242 lines
6.4 KiB
C
242 lines
6.4 KiB
C
![]() |
/*
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* arch/arm/common/bL_switcher.c -- big.LITTLE cluster switcher core driver
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*
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* Created by: Nicolas Pitre, March 2012
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* Copyright: (C) 2012-2013 Linaro Limited
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/sched.h>
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#include <linux/interrupt.h>
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#include <linux/cpu_pm.h>
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#include <linux/workqueue.h>
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#include <linux/mm.h>
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#include <linux/string.h>
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#include <linux/irqchip/arm-gic.h>
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#include <asm/smp_plat.h>
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#include <asm/suspend.h>
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#include <asm/mcpm.h>
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#include <asm/bL_switcher.h>
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/*
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* Use our own MPIDR accessors as the generic ones in asm/cputype.h have
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* __attribute_const__ and we don't want the compiler to assume any
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* constness here as the value _does_ change along some code paths.
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*/
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static int read_mpidr(void)
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{
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unsigned int id;
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asm volatile ("mrc p15, 0, %0, c0, c0, 5" : "=r" (id));
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return id & MPIDR_HWID_BITMASK;
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}
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/*
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* bL switcher core code.
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*/
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static void bL_do_switch(void *_unused)
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{
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unsigned mpidr, cpuid, clusterid, ob_cluster, ib_cluster;
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/*
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* We now have a piece of stack borrowed from the init task's.
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* Let's also switch to init_mm right away to match it.
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*/
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cpu_switch_mm(init_mm.pgd, &init_mm);
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pr_debug("%s\n", __func__);
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mpidr = read_mpidr();
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cpuid = MPIDR_AFFINITY_LEVEL(mpidr, 0);
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clusterid = MPIDR_AFFINITY_LEVEL(mpidr, 1);
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ob_cluster = clusterid;
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ib_cluster = clusterid ^ 1;
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/*
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* Our state has been saved at this point. Let's release our
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* inbound CPU.
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*/
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mcpm_set_entry_vector(cpuid, ib_cluster, cpu_resume);
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sev();
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/*
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* From this point, we must assume that our counterpart CPU might
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* have taken over in its parallel world already, as if execution
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* just returned from cpu_suspend(). It is therefore important to
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* be very careful not to make any change the other guy is not
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* expecting. This is why we need stack isolation.
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*
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* Fancy under cover tasks could be performed here. For now
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* we have none.
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*/
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/* Let's put ourself down. */
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mcpm_cpu_power_down();
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/* should never get here */
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BUG();
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}
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/*
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* Stack isolation. To ensure 'current' remains valid, we just borrow
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* a slice of the init/idle task which should be fairly lightly used.
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* The borrowed area starts just above the thread_info structure located
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* at the very bottom of the stack, aligned to a cache line.
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*/
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#define STACK_SIZE 256
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extern void call_with_stack(void (*fn)(void *), void *arg, void *sp);
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static int bL_switchpoint(unsigned long _arg)
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{
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unsigned int mpidr = read_mpidr();
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unsigned int cpuid = MPIDR_AFFINITY_LEVEL(mpidr, 0);
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unsigned int clusterid = MPIDR_AFFINITY_LEVEL(mpidr, 1);
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unsigned int cpu_index = cpuid + clusterid * MAX_CPUS_PER_CLUSTER;
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void *stack = &init_thread_info + 1;
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stack = PTR_ALIGN(stack, L1_CACHE_BYTES);
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stack += cpu_index * STACK_SIZE + STACK_SIZE;
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call_with_stack(bL_do_switch, (void *)_arg, stack);
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BUG();
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}
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/*
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* Generic switcher interface
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*/
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/*
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* bL_switch_to - Switch to a specific cluster for the current CPU
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* @new_cluster_id: the ID of the cluster to switch to.
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*
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* This function must be called on the CPU to be switched.
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* Returns 0 on success, else a negative status code.
