* published by the Free Software Foundation.
*/
+#include <linux/atomic.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/cpumask.h>
#include <linux/kthread.h>
#include <linux/wait.h>
+#include <linux/time.h>
#include <linux/clockchips.h>
#include <linux/hrtimer.h>
#include <linux/tick.h>
+#include <linux/notifier.h>
#include <linux/mm.h>
+#include <linux/mutex.h>
+#include <linux/spinlock.h>
#include <linux/string.h>
#include <linux/sysfs.h>
#include <linux/irqchip/arm-gic.h>
#include <linux/moduleparam.h>
#include <asm/smp_plat.h>
+#include <asm/cputype.h>
#include <asm/suspend.h>
#include <asm/mcpm.h>
#include <asm/bL_switcher.h>
+#define CREATE_TRACE_POINTS
+#include <trace/events/power_cpu_migrate.h>
+
/*
* Use our own MPIDR accessors as the generic ones in asm/cputype.h have
return id & MPIDR_HWID_BITMASK;
}
+/*
+ * Get a global nanosecond time stamp for tracing.
+ */
+static s64 get_ns(void)
+{
+ struct timespec ts;
+ getnstimeofday(&ts);
+ return timespec_to_ns(&ts);
+}
+
/*
* bL switcher core code.
*/
-static void bL_do_switch(void *_unused)
+static void bL_do_switch(void *_arg)
{
- unsigned mpidr, cpuid, clusterid, ob_cluster, ib_cluster;
+ unsigned ib_mpidr, ib_cpu, ib_cluster;
+ long volatile handshake, **handshake_ptr = _arg;
pr_debug("%s\n", __func__);
- mpidr = read_mpidr();
- cpuid = MPIDR_AFFINITY_LEVEL(mpidr, 0);
- clusterid = MPIDR_AFFINITY_LEVEL(mpidr, 1);
- ob_cluster = clusterid;
- ib_cluster = clusterid ^ 1;
+ ib_mpidr = cpu_logical_map(smp_processor_id());
+ ib_cpu = MPIDR_AFFINITY_LEVEL(ib_mpidr, 0);
+ ib_cluster = MPIDR_AFFINITY_LEVEL(ib_mpidr, 1);
+
+ /* Advertise our handshake location */
+ if (handshake_ptr) {
+ handshake = 0;
+ *handshake_ptr = &handshake;
+ } else
+ handshake = -1;
/*
* Our state has been saved at this point. Let's release our
* inbound CPU.
*/
- mcpm_set_entry_vector(cpuid, ib_cluster, cpu_resume);
+ mcpm_set_entry_vector(ib_cpu, ib_cluster, cpu_resume);
sev();
/*
* we have none.
*/
+ /*
+ * Let's wait until our inbound is alive.
+ */
+ while (!handshake) {
+ wfe();
+ smp_mb();
+ }
+
/* Let's put ourself down. */
mcpm_cpu_power_down();
*/
static unsigned int bL_gic_id[MAX_CPUS_PER_CLUSTER][MAX_NR_CLUSTERS];
+static int bL_switcher_cpu_pairing[NR_CPUS];
/*
* bL_switch_to - Switch to a specific cluster for the current CPU
*/
static int bL_switch_to(unsigned int new_cluster_id)
{
- unsigned int mpidr, cpuid, clusterid, ob_cluster, ib_cluster, this_cpu;
+ unsigned int mpidr, this_cpu, that_cpu;
+ unsigned int ob_mpidr, ob_cpu, ob_cluster, ib_mpidr, ib_cpu, ib_cluster;
+ struct completion inbound_alive;
struct tick_device *tdev;
