arm64: Kernel booting and initialisation

The patch adds the kernel booting and the initial setup code.
Documentation/arm64/booting.txt describes the booting protocol on the
AArch64 Linux kernel. This is subject to change following the work on
boot standardisation, ACPI.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

Documentation/arm64/booting.txt

+			Booting AArch64 Linux
+			=====================
+
+Author: Will Deacon <will.deacon@arm.com>
+Date  : 07 September 2012
+
+This document is based on the ARM booting document by Russell King and
+is relevant to all public releases of the AArch64 Linux kernel.
+
+The AArch64 exception model is made up of a number of exception levels
+(EL0 - EL3), with EL0 and EL1 having a secure and a non-secure
+counterpart.  EL2 is the hypervisor level and exists only in non-secure
+mode. EL3 is the highest priority level and exists only in secure mode.
+
+For the purposes of this document, we will use the term `boot loader'
+simply to define all software that executes on the CPU(s) before control
+is passed to the Linux kernel.  This may include secure monitor and
+hypervisor code, or it may just be a handful of instructions for
+preparing a minimal boot environment.
+
+Essentially, the boot loader should provide (as a minimum) the
+following:
+
+1. Setup and initialise the RAM
+2. Setup the device tree
+3. Decompress the kernel image
+4. Call the kernel image
+
+
+1. Setup and initialise RAM
+---------------------------
+
+Requirement: MANDATORY
+
+The boot loader is expected to find and initialise all RAM that the
+kernel will use for volatile data storage in the system.  It performs
+this in a machine dependent manner.  (It may use internal algorithms
+to automatically locate and size all RAM, or it may use knowledge of
+the RAM in the machine, or any other method the boot loader designer
+sees fit.)
+
+
+2. Setup the device tree
+-------------------------
+
+Requirement: MANDATORY
+
+The device tree blob (dtb) must be no bigger than 2 megabytes in size
+and placed at a 2-megabyte boundary within the first 512 megabytes from
+the start of the kernel image. This is to allow the kernel to map the
+blob using a single section mapping in the initial page tables.
+
+
+3. Decompress the kernel image
+------------------------------
+
+Requirement: OPTIONAL
+
+The AArch64 kernel does not currently provide a decompressor and
+therefore requires decompression (gzip etc.) to be performed by the boot
+loader if a compressed Image target (e.g. Image.gz) is used.  For
+bootloaders that do not implement this requirement, the uncompressed
+Image target is available instead.
+
+
+4. Call the kernel image
+------------------------
+
+Requirement: MANDATORY
+
+The decompressed kernel image contains a 32-byte header as follows:
+
+  u32 magic	= 0x14000008;	/* branch to stext, little-endian */
+  u32 res0	= 0;		/* reserved */
+  u64 text_offset;		/* Image load offset */
+  u64 res1	= 0;		/* reserved */
+  u64 res2	= 0;		/* reserved */
+
+The image must be placed at the specified offset (currently 0x80000)
+from the start of the system RAM and called there. The start of the
+system RAM must be aligned to 2MB.
+
+Before jumping into the kernel, the following conditions must be met:
+
+- Quiesce all DMA capable devices so that memory does not get
+  corrupted by bogus network packets or disk data.  This will save
+  you many hours of debug.
+
+- Primary CPU general-purpose register settings
+  x0 = physical address of device tree blob (dtb) in system RAM.
+  x1 = 0 (reserved for future use)
+  x2 = 0 (reserved for future use)
+  x3 = 0 (reserved for future use)
+
+- CPU mode
+  All forms of interrupts must be masked in PSTATE.DAIF (Debug, SError,
+  IRQ and FIQ).
+  The CPU must be in either EL2 (RECOMMENDED in order to have access to
+  the virtualisation extensions) or non-secure EL1.
+
+- Caches, MMUs
+  The MMU must be off.
+  Instruction cache may be on or off.
+  Data cache must be off and invalidated.
+  External caches (if present) must be configured and disabled.
+
+- Architected timers
+  CNTFRQ must be programmed with the timer frequency.
+  If entering the kernel at EL1, CNTHCTL_EL2 must have EL1PCTEN (bit 0)
+  set where available.
+
+- Coherency
+  All CPUs to be booted by the kernel must be part of the same coherency
+  domain on entry to the kernel.  This may require IMPLEMENTATION DEFINED
+  initialisation to enable the receiving of maintenance operations on
+  each CPU.
+
+- System registers
+  All writable architected system registers at the exception level where
+  the kernel image will be entered must be initialised by software at a
+  higher exception level to prevent execution in an UNKNOWN state.
+
+The boot loader is expected to enter the kernel on each CPU in the
+following manner:
+
+- The primary CPU must jump directly to the first instruction of the
+  kernel image.  The device tree blob passed by this CPU must contain
+  for each CPU node:
+
+    1. An 'enable-method' property. Currently, the only supported value
+       for this field is the string "spin-table".
+
+    2. A 'cpu-release-addr' property identifying a 64-bit,
+       zero-initialised memory location.
+
+  It is expected that the bootloader will generate these device tree
+  properties and insert them into the blob prior to kernel entry.
+
+- Any secondary CPUs must spin outside of the kernel in a reserved area
+  of memory (communicated to the kernel by a /memreserve/ region in the
+  device tree) polling their cpu-release-addr location, which must be
+  contained in the reserved region.  A wfe instruction may be inserted
+  to reduce the overhead of the busy-loop and a sev will be issued by
+  the primary CPU.  When a read of the location pointed to by the
+  cpu-release-addr returns a non-zero value, the CPU must jump directly
+  to this value.
+
+- Secondary CPU general-purpose register settings
+  x0 = 0 (reserved for future use)
+  x1 = 0 (reserved for future use)
+  x2 = 0 (reserved for future use)
+  x3 = 0 (reserved for future use)

