[RFC 1/3] support powermac G5 CPU hotplug
From: Johannes Berg <johannes@sipsolutions.net>
Date: 2006-12-12 11:27:56
This patch allows "hotplugging" of CPUs on G5 machines. CPUs that are disabled are put into an idle loop with interrupts hard-disabled, to wake them up again we kick them just like when bringing them up. Maybe there's some way to actually turn off those CPUs even more? Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
--- linux-2.6-git.orig/arch/powerpc/platforms/powermac/smp.c 2006-12-11 23:34:47.612716759 +0100
+++ linux-2.6-git/arch/powerpc/platforms/powermac/smp.c 2006-12-11 23:37:54.971716759 +0100@@ -898,7 +898,7 @@ void smp_core99_cpu_die(unsigned int cpu cpu_dead[cpu] = 0; } -#endif +#endif /* CONFIG_HOTPLUG_CPU && CONFIG_PP32 */ /* Core99 Macs (dual G4s and G5s) */ struct smp_ops_t core99_smp_ops = {
@@ -908,8 +908,16 @@ struct smp_ops_t core99_smp_ops = { .setup_cpu = smp_core99_setup_cpu, .give_timebase = smp_core99_give_timebase, .take_timebase = smp_core99_take_timebase, -#if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PPC32) +#if defined(CONFIG_HOTPLUG_CPU) +# if defined(CONFIG_PPC32) .cpu_disable = smp_core99_cpu_disable, .cpu_die = smp_core99_cpu_die, +# endif +# if defined(CONFIG_PPC64) + .cpu_disable = generic_cpu_disable, + .cpu_die = generic_cpu_die, + /* intentionally do *NOT* assign cpu_enable, + * the generic code will use kick_cpu then! */ +# endif #endif }; --- linux-2.6-git.orig/arch/powerpc/platforms/powermac/setup.c 2006-12-11 23:34:47.648716759 +0100 +++ linux-2.6-git/arch/powerpc/platforms/powermac/setup.c 2006-12-11 23:37:54.974716759 +0100
@@ -490,6 +490,9 @@ static int pmac_late_init(void) #ifdef CONFIG_SOFTWARE_SUSPEND pm_set_ops(&pmac_pm_ops); #endif /* CONFIG_SOFTWARE_SUSPEND */ + /* this is udbg (which is __init) and we can later use it during + * cpu hotplug (in smp_core99_kick_cpu) */ + ppc_md.progress = NULL; return 0; }
@@ -716,6 +719,32 @@ static int pmac_pci_probe_mode(struct pc return PCI_PROBE_NORMAL; return PCI_PROBE_DEVTREE; } + +#ifdef CONFIG_HOTPLUG_CPU +/* access per cpu vars from generic smp.c */ +DECLARE_PER_CPU(int, cpu_state); + +static void pmac_cpu_die(void) +{ + /* turn off as much as possible, we'll be + * kicked out as this will only be invoked + * on core99 platforms for now ... */ + hard_irq_disable(); + printk(KERN_DEBUG "CPU#%d offline\n", smp_processor_id()); + __get_cpu_var(cpu_state) = CPU_DEAD; + smp_wmb(); + while (1) { + ppc64_runlatch_off(); + if (ppc_md.power_save) { + ppc_md.power_save(); + } else { + HMT_low(); + HMT_very_low(); + } + } +} +#endif + #endif define_machine(powermac) {
@@ -754,6 +783,6 @@ define_machine(powermac) { .phys_mem_access_prot = pci_phys_mem_access_prot, #endif #if defined(CONFIG_HOTPLUG_CPU) && defined(CONFIG_PPC64) - .cpu_die = generic_mach_cpu_die, + .cpu_die = pmac_cpu_die, #endif }; --- linux-2.6-git.orig/arch/powerpc/kernel/smp.c 2006-12-11 23:34:47.693716759 +0100 +++ linux-2.6-git/arch/powerpc/kernel/smp.c 2006-12-11 23:37:55.017716759 +0100
@@ -558,6 +558,9 @@ int __devinit start_secondary(void *unus local_irq_enable(); + /* who knows what context the processor might have died in... */ + task_thread_info(paca[cpu].__current)->preempt_count = 0; + cpu_idle(); return 0; } --