xtensa: implement CPU hotplug
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>
diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
index 4b09c60..70a160b 100644
--- a/arch/xtensa/Kconfig
+++ b/arch/xtensa/Kconfig
@@ -140,6 +140,15 @@
range 2 32
default "4"
+config HOTPLUG_CPU
+ bool "Enable CPU hotplug support"
+ depends on SMP
+ help
+ Say Y here to allow turning CPUs off and on. CPUs can be
+ controlled through /sys/devices/system/cpu.
+
+ Say N if you want to disable CPU hotplug.
+
config MATH_EMULATION
bool "Math emulation"
help
diff --git a/arch/xtensa/include/asm/irq.h b/arch/xtensa/include/asm/irq.h
index 7d194d4..f71f88e 100644
--- a/arch/xtensa/include/asm/irq.h
+++ b/arch/xtensa/include/asm/irq.h
@@ -45,6 +45,7 @@
struct irqaction;
struct irq_domain;
+void migrate_irqs(void);
int xtensa_irq_domain_xlate(const u32 *intspec, unsigned int intsize,
unsigned long int_irq, unsigned long ext_irq,
unsigned long *out_hwirq, unsigned int *out_type);
diff --git a/arch/xtensa/include/asm/smp.h b/arch/xtensa/include/asm/smp.h
index 30ac58c..4e43f56 100644
--- a/arch/xtensa/include/asm/smp.h
+++ b/arch/xtensa/include/asm/smp.h
@@ -29,6 +29,15 @@
struct seq_file;
void show_ipi_list(struct seq_file *p, int prec);
+#ifdef CONFIG_HOTPLUG_CPU
+
+void __cpu_die(unsigned int cpu);
+int __cpu_disable(void);
+void cpu_die(void);
+void cpu_restart(void);
+
+#endif /* CONFIG_HOTPLUG_CPU */
+
#endif /* CONFIG_SMP */
#endif /* _XTENSA_SMP_H */
diff --git a/arch/xtensa/kernel/head.S b/arch/xtensa/kernel/head.S
index 74ec62c..aeeb3cc 100644
--- a/arch/xtensa/kernel/head.S
+++ b/arch/xtensa/kernel/head.S
@@ -103,7 +103,7 @@
ENDPROC(_start)
- __INIT
+ __REF
.literal_position
ENTRY(_startup)
@@ -302,6 +302,55 @@
ENDPROC(_startup)
+#ifdef CONFIG_HOTPLUG_CPU
+
+ENTRY(cpu_restart)
+
+#if XCHAL_DCACHE_IS_WRITEBACK
+ ___flush_invalidate_dcache_all a2 a3
+#else
+ ___invalidate_dcache_all a2 a3
+#endif
+ memw
+ movi a2, CCON # MX External Register to Configure Cache
+ movi a3, 0
+ wer a3, a2
+ extw
+
+ rsr a0, prid
+ neg a2, a0
+ movi a3, cpu_start_id
+ s32i a2, a3, 0
+#if XCHAL_DCACHE_IS_WRITEBACK
+ dhwbi a3, 0
+#endif
+1:
+ l32i a2, a3, 0
+ dhi a3, 0
+ bne a2, a0, 1b
+
+ /*
+ * Initialize WB, WS, and clear PS.EXCM (to allow loop instructions).
+ * Set Interrupt Level just below XCHAL_DEBUGLEVEL to allow
+ * xt-gdb to single step via DEBUG exceptions received directly
+ * by ocd.
