Commit 859e5f45 authored by Guo Ren's avatar Guo Ren
Browse files

csky: CPU-hotplug supported for SMP 



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: default avatarGuo Ren <ren_guo@c-sky.com>
parent 1d95fe4d

arch/csky/Kconfig

+9 −0
Original line number Diff line number Diff line
@@ -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"

arch/csky/include/asm/smp.h

+4 −0
Original line number Diff line number Diff line
@@ -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 */

arch/csky/kernel/smp.c

+56 −15
Original line number Diff line number Diff line
@@ -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);



	if (mask & mfcr("cr<29, 0>")) {

		send_arch_ipi(cpumask_of(cpu));

	} else {

		/* Enable cpu in SMP reset ctrl reg */

	tmp = mfcr("cr<29, 0>");

	tmp |= 1 << cpu;

	mtcr("cr<29, 0>", tmp);

		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