SPARC: Added support for SPARC LEON2 SOC Processor.

Signed-off-by: Daniel Hellstrom <daniel@gaisler.com>

1 files changed, 661 insertions, 0 deletions

diff --git a/cpu/leon2/start.S b/cpu/leon2/start.S
new file mode 100644
index 0000000..937ea1e
--- /dev/null
+++ b/cpu/leon2/start.S
@@ -0,0 +1,661 @@
+/* This is where the SPARC/LEON3 starts
+ * Copyright (C) 2007,
+ * Daniel Hellstrom, daniel@gaisler.com
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#include <config.h>
+#include <asm/asmmacro.h>
+#include <asm/winmacro.h>
+#include <asm/psr.h>
+#include <asm/stack.h>
+#include <asm/leon.h>
+#include <version.h>
+
+/* Entry for traps which jump to a programmer-specified trap handler.  */
+#define TRAPR(H)  \
+	wr 	%g0, 0xfe0, %psr; \
+	mov 	%g0, %tbr; \
+	ba 	(H); \
+	mov 	%g0, %wim;
+
+#define TRAP(H) \
+	mov	%psr, %l0; \
+	ba	(H); \
+	nop; nop;
+
+#define TRAPI(ilevel) \
+	mov 	ilevel, %l7; \
+	mov 	%psr, %l0; \
+	b 	_irq_entry; \
+	mov 	%wim, %l3
+
+/* Unexcpected trap will halt the processor by forcing it to error state */
+#undef BAD_TRAP
+#define BAD_TRAP ta 0; nop; nop; nop;
+
+/* Software trap. Treat as BAD_TRAP for the time being... */
+#define SOFT_TRAP TRAP(_hwerr)
+
+#define PSR_INIT   0x1FC0	/* Disable traps, set s and ps */
+#define WIM_INIT   2
+
+/* All traps low-level code here must end with this macro. */
+#define RESTORE_ALL b ret_trap_entry; clr %l6;
+
+#define WRITE_PAUSE nop;nop;nop
+
+WINDOWSIZE = (16 * 4)
+ARGPUSHSIZE = (6 * 4)
+ARGPUSH = (WINDOWSIZE + 4)
+MINFRAME = (WINDOWSIZE + ARGPUSHSIZE + 4)
+
+/* Number of register windows */
+#ifndef CFG_SPARC_NWINDOWS
+#error Must define number of SPARC register windows, default is 8
+#endif
+
+#define STACK_ALIGN	8
+#define SA(X)	(((X)+(STACK_ALIGN-1)) & ~(STACK_ALIGN-1))
+
+	.section ".start", "ax"
+	.globl 	_start, start, _trap_table
+	.globl  _irq_entry, nmi_trap
+	.globl  _reset_reloc
+
+/* at address 0
+ * Hardware traps
+ */
+start:
+_start:
+_trap_table:
+	TRAPR(_hardreset);		! 00 reset trap
+	BAD_TRAP;			! 01 instruction_access_exception
+	BAD_TRAP;			! 02 illegal_instruction
+	BAD_TRAP;			! 03 priveleged_instruction
+	BAD_TRAP;			! 04 fp_disabled
+	TRAP(_window_overflow);		! 05 window_overflow
+	TRAP(_window_underflow);	! 06 window_underflow
+	BAD_TRAP;			! 07 Memory Address Not Aligned
+	BAD_TRAP;			! 08 Floating Point Exception
+	BAD_TRAP;			! 09 Data Miss Exception
+	BAD_TRAP;			! 0a Tagged Instruction Ovrflw
+	BAD_TRAP;			! 0b Watchpoint Detected
+	BAD_TRAP;			! 0c
+	BAD_TRAP;			! 0d
+	BAD_TRAP;			! 0e
+	BAD_TRAP;			! 0f
+	BAD_TRAP;			! 10
+	TRAPI(1);			! 11 IRQ level 1
+	TRAPI(2);			! 12 IRQ level 2
+	TRAPI(3);			! 13 IRQ level 3
+	TRAPI(4);			! 14 IRQ level 4
+	TRAPI(5);			! 15 IRQ level 5
+	TRAPI(6);			! 16 IRQ level 6
+	TRAPI(7);			! 17 IRQ level 7
+	TRAPI(8);			! 18 IRQ level 8
+	TRAPI(9);			! 19 IRQ level 9
+	TRAPI(10);			! 1a IRQ level 10
+	TRAPI(11);			! 1b IRQ level 11
+	TRAPI(12);			! 1c IRQ level 12
+	TRAPI(13);			! 1d IRQ level 13
+	TRAPI(14);			! 1e IRQ level 14
+	TRAP(_nmi_trap);		! 1f IRQ level 15 /
+	                		! NMI (non maskable interrupt)
+	BAD_TRAP;			! 20 r_register_access_error
+	BAD_TRAP;			! 21 instruction access error
+	BAD_TRAP;			! 22
+	BAD_TRAP;			! 23
+	BAD_TRAP;			! 24 co-processor disabled
+	BAD_TRAP;			! 25 uniplemented FLUSH
+	BAD_TRAP;			! 26
+	BAD_TRAP;			! 27
+	BAD_TRAP;			! 28 co-processor exception
+	BAD_TRAP;			! 29 data access error
+	BAD_TRAP;			! 2a division by zero
+	BAD_TRAP;			! 2b data store error
+	BAD_TRAP;			! 2c data access MMU miss
+	BAD_TRAP;			! 2d
+	BAD_TRAP;			! 2e
+	BAD_TRAP;			! 2f
+	BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 30-33
+	BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 34-37
+	BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 38-3b
+	BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 3c-3f
+	BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 40-43
+	BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 44-47
+	BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 48-4b
+	BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 4c-4f
+	BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 50-53
+	BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 54-57