+ */
+ movi a1, 1
+ movi a0, 0
+ wsr a1, windowstart
+ wsr a0, windowbase
+ rsync
+
+ movi a1, LOCKLEVEL
+ wsr a1, ps
+ rsync
+
+ j _startup
+
+ENDPROC(cpu_restart)
+
+#endif /* CONFIG_HOTPLUG_CPU */
+
/*
* DATA section
*/
diff --git a/arch/xtensa/kernel/irq.c b/arch/xtensa/kernel/irq.c
index fad9e00..482868a 100644
--- a/arch/xtensa/kernel/irq.c
+++ b/arch/xtensa/kernel/irq.c
@@ -153,3 +153,52 @@
#endif
variant_init_irq();
}
+
+#ifdef CONFIG_HOTPLUG_CPU
+static void route_irq(struct irq_data *data, unsigned int irq, unsigned int cpu)
+{
+ struct irq_desc *desc = irq_to_desc(irq);
+ struct irq_chip *chip = irq_data_get_irq_chip(data);
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&desc->lock, flags);
+ if (chip->irq_set_affinity)
+ chip->irq_set_affinity(data, cpumask_of(cpu), false);
+ raw_spin_unlock_irqrestore(&desc->lock, flags);
+}
+
+/*
+ * The CPU has been marked offline. Migrate IRQs off this CPU. If
+ * the affinity settings do not allow other CPUs, force them onto any
+ * available CPU.
+ */
+void migrate_irqs(void)
+{
+ unsigned int i, cpu = smp_processor_id();
+ struct irq_desc *desc;
+
+ for_each_irq_desc(i, desc) {
+ struct irq_data *data = irq_desc_get_irq_data(desc);
+ unsigned int newcpu;
+
+ if (irqd_is_per_cpu(data))
+ continue;
+
+ if (!cpumask_test_cpu(cpu, data->affinity))
+ continue;
+
+ newcpu = cpumask_any_and(data->affinity, cpu_online_mask);
+
+ if (newcpu >= nr_cpu_ids) {
+ pr_info_ratelimited("IRQ%u no longer affine to CPU%u\n",
+ i, cpu);
+
+ cpumask_setall(data->affinity);
+ newcpu = cpumask_any_and(data->affinity,
+ cpu_online_mask);
+ }
+
+ route_irq(data, i, newcpu);
+ }
+}
+#endif /* CONFIG_HOTPLUG_CPU */
diff --git a/arch/xtensa/kernel/setup.c b/arch/xtensa/kernel/setup.c
index dfd8f52..d21bfa7 100644
--- a/arch/xtensa/kernel/setup.c
+++ b/arch/xtensa/kernel/setup.c
@@ -527,6 +527,7 @@
for_each_possible_cpu(i) {
struct cpu *cpu = &per_cpu(cpu_data, i);
+ cpu->hotpluggable = !!i;
register_cpu(cpu, i);
}
diff --git a/arch/xtensa/kernel/smp.c b/arch/xtensa/kernel/smp.c
index 46bdd14..1c7a209 100644
--- a/arch/xtensa/kernel/smp.c
+++ b/arch/xtensa/kernel/smp.c
@@ -40,6 +40,11 @@
# endif
#endif
+static void system_invalidate_dcache_range(unsigned long start,
+ unsigned long size);
+static void system_flush_invalidate_dcache_range(unsigned long start,
+ unsigned long size);
+
/* IPI (Inter Process Interrupt) */
#define IPI_IRQ 0
@@ -106,7 +111,7 @@
static int boot_secondary_processors = 1; /* Set with xt-gdb via .xt-gdb */
static DECLARE_COMPLETION(cpu_running);
-void __init secondary_start_kernel(void)
+void secondary_start_kernel(void)
{
struct mm_struct *mm = &init_mm;
unsigned int cpu = smp_processor_id();
@@ -174,6 +179,9 @@
__func__, cpu, run_stall_mask, get_er(MPSCORE));
}
+#ifdef CONFIG_HOTPLUG_CPU
+unsigned long cpu_start_id __cacheline_aligned;
+#endif
unsigned long cpu_start_ccount;
static int boot_secondary(unsigned int cpu, struct task_struct *ts)
@@ -182,6 +190,11 @@
unsigned long ccount;
int i;
+#ifdef CONFIG_HOTPLUG_CPU
+ cpu_start_id = cpu;
+ system_flush_invalidate_dcache_range(
+ (unsigned long)&cpu_start_id, sizeof(cpu_start_id));
+#endif
smp_call_function_single(0, mx_cpu_start, (void *)cpu, 1);
for (i = 0; i < 2; ++i) {
@@ -234,6 +247,85 @@
return ret;
}
+#ifdef CONFIG_HOTPLUG_CPU
+
+/*
+ * __cpu_disable runs on the processor to be shutdown.
