m68knommu: add uboot commandline argument passing support

This patch adds m68knommu support for getting the kernel command line
arguments from uboot, including the passing of an initrd image from uboot.

We use this on a 5270/5271 based board, and have used it on the 5271evb
development board.  It is based on a patch found in the linux-2.6-denx
git tree, although that tree seems to have had lots of other changes
since which are not in the main Linus kernel.  I believe this will work
on all coldfires, although other m68knommu might be missing the _init_sp
stuff in head.S as far as I can tell.  I only have the coldfire to
test on.

Signed-off-by: Lennart Sorensen <lsorense@csclub.uwaterloo.ca>
Signed-off-by: Greg Ungerer <gerg@uclinux.org>

3 files changed, 107 insertions, 2 deletions

diff --git a/arch/m68knommu/Kconfig b/arch/m68knommu/Kconfig
index e2201b9..064f591 100644
--- a/arch/m68knommu/Kconfig
+++ b/arch/m68knommu/Kconfig
@@ -533,6 +533,13 @@ config AVNET
 	default y
 	depends on (AVNET5282)
 
+config UBOOT
+	bool "Support for U-Boot command line parameters"
+	help
+	  If you say Y here kernel will try to collect command
+	  line parameters from the initial u-boot stack.
+	default n
+
 config 4KSTACKS
 	bool "Use 4Kb for kernel stacks instead of 8Kb"
 	default y
diff --git a/arch/m68knommu/kernel/setup.c b/arch/m68knommu/kernel/setup.c
index 5c2bb3e..ba92b90 100644
--- a/arch/m68knommu/kernel/setup.c
+++ b/arch/m68knommu/kernel/setup.c
@@ -29,6 +29,8 @@
 #include <linux/bootmem.h>
 #include <linux/seq_file.h>
 #include <linux/init.h>
+#include <linux/initrd.h>
+#include <linux/root_dev.h>
 
 #include <asm/setup.h>
 #include <asm/irq.h>
@@ -52,7 +54,6 @@ void (*mach_reset)(void);
 void (*mach_halt)(void);
 void (*mach_power_off)(void);
 
-
 #ifdef CONFIG_M68000
 	#define CPU "MC68000"
 #endif
@@ -111,6 +112,69 @@ void (*mach_power_off)(void);
 extern int _stext, _etext, _sdata, _edata, _sbss, _ebss, _end;
 extern int _ramstart, _ramend;
 
