MIPS: Add arch generic CPU hotplug

Each platform has to add support for CPU hotplugging itself by providing
suitable definitions for the cpu_disable and cpu_die of the smp_ops
methods and setting SYS_SUPPORTS_HOTPLUG_CPU.  A platform should only set
SYS_SUPPORTS_HOTPLUG_CPU once all it's smp_ops definitions have the
necessary changes.  This patch contains the changes to the dummy smp_ops
definition for uni-processor systems.

Parts of the code contributed by Cavium Inc.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index b29f028..eb7e8d7 100644 (file)
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -784,8 +784,17 @@ config SYS_HAS_EARLY_PRINTK
        bool
 
 config HOTPLUG_CPU
+       bool "Support for hot-pluggable CPUs"
+       depends on SMP && HOTPLUG && SYS_SUPPORTS_HOTPLUG_CPU
+       help
+         Say Y here to allow turning CPUs off and on. CPUs can be
+         controlled through /sys/devices/system/cpu.
+         (Note: power management support will enable this option
+           automatically on SMP systems. )
+         Say N if you want to disable CPU hotplug.
+
+config SYS_SUPPORTS_HOTPLUG_CPU
        bool
-       default n
 
 config I8259
        bool

diff --git a/arch/mips/include/asm/smp-ops.h b/arch/mips/include/asm/smp-ops.h
index 64ffc02..fd54554 100644 (file)
--- a/arch/mips/include/asm/smp-ops.h
+++ b/arch/mips/include/asm/smp-ops.h
@@ -26,6 +26,10 @@ struct plat_smp_ops {
        void (*boot_secondary)(int cpu, struct task_struct *idle);
        void (*smp_setup)(void);
        void (*prepare_cpus)(unsigned int max_cpus);
+#ifdef CONFIG_HOTPLUG_CPU
+       int (*cpu_disable)(void);
+       void (*cpu_die)(unsigned int cpu);
+#endif
 };
 
 extern void register_smp_ops(struct plat_smp_ops *ops);

diff --git a/arch/mips/include/asm/smp.h b/arch/mips/include/asm/smp.h
index 2f83fa8..01f813d 100644 (file)
--- a/arch/mips/include/asm/smp.h
+++ b/arch/mips/include/asm/smp.h
@@ -41,6 +41,7 @@ extern int __cpu_logical_map[NR_CPUS];
 /* Octeon - Tell another core to flush its icache */
 #define SMP_ICACHE_FLUSH       0x4
 
+extern cpumask_t cpu_callin_map;
 
 extern void asmlinkage smp_bootstrap(void);
 
@@ -56,6 +57,24 @@ static inline void smp_send_reschedule(int cpu)
        mp_ops->send_ipi_single(cpu, SMP_RESCHEDULE_YOURSELF);
 }
 
+#ifdef CONFIG_HOTPLUG_CPU
+static inline int __cpu_disable(void)
+{
+       extern struct plat_smp_ops *mp_ops;     /* private */
+
+       return mp_ops->cpu_disable();
+}
+
+static inline void __cpu_die(unsigned int cpu)
+{
+       extern struct plat_smp_ops *mp_ops;     /* private */
+
+       mp_ops->cpu_die(cpu);
+}
+
+extern void play_dead(void);
+#endif
+
 extern asmlinkage void smp_call_function_interrupt(void);
 
 extern void arch_send_call_function_single_ipi(int cpu);

diff --git a/arch/mips/kernel/process.c b/arch/mips/kernel/process.c
index 1eaaa45..c09d681 100644 (file)
--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -50,10 +50,15 @@
  */
 void __noreturn cpu_idle(void)
 {
+       int cpu;
+
+       /* CPU is going idle. */
+       cpu = smp_processor_id();
+
        /* endless idle loop with no priority at all */
        while (1) {
                tick_nohz_stop_sched_tick(1);
-               while (!need_resched()) {
+               while (!need_resched() && cpu_online(cpu)) {
 #ifdef CONFIG_MIPS_MT_SMTC
                        extern void smtc_idle_loop_hook(void);
 
