
+	ld a,(hl)
+	exx
+	ld b,a
+	cpl			; background bits
+	and d			; to background colour
+	ld c,a
+	ld a,e			; foreground bits
+	and b			; to foreground colour
+	or c			; plus background
+	exx
+	ld (de),a
+	ld a,(hl)
+	inc de
+	inc hl
+	exx
+	ld b,a
+	cpl			; background bits
+	and d			; to background colour
+	ld c,a
+	ld a,e			; foreground bits
+	and b			; to foreground colour
+	or c			; plus background
+	exx
+	ld (de),a
+	add hl,bc
+	ex af,af'
+	dec a
+	jr nz, plot_loop_slow
+	jr pop_unmap
+
 _clear_lines:
 	pop hl
 	pop de
@@ -147,7 +192,7 @@ _clear_lines:
 	inc de
 	dec bc
 	ld (hl),#0
-	jr ldir_pop
+	jp ldir_pop
 
 _clear_across:
 	pop hl
@@ -198,3 +243,6 @@ _cursor_off:
 _cursor_disable:
 _vtattr_notify:
 	ret
+
+colours:
+	.word 0