[ARM] Add basic SMP support.

Add the beginnings of SMP support to the ARM architecture, providing
smp.c, smp.h, and cpu.h.  Convert setup.c to use per-cpu for
topology initialisation.
Signed-off-by: Russell King <rmk@arm.linux.org.uk>

arch/arm/Kconfig

@@ -257,6 +257,33 @@ endmenu
 menu "General setup"
 
 # Select various configuration options depending on the machine type
+
+config SMP
+	bool "Symmetric Multi-Processing (EXPERIMENTAL)"
+	depends on EXPERIMENTAL && n
+	help
+	  This enables support for systems with more than one CPU. If you have
+	  a system with only one CPU, like most personal computers, say N. If
+	  you have a system with more than one CPU, say Y.
+
+	  If you say N here, the kernel will run on single and multiprocessor
+	  machines, but will use only one CPU of a multiprocessor machine. If
+	  you say Y here, the kernel will run on many, but not all, single
+	  processor machines. On a single processor machine, the kernel will
+	  run faster if you say N here.
+
+	  See also the <file:Documentation/smp.tex>,
+	  <file:Documentation/smp.txt>, <file:Documentation/i386/IO-APIC.txt>,
+	  <file:Documentation/nmi_watchdog.txt> and the SMP-HOWTO available at
+	  <http://www.linuxdoc.org/docs.html#howto>.
+
+	  If you don't know what to do here, say N.
+
+config NR_CPUS
+	int "Maximum number of CPUs (2-32)"
+	depends on SMP
+	default "4"
+
 config DISCONTIGMEM
 	bool
 	depends on ARCH_EDB7211 || ARCH_SA1100 || (ARCH_LH7A40X && !LH7A40X_CONTIGMEM)

arch/arm/kernel/Makefile

@@ -18,6 +18,7 @@ obj-$(CONFIG_MODULES)		+= armksyms.o module.o
 obj-$(CONFIG_ARTHUR)		+= arthur.o
 obj-$(CONFIG_ISA_DMA)		+= dma-isa.o
 obj-$(CONFIG_PCI)		+= bios32.o
+obj-$(CONFIG_SMP)		+= smp.o
 
 obj-$(CONFIG_IWMMXT)		+= iwmmxt.o
 AFLAGS_iwmmxt.o			:= -Wa,-mcpu=iwmmxt

arch/arm/kernel/setup.c

@@ -24,6 +24,7 @@
 #include <linux/cpu.h>
 #include <linux/interrupt.h>
 
+#include <asm/cpu.h>
 #include <asm/elf.h>
 #include <asm/hardware.h>
 #include <asm/io.h>
@@ -108,6 +109,8 @@ static char default_command_line[COMMAND_LINE_SIZE] __initdata = CONFIG_CMDLINE;
 static union { char c[4]; unsigned long l; } endian_test __initdata = { { 'l', '?', '?', 'b' } };
 #define ENDIANNESS ((char)endian_test.l)
 
+DEFINE_PER_CPU(struct cpuinfo_arm, cpu_data);
+
 /*
  * Standard memory resources
  */
@@ -739,11 +742,15 @@ void __init setup_arch(char **cmdline_p)
 #endif
 }
 
-static struct cpu cpu[1];
 
 static int __init topology_init(void)
 {
-	return register_cpu(cpu, 0, NULL);
+	int cpu;
+
+	for_each_cpu(cpu)
+		register_cpu(&per_cpu(cpu_data, cpu).cpu, cpu, NULL);
+
+	return 0;
 }
 
 subsys_initcall(topology_init);
@@ -784,9 +791,18 @@ static int c_show(struct seq_file *m, void *v)
 	seq_printf(m, "Processor\t: %s rev %d (%s)\n",
 		   cpu_name, (int)processor_id & 15, elf_platform);
 
+#if defined(CONFIG_SMP)
+	for_each_online_cpu(i) {
+		seq_printf(m, "Processor\t: %d\n", i);
+		seq_printf(m, "BogoMIPS\t: %lu.%02lu\n\n",
+			   per_cpu(cpu_data, i).loops_per_jiffy / (500000UL/HZ),
+			   (per_cpu(cpu_data, i).loops_per_jiffy / (5000UL/HZ)) % 100);
+	}
+#else /* CONFIG_SMP */
 	seq_printf(m, "BogoMIPS\t: %lu.%02lu\n",
 		   loops_per_jiffy / (500000/HZ),
 		   (loops_per_jiffy / (5000/HZ)) % 100);
+#endif
 
