zx128: tidy up tricks.s further, make low_bank a simple ptab ptr

diff --git a/Kernel/platform-zx128/tricks.s b/Kernel/platform-zx128/tricks.s
index 415774a..90f4267 100644 (file)
--- a/Kernel/platform-zx128/tricks.s
+++ b/Kernel/platform-zx128/tricks.s
@@ -145,12 +145,11 @@ _switchin:
        ;       it with bank 6. low_bank holds the page pointer of the
        ;       task owning the space
 
-       push de
+       ld hl, (low_bank)       ; who owns low memory
        or a
-       ld de, (low_bank)
        sbc hl, de
-       call nz, fliplow
-       pop de
+       call nz, fliplow        ; not us - need to fix that up
+       ld (low_bank), de       ; we own it now
 
         ; check u_data->u_ptab matches what we wanted
         ld hl, (U_DATA__U_PTAB) ; u_data->u_ptab
@@ -242,9 +241,9 @@ _dofork:
         ; --------- copy process ---------
 
         ld hl, (fork_proc_ptr)
+       ld (low_bank), hl               ;       low bank will become the child
         ld de, #P_TAB__P_PAGE_OFFSET   ;       bank number
         add hl, de
-       ld (low_bank), hl               ;       low bank will become the child
         ; load p_page
         ld c, (hl)
        ld hl, (U_DATA__U_PAGE)
@@ -401,7 +400,6 @@ flip1:
        ld bc, #0x7ffd
        out (c), a
        exx
-       ld (low_bank), hl       ; Update low bank pointer
        ret
 ;
 ;      For the moment
@@ -415,5 +413,5 @@ bouncebuffer:
 ;      so share with bouncebuffer
 _swapstack:
 low_bank:
-       .dw _ptab + P_TAB__P_PAGE_OFFSET        ; Init starts owning this
+       .dw _ptab                       ; Init starts owning this