4 files changed, 216 insertions, 9 deletions

diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt
index 9d620c153b04..4d4a644b505e 100644
--- a/Documentation/cpu-hotplug.txt
+++ b/Documentation/cpu-hotplug.txt
@@ -49,6 +49,12 @@ maxcpus=n    Restrict boot time cpus to n. Say if you have 4 cpus, using
 additional_cpus=n (*)   Use this to limit hotpluggable cpus. This option sets
                         cpu_possible_map = cpu_present_map + additional_cpus
 
+cede_offline={"off","on"}  Use this option to disable/enable putting offlined
+                            processors to an extended H_CEDE state on
+                            supported pseries platforms.
+                            If nothing is specified,
+                            cede_offline is set to "on".
+
 (*) Option valid only for following architectures
 - ia64
 
diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c
index ebff6d9a4e39..6ea4698d9176 100644
--- a/arch/powerpc/platforms/pseries/hotplug-cpu.c
+++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c
@@ -30,6 +30,7 @@
 #include <asm/pSeries_reconfig.h>
 #include "xics.h"
 #include "plpar_wrappers.h"
+#include "offline_states.h"
 
 /* This version can't take the spinlock, because it never returns */
 static struct rtas_args rtas_stop_self_args = {
@@ -39,6 +40,55 @@ static struct rtas_args rtas_stop_self_args = {
         .rets = &rtas_stop_self_args.args[0],
 };
 
+static DEFINE_PER_CPU(enum cpu_state_vals, preferred_offline_state) =
+                                                        CPU_STATE_OFFLINE;
+static DEFINE_PER_CPU(enum cpu_state_vals, current_state) = CPU_STATE_OFFLINE;
+
+static enum cpu_state_vals default_offline_state = CPU_STATE_OFFLINE;
+
+static int cede_offline_enabled __read_mostly = 1;
+
+/*
+ * Enable/disable cede_offline when available.
+ */
+static int __init setup_cede_offline(char *str)
+{
+        if (!strcmp(str, "off"))
+                cede_offline_enabled = 0;
+        else if (!strcmp(str, "on"))
+                cede_offline_enabled = 1;
+        else
+                return 0;
+        return 1;
+}
+
+__setup("cede_offline=", setup_cede_offline);
+
+enum cpu_state_vals get_cpu_current_state(int cpu)
+{
+        return per_cpu(current_state, cpu);
+}
+
+void set_cpu_current_state(int cpu, enum cpu_state_vals state)
+{
+        per_cpu(current_state, cpu) = state;
+}
+
+enum cpu_state_vals get_preferred_offline_state(int cpu)
+{
+        return per_cpu(preferred_offline_state, cpu);
+}
+
+void set_preferred_offline_state(int cpu, enum cpu_state_vals state)
+{
+        per_cpu(preferred_offline_state, cpu) = state;
+}
+
+void set_default_offline_state(int cpu)
+{
+        per_cpu(preferred_offline_state, cpu) = default_offline_state;
+}
+
 static void rtas_stop_self(void)
 {
         struct rtas_args *args = &rtas_stop_self_args;
@@ -56,11 +106,61 @@ static void rtas_stop_self(void)
 
 static void pseries_mach_cpu_die(void)
 {
+        unsigned int cpu = smp_processor_id();
+        unsigned int hwcpu = hard_smp_processor_id();
+        u8 cede_latency_hint = 0;
+
         local_irq_disable();
         idle_task_exit();
         xics_teardown_cpu();
-        unregister_slb_shadow(hard_smp_processor_id(), __pa(get_slb_shadow()));
-        rtas_stop_self();
+
+        if (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) {
+                set_cpu_current_state(cpu, CPU_STATE_INACTIVE);
+                cede_latency_hint = 2;
+
+                get_lppaca()->idle = 1;
+                if (!get_lppaca()->shared_proc)
+                        get_lppaca()->donate_dedicated_cpu = 1;
+
+                printk(KERN_INFO
+                        "cpu %u (hwid %u) ceding for offline with hint %d\n",
+                        cpu, hwcpu, cede_latency_hint);
+                while (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) {
+                        extended_cede_processor(cede_latency_hint);
+                        printk(KERN_INFO "cpu %u (hwid %u) returned from cede.\n",
+                                cpu, hwcpu);
+                        printk(KERN_INFO
+                        "Decrementer value = %x Timebase value = %llx\n",
+                        get_dec(), get_tb());
+                }
+
+                printk(KERN_INFO "cpu %u (hwid %u) got prodded to go online\n",
+                        cpu, hwcpu);
+
+                if (!get_lppaca()->shared_proc)
+                        get_lppaca()->donate_dedicated_cpu = 0;
+                get_lppaca()->idle = 0;
+        }
+
+        if (get_preferred_offline_state(cpu) == CPU_STATE_ONLINE) {
+                unregister_slb_shadow(hwcpu, __pa(get_slb_shadow()));
+
+                /*
+                 * NOTE: Calling start_secondary() here for now to
+                 * start new context.
+                 * However, need to do it cleanly by resetting the
+                 * stack pointer.
+                 */
+                start_secondary();
+
+        } else if (get_preferred_offline_state(cpu) == CPU_STATE_OFFLINE) {
+
+                set_cpu_current_state(cpu, CPU_STATE_OFFLINE);
+                unregister_slb_shadow(hard_smp_processor_id(),
+                                        __pa(get_slb_shadow()));
+                rtas_stop_self();
+        }
+
         /* Should never get here... */
         BUG();
         for(;;);
@@ -106,18 +206,43 @@ static int pseries_cpu_disable(void)
         return 0;
 }
 
