[RFC 07/10] powermac: support G5 CPU hotplug

Johannes Berg
2007-02-05T18:30:34Z

[-- Attachment #1: powermac-g5-cpu-offline.patch --]
[-- Type: text/plain, Size: 3395 bytes --]

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>

--- mb-wireless.orig/arch/powerpc/platforms/powermac/smp.c 2007-02-05 16:07:09.164524763 +0100
+++ mb-wireless/arch/powerpc/platforms/powermac/smp.c 2007-02-05 16:07:50.774524763 +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
};
--- mb-wireless.orig/arch/powerpc/platforms/powermac/setup.c 2007-02-05 16:07:22.024524763 +0100
+++ mb-wireless/arch/powerpc/platforms/powermac/setup.c 2007-02-05 16:07:50.784524763 +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 +719,33 @@ 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

static void __init pmac_init_irq(void)
@@ -769,6 +799,6 @@ 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
};
--- mb-wireless.orig/arch/powerpc/kernel/smp.c 2007-02-05 16:07:09.274524763 +0100
+++ mb-wireless/arch/powerpc/kernel/smp.c 2007-02-05 18:15:51.114524763 +0100
@@ -558,6 +558,11 @@ int __devinit start_secondary(void *unus

local_irq_enable();

+ /* it seems to be possible that we died from within
+ * an interrupt ... reset the in-irq counts */
+ task_thread_info(paca[cpu].__current)->preempt_count &=
+ ~(SOFTIRQ_MASK|HARDIRQ_MASK);
+
cpu_idle();
return 0;
}

--