+	BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 58-5b
+	BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 5c-5f
+
+	/* implementaion dependent */
+	BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 60-63
+	BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 64-67
+	BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 68-6b
+	BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 6c-6f
+	BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 70-73
+	BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 74-77
+	BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 78-7b
+	BAD_TRAP; BAD_TRAP; BAD_TRAP; BAD_TRAP; ! 7c-7f
+
+	/* Software traps, not handled */
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! 80-83
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! 84-87
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! 88-8b
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! 8c-8f
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! 90-93
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! 94-97
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! 98-9b
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! 9c-9f
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! a0-a3
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! a4-a7
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! a8-ab
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! ac-af
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! b0-b3
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! b4-b7
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! b8-bb
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! bc-bf
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! c0-c3
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! c4-c7
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! c8-cb
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! cc-cf
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! d0-d3
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! d4-d7
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! d8-db
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! dc-df
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! e0-e3
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! e4-e7
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! e8-eb
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! ec-ef
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! f0-f3
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! f4-f7
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! f8-fb
+	SOFT_TRAP; SOFT_TRAP; SOFT_TRAP; SOFT_TRAP;	! fc-ff
+/*
+ * Version string
+ */
+
+	.data
+	.globl	version_string
+version_string:
+	.ascii U_BOOT_VERSION
+	.ascii " (", __DATE__, " - ", __TIME__, ")"
+	.ascii CONFIG_IDENT_STRING, "\0"
+
+	.section	".text"
+	.align 4
+
+_hardreset:
+1000:
+	flush
+	nop
+	nop
+	nop
+
+	/* Init Cache */
+        set     (LEON2_PREGS+LEON_REG_CACHECTRL_OFFSET), %g1
+        set     0x0081000f, %g2
+        st      %g2, [%g1]
+
+	mov	%g0, %y
+	clr	%g1
+	clr	%g2
+	clr	%g3
+	clr	%g4
+	clr	%g5
+	clr	%g6
+	clr	%g7
+
+	mov	%asr17, %g3
+	and	%g3, 0x1f, %g3
+clear_window:
+	mov	%g0, %l0
+	mov	%g0, %l1
+	mov	%g0, %l2
+	mov	%g0, %l3
+	mov	%g0, %l4
+	mov	%g0, %l5
+	mov	%g0, %l6
+	mov	%g0, %l7
+	mov	%g0, %o0
+	mov	%g0, %o1
+	mov	%g0, %o2
+	mov	%g0, %o3
+	mov	%g0, %o4
+	mov	%g0, %o5
+	mov	%g0, %o6
+	mov	%g0, %o7
+	subcc	%g3, 1, %g3
+	bge	clear_window
+	save
+
+leon2_init:
+	/* LEON2 Register Base in g1 */
+	set	LEON2_PREGS, %g1
+
+leon2_init_cache:
+	/* Set Cache control register */
+	set	0x1000f, %g2
+	st	%g2, [%g1 + 0x14]
+
+leon2_init_clear:
+
+	/* Clear LEON2 registers */
+	st	%g0, [%g1 + LEON2_ECTRL]
+	st	%g0, [%g1 + LEON2_IMASK]
+	st	%g0, [%g1 + LEON2_IPEND]
+	st	%g0, [%g1 + LEON2_IFORCE]
+	st	%g0, [%g1 + LEON2_ICLEAR]
+	st	%g0, [%g1 + LEON2_IOREG]
+	st	%g0, [%g1 + LEON2_IODIR]
+	st	%g0, [%g1 + LEON2_IOICONF]
+	st	%g0, [%g1 + LEON2_UCTRL0]
+	st	%g0, [%g1 + LEON2_UCTRL1]
+
+leon2_init_ioport:
+	/* I/O port initialization */
+	set	0xaa00, %g2
+	st	%g2, [%g1 + LEON2_IOREG]
+
+leon2_init_mctrl:
+
+	/* memory config register 1 */
+	set	CFG_GRLIB_MEMCFG1, %g2
+	ld	[%g1], %g3		!
