[PATCH] xtensa: Architecture support for Tensilica Xtensa Part 3

The attached patches provides part 3 of an architecture implementation for the
Tensilica Xtensa CPU series.

Signed-off-by: Chris Zankel <chris@zankel.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 237 insertions, 0 deletions

diff --git a/arch/xtensa/kernel/head.S b/arch/xtensa/kernel/head.S
new file mode 100644
index 0000000..6e9b522
--- /dev/null
+++ b/arch/xtensa/kernel/head.S
@@ -0,0 +1,237 @@
+/*
+ * arch/xtensa/kernel/head.S
+ *
+ * Xtensa Processor startup code.
+ *
+ * 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.
+ *
+ * Copyright (C) 2001 - 2005 Tensilica Inc.
+ *
+ * Chris Zankel <chris@zankel.net>
+ * Marc Gauthier <marc@tensilica.com, marc@alumni.uwaterloo.ca>
+ * Joe Taylor <joe@tensilica.com, joetylr@yahoo.com>
+ * Kevin Chea
+ */
+
+#include <xtensa/cacheasm.h>
+#include <linux/config.h>
+#include <asm/processor.h>
+#include <asm/page.h>
+
+/*
+ * This module contains the entry code for kernel images. It performs the
+ * minimal setup needed to call the generic C routines.
+ *
+ * Prerequisites:
+ *
+ * - The kernel image has been loaded to the actual address where it was
+ *   compiled to.
+ * - a2 contains either 0 or a pointer to a list of boot parameters.
+ *   (see setup.c for more details)
+ *
+ */
+
+	.macro	iterate	from, to , cmd
+		.ifeq	((\to - \from) & ~0xfff)
+			\cmd	\from
+			iterate "(\from+1)", \to, \cmd
+		.endif
+	.endm
+
+/*
+ *  _start
+ *
+ *  The bootloader passes a pointer to a list of boot parameters in a2.
+ */
+
+	/* The first bytes of the kernel image must be an instruction, so we
+	 * manually allocate and define the literal constant we need for a jx
+	 * instruction.
+	 */
+
+	.section .head.text, "ax"
+	.globl _start
+_start:	_j	2f
+	.align	4
+1:	.word	_startup
+2:	l32r	a0, 1b
+	jx	a0
+
+	.text
+	.align 4
+_startup:
+
+	/* Disable interrupts and exceptions. */
+
+	movi	a0, XCHAL_PS_EXCM_MASK
+	wsr	a0, PS
+
+	/* Preserve the pointer to the boot parameter list in EXCSAVE_1 */
+
+	wsr	a2, EXCSAVE_1
+
+	/* Start with a fresh windowbase and windowstart.  */
+
+	movi	a1, 1
+	movi	a0, 0
+	wsr	a1, WINDOWSTART
+	wsr	a0, WINDOWBASE
+	rsync
+
+	/* Set a0 to 0 for the remaining initialization. */
+
+	movi	a0, 0
+
+	/* Clear debugging registers. */
+
+#if XCHAL_HAVE_DEBUG
+	wsr	a0, IBREAKENABLE
+	wsr	a0, ICOUNT
+	movi	a1, 15
+	wsr	a0, ICOUNTLEVEL
+
+	.macro reset_dbreak num
+	wsr	a0, DBREAKC + \num
+	.endm
+
+        iterate 0, XCHAL_NUM_IBREAK-1, reset_dbreak
+#endif
+
+	/* Clear CCOUNT (not really necessary, but nice) */
+
+	wsr	a0, CCOUNT	# not really necessary, but nice
+
+	/* Disable zero-loops. */
+
+#if XCHAL_HAVE_LOOPS
+	wsr	a0, LCOUNT
+#endif
+
+	/* Disable all timers. */
+
+	.macro	reset_timer	num
+	wsr	a0, CCOMPARE_0 + \num
+	.endm
+	iterate	0, XCHAL_NUM_TIMERS-1, reset_timer