 	/* dump out the processor features */
 	seq_puts(m, "Features\t: ");

arch/arm/kernel/smp.c

+/*
+ *  linux/arch/arm/kernel/smp.c
+ *
+ *  Copyright (C) 2002 ARM Limited, All Rights Reserved.
+ *
+ * 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/config.h>
+#include <linux/delay.h>
+#include <linux/init.h>
+#include <linux/spinlock.h>
+#include <linux/sched.h>
+#include <linux/interrupt.h>
+#include <linux/cache.h>
+#include <linux/profile.h>
+#include <linux/errno.h>
+#include <linux/mm.h>
+#include <linux/seq_file.h>
+
+#include <asm/atomic.h>
+#include <asm/cpu.h>
+#include <asm/processor.h>
+#include <asm/smp.h>
+#include <asm/ptrace.h>
+
+#include <asm/cacheflush.h>
+#include <asm/tlbflush.h>
+
+/*
+ * bitmask of present and online CPUs.
+ * The present bitmask indicates that the CPU is physically present.
+ * The online bitmask indicates that the CPU is up and running.
+ */
+cpumask_t cpu_present_mask;
+cpumask_t cpu_online_map;
+
+/*
+ * structures for inter-processor calls
+ * - A collection of single bit ipi messages.
+ */
+struct ipi_data {
+	spinlock_t lock;
+	unsigned long bits;
+};
+
+static DEFINE_PER_CPU(struct ipi_data, ipi_data) = {
+	.lock	= SPIN_LOCK_UNLOCKED,
+};
+
+enum ipi_msg_type {
+	IPI_TIMER,
+	IPI_RESCHEDULE,
+	IPI_CALL_FUNC,
+	IPI_CPU_STOP,
+};
+
+struct smp_call_struct {
+	void (*func)(void *info);
+	void *info;
+	int wait;
+	cpumask_t pending;
+	cpumask_t unfinished;
+};
+
+static struct smp_call_struct * volatile smp_call_function_data;
+static spinlock_t smp_call_function_lock = SPIN_LOCK_UNLOCKED;
+
+int __init __cpu_up(unsigned int cpu)
+{
+	struct task_struct *idle;
+	int ret;
+
+	/*
+	 * Spawn a new process manually.  Grab a pointer to
+	 * its task struct so we can mess with it
+	 */
+	idle = fork_idle(cpu);
+	if (IS_ERR(idle)) {
+		printk(KERN_ERR "CPU%u: fork() failed\n", cpu);
+		return PTR_ERR(idle);
+	}
+
+	/*
+	 * Now bring the CPU into our world.
+	 */
+	ret = boot_secondary(cpu, idle);
+	if (ret) {
+		printk(KERN_CRIT "cpu_up: processor %d failed to boot\n", cpu);
+		/*
+		 * FIXME: We need to clean up the new idle thread. --rmk
+		 */
+	}
+
+	return ret;
+}
+
+/*
+ * Called by both boot and secondaries to move global data into
+ * per-processor storage.
+ */
+void __init smp_store_cpu_info(unsigned int cpuid)
+{
+	struct cpuinfo_arm *cpu_info = &per_cpu(cpu_data, cpuid);
+
+	cpu_info->loops_per_jiffy = loops_per_jiffy;
+}
+
+void __init smp_cpus_done(unsigned int max_cpus)
+{
+	int cpu;
+	unsigned long bogosum = 0;
+
+	for_each_online_cpu(cpu)
+		bogosum += per_cpu(cpu_data, cpu).loops_per_jiffy;
+
+	printk(KERN_INFO "SMP: Total of %d processors activated "
+	       "(%lu.%02lu BogoMIPS).\n",
+	       num_online_cpus(),
+	       bogosum / (500000/HZ),
+	       (bogosum / (5000/HZ)) % 100);
+}
+
+void __init smp_prepare_boot_cpu(void)
+{
+	unsigned int cpu = smp_processor_id();
+
+	cpu_set(cpu, cpu_present_mask);
+	cpu_set(cpu, cpu_online_map);
+}
+
+static void send_ipi_message(cpumask_t callmap, enum ipi_msg_type msg)
+{
+	unsigned long flags;
+	unsigned int cpu;
+
+	local_irq_save(flags);
+
+	for_each_cpu_mask(cpu, callmap) {
+		struct ipi_data *ipi = &per_cpu(ipi_data, cpu);
+
+		spin_lock(&ipi->lock);
+		ipi->bits |= 1 << msg;
+		spin_unlock(&ipi->lock);
+	}
+
+	/*
+	 * Call the platform specific cross-CPU call function.
+	 */
+	smp_cross_call(callmap);
+
+	local_irq_restore(flags);
+}
+
+/*
+ * You must not call this function with disabled interrupts, from a
+ * hardware interrupt handler, nor from a bottom half handler.
+ */
+int smp_call_function_on_cpu(void (*func)(void *info), void *info, int retry,
+                             int wait, cpumask_t callmap)
+{
+	struct smp_call_struct data;
+	unsigned long timeout;
+	int ret = 0;
+
+	data.func = func;
+	data.info = info;
+	data.wait = wait;
+
+	cpu_clear(smp_processor_id(), callmap);
+	if (cpus_empty(callmap))
+		goto out;
+
+	data.pending = callmap;
+	if (wait)
+		data.unfinished = callmap;
+
+	/*
+	 * try to get the mutex on smp_call_function_data
+	 */
+	spin_lock(&smp_call_function_lock);
+	smp_call_function_data = &data;
+
+	send_ipi_message(callmap, IPI_CALL_FUNC);
+
+	timeout = jiffies + HZ;
+	while (!cpus_empty(data.pending) && time_before(jiffies, timeout))
+		barrier();
+
+	/*
+	 * did we time out?
+	 */