+	and	%g3, 0x300, %g3
+	or	%g2, %g3, %g2
+	st	%g2, [%g1 + LEON2_MCFG1]
+	set	CFG_GRLIB_MEMCFG2, %g2		! Load memory config register 2
+#if !( defined(TSIM) || !defined(BZIMAGE))
+	st	%g2, [%g1 + LEON2_MCFG2]	! only for prom version, else done by "dumon -i"
+#endif
+	set	CFG_GRLIB_MEMCFG3, %g2		! Init FT register
+	st	%g2, [%g1 + LEON2_ECTRL]
+	ld	[%g1 + LEON2_ECTRL], %g2
+	srl	%g2, 30, %g2
+	andcc	%g2, 3, %g6
+	bne,a	leon2_init_wim
+	mov	%g0, %asr16		! clear err_reg
+
+leon2_init_wim:
+	set	WIM_INIT, %g3
+	mov	%g3, %wim
+
+leon2_init_psr:
+	set	0x1000, %g3
+	mov	%psr, %g2
+	wr	%g2, %g3, %psr
+	nop
+	nop
+	nop
+
+leon2_init_stackp:
+	set	CFG_INIT_SP_OFFSET, %fp
+	andn	%fp, 0x0f, %fp
+	sub	%fp, 64, %sp
+
+cpu_init_unreloc:
+	call	cpu_init_f
+	nop
+
+/* un relocated start address of monitor */
+#define TEXT_START _text
+
+/* un relocated end address of monitor */
+#define DATA_END __init_end
+
+reloc:
+	set	TEXT_START,%g2
+	set	DATA_END,%g3
+	set	CFG_RELOC_MONITOR_BASE,%g4
+reloc_loop:
+	ldd	[%g2],%l0
+	ldd	[%g2+8],%l2
+	std	%l0,[%g4]
+	std	%l2,[%g4+8]
+	inc	16,%g2
+	subcc	%g3,%g2,%g0
+	bne	reloc_loop
+	inc	16,%g4
+
+	clr	%l0
+	clr	%l1
+	clr	%l2
+	clr	%l3
+	clr	%g2
+
+/* register g4 contain address to start
+ * This means that BSS must be directly after data and code segments
+ *
+ * g3 is length of bss = (__bss_end-__bss_start)
+ *
+ */
+
+clr_bss:
+/* clear bss area (the relocated) */
+	set	__bss_start,%g2
+	set	__bss_end,%g3
+	sub	%g3,%g2,%g3
+	add	%g3,%g4,%g3
+	clr	%g1	/* std %g0 uses g0 and g1 */
+/* clearing 16byte a time ==> linker script need to align to 16 byte offset */
+clr_bss_16:
+	std	%g0,[%g4]
+	std	%g0,[%g4+8]
+	inc	16,%g4
+	cmp	%g3,%g4
+	bne	clr_bss_16
+	nop
+
+/* add offsets to GOT table */
+fixup_got:
+	set	__got_start,%g4
+	set	__got_end,%g3
+/*
+ * new got offset = (old GOT-PTR (read with ld) -
+ *   CFG_RELOC_MONITOR_BASE(from define) ) +
+ *   Destination Address (from define)
+ */
+	set	CFG_RELOC_MONITOR_BASE,%g2
+	set	TEXT_START, %g1
+	add	%g4,%g2,%g4
+	sub	%g4,%g1,%g4
+	add	%g3,%g2,%g3
+	sub	%g3,%g1,%g3
+	sub	%g2,%g1,%g2	! prepare register with (new base address) -
+				!  (old base address)
+got_loop:
+	ld	[%g4],%l0	! load old GOT-PTR
+	add	%l0,%g2,%l0	! increase with (new base address) -
+				!  (old base)
+	st	%l0,[%g4]
+	inc	4,%g4
+	cmp	%g3,%g4
+	bne	got_loop
+	nop
+
+prom_relocate:
+	set	__prom_start, %g2
+	set	__prom_end, %g3
+	set	CFG_PROM_OFFSET, %g4
+
+prom_relocate_loop:
+	ldd	[%g2],%l0
+	ldd	[%g2+8],%l2
+	std	%l0,[%g4]
+	std	%l2,[%g4+8]
+	inc	16,%g2
+	subcc	%g3,%g2,%g0
+	bne	prom_relocate_loop
+	inc	16,%g4
+
+/* Trap table has been moved, lets tell CPU about
+ * the new trap table address
+ */
+
+	set	CFG_RELOC_MONITOR_BASE, %g2
+	wr	%g0, %g2, %tbr
+
+/*	call	relocate*/
+	nop
+/* Call relocated init functions */
+jump:
+	set	cpu_init_f2,%o1
+	set	CFG_RELOC_MONITOR_BASE,%o2
+	add	%o1,%o2,%o1
+	sub	%o1,%g1,%o1
+	call	%o1
+	clr	%o0
+
+	set	board_init_f,%o1
+	set	CFG_RELOC_MONITOR_BASE,%o2
+	add	%o1,%o2,%o1
+	sub	%o1,%g1,%o1
+	call	%o1
+	clr	%o0
+
+dead:	ta 0				! if call returns...