+#if defined(CONFIG_UBOOT)
+/*
+ * parse_uboot_commandline
+ *
+ * Copies u-boot commandline arguments and store them in the proper linux
+ * variables.
+ *
+ * Assumes:
+ *	_init_sp global contains the address in the stack pointer when the
+ *	kernel starts (see head.S::_start)
+ *
+ *	U-Boot calling convention:
+ *	(*kernel) (kbd, initrd_start, initrd_end, cmd_start, cmd_end);
+ *
+ *	_init_sp can be parsed as such
+ *
+ *	_init_sp+00 = u-boot cmd after jsr into kernel (skip)
+ *	_init_sp+04 = &kernel board_info (residual data)
+ *	_init_sp+08 = &initrd_start
+ *	_init_sp+12 = &initrd_end
+ *	_init_sp+16 = &cmd_start
+ *	_init_sp+20 = &cmd_end
+ *
+ *	This also assumes that the memory locations pointed to are still
+ *	unmodified. U-boot places them near the end of external SDRAM.
+ *
+ * Argument(s):
+ *	commandp = the linux commandline arg container to fill.
+ *	size     = the sizeof commandp.
+ *
+ * Returns:
+ */
+void parse_uboot_commandline(char *commandp, int size)
+{
+	extern unsigned long _init_sp;
+	unsigned long *sp;
+	unsigned long uboot_kbd;
+	unsigned long uboot_initrd_start, uboot_initrd_end;
+	unsigned long uboot_cmd_start, uboot_cmd_end;
+
+
+	sp = (unsigned long *)_init_sp;
+	uboot_kbd = sp[1];
+	uboot_initrd_start = sp[2];
+	uboot_initrd_end = sp[3];
+	uboot_cmd_start = sp[4];
+	uboot_cmd_end = sp[5];
+
+	if (uboot_cmd_start && uboot_cmd_end)
+		strncpy(commandp, (const char *)uboot_cmd_start, size);
+#if defined(CONFIG_BLK_DEV_INITRD)
+	if (uboot_initrd_start && uboot_initrd_end &&
+		(uboot_initrd_end > uboot_initrd_start)) {
+		initrd_start = uboot_initrd_start;
+		initrd_end = uboot_initrd_end;
+		ROOT_DEV = Root_RAM0;
+		printk(KERN_INFO "initrd at 0x%lx:0x%lx\n",
+			initrd_start, initrd_end);
+	}
+#endif /* if defined(CONFIG_BLK_DEV_INITRD) */
+}
+#endif /* #if defined(CONFIG_UBOOT) */
+
 void __init setup_arch(char **cmdline_p)
 {
 	int bootmap_size;
@@ -128,7 +192,24 @@ void __init setup_arch(char **cmdline_p)
 #if defined(CONFIG_BOOTPARAM)
 	strncpy(&command_line[0], CONFIG_BOOTPARAM_STRING, sizeof(command_line));
 	command_line[sizeof(command_line) - 1] = 0;
-#endif
+#endif /* CONFIG_BOOTPARAM */
+
+#if defined(CONFIG_UBOOT)
+	/* CONFIG_UBOOT and CONFIG_BOOTPARAM defined, concatenate cmdline */
+	#if defined(CONFIG_BOOTPARAM)
+		/* Add the whitespace separator */
+		command_line[strlen(CONFIG_BOOTPARAM_STRING)] = ' ';
+		/* Parse uboot command line into the rest of the buffer */
+		parse_uboot_commandline(
+			&command_line[(strlen(CONFIG_BOOTPARAM_STRING)+1)],
+			(sizeof(command_line) -
+			(strlen(CONFIG_BOOTPARAM_STRING)+1)));
+	/* Only CONFIG_UBOOT defined, create cmdline */
+	#else
+		parse_uboot_commandline(&command_line[0], sizeof(command_line));
+	#endif /* CONFIG_BOOTPARAM */
+	command_line[sizeof(command_line) - 1] = 0;
+#endif /* CONFIG_UBOOT */
 
 	printk(KERN_INFO "\x0F\r\n\nuClinux/" CPU "\n");
 
@@ -204,6 +285,13 @@ void __init setup_arch(char **cmdline_p)
 	free_bootmem(memory_start, memory_end - memory_start);
 	reserve_bootmem(memory_start, bootmap_size, BOOTMEM_DEFAULT);
 
+#if defined(CONFIG_UBOOT) && defined(CONFIG_BLK_DEV_INITRD)
+	if ((initrd_start > 0) && (initrd_start < initrd_end) &&
+			(initrd_end < memory_end))
+		reserve_bootmem(initrd_start, initrd_end - initrd_start,
+				 BOOTMEM_DEFAULT);
+#endif /* if defined(CONFIG_BLK_DEV_INITRD) */
+
 	/*
 	 * Get kmalloc into gear.
 	 */
diff --git a/arch/m68knommu/platform/coldfire/head.S b/arch/m68knommu/platform/coldfire/head.S
index 2b0d73c..4b91aa2 100644
--- a/arch/m68knommu/platform/coldfire/head.S
+++ b/arch/m68knommu/platform/coldfire/head.S
@@ -106,6 +106,9 @@
 .global _ramvec
 .global	_ramstart
 .global	_ramend
+#if defined(CONFIG_UBOOT)
+.global	_init_sp
+#endif
 
 /*****************************************************************************/
 
@@ -124,6 +127,10 @@ _ramstart:
 .long	0
 _ramend:
 .long	0
+#if defined(CONFIG_UBOOT)
+_init_sp:
+.long	0
+#endif
 
 /*****************************************************************************/
 
@@ -137,6 +144,9 @@ __HEAD
 _start:
 	nop					/* filler */
 	movew	#0x2700, %sr			/* no interrupts */
+#if defined(CONFIG_UBOOT)
+	movel	%sp,_init_sp			/* save initial stack pointer */
+#endif
 
 	/*
 	 *	Do any platform or board specific setup now. Most boards