+	if (!cpus_empty(data.pending)) {
+		/*
+		 * this may be causing our panic - report it
+		 */
+		printk(KERN_CRIT
+		       "CPU%u: smp_call_function timeout for %p(%p)\n"
+		       "      callmap %lx pending %lx, %swait\n",
+		       smp_processor_id(), func, info, callmap, data.pending,
+		       wait ? "" : "no ");
+
+		/*
+		 * TRACE
+		 */
+		timeout = jiffies + (5 * HZ);
+		while (!cpus_empty(data.pending) && time_before(jiffies, timeout))
+			barrier();
+
+		if (cpus_empty(data.pending))
+			printk(KERN_CRIT "     RESOLVED\n");
+		else
+			printk(KERN_CRIT "     STILL STUCK\n");
+	}
+
+	/*
+	 * whatever happened, we're done with the data, so release it
+	 */
+	smp_call_function_data = NULL;
+	spin_unlock(&smp_call_function_lock);
+
+	if (!cpus_empty(data.pending)) {
+		ret = -ETIMEDOUT;
+		goto out;
+	}
+
+	if (wait)
+		while (!cpus_empty(data.unfinished))
+			barrier();
+ out:
+
+	return 0;
+}
+
+int smp_call_function(void (*func)(void *info), void *info, int retry,
+                      int wait)
+{
+	return smp_call_function_on_cpu(func, info, retry, wait,
+					cpu_online_map);
+}
+
+void show_ipi_list(struct seq_file *p)
+{
+	int cpu;
+
+	seq_printf(p, "IPI: ");
+
+	for_each_online_cpu(cpu)
+		seq_printf(p, "%10lu ", per_cpu(cpu_data, cpu).ipi_count);
+
+	seq_putc(p, '\n');
+}
+
+static void ipi_timer(struct pt_regs *regs)
+{
+	int user = user_mode(regs);
+
+	irq_enter();
+	profile_tick(CPU_PROFILING, regs);
+	update_process_times(user);
+	irq_exit();
+}
+
+/*
+ * ipi_call_function - handle IPI from smp_call_function()
+ *
+ * Note that we copy data out of the cross-call structure and then
+ * let the caller know that we're here and have done with their data
+ */
+static void ipi_call_function(unsigned int cpu)
+{
+	struct smp_call_struct *data = smp_call_function_data;
+	void (*func)(void *info) = data->func;
+	void *info = data->info;
+	int wait = data->wait;
+
+	cpu_clear(cpu, data->pending);
+
+	func(info);
+
+	if (wait)
+		cpu_clear(cpu, data->unfinished);
+}
+
+static spinlock_t stop_lock = SPIN_LOCK_UNLOCKED;
+
+/*
+ * ipi_cpu_stop - handle IPI from smp_send_stop()
+ */
+static void ipi_cpu_stop(unsigned int cpu)
+{
+	spin_lock(&stop_lock);
+	printk(KERN_CRIT "CPU%u: stopping\n", cpu);
+	dump_stack();
+	spin_unlock(&stop_lock);
+
+	cpu_clear(cpu, cpu_online_map);
+
+	local_fiq_disable();
+	local_irq_disable();
+
+	while (1)
+		cpu_relax();
+}
+
+/*
+ * Main handler for inter-processor interrupts
+ *
+ * For ARM, the ipimask now only identifies a single
+ * category of IPI (Bit 1 IPIs have been replaced by a
+ * different mechanism):
+ *
+ *  Bit 0 - Inter-processor function call
+ */
+void do_IPI(unsigned int ipimask, struct pt_regs *regs)
+{
+	unsigned int cpu = smp_processor_id();
+
+	per_cpu(cpu_data, cpu).ipi_count++;
+
+	if (ipimask & (1 << 0)) {
+		struct ipi_data *ipi = &per_cpu(ipi_data, cpu);
+
+		for (;;) {
+			unsigned long msgs;
+
+			spin_lock(&ipi->lock);
+			msgs = ipi->bits;
+			ipi->bits = 0;
+			spin_unlock(&ipi->lock);
+
+			if (!msgs)
+				break;
+
+			do {
+				unsigned nextmsg;
+
+				nextmsg = msgs & -msgs;
+				msgs &= ~nextmsg;
+				nextmsg = ffz(~nextmsg);
+
+				switch (nextmsg) {
+				case IPI_TIMER:
+					ipi_timer(regs);
+					break;
+
+				case IPI_RESCHEDULE:
+					/*
+					 * nothing more to do - eveything is
+					 * done on the interrupt return path
+					 */
+					break;
+
+				case IPI_CALL_FUNC:
+					ipi_call_function(cpu);
+					break;
+
+				case IPI_CPU_STOP:
+					ipi_cpu_stop(cpu);
+					break;
+
+				default:
+					printk(KERN_CRIT "CPU%u: Unknown IPI message 0x%x\n",
+					       cpu, nextmsg);
+					break;
+				}
+			} while (msgs);
+		}
+
+		ipimask &= ~0x01;
+	}
+
+	if (ipimask) {
+		printk(KERN_CRIT "CPU %d: Unknown IPI signal %x!\n",
+		       cpu, ipimask);
+		BUG();
+	}
+}
+
+void smp_send_reschedule(int cpu)
+{
+	send_ipi_message(cpumask_of_cpu(cpu), IPI_RESCHEDULE);
+}
+
+void smp_send_timer(void)
+{
+	cpumask_t mask = cpu_online_map;
+	cpu_clear(smp_processor_id(), mask);
+	send_ipi_message(mask, IPI_TIMER);
+}
+
+void smp_send_stop(void)
+{
+	cpumask_t mask = cpu_online_map;
+	cpu_clear(smp_processor_id(), mask);
+	send_ipi_message(mask, IPI_CPU_STOP);
+}
+
+/*
+ * not supported here
+ */
+int __init setup_profiling_timer(unsigned int multiplier)
+{
+	return -EINVAL;
+}