@@ -62,6 +67,12 @@ void __noreturn cpu_idle(void)
                        if (cpu_wait)
                                (*cpu_wait)();
                }
+#ifdef CONFIG_HOTPLUG_CPU
+               if (!cpu_online(cpu) && !cpu_isset(cpu, cpu_callin_map) &&
+                   (system_state == SYSTEM_RUNNING ||
+                    system_state == SYSTEM_BOOTING))
+                       play_dead();
+#endif
                tick_nohz_restart_sched_tick();
                preempt_enable_no_resched();
                schedule();

diff --git a/arch/mips/kernel/smp-up.c b/arch/mips/kernel/smp-up.c
index 878e373..2508d55 100644 (file)
--- a/arch/mips/kernel/smp-up.c
+++ b/arch/mips/kernel/smp-up.c
@@ -55,6 +55,18 @@ static void __init up_prepare_cpus(unsigned int max_cpus)
 {
 }
 
+#ifdef CONFIG_HOTPLUG_CPU
+static int up_cpu_disable(void)
+{
+       return -ENOSYS;
+}
+
+static void up_cpu_die(unsigned int cpu)
+{
+       BUG();
+}
+#endif
+
 struct plat_smp_ops up_smp_ops = {
        .send_ipi_single        = up_send_ipi_single,
        .send_ipi_mask          = up_send_ipi_mask,
@@ -64,4 +76,8 @@ struct plat_smp_ops up_smp_ops = {
        .boot_secondary         = up_boot_secondary,
        .smp_setup              = up_smp_setup,
        .prepare_cpus           = up_prepare_cpus,
+#ifdef CONFIG_HOTPLUG_CPU
+       .cpu_disable            = up_cpu_disable,
+       .cpu_die                = up_cpu_die,
+#endif
 };

diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c
index 58f4679..bc7d9b0 100644 (file)
--- a/arch/mips/kernel/smp.c
+++ b/arch/mips/kernel/smp.c
@@ -45,7 +45,7 @@
 #include <asm/mipsmtregs.h>
 #endif /* CONFIG_MIPS_MT_SMTC */
 
-static volatile cpumask_t cpu_callin_map;      /* Bitmask of started secondaries */
+volatile cpumask_t cpu_callin_map;     /* Bitmask of started secondaries */
 int __cpu_number_map[NR_CPUS];         /* Map physical to logical */
 int __cpu_logical_map[NR_CPUS];                /* Map logical to physical */
 
@@ -201,6 +201,8 @@ void __devinit smp_prepare_boot_cpu(void)
  * and keep control until "cpu_online(cpu)" is set.  Note: cpu is
  * physical, not logical.
  */
+static struct task_struct *cpu_idle_thread[NR_CPUS];
+
 int __cpuinit __cpu_up(unsigned int cpu)
 {
        struct task_struct *idle;
@@ -210,9 +212,16 @@ int __cpuinit __cpu_up(unsigned int cpu)
         * The following code is purely to make sure
         * Linux can schedule processes on this slave.
         */
-       idle = fork_idle(cpu);
-       if (IS_ERR(idle))
-               panic(KERN_ERR "Fork failed for CPU %d", cpu);
+       if (!cpu_idle_thread[cpu]) {
+               idle = fork_idle(cpu);
+               cpu_idle_thread[cpu] = idle;
+
+               if (IS_ERR(idle))
+                       panic(KERN_ERR "Fork failed for CPU %d", cpu);
+       } else {
+               idle = cpu_idle_thread[cpu];
+               init_idle(idle, cpu);
+       }
 
        mp_ops->boot_secondary(cpu, idle);
 

diff --git a/arch/mips/kernel/topology.c b/arch/mips/kernel/topology.c
index 660e44e..cf3eb61 100644 (file)
--- a/arch/mips/kernel/topology.c
+++ b/arch/mips/kernel/topology.c
@@ -17,7 +17,10 @@ static int __init topology_init(void)
 #endif /* CONFIG_NUMA */
 
        for_each_present_cpu(i) {
-               ret = register_cpu(&per_cpu(cpu_devices, i), i);
+               struct cpu *c = &per_cpu(cpu_devices, i);
+
+               c->hotpluggable = 1;
+               ret = register_cpu(c, i);
                if (ret)
                        printk(KERN_WARNING "topology_init: register_cpu %d "
                               "failed (%d)\n", i, ret);