--- /dev/null
+/*
+ * arch/arm/common/bL_switcher.c -- big.LITTLE cluster switcher core driver
+ *
+ * Created by: Nicolas Pitre, March 2012
+ * Copyright: (C) 2012-2013 Linaro Limited
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/interrupt.h>
+#include <linux/cpu_pm.h>
+#include <linux/workqueue.h>
+#include <linux/mm.h>
+#include <linux/string.h>
+#include <linux/irqchip/arm-gic.h>
+
+#include <asm/smp_plat.h>
+#include <asm/suspend.h>
+#include <asm/mcpm.h>
+#include <asm/bL_switcher.h>
+
+
+/*
+ * Use our own MPIDR accessors as the generic ones in asm/cputype.h have
+ * __attribute_const__ and we don't want the compiler to assume any
+ * constness here as the value _does_ change along some code paths.
+ */
+
+static int read_mpidr(void)
+{
+ unsigned int id;
+ asm volatile ("mrc p15, 0, %0, c0, c0, 5" : "=r" (id));
+ return id & MPIDR_HWID_BITMASK;
+}
+
+/*
+ * bL switcher core code.
+ */
+
+static void bL_do_switch(void *_unused)
+{
+ unsigned mpidr, cpuid, clusterid, ob_cluster, ib_cluster;
+
+ /*
+ * We now have a piece of stack borrowed from the init task's.
+ * Let's also switch to init_mm right away to match it.
+ */
+ cpu_switch_mm(init_mm.pgd, &init_mm);
+
+ 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;
+
+ /*
+ * Our state has been saved at this point. Let's release our
+ * inbound CPU.
+ */
+ mcpm_set_entry_vector(cpuid, ib_cluster, cpu_resume);
+ sev();
+
+ /*
+ * From this point, we must assume that our counterpart CPU might
+ * have taken over in its parallel world already, as if execution
+ * just returned from cpu_suspend(). It is therefore important to
+ * be very careful not to make any change the other guy is not
+ * expecting. This is why we need stack isolation.
+ *
+ * Fancy under cover tasks could be performed here. For now
+ * we have none.
+ */
+
+ /* Let's put ourself down. */
+ mcpm_cpu_power_down();
+
+ /* should never get here */
+ BUG();
+}
+
+/*
+ * Stack isolation. To ensure 'current' remains valid, we just borrow
+ * a slice of the init/idle task which should be fairly lightly used.
+ * The borrowed area starts just above the thread_info structure located
+ * at the very bottom of the stack, aligned to a cache line.
+ */
+#define STACK_SIZE 256
+extern void call_with_stack(void (*fn)(void *), void *arg, void *sp);
+static int bL_switchpoint(unsigned long _arg)
+{
+ unsigned int mpidr = read_mpidr();
+ unsigned int cpuid = MPIDR_AFFINITY_LEVEL(mpidr, 0);
+ unsigned int clusterid = MPIDR_AFFINITY_LEVEL(mpidr, 1);
+ unsigned int cpu_index = cpuid + clusterid * MAX_CPUS_PER_CLUSTER;
+ void *stack = &init_thread_info + 1;
+ stack = PTR_ALIGN(stack, L1_CACHE_BYTES);
+ stack += cpu_index * STACK_SIZE + STACK_SIZE;
+ call_with_stack(bL_do_switch, (void *)_arg, stack);
+ BUG();
+}
+
+/*
+ * Generic switcher interface
+ */
+
+/*
+ * bL_switch_to - Switch to a specific cluster for the current CPU
+ * @new_cluster_id: the ID of the cluster to switch to.
+ *
+ * This function must be called on the CPU to be switched.
+ * Returns 0 on success, else a negative status code.
+ */
+static int bL_switch_to(unsigned int new_cluster_id)
+{
+ unsigned int mpidr, cpuid, clusterid, ob_cluster, ib_cluster, this_cpu;
+ int ret;
+
+ mpidr = read_mpidr();
+ cpuid = MPIDR_AFFINITY_LEVEL(mpidr, 0);
+ clusterid = MPIDR_AFFINITY_LEVEL(mpidr, 1);
+ ob_cluster = clusterid;
+ ib_cluster = clusterid ^ 1;
+
+ if (new_cluster_id == clusterid)
+ return 0;
+
+ pr_debug("before switch: CPU %d in cluster %d\n", cpuid, clusterid);
+
+ /* Close the gate for our entry vectors */
+ mcpm_set_entry_vector(cpuid, ob_cluster, NULL);
+ mcpm_set_entry_vector(cpuid, ib_cluster, NULL);
+
+ /*
+ * 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);
+ if (ret) {
+ pr_err("%s: mcpm_cpu_power_up() returned %d\n", __func__, ret);
+ return ret;
+ }
+
+ /*
+ * 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();
+
+ /* redirect GIC's SGIs to our counterpart */
+ gic_migrate_target(cpuid + ib_cluster*4);
+
+ /*
+ * 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));
+
+ ret = cpu_pm_enter();
+
+ /* we can not tolerate errors at this point */
+ 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);
+
+ /* Let's do the actual CPU switch. */
+ ret = cpu_suspend(0, 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);
+
+ mcpm_cpu_powered_up();
+
+ ret = cpu_pm_exit();
+
+ local_fiq_enable();
+ local_irq_enable();
+
+ if (ret)
+ pr_err("%s exiting with error %d\n", __func__, ret);
+ return ret;
+}
+
+struct switch_args {
+ unsigned int cluster;
+ struct work_struct work;
+};
+
+static void __bL_switch_to(struct work_struct *work)
+{
+ struct switch_args *args = container_of(work, struct switch_args, work);
+ bL_switch_to(args->cluster);
+}
+
+/*
+ * bL_switch_request - Switch to a specific cluster for the given CPU
+ *
+ * @cpu: the CPU to switch
+ * @new_cluster_id: the ID of the cluster to switch to.
+ *
+ * This function causes a cluster switch on the given CPU. If the given
+ * CPU is the same as the calling CPU then the switch happens right away.
+ * Otherwise the request is put on a work queue to be scheduled on the
+ * remote CPU.
+ */
+void bL_switch_request(unsigned int cpu, unsigned int new_cluster_id)
+{
+ unsigned int this_cpu = get_cpu();
+ struct switch_args args;
+
+ if (cpu == this_cpu) {
+ bL_switch_to(new_cluster_id);
+ put_cpu();
+ return;
+ }
+ put_cpu();
+
+ args.cluster = new_cluster_id;
+ INIT_WORK_ONSTACK(&args.work, __bL_switch_to);
+ schedule_work_on(cpu, &args.work);
+ flush_work(&args.work);
+}
+EXPORT_SYMBOL_GPL(bL_switch_request);
projects / platform / kernel / linux-exynos.git / commitdiff