include/asm-arm/cpu.h

+/*
+ *  linux/include/asm-arm/cpu.h
+ *
+ *  Copyright (C) 2004-2005 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.
+ */
+#ifndef __ASM_ARM_CPU_H
+#define __ASM_ARM_CPU_H
+
+#include <linux/config.h>
+#include <linux/percpu.h>
+
+struct cpuinfo_arm {
+	struct cpu	cpu;
+#ifdef CONFIG_SMP
+	unsigned int	loops_per_jiffy;
+	unsigned long	ipi_count;
+#endif
+};
+
+DECLARE_PER_CPU(struct cpuinfo_arm, cpu_data);
+
+#endif

include/asm-arm/smp.h

-#ifndef __ASM_SMP_H
-#define __ASM_SMP_H
+/*
+ *  linux/include/asm-arm/smp.h
+ *
+ *  Copyright (C) 2004-2005 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.
+ */
+#ifndef __ASM_ARM_SMP_H
+#define __ASM_ARM_SMP_H
 
 #include <linux/config.h>
+#include <linux/threads.h>
+#include <linux/cpumask.h>
+#include <linux/thread_info.h>
 
-#ifdef CONFIG_SMP
-#error SMP not supported
-#endif
+#include <asm/arch/smp.h>
 
+#ifndef CONFIG_SMP
+# error "<asm-arm/smp.h> included in non-SMP build"
 #endif
+
+#define smp_processor_id()	(current_thread_info()->cpu)
+
+extern cpumask_t cpu_present_mask;
+#define cpu_possible_map cpu_present_mask
+
+/*
+ * at the moment, there's not a big penalty for changing CPUs
+ * (the >big< penalty is running SMP in the first place)
+ */
+#define PROC_CHANGE_PENALTY		15
+
+/*
+ * Move global data into per-processor storage.
+ */
+extern void smp_store_cpu_info(unsigned int cpuid);
+
+/*
+ * Raise an IPI cross call on CPUs in callmap.
+ */
+extern void smp_cross_call(cpumask_t callmap);
+
+/*
+ * Boot a secondary CPU, and assign it the specified idle task.
+ * This also gives us the initial stack to use for this CPU.
+ */
+extern int __init boot_secondary(unsigned int cpu, struct task_struct *);
+
+#endif /* ifndef __ASM_ARM_SMP_H */