arch/arm64/include/asm/setup.h

+/*
+ * Based on arch/arm/include/asm/setup.h
+ *
+ * Copyright (C) 1997-1999 Russell King
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef __ASM_SETUP_H
+#define __ASM_SETUP_H
+
+#include <linux/types.h>
+
+#define COMMAND_LINE_SIZE	2048
+
+#endif

arch/arm64/kernel/setup.c

+/*
+ * Based on arch/arm/kernel/setup.c
+ *
+ * Copyright (C) 1995-2001 Russell King
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * 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.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/stddef.h>
+#include <linux/ioport.h>
+#include <linux/delay.h>
+#include <linux/utsname.h>
+#include <linux/initrd.h>
+#include <linux/console.h>
+#include <linux/bootmem.h>
+#include <linux/seq_file.h>
+#include <linux/screen_info.h>
+#include <linux/init.h>
+#include <linux/kexec.h>
+#include <linux/crash_dump.h>
+#include <linux/root_dev.h>
+#include <linux/cpu.h>
+#include <linux/interrupt.h>
+#include <linux/smp.h>
+#include <linux/fs.h>
+#include <linux/proc_fs.h>
+#include <linux/memblock.h>
+#include <linux/of_fdt.h>
+
+#include <asm/cputype.h>
+#include <asm/elf.h>
+#include <asm/cputable.h>
+#include <asm/sections.h>
+#include <asm/setup.h>
+#include <asm/cacheflush.h>
+#include <asm/tlbflush.h>
+#include <asm/traps.h>
+#include <asm/memblock.h>
+
+unsigned int processor_id;
+EXPORT_SYMBOL(processor_id);
+
+unsigned int elf_hwcap __read_mostly;
+EXPORT_SYMBOL_GPL(elf_hwcap);
+
+static const char *cpu_name;
+static const char *machine_name;
+phys_addr_t __fdt_pointer __initdata;
+
+/*
+ * Standard memory resources
+ */
+static struct resource mem_res[] = {
+	{
+		.name = "Kernel code",
+		.start = 0,
+		.end = 0,
+		.flags = IORESOURCE_MEM
+	},
+	{
+		.name = "Kernel data",
+		.start = 0,
+		.end = 0,
+		.flags = IORESOURCE_MEM
+	}
+};
+
+#define kernel_code mem_res[0]
+#define kernel_data mem_res[1]
+
+void __init early_print(const char *str, ...)
+{
+	char buf[256];
+	va_list ap;
+
+	va_start(ap, str);
+	vsnprintf(buf, sizeof(buf), str, ap);
+	va_end(ap);
+
+	printk("%s", buf);
+}
+
+static void __init setup_processor(void)
+{
+	struct cpu_info *cpu_info;
+
+	/*
+	 * locate processor in the list of supported processor
+	 * types.  The linker builds this table for us from the
+	 * entries in arch/arm/mm/proc.S
+	 */
+	cpu_info = lookup_processor_type(read_cpuid_id());
+	if (!cpu_info) {
+		printk("CPU configuration botched (ID %08x), unable to continue.\n",
+		       read_cpuid_id());
+		while (1);
+	}
+
+	cpu_name = cpu_info->cpu_name;
+
+	printk("CPU: %s [%08x] revision %d\n",
+	       cpu_name, read_cpuid_id(), read_cpuid_id() & 15);
+
+	sprintf(init_utsname()->machine, "aarch64");
+	elf_hwcap = 0;
+}
+
+static void __init setup_machine_fdt(phys_addr_t dt_phys)