+	nop
+
+/* Interrupt handler caller,
+ * reg L7: interrupt number
+ * reg L0: psr after interrupt
+ * reg L1: PC
+ * reg L2: next PC
+ * reg L3: wim
+ */
+_irq_entry:
+	SAVE_ALL
+
+	or	%l0, PSR_PIL, %g2
+	wr	%g2, 0x0, %psr
+	WRITE_PAUSE
+	wr	%g2, PSR_ET, %psr
+	WRITE_PAUSE
+	mov	%l7, %o0		! irq level
+	set	handler_irq, %o1
+	set	(CFG_RELOC_MONITOR_BASE-TEXT_BASE), %o2
+	add	%o1, %o2, %o1
+	call	%o1
+	add	%sp, SF_REGS_SZ, %o1	! pt_regs ptr
+	or	%l0, PSR_PIL, %g2	! restore PIL after handler_irq
+	wr	%g2, PSR_ET, %psr	! keep ET up
+	WRITE_PAUSE
+
+	RESTORE_ALL
+
+!Window overflow trap handler.
+	.global _window_overflow
+
+_window_overflow:
+
+	mov	%wim, %l3		! Calculate next WIM
+	mov	%g1, %l7
+	srl	%l3, 1, %g1
+	sll	%l3, (CFG_SPARC_NWINDOWS-1) , %l4
+	or	%l4, %g1, %g1
+
+	save				! Get into window to be saved.
+	mov	%g1, %wim
+	nop;
+	nop;
+	nop
+	st	%l0, [%sp + 0];
+	st	%l1, [%sp + 4];
+	st	%l2, [%sp + 8];
+	st	%l3, [%sp + 12];
+	st	%l4, [%sp + 16];
+	st	%l5, [%sp + 20];
+	st	%l6, [%sp + 24];
+	st	%l7, [%sp + 28];
+	st	%i0, [%sp + 32];
+	st	%i1, [%sp + 36];
+	st	%i2, [%sp + 40];
+	st	%i3, [%sp + 44];
+	st	%i4, [%sp + 48];
+	st	%i5, [%sp + 52];
+	st	%i6, [%sp + 56];
+	st	%i7, [%sp + 60];
+	restore				! Go back to trap window.
+	mov	%l7, %g1
+	jmp	%l1			! Re-execute save.
+	rett	%l2
+
+/* Window underflow trap handler.  */
+
+	.global  _window_underflow
+
+_window_underflow:
+
+	mov  %wim, %l3			! Calculate next WIM
+	sll  %l3, 1, %l4
+	srl  %l3, (CFG_SPARC_NWINDOWS-1), %l5
+	or   %l5, %l4, %l5
+	mov  %l5, %wim
+	nop; nop; nop
+	restore				! Two restores to get into the
+	restore				! window to restore
+	ld	[%sp + 0], %l0; 	! Restore window from the stack
+	ld	[%sp + 4], %l1;
+	ld	[%sp + 8], %l2;
+	ld	[%sp + 12], %l3;
+	ld	[%sp + 16], %l4;
+	ld	[%sp + 20], %l5;
+	ld	[%sp + 24], %l6;
+	ld	[%sp + 28], %l7;
+	ld	[%sp + 32], %i0;
+	ld	[%sp + 36], %i1;
+	ld	[%sp + 40], %i2;
+	ld	[%sp + 44], %i3;
+	ld	[%sp + 48], %i4;
+	ld	[%sp + 52], %i5;
+	ld	[%sp + 56], %i6;
+	ld	[%sp + 60], %i7;
+	save				! Get back to the trap window.
