From a398b21a52a7b53cf947403d69913721aa268a9c Mon Sep 17 00:00:00 2001
From: Will Sowerbutts <will@sowerbutts.com>
Date: Thu, 1 Jan 2015 15:56:36 +0000
Subject: [PATCH] Kernel: Fix Z180 startup code for platforms where RAM does
 not start at physical address 0

---
 Kernel/cpu-z180/z180.s | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/Kernel/cpu-z180/z180.s b/Kernel/cpu-z180/z180.s
index f0f660ac..61f401ea 100644
--- a/Kernel/cpu-z180/z180.s
+++ b/Kernel/cpu-z180/z180.s
@@ -60,10 +60,10 @@ z180_init_early:
         in0 a, (MMU_BBR)
         cp #(OS_BANK + FIRST_RAM_BANK)
         jr z, dommu             ; we're in position already
-        cp #15
-        jr nc, finalcopy        ; we're running above 64K
-        ; we are running at least in part below 64K -- copy us up to 128KB temporarily
-        ld a, #0x02
+        cp #(OS_BANK + FIRST_RAM_BANK + 0x10)
+        jr nc, finalcopy        ; greater than -- we're running above 64K
+        ; we are running at least in part in the first 64K of RAM -- copy us up to 128KB temporarily
+        ld a, #((0x20 + FIRST_RAM_BANK) >> 4)
         call copykernel
 .if DEBUGCOMMON
         ld a, #'<'
@@ -73,7 +73,8 @@ z180_init_early:
         ld a, #'='
         call outchar
 .endif
-        ld a, #0x20             ; reprogram the MMU to use the copy at 128KB
+        ; reprogram the MMU to use the copy at 128KB
+        ld a, #(0x20 + FIRST_RAM_BANK)
         out0 (MMU_BBR), a
         out0 (MMU_CBR), a
 .if DEBUGCOMMON
@@ -96,7 +97,8 @@ dommu:
         ld a, #'='
         call outchar
 .endif
-        ld a, #(OS_BANK + FIRST_RAM_BANK)   ; reprogram MMU to use copy at physical
+        ; reprogram the MMU to use the copy at bottom of RAM
+        ld a, #(OS_BANK + FIRST_RAM_BANK)
         out0 (MMU_BBR), a       ; low 60K
         out0 (MMU_CBR), a       ; upper 4K (including our stack)
 .if DEBUGCOMMON
-- 
2.34.1