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Subject[PATCH 07/14] csky: CPU-hotplug supported for SMP
Date
From: Guo Ren <ren_guo@c-sky.com>

This is a simple implement of CPU-hotplug for power saving. CPU use
wait instruction to enter power saving mode and waiting for IPI wakeup
signal.

Signed-off-by: Guo Ren <ren_guo@c-sky.com>
---
arch/csky/Kconfig | 9 ++++++
arch/csky/include/asm/smp.h | 4 +++
arch/csky/kernel/smp.c | 71 +++++++++++++++++++++++++++++++++++----------
3 files changed, 69 insertions(+), 15 deletions(-)

diff --git a/arch/csky/Kconfig b/arch/csky/Kconfig
index cb64f8d..8bdbe92 100644
--- a/arch/csky/Kconfig
+++ b/arch/csky/Kconfig
@@ -198,6 +198,15 @@ config RAM_BASE
hex "DRAM start addr (the same with memory-section in dts)"
default 0x0

+config HOTPLUG_CPU
+ bool "Support for hot-pluggable CPUs"
+ select GENERIC_IRQ_MIGRATION
+ depends on SMP
+ help
+ Say Y here to allow turning CPUs off and on. CPUs can be
+ controlled through /sys/devices/system/cpu/cpu1/hotplug/target.
+
+ Say N if you want to disable CPU hotplug.
endmenu

source "kernel/Kconfig.hz"
diff --git a/arch/csky/include/asm/smp.h b/arch/csky/include/asm/smp.h
index 4a929c4..668b79c 100644
--- a/arch/csky/include/asm/smp.h
+++ b/arch/csky/include/asm/smp.h
@@ -21,6 +21,10 @@ void __init set_send_ipi(void (*func)(const struct cpumask *mask), int irq);

#define raw_smp_processor_id() (current_thread_info()->cpu)

+int __cpu_disable(void);
+
+void __cpu_die(unsigned int cpu);
+
#endif /* CONFIG_SMP */

#endif /* __ASM_CSKY_SMP_H */
diff --git a/arch/csky/kernel/smp.c b/arch/csky/kernel/smp.c
index 74d6273..ddc4dd7 100644
--- a/arch/csky/kernel/smp.c
+++ b/arch/csky/kernel/smp.c
@@ -16,6 +16,7 @@
#include <linux/of.h>
#include <linux/sched/task_stack.h>
#include <linux/sched/mm.h>
+#include <linux/sched/hotplug.h>
#include <asm/irq.h>
#include <asm/traps.h>
#include <asm/sections.h>
@@ -112,12 +113,8 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
{
}

-static void __init enable_smp_ipi(void)
-{
- enable_percpu_irq(ipi_irq, 0);
-}
-
static int ipi_dummy_dev;
+
void __init setup_smp_ipi(void)
{
int rc;
@@ -130,7 +127,7 @@ void __init setup_smp_ipi(void)
if (rc)
panic("%s IRQ request failed\n", __func__);

- enable_smp_ipi();
+ enable_percpu_irq(ipi_irq, 0);
}

void __init setup_smp(void)
@@ -161,12 +158,10 @@ volatile unsigned int secondary_stack;

int __cpu_up(unsigned int cpu, struct task_struct *tidle)
{
- unsigned int tmp;
-
- secondary_stack = (unsigned int)tidle->stack + THREAD_SIZE;
+ unsigned long mask = 1 << cpu;

+ secondary_stack = (unsigned int)tidle->stack + THREAD_SIZE - 8;
secondary_hint = mfcr("cr31");
-
secondary_ccr = mfcr("cr18");

/*
@@ -176,10 +171,13 @@ int __cpu_up(unsigned int cpu, struct task_struct *tidle)
*/
mtcr("cr17", 0x22);

- /* Enable cpu in SMP reset ctrl reg */
- tmp = mfcr("cr<29, 0>");
- tmp |= 1 << cpu;
- mtcr("cr<29, 0>", tmp);
+ if (mask & mfcr("cr<29, 0>")) {
+ send_arch_ipi(cpumask_of(cpu));
+ } else {
+ /* Enable cpu in SMP reset ctrl reg */
+ mask |= mfcr("cr<29, 0>");
+ mtcr("cr<29, 0>", mask);
+ }

/* Wait for the cpu online */
while (!cpu_online(cpu));
@@ -219,7 +217,7 @@ void csky_start_secondary(void)
init_fpu();
#endif

- enable_smp_ipi();
+ enable_percpu_irq(ipi_irq, 0);

mmget(mm);
mmgrab(mm);
@@ -235,3 +233,46 @@ void csky_start_secondary(void)
preempt_disable();
cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
}
+
+#ifdef CONFIG_HOTPLUG_CPU
+int __cpu_disable(void)
+{
+ unsigned int cpu = smp_processor_id();
+
+ set_cpu_online(cpu, false);
+
+ irq_migrate_all_off_this_cpu();
+
+ clear_tasks_mm_cpumask(cpu);
+
+ return 0;
+}
+
+void __cpu_die(unsigned int cpu)
+{
+ if (!cpu_wait_death(cpu, 5)) {
+ pr_crit("CPU%u: shutdown failed\n", cpu);
+ return;
+ }
+ pr_notice("CPU%u: shutdown\n", cpu);
+}
+
+void arch_cpu_idle_dead(void)
+{
+ idle_task_exit();
+
+ cpu_report_death();
+
+ while (!secondary_stack)
+ arch_cpu_idle();
+
+ local_irq_disable();
+
+ asm volatile(
+ "mov sp, %0\n"
+ "mov r8, %0\n"
+ "jmpi csky_start_secondary"
+ :
+ : "r" (secondary_stack));
+}
+#endif
--
2.7.4
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