+	save
+	jmp	%l1			! Re-execute restore.
+	rett	%l2
+
+	retl
+
+_nmi_trap:
+	nop
+	jmp %l1
+	rett %l2
+
+_hwerr:
+	ta 0
+	nop
+	nop
+	b _hwerr 			! loop infinite
+	nop
+
+/* Registers to not touch at all. */
+#define t_psr      l0 /* Set by caller */
+#define t_pc       l1 /* Set by caller */
+#define t_npc      l2 /* Set by caller */
+#define t_wim      l3 /* Set by caller */
+#define t_twinmask l4 /* Set at beginning of this entry routine. */
+#define t_kstack   l5 /* Set right before pt_regs frame is built */
+#define t_retpc    l6 /* If you change this, change winmacro.h header file */
+#define t_systable l7 /* Never touch this, could be the syscall table ptr. */
+#define curptr     g6 /* Set after pt_regs frame is built */
+
+trap_setup:
+/* build a pt_regs trap frame. */
+	sub	%fp, (SF_REGS_SZ + PT_REGS_SZ), %t_kstack
+	PT_STORE_ALL(t_kstack, t_psr, t_pc, t_npc, g2)
+
+	/* See if we are in the trap window. */
+	mov	1, %t_twinmask
+	sll	%t_twinmask, %t_psr, %t_twinmask ! t_twinmask = (1 << psr)
+	andcc	%t_twinmask, %t_wim, %g0
+	beq	1f		! in trap window, clean up
+	nop
+
+	/*-------------------------------------------------
+	 * Spill , adjust %wim and go.
+	 */
+	srl	%t_wim, 0x1, %g2		! begin computation of new %wim
+
+	set	(CFG_SPARC_NWINDOWS-1), %g3	!NWINDOWS-1
+
+	sll	%t_wim, %g3, %t_wim	! NWINDOWS-1
+	or	%t_wim, %g2, %g2
+	and	%g2, 0xff, %g2
+
+	save	%g0, %g0, %g0           ! get in window to be saved
+
+	/* Set new %wim value */
+	wr	%g2, 0x0, %wim
+
+	/* Save the kernel window onto the corresponding stack. */
+	RW_STORE(sp)
+
+	restore	%g0, %g0, %g0
+	/*-------------------------------------------------*/
+
+1:
+	/* Trap from kernel with a window available.
+	 * Just do it...
+	 */
+	jmpl	%t_retpc + 0x8, %g0	! return to caller
+	 mov	%t_kstack, %sp		! jump onto new stack
+
+#define twin_tmp1 l4
+#define glob_tmp  g4
+#define curptr    g6
+ret_trap_entry:
+	wr	%t_psr, 0x0, %psr       ! enable nesting again, clear ET
+
+	/* Will the rett land us in the invalid window? */
+	mov	2, %g1
+	sll	%g1, %t_psr, %g1
+
+	set	CFG_SPARC_NWINDOWS, %g2	!NWINDOWS
+
+	srl	%g1, %g2, %g2
+	or	%g1, %g2, %g1
+	rd	%wim, %g2
+	andcc	%g2, %g1, %g0
+	be	1f		! Nope, just return from the trap
+	 sll	%g2, 0x1, %g1
+
+	/* We have to grab a window before returning. */
+	set	(CFG_SPARC_NWINDOWS-1), %g3	!NWINDOWS-1
+
+	srl	%g2, %g3,  %g2
+	or	%g1, %g2, %g1
+	and	%g1, 0xff, %g1
+
+	wr	%g1, 0x0, %wim
+
+	/* Grrr, make sure we load from the right %sp... */
+	PT_LOAD_ALL(sp, t_psr, t_pc, t_npc, g1)
+
+	restore	%g0, %g0, %g0
+	RW_LOAD(sp)
+	b	2f
+	save	%g0, %g0, %g0
+
+	/* Reload the entire frame in case this is from a
+	 * kernel system call or whatever...
+	 */
+1:
+	PT_LOAD_ALL(sp, t_psr, t_pc, t_npc, g1)
+2:
+	wr	%t_psr, 0x0, %psr
+	nop;
+	nop;
+	nop
+
+	jmp	%t_pc
+	rett	%t_npc
+
+/* This is called from relocated C-code.
+ * It resets the system by jumping to _start
+ */
+_reset_reloc:
+	set	start, %l0
+	call	%l0
+	nop