+/*
+ * pseries_cpu_die: Wait for the cpu to die.
+ * @cpu: logical processor id of the CPU whose death we're awaiting.
+ *
+ * This function is called from the context of the thread which is performing
+ * the cpu-offline. Here we wait for long enough to allow the cpu in question
+ * to self-destroy so that the cpu-offline thread can send the CPU_DEAD
+ * notifications.
+ *
+ * OTOH, pseries_mach_cpu_die() is called by the @cpu when it wants to
+ * self-destruct.
+ */
 static void pseries_cpu_die(unsigned int cpu)
 {
         int tries;
-        int cpu_status;
+        int cpu_status = 1;
         unsigned int pcpu = get_hard_smp_processor_id(cpu);
 
-        for (tries = 0; tries < 25; tries++) {
-                cpu_status = query_cpu_stopped(pcpu);
-                if (cpu_status == 0 || cpu_status == -1)
-                        break;
-                cpu_relax();
+        if (get_preferred_offline_state(cpu) == CPU_STATE_INACTIVE) {
+                cpu_status = 1;
+                for (tries = 0; tries < 1000; tries++) {
+                        if (get_cpu_current_state(cpu) == CPU_STATE_INACTIVE) {
+                                cpu_status = 0;
+                                break;
+                        }
+                        cpu_relax();
+                }
+        } else if (get_preferred_offline_state(cpu) == CPU_STATE_OFFLINE) {
+
+                for (tries = 0; tries < 25; tries++) {
+                        cpu_status = query_cpu_stopped(pcpu);
+                        if (cpu_status == 0 || cpu_status == -1)
+                                break;
+                        cpu_relax();
+                }
         }
+
         if (cpu_status != 0) {
                 printk("Querying DEAD? cpu %i (%i) shows %i\n",
                        cpu, pcpu, cpu_status);
@@ -252,10 +377,41 @@ static struct notifier_block pseries_smp_nb = {
         .notifier_call = pseries_smp_notifier,
 };
 
+#define MAX_CEDE_LATENCY_LEVELS         4
+#define CEDE_LATENCY_PARAM_LENGTH       10
+#define CEDE_LATENCY_PARAM_MAX_LENGTH   \
+        (MAX_CEDE_LATENCY_LEVELS * CEDE_LATENCY_PARAM_LENGTH * sizeof(char))
+#define CEDE_LATENCY_TOKEN              45
+
+static char cede_parameters[CEDE_LATENCY_PARAM_MAX_LENGTH];
+
+static int parse_cede_parameters(void)
+{
+        int call_status;
+
+        memset(cede_parameters, 0, CEDE_LATENCY_PARAM_MAX_LENGTH);
+        call_status = rtas_call(rtas_token("ibm,get-system-parameter"), 3, 1,
+                                NULL,
+                                CEDE_LATENCY_TOKEN,
+                                __pa(cede_parameters),
+                                CEDE_LATENCY_PARAM_MAX_LENGTH);
+
+        if (call_status != 0)
+                printk(KERN_INFO "CEDE_LATENCY: \
+                        %s %s Error calling get-system-parameter(0x%x)\n",
+                        __FILE__, __func__, call_status);
+        else
+                printk(KERN_INFO "CEDE_LATENCY: \
+                        get-system-parameter successful.\n");
+
+        return call_status;
+}
+
 static int __init pseries_cpu_hotplug_init(void)
 {
         struct device_node *np;
         const char *typep;
+        int cpu;
 
         for_each_node_by_name(np, "interrupt-controller") {
                 typep = of_get_property(np, "compatible", NULL);
@@ -283,8 +439,16 @@ static int __init pseries_cpu_hotplug_init(void)
         smp_ops->cpu_die = pseries_cpu_die;
 