+{
+	struct boot_param_header *devtree;
+	unsigned long dt_root;
+
+	/* Check we have a non-NULL DT pointer */
+	if (!dt_phys) {
+		early_print("\n"
+			"Error: NULL or invalid device tree blob\n"
+			"The dtb must be 8-byte aligned and passed in the first 512MB of memory\n"
+			"\nPlease check your bootloader.\n");
+
+		while (true)
+			cpu_relax();
+
+	}
+
+	devtree = phys_to_virt(dt_phys);
+
+	/* Check device tree validity */
+	if (be32_to_cpu(devtree->magic) != OF_DT_HEADER) {
+		early_print("\n"
+			"Error: invalid device tree blob at physical address 0x%p (virtual address 0x%p)\n"
+			"Expected 0x%x, found 0x%x\n"
+			"\nPlease check your bootloader.\n",
+			dt_phys, devtree, OF_DT_HEADER,
+			be32_to_cpu(devtree->magic));
+
+		while (true)
+			cpu_relax();
+	}
+
+	initial_boot_params = devtree;
+	dt_root = of_get_flat_dt_root();
+
+	machine_name = of_get_flat_dt_prop(dt_root, "model", NULL);
+	if (!machine_name)
+		machine_name = of_get_flat_dt_prop(dt_root, "compatible", NULL);
+	if (!machine_name)
+		machine_name = "<unknown>";
+	pr_info("Machine: %s\n", machine_name);
+
+	/* Retrieve various information from the /chosen node */
+	of_scan_flat_dt(early_init_dt_scan_chosen, boot_command_line);
+	/* Initialize {size,address}-cells info */
+	of_scan_flat_dt(early_init_dt_scan_root, NULL);
+	/* Setup memory, calling early_init_dt_add_memory_arch */
+	of_scan_flat_dt(early_init_dt_scan_memory, NULL);
+}
+
+void __init early_init_dt_add_memory_arch(u64 base, u64 size)
+{
+	size &= PAGE_MASK;
+	memblock_add(base, size);
+}
+
+void * __init early_init_dt_alloc_memory_arch(u64 size, u64 align)
+{
+	return __va(memblock_alloc(size, align));
+}
+
+/*
+ * Limit the memory size that was specified via FDT.
+ */
+static int __init early_mem(char *p)
+{
+	phys_addr_t limit;
+
+	if (!p)
+		return 1;
+
+	limit = memparse(p, &p) & PAGE_MASK;
+	pr_notice("Memory limited to %lldMB\n", limit >> 20);
+
+	memblock_enforce_memory_limit(limit);
+
+	return 0;
+}
+early_param("mem", early_mem);
+
+static void __init request_standard_resources(void)
+{
+	struct memblock_region *region;
+	struct resource *res;
+
+	kernel_code.start   = virt_to_phys(_text);
+	kernel_code.end     = virt_to_phys(_etext - 1);
+	kernel_data.start   = virt_to_phys(_sdata);
+	kernel_data.end     = virt_to_phys(_end - 1);
+
+	for_each_memblock(memory, region) {
+		res = alloc_bootmem_low(sizeof(*res));
+		res->name  = "System RAM";
+		res->start = __pfn_to_phys(memblock_region_memory_base_pfn(region));
+		res->end = __pfn_to_phys(memblock_region_memory_end_pfn(region)) - 1;
+		res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
+
+		request_resource(&iomem_resource, res);
+
+		if (kernel_code.start >= res->start &&