enum clock_event_mode tdev_mode;
- int ret;
+ long volatile *handshake_ptr;
+ int ipi_nr, ret;
- mpidr = read_mpidr();
- cpuid = MPIDR_AFFINITY_LEVEL(mpidr, 0);
- clusterid = MPIDR_AFFINITY_LEVEL(mpidr, 1);
- ob_cluster = clusterid;
- ib_cluster = clusterid ^ 1;
+ this_cpu = smp_processor_id();
+ ob_mpidr = read_mpidr();
+ ob_cpu = MPIDR_AFFINITY_LEVEL(ob_mpidr, 0);
+ ob_cluster = MPIDR_AFFINITY_LEVEL(ob_mpidr, 1);
+ BUG_ON(cpu_logical_map(this_cpu) != ob_mpidr);
- if (new_cluster_id == clusterid)
+ if (new_cluster_id == ob_cluster)
return 0;
- pr_debug("before switch: CPU %d in cluster %d\n", cpuid, clusterid);
+ that_cpu = bL_switcher_cpu_pairing[this_cpu];
+ ib_mpidr = cpu_logical_map(that_cpu);
+ ib_cpu = MPIDR_AFFINITY_LEVEL(ib_mpidr, 0);
+ ib_cluster = MPIDR_AFFINITY_LEVEL(ib_mpidr, 1);
+
+ pr_debug("before switch: CPU %d MPIDR %#x -> %#x\n",
+ this_cpu, ob_mpidr, ib_mpidr);
+
+ this_cpu = smp_processor_id();
/* Close the gate for our entry vectors */
- mcpm_set_entry_vector(cpuid, ob_cluster, NULL);
- mcpm_set_entry_vector(cpuid, ib_cluster, NULL);
+ mcpm_set_entry_vector(ob_cpu, ob_cluster, NULL);
+ mcpm_set_entry_vector(ib_cpu, ib_cluster, NULL);
+
+ /* Install our "inbound alive" notifier. */
+ init_completion(&inbound_alive);
+ ipi_nr = register_ipi_completion(&inbound_alive, this_cpu);
+ ipi_nr |= ((1 << 16) << bL_gic_id[ob_cpu][ob_cluster]);
+ mcpm_set_early_poke(ib_cpu, ib_cluster, gic_get_sgir_physaddr(), ipi_nr);
/*
* Let's wake up the inbound CPU now in case it requires some delay
* to come online, but leave it gated in our entry vector code.
*/
- ret = mcpm_cpu_power_up(cpuid, ib_cluster);
+ ret = mcpm_cpu_power_up(ib_cpu, ib_cluster);
if (ret) {
pr_err("%s: mcpm_cpu_power_up() returned %d\n", __func__, ret);
return ret;
}
+ /*
+ * Raise a SGI on the inbound CPU to make sure it doesn't stall
+ * in a possible WFI, such as in bL_power_down().
+ */
+ gic_send_sgi(bL_gic_id[ib_cpu][ib_cluster], 0);
+
+ /*
+ * Wait for the inbound to come up. This allows for other
+ * tasks to be scheduled in the mean time.
+ */
+ wait_for_completion(&inbound_alive);
+ mcpm_set_early_poke(ib_cpu, ib_cluster, 0, 0);
+
/*
* From this point we are entering the switch critical zone
* and can't take any interrupts anymore.
*/
local_irq_disable();
local_fiq_disable();
-
- this_cpu = smp_processor_id();
+ trace_cpu_migrate_begin(get_ns(), ob_mpidr);
/* redirect GIC's SGIs to our counterpart */
- gic_migrate_target(bL_gic_id[cpuid][ib_cluster]);
-
- /*
- * Raise a SGI on the inbound CPU to make sure it doesn't stall
- * in a possible WFI, such as in mcpm_power_down().
