From de9a3869a13bc7368a6129f1ab517b4e130db082 Mon Sep 17 00:00:00 2001
From: Alan Cox <alan@linux.intel.com>
Date: Tue, 15 Aug 2017 22:20:50 +0100
Subject: [PATCH] plus3: do some initial changes

At this point we are not yet booting. We start the image but not everything
ends up in the right place to enter the C code
---
 Kernel/platform-plus3/README.md |  1 +
 Kernel/platform-plus3/crt0.s    |  9 +++------
 Kernel/platform-plus3/fuzix.lnk |  7 ++++---
 Kernel/platform-plus3/plus3.s   | 24 ++++--------------------
 Kernel/platform-plus3/zxvideo.s |  3 ++-
 5 files changed, 14 insertions(+), 30 deletions(-)

diff --git a/Kernel/platform-plus3/README.md b/Kernel/platform-plus3/README.md
index 6e211ba7..000348af 100644
--- a/Kernel/platform-plus3/README.md
+++ b/Kernel/platform-plus3/README.md
@@ -26,6 +26,7 @@ We then map
 0/1/2/3	-	user process 0: 48K, 16K common
 4/5/6/3 -	user process 1: 32K, 16K common, 16K is kernel reserved
 4/7/6/3 -	kernel: 48K minus screen, common 16K (some kernel in it)
+		(conveniently the map 'BOOT' uses)
 
 As an aside this only works for the +2A/+3. The various clones even with
 lots of RAM clone the original 128K and add more pages of memory in the top
diff --git a/Kernel/platform-plus3/crt0.s b/Kernel/platform-plus3/crt0.s
index 2d93b0fe..b50fb7b8 100644
--- a/Kernel/platform-plus3/crt0.s
+++ b/Kernel/platform-plus3/crt0.s
@@ -2,14 +2,12 @@
 
         .module crt0
 
-	;
-	; Bank 4-7
-	;
-        .area _CODE
-        .area _CODE2
+        .area _CODE		; Code lives at 0000-0x3FFF in bank 4
+        .area _CODE2		; Lives at 0x5B00 onwards in bank 7/6
 	.area _CODE3
         .area _CONST
 	.area _VIDEO
+	.area _FONT
         .area _INITIALIZED
         .area _DATA
         .area _BSEG
@@ -21,7 +19,6 @@
         .area _GSINIT
         .area _GSFINAL
 	.area _DISCARD
-	.area _FONT
 	;
 	;	Above 0xC000 in the top of bank 3
 	;
diff --git a/Kernel/platform-plus3/fuzix.lnk b/Kernel/platform-plus3/fuzix.lnk
index e4f6246b..29de6f78 100644
--- a/Kernel/platform-plus3/fuzix.lnk
+++ b/Kernel/platform-plus3/fuzix.lnk
@@ -1,9 +1,10 @@
 -mwxuy
--r
 -i fuzix.ihx
 -b _COMMONDATA=0xF800
--b _CODE=0x0000
--b _DISCARD=0xC000
+-b _COMMONMEM=0xF000
+-b _CODE=0x0100
+-b _CODE2=0x5B00
+-b _DISCARD=0xE400
 -l z80
 platform-plus3/crt0.rel
 platform-plus3/commonmem.rel
diff --git a/Kernel/platform-plus3/plus3.s b/Kernel/platform-plus3/plus3.s
index 36ac2561..088af138 100644
--- a/Kernel/platform-plus3/plus3.s
+++ b/Kernel/platform-plus3/plus3.s
@@ -27,8 +27,6 @@
         .globl map_restore
 	.globl map_process_save
 	.globl map_kernel_restore
-	.globl map_video
-	.globl unmap_video
 	.globl map_for_swap
 
         .globl _need_resched
@@ -97,11 +95,10 @@ init_hardware:
         ld hl, #(128 - 64)        ; 64K for kernel/screen/etc
         ld (_procmem), hl
 
-	call map_video
         ; screen initialization
         ; clear
-        ld hl, #0xC000
-        ld de, #0xC001
+        ld hl, #0x4000
+        ld de, #0x4001
         ld bc, #0x1800            ; There should be 0x17FF, but we are going
         xor a                     ; to copy additional byte to avoid need of
         ld (hl), a                ; DE and HL increment before attribute
@@ -113,7 +110,6 @@ init_hardware:
         ld (hl), a
         ldir
 
-	call unmap_video
         ret
 
 ;------------------------------------------------------------------------------
@@ -160,8 +156,7 @@ _program_vectors:
 
 switch_kernel:
 	ld a, (port_map)
-	and #0xF8		; Preserve the other bits
-	or #0x05		; Map 4,5,6,3
+	or #0x07		; Map 4,7,6,3
 switchit:
 	push bc
 	ld (port_map), a
@@ -174,11 +169,7 @@ switch_user:
 	ld a, (port_map)
 	and #0xF8		; Preserve the other bits
 	and #0x01		; Map 0,1,2,3
-	jr switch_kernel
-
-switch_video:
-	ld a, (port_map)
-	or #0x7			; Map 4,7,6,3
+	or #0x04
 	jr switchit
 
 map_process:
@@ -192,7 +183,6 @@ map_process_always:
 	pop af
 	ret
 
-unmap_video:
 map_kernel:
 map_kernel_restore:
 	push af
@@ -200,12 +190,6 @@ map_kernel_restore:
 	pop af
 	ret
 
-map_video:
-	push af
-	call switch_video
-	pop af
-	ret
-
 map_save:
 	push af
         ld a, (port_map)
diff --git a/Kernel/platform-plus3/zxvideo.s b/Kernel/platform-plus3/zxvideo.s
index 0efba37f..47ba3762 100644
--- a/Kernel/platform-plus3/zxvideo.s
+++ b/Kernel/platform-plus3/zxvideo.s
@@ -35,7 +35,7 @@ videopos:
         ld e,a
         ld a,d
         and #0x18
-        or #0xC0	    ; not 0x40 as in screen 7
+        or #0x40	    ; page 7 is mapped here
         ld d,a
         ret
 
@@ -71,6 +71,7 @@ nofiddle:
         rl b
         ld c, a
 
+	; FIXME: Can't do this any more!
         ld hl, #0x3C00	    ; ROM font
         add hl, bc          ; hl points to first byte of char data
 
-- 
2.34.1