xtensa: make bootparam parsing optional

A kernel may not need any boot parameters from the bootloader, allow
disabling bootparam parsing in that case.
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

arch/xtensa/Kconfig

@@ -473,6 +473,15 @@ config BUILTIN_DTB
 	string "DTB to build into the kernel image"
 	depends on OF
 
+config PARSE_BOOTPARAM
+	bool "Parse bootparam block"
+	default y
+	help
+	  Parse parameters passed to the kernel from the bootloader. It may
+	  be disabled if the kernel is known to run without the bootloader.
+
+	  If unsure, say Y.
+
 config BLK_DEV_SIMDISK
 	tristate "Host file-based simulated block device support"
 	default n

arch/xtensa/boot/boot-elf/bootstrap.S

@@ -42,7 +42,10 @@ RomInitAddr:
 	.word	KERNELOFFSET
 #endif
 RomBootParam:
-	.word _bootparam
+#ifndef CONFIG_PARSE_BOOTPARAM
+	.word	0
+#else
+	.word	_bootparam
 _bootparam:
 	.short	BP_TAG_FIRST
 	.short	4
@@ -50,6 +53,7 @@ _bootparam:
 	.short	BP_TAG_LAST
 	.short	0
 	.long	0
+#endif
 
 	.align  4
 _SetupMMU:

arch/xtensa/kernel/setup.c

@@ -79,6 +79,7 @@ static char __initdata command_line[COMMAND_LINE_SIZE];
 static char default_command_line[COMMAND_LINE_SIZE] __initdata = CONFIG_CMDLINE;
 #endif
 
+#ifdef CONFIG_PARSE_BOOTPARAM
 /*
  * Boot parameter parsing.
  *
@@ -176,6 +177,13 @@ static int __init parse_bootparam(const bp_tag_t* tag)
 
 	return 0;
 }
+#else
+static int __init parse_bootparam(const bp_tag_t *tag)
+{
+	pr_info("Ignoring boot parameters at %p\n", tag);
+	return 0;
+}
+#endif
 
 #ifdef CONFIG_OF