/* * arch/arm/common/bL_switcher.c -- big.LITTLE cluster switcher core driver * * Created by: Nicolas Pitre, March 2012 * Copyright: (C) 2012 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 #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * 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. */ static int read_mpidr(void) { unsigned int id; asm volatile ("mrc\tp15, 0, %0, c0, c0, 5" : "=r" (id)); return id; } /* * 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; struct tick_device *tdev; enum clock_event_mode tdev_mode; 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 sleep/schedule 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)); tdev = tick_get_device(this_cpu); if (tdev && !cpumask_equal(tdev->evtdev->cpumask, cpumask_of(this_cpu))) tdev = NULL; if (tdev) { tdev_mode = tdev->evtdev->mode; clockevents_set_mode(tdev->evtdev, CLOCK_EVT_MODE_SHUTDOWN); } 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. * This must be flushed to RAM as the resume code * needs to access it while the caches are still disabled. */ cpu_logical_map(this_cpu) ^= (1 << 8); __cpuc_flush_dcache_area(&cpu_logical_map(this_cpu), sizeof(cpu_logical_map(this_cpu))); /* 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(); if (tdev) { clockevents_set_mode(tdev->evtdev, tdev_mode); clockevents_program_event(tdev->evtdev, tdev->evtdev->next_event, 1); } 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);