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*/
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static int bL_switch_to(unsigned int new_cluster_id)
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{
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unsigned int mpidr, cpuid, clusterid, ob_cluster, ib_cluster, this_cpu;
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int ret;
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mpidr = read_mpidr();
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cpuid = MPIDR_AFFINITY_LEVEL(mpidr, 0);
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clusterid = MPIDR_AFFINITY_LEVEL(mpidr, 1);
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ob_cluster = clusterid;
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ib_cluster = clusterid ^ 1;
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if (new_cluster_id == clusterid)
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return 0;
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pr_debug("before switch: CPU %d in cluster %d\n", cpuid, clusterid);
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/* Close the gate for our entry vectors */
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mcpm_set_entry_vector(cpuid, ob_cluster, NULL);
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mcpm_set_entry_vector(cpuid, ib_cluster, NULL);
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/*
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* Let's wake up the inbound CPU now in case it requires some delay
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* to come online, but leave it gated in our entry vector code.
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*/
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ret = mcpm_cpu_power_up(cpuid, ib_cluster);
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if (ret) {
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pr_err("%s: mcpm_cpu_power_up() returned %d\n", __func__, ret);
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return ret;
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}
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/*
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* From this point we are entering the switch critical zone
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* and can't take any interrupts anymore.
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*/
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local_irq_disable();
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local_fiq_disable();
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this_cpu = smp_processor_id();
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/* redirect GIC's SGIs to our counterpart */
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gic_migrate_target(cpuid + ib_cluster*4);
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/*
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* Raise a SGI on the inbound CPU to make sure it doesn't stall
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* in a possible WFI, such as in mcpm_power_down().
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*/
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arch_send_wakeup_ipi_mask(cpumask_of(this_cpu));
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ret = cpu_pm_enter();
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/* we can not tolerate errors at this point */
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if (ret)
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panic("%s: cpu_pm_enter() returned %d\n", __func__, ret);
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/* Flip the cluster in the CPU logical map for this CPU. */
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cpu_logical_map(this_cpu) ^= (1 << 8);
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/* Let's do the actual CPU switch. */
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ret = cpu_suspend(0, bL_switchpoint);
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if (ret > 0)
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panic("%s: cpu_suspend() returned %d\n", __func__, ret);
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/* We are executing on the inbound CPU at this point */
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mpidr = read_mpidr();
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cpuid = MPIDR_AFFINITY_LEVEL(mpidr, 0);
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clusterid = MPIDR_AFFINITY_LEVEL(mpidr, 1);
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pr_debug("after switch: CPU %d in cluster %d\n", cpuid, clusterid);
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BUG_ON(clusterid != ib_cluster);
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mcpm_cpu_powered_up();
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ret = cpu_pm_exit();
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local_fiq_enable();
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local_irq_enable();
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if (ret)
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pr_err("%s exiting with error %d\n", __func__, ret);
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return ret;
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}
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struct switch_args {
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unsigned int cluster;
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struct work_struct work;
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};
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static void __bL_switch_to(struct work_struct *work)
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{
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struct switch_args *args = container_of(work, struct switch_args, work);
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bL_switch_to(args->cluster);
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}
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/*
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* bL_switch_request - Switch to a specific cluster for the given CPU
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*
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* @cpu: the CPU to switch
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* @new_cluster_id: the ID of the cluster to switch to.
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*
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* This function causes a cluster switch on the given CPU. If the given
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* CPU is the same as the calling CPU then the switch happens right away.
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* Otherwise the request is put on a work queue to be scheduled on the
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* remote CPU.
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*/
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void bL_switch_request(unsigned int cpu, unsigned int new_cluster_id)
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{
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unsigned int this_cpu = get_cpu();
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struct switch_args args;
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if (cpu == this_cpu) {
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bL_switch_to(new_cluster_id);
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put_cpu();
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return;
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}
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put_cpu();
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args.cluster = new_cluster_id;
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INIT_WORK_ONSTACK(&args.work, __bL_switch_to);
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schedule_work_on(cpu, &args.work);
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flush_work(&args.work);
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}
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EXPORT_SYMBOL_GPL(bL_switch_request);
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