C6X: early boot code

Original port to early 2.6 kernel using TI COFF toolchain.
Brought up to date by Mark Salter <msalter@redhat.com>

This patch provides the early boot code for C6X architecture. There is a
16 entry vector table which is used to direct reset and interrupt events. The
vector table entries contain a small amount of code (maximum of 8 opcodes)
which simply branches to the actual event handling code.

The head.S code simply clears BSS, setups up a few control registers, and calls
machine_init followed by start_kernel. The machine_init code in setup.c does
the early flat tree parsing (memory, commandline, etc). At setup_arch time, the
code does the usual memory setup and minimally scans the devicetree for any
needed information.

Signed-off-by: Aurelien Jacquiot <a-jacquiot@ti.com>
Signed-off-by: Mark Salter <msalter@redhat.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

arch/c6x/kernel/head.S

@@ -0,0 +1,84 @@
+;
+;  Port on Texas Instruments TMS320C6x architecture
+;
+;  Copyright (C) 2004, 2009, 2010, 2011 Texas Instruments Incorporated
+;  Author: Aurelien Jacquiot (aurelien.jacquiot@jaluna.com)
+;
+;  This program is free software; you can redistribute it and/or modify
+;  it under the terms of the GNU General Public License version 2 as
+;  published by the Free Software Foundation.
+;
+#include <linux/linkage.h>
+#include <linux/of_fdt.h>
+#include <asm/asm-offsets.h>
+
+	__HEAD
+ENTRY(_c_int00)
+	;; Save magic and pointer
+	MV	.S1	A4,A10
+	MV	.S2	B4,B10
+	MVKL	.S2	__bss_start,B5
+	MVKH	.S2	__bss_start,B5
+	MVKL	.S2	__bss_stop,B6
+	MVKH	.S2	__bss_stop,B6
+	SUB	.L2	B6,B5,B6 ; bss size
+
+	;; Set the stack pointer
+	MVKL	.S2	current_ksp,B0
+	MVKH	.S2	current_ksp,B0
+	LDW	.D2T2	*B0,B15
+
+	;; clear bss
+	SHR	.S2	B6,3,B0	  ; number of dwords to clear
+	ZERO	.L2	B13
+	ZERO	.L2	B12
+bss_loop:
+	BDEC	.S2	bss_loop,B0
+	NOP	3
+	CMPLT	.L2	B0,0,B1
+ [!B1]	STDW	.D2T2	B13:B12,*B5++[1]
+
+	NOP	4
+	AND	.D2	~7,B15,B15
+
+	;; Clear GIE and PGIE
+	MVC	.S2	CSR,B2
+	CLR	.S2	B2,0,1,B2
+	MVC	.S2	B2,CSR
+	MVC	.S2	TSR,B2
+	CLR	.S2	B2,0,1,B2
+	MVC	.S2	B2,TSR
+	MVC	.S2	ITSR,B2
+	CLR	.S2	B2,0,1,B2
+	MVC	.S2	B2,ITSR
+	MVC	.S2	NTSR,B2
+	CLR	.S2	B2,0,1,B2
+	MVC	.S2	B2,NTSR
+
+	;; pass DTB pointer to machine_init (or zero if none)
+	MVKL	.S1	OF_DT_HEADER,A0
+	MVKH	.S1	OF_DT_HEADER,A0
+	CMPEQ	.L1	A10,A0,A0
+  [A0]	MV	.S1X	B10,A4
+  [!A0] MVK	.S1	0,A4
+
+#ifdef CONFIG_C6X_BIG_KERNEL
+	MVKL	.S1	machine_init,A0
+	MVKH	.S1	machine_init,A0
+	B	.S2X	A0
+	ADDKPC  .S2     0f,B3,4
+0:
+#else
+	CALLP	.S2	machine_init,B3
+#endif
+
+	;; Jump to Linux init
+#ifdef CONFIG_C6X_BIG_KERNEL
+	MVKL	.S1	start_kernel,A0
+	MVKH	.S1	start_kernel,A0
+	B	.S2X	A0
+#else
+	B	.S2	start_kernel
+#endif
+	NOP	5
+L1:	BNOP	.S2	L1,5