         /* Processors can be added/removed only on LPAR */
-        if (firmware_has_feature(FW_FEATURE_LPAR))
+        if (firmware_has_feature(FW_FEATURE_LPAR)) {
                 pSeries_reconfig_notifier_register(&pseries_smp_nb);
+                cpu_maps_update_begin();
+                if (cede_offline_enabled && parse_cede_parameters() == 0) {
+                        default_offline_state = CPU_STATE_INACTIVE;
+                        for_each_online_cpu(cpu)
+                                set_default_offline_state(cpu);
+                }
+                cpu_maps_update_done();
+        }
 
         return 0;
 }
diff --git a/arch/powerpc/platforms/pseries/offline_states.h b/arch/powerpc/platforms/pseries/offline_states.h
new file mode 100644
index 000000000000..22574e0d9d91
--- /dev/null
+++ b/arch/powerpc/platforms/pseries/offline_states.h
@@ -0,0 +1,18 @@
+#ifndef _OFFLINE_STATES_H_
+#define _OFFLINE_STATES_H_
+
+/* Cpu offline states go here */
+enum cpu_state_vals {
+        CPU_STATE_OFFLINE,
+        CPU_STATE_INACTIVE,
+        CPU_STATE_ONLINE,
+        CPU_MAX_OFFLINE_STATES
+};
+
+extern enum cpu_state_vals get_cpu_current_state(int cpu);
+extern void set_cpu_current_state(int cpu, enum cpu_state_vals state);
+extern enum cpu_state_vals get_preferred_offline_state(int cpu);
+extern void set_preferred_offline_state(int cpu, enum cpu_state_vals state);
+extern void set_default_offline_state(int cpu);
+extern int start_secondary(void);
+#endif
diff --git a/arch/powerpc/platforms/pseries/smp.c b/arch/powerpc/platforms/pseries/smp.c
index 440000cc7130..8868c012268a 100644
--- a/arch/powerpc/platforms/pseries/smp.c
+++ b/arch/powerpc/platforms/pseries/smp.c
@@ -48,6 +48,7 @@
 #include "plpar_wrappers.h"
 #include "pseries.h"
 #include "xics.h"
+#include "offline_states.h"
 
 
 /*
@@ -84,6 +85,9 @@ static inline int __devinit smp_startup_cpu(unsigned int lcpu)
         /* Fixup atomic count: it exited inside IRQ handler. */
         task_thread_info(paca[lcpu].__current)->preempt_count   = 0;
 
+        if (get_cpu_current_state(lcpu) == CPU_STATE_INACTIVE)
+                goto out;
+
         /* 
          * If the RTAS start-cpu token does not exist then presume the
          * cpu is already spinning.
@@ -98,6 +102,7 @@ static inline int __devinit smp_startup_cpu(unsigned int lcpu)
                 return 0;
         }
 
+out:
         return 1;
 }
 
@@ -111,12 +116,16 @@ static void __devinit smp_xics_setup_cpu(int cpu)
                 vpa_init(cpu);
 
         cpu_clear(cpu, of_spin_map);
+        set_cpu_current_state(cpu, CPU_STATE_ONLINE);
+        set_default_offline_state(cpu);
 
 }
 #endif /* CONFIG_XICS */
 
 static void __devinit smp_pSeries_kick_cpu(int nr)
 {
+        long rc;
+        unsigned long hcpuid;
         BUG_ON(nr < 0 || nr >= NR_CPUS);
 
         if (!smp_startup_cpu(nr))
@@ -128,6 +137,16 @@ static void __devinit smp_pSeries_kick_cpu(int nr)
          * the processor will continue on to secondary_start
          */
         paca[nr].cpu_start = 1;
+
+        set_preferred_offline_state(nr, CPU_STATE_ONLINE);
+
+        if (get_cpu_current_state(nr) == CPU_STATE_INACTIVE) {
+                hcpuid = get_hard_smp_processor_id(nr);
+                rc = plpar_hcall_norets(H_PROD, hcpuid);
+                if (rc != H_SUCCESS)
+                        panic("Error: Prod to wake up processor %d Ret= %ld\n",
+                                nr, rc);
+        }
 }
 
 static int smp_pSeries_cpu_bootable(unsigned int nr)