nios2: Kernel booting and initialization

This patch adds the kernel booting and the initial setup code.

Signed-off-by: Ley Foon Tan <lftan@altera.com>

1 files changed, 175 insertions, 0 deletions

diff --git a/arch/nios2/kernel/head.S b/arch/nios2/kernel/head.S
new file mode 100644
index 00000000000..372ce4a3301
--- /dev/null
+++ b/arch/nios2/kernel/head.S
@@ -0,0 +1,175 @@
+/*
+ * Copyright (C) 2009 Wind River Systems Inc
+ *   Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
+ * Copyright (C) 2004 Microtronix Datacom Ltd
+ * Copyright (C) 2001 Vic Phillips, Microtronix Datacom Ltd.
+ *
+ * Based on head.S for Altera's Excalibur development board with nios processor
+ *
+ * Based on the following from the Excalibur sdk distribution:
+ *	NA_MemoryMap.s, NR_JumpToStart.s, NR_Setup.s, NR_CWPManager.s
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file "COPYING" in the main directory of this archive
+ * for more details.
+ */
+
+#include <linux/init.h>
+#include <linux/linkage.h>
+#include <asm/thread_info.h>
+#include <asm/processor.h>
+#include <asm/cache.h>
+#include <asm/page.h>
+#include <asm/asm-offsets.h>
+#include <asm/asm-macros.h>
+
+/*
+ * ZERO_PAGE is a special page that is used for zero-initialized
+ * data and COW.
+ */
+.data
+.global empty_zero_page
+.align 12
+empty_zero_page:
+	.space	PAGE_SIZE
+
+/*
+ * This global variable is used as an extension to the nios'
+ * STATUS register to emulate a user/supervisor mode.
+ */
+	.data
+	.align	2
+	.set noat
+
+	.global _current_thread
+_current_thread:
+	.long	0
+/*
+ * Input(s): passed from u-boot
+ *   r4 - Optional pointer to a board information structure.
+ *   r5 - Optional pointer to the physical starting address of the init RAM
+ *        disk.
+ *   r6 - Optional pointer to the physical ending address of the init RAM
+ *        disk.
+ *   r7 - Optional pointer to the physical starting address of any kernel
+ *        command-line parameters.
+ */
+
+/*
+ * First executable code - detected and jumped to by the ROM bootstrap
+ * if the code resides in flash (looks for "Nios" at offset 0x0c from
+ * the potential executable image).
+ */
+	__HEAD
+ENTRY(_start)
+	wrctl	status, r0		/* Disable interrupts */
+
+	/* Initialize all cache lines within the instruction cache */
+	movia	r1, NIOS2_ICACHE_SIZE
+	movui	r2, NIOS2_ICACHE_LINE_SIZE
+
+icache_init:
+	initi	r1
+	sub	r1, r1, r2
+	bgt	r1, r0, icache_init
+	br	1f
+
+	/*
+	 * This is the default location for the exception handler. Code in jump
+	 * to our handler
+	 */
+ENTRY(exception_handler_hook)
+	movia	r24, inthandler
+	jmp	r24
+
+ENTRY(fast_handler)
+	nextpc et
+helper:
+	stw	r3, r3save - helper(et)
+
+	rdctl	r3 , pteaddr
+	srli	r3, r3, 12
+	slli	r3, r3, 2
+	movia	et, pgd_current
+
+	ldw	et, 0(et)
+	add	r3, et, r3
+	ldw	et, 0(r3)
+
+	rdctl	r3, pteaddr
+	andi	r3, r3, 0xfff
+	add	et, r3, et
+	ldw	et, 0(et)
+	wrctl	tlbacc, et
+	nextpc	et
+helper2:
+	ldw	r3, r3save - helper2(et)
+	subi	ea, ea, 4
+	eret
+r3save:
+	.word 0x0
+ENTRY(fast_handler_end)
+
+1:
+	/*
+	 * After the instruction cache is initialized, the data cache must
+	 * also be initialized.
+	 */
+	movia	r1, NIOS2_DCACHE_SIZE
+	movui	r2, NIOS2_DCACHE_LINE_SIZE
+
+dcache_init:
+	initd	0(r1)
+	sub	r1, r1, r2
+	bgt	r1, r0, dcache_init
+
+	nextpc	r1			/* Find out where we are */
+chkadr:
+	movia	r2, chkadr
+	beq	r1, r2,finish_move	/* We are running in RAM done */
+	addi	r1, r1,(_start - chkadr)	/* Source */
+	movia	r2, _start		/* Destination */
+	movia	r3, __bss_start		/* End of copy */
+
+loop_move:				/* r1: src, r2: dest, r3: last dest */
+	ldw	r8, 0(r1)		/* load a word from [r1] */
+	stw	r8, 0(r2)		/* store a word to dest [r2] */
+	flushd	0(r2)			/* Flush cache for safety */
+	addi 	r1, r1, 4		/* inc the src addr */
+	addi	r2, r2, 4		/* inc the dest addr */
+	blt	r2, r3, loop_move
+
+	movia	r1, finish_move		/* VMA(_start)->l1 */
+	jmp	r1			/* jmp to _start */
+
+finish_move:
+
+	/* Mask off all possible interrupts */
+	wrctl	ienable, r0
+
+	/* Clear .bss */
+	movia	r2, __bss_start
+	movia	r1, __bss_stop
+1:
+	stb	r0, 0(r2)
+	addi	r2, r2, 1
+	bne	r1, r2, 1b
+
+	movia	r1, init_thread_union	/* set stack at top of the task union */
+	addi	sp, r1, THREAD_SIZE
+	movia	r2, _current_thread	/* Remember current thread */
+	stw	r1, 0(r2)
+
+	movia	r1, nios2_boot_init	/* save args r4-r7 passed from u-boot */
+	callr	r1
+
+	movia	r1, start_kernel	/* call start_kernel as a subroutine */
+	callr	r1
+
+	/* If we return from start_kernel, break to the oci debugger and
+	 * buggered we are.
+	 */
+	break
+
+	/* End of startup code */
+.set at