MIPS: generic: Introduce generic DT-based board support

Introduce a "generic" platform, which aims to be board-agnostic by
making use of device trees passed by the boot protocol defined in the
MIPS UHI (Universal Hosting Interface) specification. Provision is made
for supporting boards which use a legacy boot protocol that can't be
changed, but adding support for such boards or any others is left to
followon patches.

Right now the built kernels expect to be loaded to 0x80100000, ie. in
kseg0. This is fine for the vast majority of MIPS platforms, but
nevertheless it would be good to remove this limitation in the future by
mapping the kernel via the TLB such that it can be loaded anywhere & map
itself appropriately.

Configuration is handled by dynamically generating configs using
scripts/kconfig/merge_config.sh, somewhat similar to the way powerpc
makes use of it. This allows for variations upon the configuration, eg.
differing architecture revisions or subsets of driver support for
differing boards, to be handled without having a large number of
defconfig files.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14353/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 63 insertions, 0 deletions

diff --git a/arch/mips/include/asm/machine.h b/arch/mips/include/asm/machine.h
new file mode 100644
index 000000000000..6b444cd9526f
--- /dev/null
+++ b/arch/mips/include/asm/machine.h
@@ -0,0 +1,63 @@
+/*
+ * Copyright (C) 2016 Imagination Technologies
+ * Author: Paul Burton <paul.burton@imgtec.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation;  either version 2 of the  License, or (at your
+ * option) any later version.
+ */
+
+#ifndef __MIPS_ASM_MACHINE_H__
+#define __MIPS_ASM_MACHINE_H__
+
+#include <linux/libfdt.h>
+#include <linux/of.h>
+
+struct mips_machine {
+	const struct of_device_id *matches;
+	const void *fdt;
+	bool (*detect)(void);
+	const void *(*fixup_fdt)(const void *fdt, const void *match_data);
+	unsigned int (*measure_hpt_freq)(void);
+};
+
+extern long __mips_machines_start;
+extern long __mips_machines_end;
+
+#define MIPS_MACHINE(name)						\
+	static const struct mips_machine __mips_mach_##name		\
+		__used __section(.mips.machines.init)
+
+#define for_each_mips_machine(mach)					\
+	for ((mach) = (struct mips_machine *)&__mips_machines_start;	\
+	     (mach) < (struct mips_machine *)&__mips_machines_end;	\
+	     (mach)++)
+
+/**
+ * mips_machine_is_compatible() - check if a machine is compatible with an FDT
+ * @mach: the machine struct to check
+ * @fdt: the FDT to check for compatibility with
+ *
+ * Check whether the given machine @mach is compatible with the given flattened
+ * device tree @fdt, based upon the compatibility property of the root node.
+ *
+ * Return: the device id matched if any, else NULL
+ */
+static inline const struct of_device_id *
+mips_machine_is_compatible(const struct mips_machine *mach, const void *fdt)
+{
+	const struct of_device_id *match;
+
+	if (!mach->matches)
+		return NULL;
+
+	for (match = mach->matches; match->compatible; match++) {
+		if (fdt_node_check_compatible(fdt, 0, match->compatible) == 0)
+			return match;
+	}
+
+	return NULL;
+}
+
+#endif /* __MIPS_ASM_MACHINE_H__ */