+		    kernel_code.end <= res->end)
+			request_resource(res, &kernel_code);
+		if (kernel_data.start >= res->start &&
+		    kernel_data.end <= res->end)
+			request_resource(res, &kernel_data);
+	}
+}
+
+void __init setup_arch(char **cmdline_p)
+{
+	setup_processor();
+
+	setup_machine_fdt(__fdt_pointer);
+
+	init_mm.start_code = (unsigned long) _text;
+	init_mm.end_code   = (unsigned long) _etext;
+	init_mm.end_data   = (unsigned long) _edata;
+	init_mm.brk	   = (unsigned long) _end;
+
+	*cmdline_p = boot_command_line;
+
+	parse_early_param();
+
+	arm64_memblock_init();
+
+	paging_init();
+	request_standard_resources();
+
+	unflatten_device_tree();
+
+#ifdef CONFIG_SMP
+	smp_init_cpus();
+#endif
+
+#ifdef CONFIG_VT
+#if defined(CONFIG_VGA_CONSOLE)
+	conswitchp = &vga_con;
+#elif defined(CONFIG_DUMMY_CONSOLE)
+	conswitchp = &dummy_con;
+#endif
+#endif
+}
+
+static DEFINE_PER_CPU(struct cpu, cpu_data);
+
+static int __init topology_init(void)
+{
+	int i;
+
+	for_each_possible_cpu(i) {
+		struct cpu *cpu = &per_cpu(cpu_data, i);
+		cpu->hotpluggable = 1;
+		register_cpu(cpu, i);
+	}
+
+	return 0;
+}
+subsys_initcall(topology_init);
+
+static const char *hwcap_str[] = {
+	"fp",
+	"asimd",
+	NULL
+};
+
+static int c_show(struct seq_file *m, void *v)
+{
+	int i;
+
+	seq_printf(m, "Processor\t: %s rev %d (%s)\n",
+		   cpu_name, read_cpuid_id() & 15, ELF_PLATFORM);
+
+	for_each_online_cpu(i) {
+		/*
+		 * glibc reads /proc/cpuinfo to determine the number of
+		 * online processors, looking for lines beginning with
+		 * "processor".  Give glibc what it expects.
+		 */
+#ifdef CONFIG_SMP
+		seq_printf(m, "processor\t: %d\n", i);
+#endif
+		seq_printf(m, "BogoMIPS\t: %lu.%02lu\n\n",
+			   loops_per_jiffy / (500000UL/HZ),
+			   loops_per_jiffy / (5000UL/HZ) % 100);
+	}
+
+	/* dump out the processor features */
+	seq_puts(m, "Features\t: ");
+
+	for (i = 0; hwcap_str[i]; i++)
+		if (elf_hwcap & (1 << i))
+			seq_printf(m, "%s ", hwcap_str[i]);
+
+	seq_printf(m, "\nCPU implementer\t: 0x%02x\n", read_cpuid_id() >> 24);
+	seq_printf(m, "CPU architecture: AArch64\n");
+	seq_printf(m, "CPU variant\t: 0x%x\n", (read_cpuid_id() >> 20) & 15);
+	seq_printf(m, "CPU part\t: 0x%03x\n", (read_cpuid_id() >> 4) & 0xfff);
+	seq_printf(m, "CPU revision\t: %d\n", read_cpuid_id() & 15);
+
+	seq_puts(m, "\n");
+
+	seq_printf(m, "Hardware\t: %s\n", machine_name);
+
+	return 0;
+}
+
+static void *c_start(struct seq_file *m, loff_t *pos)
+{
+	return *pos < 1 ? (void *)1 : NULL;
+}
+
+static void *c_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	++*pos;
+	return NULL;
+}
+
+static void c_stop(struct seq_file *m, void *v)
+{
+}
+
+const struct seq_operations cpuinfo_op = {
+	.start	= c_start,
+	.next	= c_next,
+	.stop	= c_stop,
+	.show	= c_show
+};