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, 176 insertions, 0 deletions

diff --git a/arch/mips/generic/init.c b/arch/mips/generic/init.c
new file mode 100644
index 000000000000..0ea73e845440
--- /dev/null
+++ b/arch/mips/generic/init.c
@@ -0,0 +1,176 @@
+/*
+ * 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.
+ */
+
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/clocksource.h>
+#include <linux/init.h>
+#include <linux/irqchip.h>
+#include <linux/of_fdt.h>
+#include <linux/of_platform.h>
+
+#include <asm/fw/fw.h>
+#include <asm/irq_cpu.h>
+#include <asm/machine.h>
+#include <asm/mips-cpc.h>
+#include <asm/prom.h>
+#include <asm/smp-ops.h>
+#include <asm/time.h>
+
+static __initdata const void *fdt;
+static __initdata const struct mips_machine *mach;
+static __initdata const void *mach_match_data;
+
+void __init prom_init(void)
+{
+	const struct mips_machine *check_mach;
+	const struct of_device_id *match;
+
+	if ((fw_arg0 == -2) && !fdt_check_header((void *)fw_arg1)) {
+		/*
+		 * We booted using the UHI boot protocol, so we have been
+		 * provided with the appropriate device tree for the board.
+		 * Make use of it & search for any machine struct based upon
+		 * the root compatible string.
+		 */
+		fdt = (void *)fw_arg1;
+
+		for_each_mips_machine(check_mach) {
+			match = mips_machine_is_compatible(check_mach, fdt);
+			if (match) {
+				mach = check_mach;
+				mach_match_data = match->data;
+				break;
+			}
+		}
+	} else if (IS_ENABLED(CONFIG_LEGACY_BOARDS)) {
+		/*
+		 * We weren't booted using the UHI boot protocol, but do
+		 * support some number of boards with legacy boot protocols.
+		 * Attempt to find the right one.
+		 */
+		for_each_mips_machine(check_mach) {
+			if (!check_mach->detect)
+				continue;
+
+			if (!check_mach->detect())
+				continue;
+
+			mach = check_mach;
+		}
+
+		/*
+		 * If we don't recognise the machine then we can't continue, so
+		 * die here.
+		 */
+		BUG_ON(!mach);
+
+		/* Retrieve the machine's FDT */
+		fdt = mach->fdt;
+	}
+
+	BUG_ON(!fdt);
+}
+
+void __init *plat_get_fdt(void)
+{
+	return (void *)fdt;
+}
+
+void __init plat_mem_setup(void)
+{
+	if (mach && mach->fixup_fdt)
+		fdt = mach->fixup_fdt(fdt, mach_match_data);
+
+	strlcpy(arcs_cmdline, boot_command_line, COMMAND_LINE_SIZE);
+	__dt_setup_arch((void *)fdt);
+}
+
+void __init device_tree_init(void)
+{
+	int err;
+
+	unflatten_and_copy_device_tree();
+	mips_cpc_probe();
+
+	err = register_cps_smp_ops();
+	if (err)
+		err = register_up_smp_ops();
+}
+
+void __init plat_time_init(void)
+{
+	struct device_node *np;
+	struct clk *clk;
+
+	of_clk_init(NULL);
+
+	if (!cpu_has_counter) {
+		mips_hpt_frequency = 0;
+	} else if (mach && mach->measure_hpt_freq) {
+		mips_hpt_frequency = mach->measure_hpt_freq();
+	} else {
+		np = of_get_cpu_node(0, NULL);
+		if (!np) {
+			pr_err("Failed to get CPU node\n");
+			return;
+		}
+
+		clk = of_clk_get(np, 0);
+		if (IS_ERR(clk)) {
+			pr_err("Failed to get CPU clock: %ld\n", PTR_ERR(clk));
+			return;
+		}
+
+		mips_hpt_frequency = clk_get_rate(clk);
+		clk_put(clk);
+
+		switch (boot_cpu_type()) {
+		case CPU_20KC:
+		case CPU_25KF:
+			/* The counter runs at the CPU clock rate */
+			break;
+		default:
+			/* The counter runs at half the CPU clock rate */
+			mips_hpt_frequency /= 2;
+			break;
+		}
+	}
+
+	clocksource_probe();
+}
+
+void __init arch_init_irq(void)
+{
+	struct device_node *intc_node;
+
+	intc_node = of_find_compatible_node(NULL, NULL,
+					    "mti,cpu-interrupt-controller");
+	if (!cpu_has_veic && !intc_node)
+		mips_cpu_irq_init();
+
+	irqchip_init();
+}
+
+static int __init publish_devices(void)
+{
+	if (!of_have_populated_dt())
+		panic("Device-tree not present");
+
+	if (of_platform_populate(NULL, of_default_bus_match_table, NULL, NULL))
+		panic("Failed to populate DT");
+
+	return 0;
+}
+arch_initcall(publish_devices);
+
+void __init prom_free_prom_memory(void)
+{
+}