- */
- arch_send_wakeup_ipi_mask(cpumask_of(this_cpu));
+ gic_migrate_target(bL_gic_id[ib_cpu][ib_cluster]);
tdev = tick_get_device(this_cpu);
if (tdev && !cpumask_equal(tdev->evtdev->cpumask, cpumask_of(this_cpu)))
if (ret)
panic("%s: cpu_pm_enter() returned %d\n", __func__, ret);
- /* Flip the cluster in the CPU logical map for this CPU. */
- cpu_logical_map(this_cpu) ^= (1 << 8);
+ /* Swap the physical CPUs in the logical map for this logical CPU. */
+ cpu_logical_map(this_cpu) = ib_mpidr;
+ cpu_logical_map(that_cpu) = ob_mpidr;
/* Let's do the actual CPU switch. */
- ret = cpu_suspend(0, bL_switchpoint);
+ ret = cpu_suspend((unsigned long)&handshake_ptr, bL_switchpoint);
if (ret > 0)
panic("%s: cpu_suspend() returned %d\n", __func__, ret);
/* We are executing on the inbound CPU at this point */
mpidr = read_mpidr();
- cpuid = MPIDR_AFFINITY_LEVEL(mpidr, 0);
- clusterid = MPIDR_AFFINITY_LEVEL(mpidr, 1);
- pr_debug("after switch: CPU %d in cluster %d\n", cpuid, clusterid);
- BUG_ON(clusterid != ib_cluster);
+ pr_debug("after switch: CPU %d MPIDR %#x\n", this_cpu, mpidr);
+ BUG_ON(mpidr != ib_mpidr);
mcpm_cpu_powered_up();
tdev->evtdev->next_event, 1);
}
+ trace_cpu_migrate_finish(get_ns(), ib_mpidr);
local_fiq_enable();
local_irq_enable();
+ *handshake_ptr = 1;
+ dsb_sev();
+
if (ret)
pr_err("%s exiting with error %d\n", __func__, ret);
return ret;
}
struct bL_thread {
+ spinlock_t lock;
struct task_struct *task;
wait_queue_head_t wq;
int wanted_cluster;
struct completion started;
+ bL_switch_completion_handler completer;
+ void *completer_cookie;
};
static struct bL_thread bL_threads[NR_CPUS];
struct bL_thread *t = arg;
struct sched_param param = { .sched_priority = 1 };
int cluster;
+ bL_switch_completion_handler completer;
+ void *completer_cookie;
sched_setscheduler_nocheck(current, SCHED_FIFO, ¶m);
complete(&t->started);
wait_event_interruptible(t->wq,
t->wanted_cluster != -1 ||
kthread_should_stop());
- cluster = xchg(&t->wanted_cluster, -1);
- if (cluster != -1)
+
+ spin_lock(&t->lock);
+ cluster = t->wanted_cluster;
+ completer = t->completer;
+ completer_cookie = t->completer_cookie;
+ t->wanted_cluster = -1;
+ t->completer = NULL;
+ spin_unlock(&t->lock);
+
+ if (cluster != -1) {
bL_switch_to(cluster);
+
+ if (completer)
+ completer(completer_cookie);
+ }
} while (!kthread_should_stop());
return 0;
}
/*
- * bL_switch_request - Switch to a specific cluster for the given CPU
+ * bL_switch_request_cb - Switch to a specific cluster for the given CPU,
+ * with completion notification via a callback
*
* @cpu: the CPU to switch
* @new_cluster_id: the ID of the cluster to switch to.
+ * @completer: switch completion callback. if non-NULL,
+ * @completer(@completer_cookie) will be called on completion of
+ * the switch, in non-atomic context.
+ * @completer_cookie: opaque context argument for @completer.
*
* This function causes a cluster switch on the given CPU by waking up
* the appropriate switcher thread. This function may or may not return
* before the switch has occurred.
+ *
+ * If a @completer callback function is supplied, it will be called when
+ * the switch is complete. This can be used to determine asynchronously
+ * when the switch is complete, regardless of when bL_switch_request()
+ * returns. When @completer is supplied, no new switch request is permitted
+ * for the affected CPU until after the switch is complete, and @completer
+ * has returned.