+ */
+int __cpu_disable(void)
+{
+ unsigned int cpu = smp_processor_id();
+
+ /*
+ * Take this CPU offline. Once we clear this, we can't return,
+ * and we must not schedule until we're ready to give up the cpu.
+ */
+ set_cpu_online(cpu, false);
+
+ /*
+ * OK - migrate IRQs away from this CPU
+ */
+ migrate_irqs();
+
+ /*
+ * Flush user cache and TLB mappings, and then remove this CPU
+ * from the vm mask set of all processes.
+ */
+ local_flush_cache_all();
+ local_flush_tlb_all();
+ invalidate_page_directory();
+
+ clear_tasks_mm_cpumask(cpu);
+
+ return 0;
+}
+
+static void platform_cpu_kill(unsigned int cpu)
+{
+ smp_call_function_single(0, mx_cpu_stop, (void *)cpu, true);
+}
+
+/*
+ * called on the thread which is asking for a CPU to be shutdown -
+ * waits until shutdown has completed, or it is timed out.
+ */
+void __cpu_die(unsigned int cpu)
+{
+ unsigned long timeout = jiffies + msecs_to_jiffies(1000);
+ while (time_before(jiffies, timeout)) {
+ system_invalidate_dcache_range((unsigned long)&cpu_start_id,
+ sizeof(cpu_start_id));
+ if (cpu_start_id == -cpu) {
+ platform_cpu_kill(cpu);
+ return;
+ }
+ }
+ pr_err("CPU%u: unable to kill\n", cpu);
+}
+
+void arch_cpu_idle_dead(void)
+{
+ cpu_die();
+}
+/*
+ * Called from the idle thread for the CPU which has been shutdown.
+ *
+ * Note that we disable IRQs here, but do not re-enable them
+ * before returning to the caller. This is also the behaviour
+ * of the other hotplug-cpu capable cores, so presumably coming
+ * out of idle fixes this.
+ */
+void __ref cpu_die(void)
+{
+ idle_task_exit();
+ local_irq_disable();
+ __asm__ __volatile__(
+ " movi a2, cpu_restart\n"
+ " jx a2\n");
+}
+
+#endif /* CONFIG_HOTPLUG_CPU */
+
enum ipi_msg_type {
IPI_RESCHEDULE = 0,
IPI_CALL_FUNC,
@@ -463,3 +555,37 @@
};
on_each_cpu(ipi_flush_icache_range, &fd, 1);
}
+
+/* ------------------------------------------------------------------------- */
+
+static void ipi_invalidate_dcache_range(void *arg)
+{
+ struct flush_data *fd = arg;
+ __invalidate_dcache_range(fd->addr1, fd->addr2);
+}
+
+static void system_invalidate_dcache_range(unsigned long start,
+ unsigned long size)
+{
+ struct flush_data fd = {
+ .addr1 = start,
+ .addr2 = size,
+ };
+ on_each_cpu(ipi_invalidate_dcache_range, &fd, 1);
+}
+
+static void ipi_flush_invalidate_dcache_range(void *arg)
+{
+ struct flush_data *fd = arg;
+ __flush_invalidate_dcache_range(fd->addr1, fd->addr2);
+}
+
+static void system_flush_invalidate_dcache_range(unsigned long start,
+ unsigned long size)
+{
+ struct flush_data fd = {
+ .addr1 = start,
+ .addr2 = size,
+ };
+ on_each_cpu(ipi_flush_invalidate_dcache_range, &fd, 1);
+}
diff --git a/arch/xtensa/kernel/traps.c b/arch/xtensa/kernel/traps.c
index 3c0ff57..eebbfd8 100644
--- a/arch/xtensa/kernel/traps.c
+++ b/arch/xtensa/kernel/traps.c
@@ -332,7 +332,7 @@
}
-static void __init trap_init_excsave(void)
+static void trap_init_excsave(void)
{
unsigned long excsave1 = (unsigned long)this_cpu_ptr(exc_table);
__asm__ __volatile__("wsr %0, excsave1\n" : : "a" (excsave1));
@@ -384,7 +384,7 @@
}
#ifdef CONFIG_SMP
-void __init secondary_trap_init(void)
+void secondary_trap_init(void)
{
trap_init_excsave();
}