Commit 31139971 authored by Paul Mackerras's avatar Paul Mackerras Committed by Linus Torvalds
Browse files

[PATCH] ppc32: support hotplug cpu on powermacs 



This allows cpus to be off-lined on 32-bit SMP powermacs.  When a cpu
is off-lined, it is put into sleep mode with interrupts disabled.  It
can be on-lined again by asserting its soft-reset pin, which is
connected to a GPIO pin.

With this I can off-line the second cpu in my dual G4 powermac, which
means that I can then suspend the machine (the suspend/resume code
refuses to suspend if more than one cpu is online, and making it cope
with multiple cpus is surprisingly messy).

Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent bb0bb3b6

arch/ppc/Kconfig

+9 −0
Original line number Diff line number Diff line
@@ -265,6 +265,15 @@ config PPC601_SYNC_FIX 


	  If in doubt, say Y here.



config HOTPLUG_CPU

	bool "Support for enabling/disabling CPUs"

	depends on SMP && HOTPLUG && EXPERIMENTAL && PPC_PMAC

	---help---

	  Say Y here to be able to disable and re-enable individual

	  CPUs at runtime on SMP machines.



	  Say N if you are unsure.



source arch/ppc/platforms/4xx/Kconfig

source arch/ppc/platforms/85xx/Kconfig

arch/ppc/kernel/head.S

+13 −15
Original line number Diff line number Diff line
@@ -1023,23 +1023,21 @@ __secondary_start_gemini: 
        andc    r4,r4,r3

        mtspr   SPRN_HID0,r4

        sync

        bl      gemini_prom_init

        b       __secondary_start

#endif /* CONFIG_GEMINI */

	.globl	__secondary_start_psurge

__secondary_start_psurge:

	li	r24,1			/* cpu # */

	b	__secondary_start_psurge99

	.globl	__secondary_start_psurge2

__secondary_start_psurge2:

	li	r24,2			/* cpu # */

	b	__secondary_start_psurge99

	.globl	__secondary_start_psurge3

__secondary_start_psurge3:

	li	r24,3			/* cpu # */

	b	__secondary_start_psurge99

__secondary_start_psurge99:

	/* we come in here with IR=0 and DR=1, and DBAT 0



	.globl	__secondary_start_pmac_0

__secondary_start_pmac_0:

	/* NB the entries for cpus 0, 1, 2 must each occupy 8 bytes. */

	li	r24,0

	b	1f

	li	r24,1

	b	1f

	li	r24,2

	b	1f

	li	r24,3

1:

	/* on powersurge, we come in here with IR=0 and DR=1, and DBAT 0

	   set to map the 0xf0000000 - 0xffffffff region */

	mfmsr	r0

	rlwinm	r0,r0,0,28,26		/* clear DR (0x10) */

arch/ppc/kernel/idle.c

+5 −1
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ 
#include <linux/ptrace.h>

#include <linux/slab.h>

#include <linux/sysctl.h>

#include <linux/cpu.h>



#include <asm/pgtable.h>

#include <asm/uaccess.h>
@@ -35,6 +36,7 @@ 
void default_idle(void)

{

	void (*powersave)(void);

	int cpu = smp_processor_id();



	powersave = ppc_md.power_save;
@@ -44,7 +46,7 @@ void default_idle(void) 
#ifdef CONFIG_SMP

		else {

			set_thread_flag(TIF_POLLING_NRFLAG);

			while (!need_resched())

			while (!need_resched() && !cpu_is_offline(cpu))

				barrier();

			clear_thread_flag(TIF_POLLING_NRFLAG);

		}
@@ -52,6 +54,8 @@ void default_idle(void) 
	}

	if (need_resched())

		schedule();

	if (cpu_is_offline(cpu) && system_state == SYSTEM_RUNNING)

		cpu_die();

}



/*

arch/ppc/kernel/smp.c

+30 −14
Original line number Diff line number Diff line
@@ -45,6 +45,7 @@ cpumask_t cpu_online_map; 
cpumask_t cpu_possible_map;

int smp_hw_index[NR_CPUS];

struct thread_info *secondary_ti;

static struct task_struct *idle_tasks[NR_CPUS];



EXPORT_SYMBOL(cpu_online_map);

EXPORT_SYMBOL(cpu_possible_map);
@@ -286,7 +287,8 @@ static void __devinit smp_store_cpu_info(int id) 


void __init smp_prepare_cpus(unsigned int max_cpus)

{

	int num_cpus, i;

	int num_cpus, i, cpu;

	struct task_struct *p;



	/* Fixup boot cpu */

        smp_store_cpu_info(smp_processor_id());
@@ -308,6 +310,17 @@ void __init smp_prepare_cpus(unsigned int max_cpus) 


	if (smp_ops->space_timers)

		smp_ops->space_timers(num_cpus);



	for_each_cpu(cpu) {

		if (cpu == smp_processor_id())

			continue;

		/* create a process for the processor */

		p = fork_idle(cpu);

		if (IS_ERR(p))

			panic("failed fork for CPU %u: %li", cpu, PTR_ERR(p));

		p->thread_info->cpu = cpu;

		idle_tasks[cpu] = p;

	}

}



void __devinit smp_prepare_boot_cpu(void)
@@ -334,12 +347,17 @@ int __devinit start_secondary(void *unused) 
	set_dec(tb_ticks_per_jiffy);

	cpu_callin_map[cpu] = 1;



	printk("CPU %i done callin...\n", cpu);

	printk("CPU %d done callin...\n", cpu);

	smp_ops->setup_cpu(cpu);

	printk("CPU %i done setup...\n", cpu);

	local_irq_enable();

	printk("CPU %d done setup...\n", cpu);

	smp_ops->take_timebase();

	printk("CPU %i done timebase take...\n", cpu);

	printk("CPU %d done timebase take...\n", cpu);



	spin_lock(&call_lock);

	cpu_set(cpu, cpu_online_map);

	spin_unlock(&call_lock);



	local_irq_enable();



	cpu_idle();

	return 0;
@@ -347,17 +365,11 @@ int __devinit start_secondary(void *unused) 


int __cpu_up(unsigned int cpu)

{

	struct task_struct *p;

	char buf[32];

	int c;



	/* create a process for the processor */

	/* only regs.msr is actually used, and 0 is OK for it */

	p = fork_idle(cpu);

	if (IS_ERR(p))

		panic("failed fork for CPU %u: %li", cpu, PTR_ERR(p));

	secondary_ti = p->thread_info;

	p->thread_info->cpu = cpu;

	secondary_ti = idle_tasks[cpu]->thread_info;

	mb();



	/*

	 * There was a cache flush loop here to flush the cache
@@ -389,7 +401,11 @@ int __cpu_up(unsigned int cpu) 
	printk("Processor %d found.\n", cpu);



	smp_ops->give_timebase();

	cpu_set(cpu, cpu_online_map);



	/* Wait until cpu puts itself in the online map */

	while (!cpu_online(cpu))

		cpu_relax();



	return 0;

}

arch/ppc/platforms/pmac_sleep.S

+2 −0
Original line number Diff line number Diff line
@@ -161,6 +161,8 @@ _GLOBAL(low_sleep_handler) 
	addi r3,r3,sleep_storage@l

	stw r5,0(r3)



	.globl	low_cpu_die

low_cpu_die:

	/* Flush & disable all caches */

	bl	flush_disable_caches

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