*/
-int bL_switch_request(unsigned int cpu, unsigned int new_cluster_id)
+int bL_switch_request_cb(unsigned int cpu, unsigned int new_cluster_id,
+ bL_switch_completion_handler completer,
+ void *completer_cookie)
{
struct bL_thread *t;
}
t = &bL_threads[cpu];
+
if (IS_ERR(t->task))
return PTR_ERR(t->task);
if (!t->task)
return -ESRCH;
+ spin_lock(&t->lock);
+ if (t->completer) {
+ spin_unlock(&t->lock);
+ return -EBUSY;
+ }
+ t->completer = completer;
+ t->completer_cookie = completer_cookie;
t->wanted_cluster = new_cluster_id;
+ spin_unlock(&t->lock);
wake_up(&t->wq);
return 0;
}
-EXPORT_SYMBOL_GPL(bL_switch_request);
+EXPORT_SYMBOL_GPL(bL_switch_request_cb);
/*
* Activation and configuration code.
*/
+static DEFINE_MUTEX(bL_switcher_activation_lock);
+static BLOCKING_NOTIFIER_HEAD(bL_activation_notifier);
static unsigned int bL_switcher_active;
-static unsigned int bL_switcher_cpu_original_cluster[MAX_CPUS_PER_CLUSTER];
+static unsigned int bL_switcher_cpu_original_cluster[NR_CPUS];
static cpumask_t bL_switcher_removed_logical_cpus;
+int bL_switcher_register_notifier(struct notifier_block *nb)
+{
+ return blocking_notifier_chain_register(&bL_activation_notifier, nb);
+}
+EXPORT_SYMBOL_GPL(bL_switcher_register_notifier);
+
+int bL_switcher_unregister_notifier(struct notifier_block *nb)
+{
+ return blocking_notifier_chain_unregister(&bL_activation_notifier, nb);
+}
+EXPORT_SYMBOL_GPL(bL_switcher_unregister_notifier);
+
+static int bL_activation_notify(unsigned long val)
+{
+ int ret;
+
+ ret = blocking_notifier_call_chain(&bL_activation_notifier, val, NULL);
+ if (ret & NOTIFY_STOP_MASK)
+ pr_err("%s: notifier chain failed with status 0x%x\n",
+ __func__, ret);
+ return notifier_to_errno(ret);
+}
+
static void bL_switcher_restore_cpus(void)
{
int i;
static int bL_switcher_halve_cpus(void)
{
- int cpu, cluster, i, ret;
- cpumask_t cluster_mask[2], common_mask;
-
- cpumask_clear(&bL_switcher_removed_logical_cpus);
- cpumask_clear(&cluster_mask[0]);
- cpumask_clear(&cluster_mask[1]);
+ int i, j, cluster_0, gic_id, ret;
+ unsigned int cpu, cluster, mask;
+ cpumask_t available_cpus;
+ /* First pass to validate what we have */
+ mask = 0;
for_each_online_cpu(i) {
- cpu = cpu_logical_map(i) & 0xff;
- cluster = (cpu_logical_map(i) >> 8) & 0xff;
+ cpu = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 0);
+ cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 1);
if (cluster >= 2) {
pr_err("%s: only dual cluster systems are supported\n", __func__);
return -EINVAL;
}
- cpumask_set_cpu(cpu, &cluster_mask[cluster]);
+ if (WARN_ON(cpu >= MAX_CPUS_PER_CLUSTER))
+ return -EINVAL;
+ mask |= (1 << cluster);
}
-
- if (!cpumask_and(&common_mask, &cluster_mask[0], &cluster_mask[1])) {
- pr_err("%s: no common set of CPUs\n", __func__);
+ if (mask != 3) {
+ pr_err("%s: no CPU pairing possible\n", __func__);
return -EINVAL;
}
- for_each_online_cpu(i) {
- cpu = cpu_logical_map(i) & 0xff;
- cluster = (cpu_logical_map(i) >> 8) & 0xff;
-
- if (cpumask_test_cpu(cpu, &common_mask)) {
- /* Let's take note of the GIC ID for this CPU */
- int gic_id = gic_get_cpu_id(i);
- if (gic_id < 0) {
- pr_err("%s: bad GIC ID for CPU %d\n", __func__, i);
- return -EINVAL;
- }
- bL_gic_id[cpu][cluster] = gic_id;
- pr_info("GIC ID for CPU %u cluster %u is %u\n",
- cpu, cluster, gic_id);
-
+ /*
+ * Now let's do the pairing. We match each CPU with another CPU
+ * from a different cluster. To get a uniform scheduling behavior
+ * without fiddling with CPU topology and compute capacity data,
+ * we'll use logical CPUs initially belonging to the same cluster.