+
+	/* Interrupt initialization. */
+
+	movi	a2, XCHAL_INTTYPE_MASK_SOFTWARE | XCHAL_INTTYPE_MASK_EXTERN_EDGE
+	wsr	a0, INTENABLE
+	wsr	a2, INTCLEAR
+
+	/* Disable coprocessors. */
+
+#if XCHAL_CP_NUM > 0
+	wsr	a0, CPENABLE
+#endif
+
+	/* Set PS.INTLEVEL=1, PS.WOE=0, kernel stack, PS.EXCM=0
+	 *
+	 * Note: PS.EXCM must be cleared before using any loop
+	 *	 instructions; otherwise, they are silently disabled, and
+	 * 	 at most one iteration of the loop is executed.
+	 */
+
+	movi	a1, 1
+	wsr	a1, PS
+	rsync
+
+	/*  Initialize the caches.
+	 *  Does not include flushing writeback d-cache.
+	 *  a6, a7 are just working registers (clobbered).
+	 */
+
+	icache_reset  a2, a3
+	dcache_reset  a2, a3
+
+	/* Unpack data sections
+	 *
+	 * The linker script used to build the Linux kernel image
+	 * creates a table located at __boot_reloc_table_start
+	 * that contans the information what data needs to be unpacked.
+	 *
+	 * Uses a2-a7.
+	 */
+
+	movi	a2, __boot_reloc_table_start
+	movi	a3, __boot_reloc_table_end
+
+1:	beq	a2, a3, 3f	# no more entries?
+	l32i	a4, a2, 0	# start destination (in RAM)
+	l32i	a5, a2, 4	# end desination (in RAM)
+	l32i	a6, a2, 8	# start source (in ROM)
+	addi	a2, a2, 12	# next entry
+	beq	a4, a5, 1b	# skip, empty entry
+	beq	a4, a6, 1b	# skip, source and dest. are the same
+
+2:	l32i	a7, a6, 0	# load word
+	addi	a6, a6, 4
+	s32i	a7, a4, 0	# store word
+	addi	a4, a4, 4
+	bltu	a4, a5, 2b
+	j	1b
+
+3:
+	/* All code and initialized data segments have been copied.
+	 * Now clear the BSS segment.
+	 */
+
+	movi	a2, _bss_start	# start of BSS
+	movi	a3, _bss_end	# end of BSS
+
+1:	addi	a2, a2, 4
+	s32i	a0, a2, 0
+	blt	a2, a3, 1b
+
+#if XCHAL_DCACHE_IS_WRITEBACK
+
+	/* After unpacking, flush the writeback cache to memory so the
+	 * instructions/data are available.
+	 */
+
+	dcache_writeback_all	a2, a3
+#endif
+
+	/* Setup stack and enable window exceptions (keep irqs disabled) */
+
+	movi	a1, init_thread_union
+	addi	a1, a1, KERNEL_STACK_SIZE
+
+	movi	a2, 0x00040001		# WOE=1, INTLEVEL=1, UM=0
+	wsr	a2, PS			# (enable reg-windows; progmode stack)
+	rsync
+
+	/* Set up EXCSAVE[DEBUGLEVEL] to point to the Debug Exception Handler.*/
+
+	movi	a2, debug_exception
+	wsr	a2, EXCSAVE + XCHAL_DEBUGLEVEL
+
+	/* Set up EXCSAVE[1] to point to the exc_table. */
+
+	movi	a6, exc_table
+	xsr	a6, EXCSAVE_1
+
+	/* init_arch kick-starts the linux kernel */
+
+	movi	a4, init_arch
+	callx4	a4
+
+	movi	a4, start_kernel
+	callx4	a4
+
+should_never_return:
+	j	should_never_return
+
+	/* Define some common data structures here.  We define them
+	 * here in this assembly file due to their unusual alignment
+	 * requirements.
+	 */
+
+	.comm   swapper_pg_dir,PAGE_SIZE,PAGE_SIZE
+	.comm	empty_bad_page_table,PAGE_SIZE,PAGE_SIZE
+	.comm	empty_bad_page,PAGE_SIZE,PAGE_SIZE
+	.comm	empty_zero_page,PAGE_SIZE,PAGE_SIZE
+