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>
diff --git a/arch/nios2/kernel/head.S b/arch/nios2/kernel/head.S
new file mode 100644
index 0000000..372ce4a
--- /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