+ */
+ memset(bL_switcher_cpu_pairing, -1, sizeof(bL_switcher_cpu_pairing));
+ cpumask_copy(&available_cpus, cpu_online_mask);
+ cluster_0 = -1;
+ for_each_cpu(i, &available_cpus) {
+ int match = -1;
+ cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 1);
+ if (cluster_0 == -1)
+ cluster_0 = cluster;
+ if (cluster != cluster_0)
+ continue;
+ cpumask_clear_cpu(i, &available_cpus);
+ for_each_cpu(j, &available_cpus) {
+ cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(j), 1);
/*
- * We keep only those logical CPUs which number
- * is equal to their physical CPU number. This is
- * not perfect but good enough for now.
+ * Let's remember the last match to create "odd"
+ * pairings on purpose in order for other code not
+ * to assume any relation between physical and
+ * logical CPU numbers.
*/
- if (cpu == i) {
- bL_switcher_cpu_original_cluster[cpu] = cluster;
- continue;
- }
+ if (cluster != cluster_0)
+ match = j;
+ }
+ if (match != -1) {
+ bL_switcher_cpu_pairing[i] = match;
+ cpumask_clear_cpu(match, &available_cpus);
+ pr_info("CPU%d paired with CPU%d\n", i, match);
+ }
+ }
+
+ /*
+ * Now we disable the unwanted CPUs i.e. everything that has no
+ * pairing information (that includes the pairing counterparts).
+ */
+ cpumask_clear(&bL_switcher_removed_logical_cpus);
+ for_each_online_cpu(i) {
+ cpu = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 0);
+ cluster = MPIDR_AFFINITY_LEVEL(cpu_logical_map(i), 1);
+
+ /* Let's take note of the GIC ID for this CPU */
+ gic_id = gic_get_cpu_id(i);
+ if (gic_id < 0) {
+ pr_err("%s: bad GIC ID for CPU %d\n", __func__, i);
+ bL_switcher_restore_cpus();
+ return -EINVAL;
+ }
+ bL_gic_id[cpu][cluster] = gic_id;
+ pr_info("GIC ID for CPU %u cluster %u is %u\n",
+ cpu, cluster, gic_id);
+
+ if (bL_switcher_cpu_pairing[i] != -1) {
+ bL_switcher_cpu_original_cluster[i] = cluster;
+ continue;
}
ret = cpu_down(i);
{
int cpu, ret;
+ mutex_lock(&bL_switcher_activation_lock);
cpu_hotplug_driver_lock();
if (bL_switcher_active) {
cpu_hotplug_driver_unlock();
+ mutex_unlock(&bL_switcher_activation_lock);
return 0;
}
pr_info("big.LITTLE switcher initializing\n");
+ ret = bL_activation_notify(BL_NOTIFY_PRE_ENABLE);
+ if (ret)
+ goto error;
+
ret = bL_switcher_halve_cpus();
- if (ret) {
- cpu_hotplug_driver_unlock();
- return ret;
- }
+ if (ret)
+ goto error;
for_each_online_cpu(cpu) {
struct bL_thread *t = &bL_threads[cpu];
+ spin_lock_init(&t->lock);
init_waitqueue_head(&t->wq);
init_completion(&t->started);
t->wanted_cluster = -1;
}
bL_switcher_active = 1;
- cpu_hotplug_driver_unlock();
-
+ bL_activation_notify(BL_NOTIFY_POST_ENABLE);
pr_info("big.LITTLE switcher initialized\n");
- return 0;
+ goto out;
+
+error:
+ pr_warn("big.LITTLE switcher initialization failed\n");
+ bL_activation_notify(BL_NOTIFY_POST_DISABLE);
+
+out:
+ cpu_hotplug_driver_unlock();
+ mutex_unlock(&bL_switcher_activation_lock);
+ return ret;
}
#ifdef CONFIG_SYSFS
static void bL_switcher_disable(void)
{
- unsigned int cpu, cluster, i;
+ unsigned int cpu, cluster;
struct bL_thread *t;
struct task_struct *task;
+ mutex_lock(&bL_switcher_activation_lock);
cpu_hotplug_driver_lock();
- if (!bL_switcher_active) {
- cpu_hotplug_driver_unlock();
- return;
+
+ if (!bL_switcher_active)
+ goto out;
+
+ if (bL_activation_notify(BL_NOTIFY_PRE_DISABLE) != 0) {
+ bL_activation_notify(BL_NOTIFY_POST_ENABLE);
+ goto out;
}
+
bL_switcher_active = 0;
/*
* possibility for interference from external requests.
