MIPS: Add generic support for multiple machines within a single kernel

This patch adds a generic solution to support multiple machines based on
a given SoC within a single kernel image. It is implemented already for
several other architectures but MIPS has no generic support for that yet.

[Ralf: This competes with DT but DT is a much more complex solution and this
code has been used by OpenWRT for a long time so for now DT is a bad reason
to stop the merge but longer term this should be migrated to DT.]

Signed-off-by: Gabor Juhos <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Cc: Luis R. Rodriguez <[e-mail]>
Cc: Cliff Holden <[e-mail]>
Patchwork: https://patchwork.linux-mips.org/patch/1814/
Signed-off-by: Ralf Baechle <[e-mail]>

arch/mips/Kconfig

···
 config SYNC_R4K
 	bool
 
+config MIPS_MACHINE
+	def_bool n
+
 config NO_IOPORT
 	def_bool n
 

arch/mips/include/asm/mips_machine.h

···
+/*
+ *  Copyright (C) 2008-2010 Gabor Juhos <[e-mail]>
+ *
+ *  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.
+ *
+ */
+
+#ifndef __ASM_MIPS_MACHINE_H
+#define __ASM_MIPS_MACHINE_H
+
+#include <linux/init.h>
+#include <linux/stddef.h>
+
+#include <asm/bootinfo.h>
+
+struct mips_machine {
+	unsigned long		mach_type;
+	const char		*mach_id;
+	const char		*mach_name;
+	void			(*mach_setup)(void);
+};
+
+#define MIPS_MACHINE(_type, _id, _name, _setup)			\
+static const char machine_name_##_type[] __initconst		\
+			__aligned(1) = _name;			\
+static const char machine_id_##_type[] __initconst		\
+			__aligned(1) = _id;			\
+static struct mips_machine machine_##_type			\
+		__used __section(.mips.machines.init) =		\
+{								\
+	.mach_type	= _type,				\
+	.mach_id	= machine_id_##_type,			\
+	.mach_name	= machine_name_##_type,			\
+	.mach_setup	= _setup,				\
+};
+
+extern long __mips_machines_start;
+extern long __mips_machines_end;
+
+#ifdef CONFIG_MIPS_MACHINE
+int  mips_machtype_setup(char *id) __init;
+void mips_machine_setup(void) __init;
+void mips_set_machine_name(const char *name) __init;
+char *mips_get_machine_name(void);
+#else
+static inline int mips_machtype_setup(char *id) { return 1; }
+static inline void mips_machine_setup(void) { }
+static inline void mips_set_machine_name(const char *name) { }
+static inline char *mips_get_machine_name(void) { return NULL; }
+#endif /* CONFIG_MIPS_MACHINE */
+
+#endif /* __ASM_MIPS_MACHINE_H */

arch/mips/kernel/Makefile

···
 obj-$(CONFIG_KEXEC)		+= machine_kexec.o relocate_kernel.o
 obj-$(CONFIG_EARLY_PRINTK)	+= early_printk.o
 obj-$(CONFIG_SPINLOCK_TEST)	+= spinlock_test.o
+obj-$(CONFIG_MIPS_MACHINE)	+= mips_machine.o
 
 obj-$(CONFIG_OF)		+= prom.o
 

arch/mips/kernel/mips_machine.c

···
+/*
+ *  Copyright (C) 2008-2010 Gabor Juhos <[e-mail]>
+ *
+ *  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/mm.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+
+#include <asm/mips_machine.h>
+
+static struct mips_machine *mips_machine __initdata;
+static char *mips_machine_name = "Unknown";
+
+#define for_each_machine(mach) \
+	for ((mach) = (struct mips_machine *)&__mips_machines_start; \
+	     (mach) && \
+	     (unsigned long)(mach) < (unsigned long)&__mips_machines_end; \
+	     (mach)++)
+
+__init void mips_set_machine_name(const char *name)
+{
+	char *p;
+
+	if (name == NULL)
+		return;
+
+	p = kstrdup(name, GFP_KERNEL);
+	if (!p)
+		pr_err("MIPS: no memory for machine_name\n");
+
+	mips_machine_name = p;
+}
+
+char *mips_get_machine_name(void)
+{
+	return mips_machine_name;
+}
+
+__init int mips_machtype_setup(char *id)
+{
+	struct mips_machine *mach;
+
+	for_each_machine(mach) {
+		if (mach->mach_id == NULL)
+			continue;
+
+		if (strcmp(mach->mach_id, id) == 0) {
+			mips_machtype = mach->mach_type;
+			return 0;
+		}
+	}
+
+	pr_err("MIPS: no machine found for id '%s', supported machines:\n", id);
+	pr_err("%-24s %s\n", "id", "name");
+	for_each_machine(mach)
+		pr_err("%-24s %s\n", mach->mach_id, mach->mach_name);
+
+	return 1;
+}
+
+__setup("machtype=", mips_machtype_setup);
+
+__init void mips_machine_setup(void)
+{
+	struct mips_machine *mach;
+
+	for_each_machine(mach) {
+		if (mips_machtype == mach->mach_type) {
+			mips_machine = mach;
+			break;
+		}
+	}
+
+	if (!mips_machine)
+		return;
+
+	mips_set_machine_name(mips_machine->mach_name);
+	pr_info("MIPS: machine is %s\n", mips_machine_name);
+
+	if (mips_machine->mach_setup)
+		mips_machine->mach_setup();
+}

arch/mips/kernel/proc.c

···
 #include <asm/cpu-features.h>
 #include <asm/mipsregs.h>
 #include <asm/processor.h>
+#include <asm/mips_machine.h>
 
 unsigned int vced_count, vcei_count;
 
···
 	/*
 	 * For the first processor also print the system type
 	 */
-	if (n == 0)
+	if (n == 0) {
 		seq_printf(m, "system type\t\t: %s\n", get_system_type());
+		if (mips_get_machine_name())
+			seq_printf(m, "machine\t\t\t: %s\n",
+				   mips_get_machine_name());
+	}
 
 	seq_printf(m, "processor\t\t: %ld\n", n);
 	sprintf(fmt, "cpu model\t\t: %%s V%%d.%%d%s\n",

arch/mips/kernel/vmlinux.lds.S

···
 	INIT_TEXT_SECTION(PAGE_SIZE)
 	INIT_DATA_SECTION(16)
 
+	. = ALIGN(4);
+	.mips.machines.init : AT(ADDR(.mips.machines.init) - LOAD_OFFSET) {
+		__mips_machines_start = .;
+		*(.mips.machines.init)
+		__mips_machines_end = .;
+	}
+
 	/* .exit.text is discarded at runtime, not link time, to deal with
 	 * references from .rodata
 	 */