*/
for_each_online_cpu(cpu) {
- BUG_ON(cpu != (cpu_logical_map(cpu) & 0xff));
t = &bL_threads[cpu];
task = t->task;
t->task = NULL;
/* If execution gets here, we're in trouble. */
pr_crit("%s: unable to restore original cluster for CPU %d\n",
__func__, cpu);
- for_each_cpu(i, &bL_switcher_removed_logical_cpus) {
- if ((cpu_logical_map(i) & 0xff) != cpu)
- continue;
- pr_crit("%s: CPU %d can't be restored\n",
- __func__, i);
- cpumask_clear_cpu(i, &bL_switcher_removed_logical_cpus);
- break;
- }
+ pr_crit("%s: CPU %d can't be restored\n",
+ __func__, bL_switcher_cpu_pairing[cpu]);
+ cpumask_clear_cpu(bL_switcher_cpu_pairing[cpu],
+ &bL_switcher_removed_logical_cpus);
}
bL_switcher_restore_cpus();
+ bL_activation_notify(BL_NOTIFY_POST_DISABLE);
+
+out:
cpu_hotplug_driver_unlock();
+ mutex_unlock(&bL_switcher_activation_lock);
}
static ssize_t bL_switcher_active_show(struct kobject *kobj,
#endif /* CONFIG_SYSFS */
+bool bL_switcher_get_enabled(void)
+{
+ mutex_lock(&bL_switcher_activation_lock);
+
+ return bL_switcher_active;
+}
+EXPORT_SYMBOL_GPL(bL_switcher_get_enabled);
+
+void bL_switcher_put_enabled(void)
+{
+ mutex_unlock(&bL_switcher_activation_lock);
+}
+EXPORT_SYMBOL_GPL(bL_switcher_put_enabled);
+
+/*
+ * Veto any CPU hotplug operation on those CPUs we've removed
+ * while the switcher is active.
+ * We're just not ready to deal with that given the trickery involved.
+ */
+static int bL_switcher_hotplug_callback(struct notifier_block *nfb,
+ unsigned long action, void *hcpu)
+{
+ if (bL_switcher_active) {
+ int pairing = bL_switcher_cpu_pairing[(unsigned long)hcpu];
+ switch (action & 0xf) {
+ case CPU_UP_PREPARE:
+ case CPU_DOWN_PREPARE:
+ if (pairing == -1)
+ return NOTIFY_BAD;
+ }
+ }
+ return NOTIFY_DONE;
+}
+
static bool no_bL_switcher;
core_param(no_bL_switcher, no_bL_switcher, bool, 0644);
return -EINVAL;
}
+ cpu_notifier(bL_switcher_hotplug_callback, 0);
+
if (!no_bL_switcher) {
ret = bL_switcher_enable();
if (ret)