/*
 * SMP initialisation and IPI support
 * Based on arch/arm/kernel/smp.c
 *
 * Copyright (C) 2012 ARM Ltd.
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <linux/delay.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/cache.h>
#include <linux/profile.h>
#include <linux/errno.h>
#include <linux/mm.h>
#include <linux/err.h>
#include <linux/cpu.h>
#include <linux/smp.h>
#include <linux/seq_file.h>
#include <linux/irq.h>
#include <linux/percpu.h>
#include <linux/clockchips.h>
#include <linux/completion.h>
#include <linux/of.h>
#include <linux/irq_work.h>

#include <asm/alternative.h>
#include <asm/atomic.h>
#include <asm/cacheflush.h>
#include <asm/cpu.h>
#include <asm/cputype.h>
#include <asm/cpu_ops.h>
#include <asm/mmu_context.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/processor.h>
#include <asm/smp_plat.h>
#include <asm/sections.h>
#include <asm/tlbflush.h>
#include <asm/ptrace.h>

#define CREATE_TRACE_POINTS
#include <trace/events/ipi.h>

/*
 * as from 2.5, kernels no longer have an init_tasks structure
 * so we need some other way of telling a new secondary core
 * where to place its SVC stack
 */
struct secondary_data secondary_data;

enum ipi_msg_type {
        IPI_RESCHEDULE,
        IPI_CALL_FUNC,
        IPI_CALL_FUNC_SINGLE,
        IPI_CPU_STOP,
        IPI_TIMER,
        IPI_IRQ_WORK,
};

/*
 * Boot a secondary CPU, and assign it the specified idle task.
 * This also gives us the initial stack to use for this CPU.
 */
static int boot_secondary(unsigned int cpu, struct task_struct *idle)
{
        if (cpu_ops[cpu]->cpu_boot)
                return cpu_ops[cpu]->cpu_boot(cpu);

        return -EOPNOTSUPP;
}

static DECLARE_COMPLETION(cpu_running);

int __cpu_up(unsigned int cpu, struct task_struct *idle)
{
        int ret;

        /*
         * We need to tell the secondary core where to find its stack and the
         * page tables.
         */
        secondary_data.stack = task_stack_page(idle) + THREAD_START_SP;
        __flush_dcache_area(&secondary_data, sizeof(secondary_data));

        /*
         * Now bring the CPU into our world.
         */
        ret = boot_secondary(cpu, idle);
        if (ret == 0) {
                /*
                 * CPU was successfully started, wait for it to come online or
                 * time out.
                 */
                wait_for_completion_timeout(&cpu_running,
                                            msecs_to_jiffies(1000));

                if (!cpu_online(cpu)) {
                        pr_crit("CPU%u: failed to come online\n", cpu);
                        ret = -EIO;
                }
        } else {
                pr_err("CPU%u: failed to boot: %d\n", cpu, ret);
        }

        secondary_data.stack = NULL;

        return ret;
}

static void smp_store_cpu_info(unsigned int cpuid)
{
        store_cpu_topology(cpuid);
}

/*
 * This is the secondary CPU boot entry.  We're using this CPUs
 * idle thread stack, but a set of temporary page tables.
 */
asmlinkage void secondary_start_kernel(void)
{
        struct mm_struct *mm = &init_mm;
        unsigned int cpu = smp_processor_id();

        /*
         * All kernel threads share the same mm context; grab a
         * reference and switch to it.
         */
        atomic_inc(&mm->mm_count);
        current->active_mm = mm;
        cpumask_set_cpu(cpu, mm_cpumask(mm));

        set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
        printk("CPU%u: Booted secondary processor\n", cpu);

        /*
         * TTBR0 is only used for the identity mapping at this stage. Make it
         * point to zero page to avoid speculatively fetching new entries.
         */
        cpu_set_reserved_ttbr0();
        flush_tlb_all();

        preempt_disable();
        trace_hardirqs_off();

        if (cpu_ops[cpu]->cpu_postboot)
                cpu_ops[cpu]->cpu_postboot();

        /*
         * Log the CPU info before it is marked online and might get read.
         */
        cpuinfo_store_cpu();

        /*
         * Enable GIC and timers.
         */
        notify_cpu_starting(cpu);

        smp_store_cpu_info(cpu);

        /*
         * OK, now it's safe to let the boot CPU continue.  Wait for
         * the CPU migration code to notice that the CPU is online
         * before we continue.
         */
        set_cpu_online(cpu, true);
        complete(&cpu_running);

        local_dbg_enable();
        local_irq_enable();
        local_async_enable();

        /*
         * OK, it's off to the idle thread for us
         */
        cpu_startup_entry(CPUHP_ONLINE);
}

#ifdef CONFIG_HOTPLUG_CPU
static int op_cpu_disable(unsigned int cpu)
{
        /*
         * If we don't have a cpu_die method, abort before we reach the point
         * of no return. CPU0 may not have an cpu_ops, so test for it.
         */
        if (!cpu_ops[cpu] || !cpu_ops[cpu]->cpu_die)
                return -EOPNOTSUPP;

        /*
         * We may need to abort a hot unplug for some other mechanism-specific
         * reason.
         */
        if (cpu_ops[cpu]->cpu_disable)
                return cpu_ops[cpu]->cpu_disable(cpu);

        return 0;
}

/*
 * __cpu_disable runs on the processor to be shutdown.
 */
int __cpu_disable(void)
{
        unsigned int cpu = smp_processor_id();
        int ret;

        ret = op_cpu_disable(cpu);
        if (ret)
                return ret;

        /*
         * Take this CPU offline.  Once we clear this, we can't return,
         * and we must not schedule until we're ready to give up the cpu.
         */
        set_cpu_online(cpu, false);

        /*
         * OK - migrate IRQs away from this CPU
         */
        migrate_irqs();

        /*
         * Remove this CPU from the vm mask set of all processes.
         */
        clear_tasks_mm_cpumask(cpu);

        return 0;
}

static int op_cpu_kill(unsigned int cpu)
{
        /*
         * If we have no means of synchronising with the dying CPU, then assume
         * that it is really dead. We can only wait for an arbitrary length of
         * time and hope that it's dead, so let's skip the wait and just hope.
         */
        if (!cpu_ops[cpu]->cpu_kill)
                return 1;

        return cpu_ops[cpu]->cpu_kill(cpu);
}

static DECLARE_COMPLETION(cpu_died);

/*
 * called on the thread which is asking for a CPU to be shutdown -
 * waits until shutdown has completed, or it is timed out.
 */
void __cpu_die(unsigned int cpu)
{
        if (!wait_for_completion_timeout(&cpu_died, msecs_to_jiffies(5000))) {
                pr_crit("CPU%u: cpu didn't die\n", cpu);
                return;
        }
        pr_notice("CPU%u: shutdown\n", cpu);

        /*
         * Now that the dying CPU is beyond the point of no return w.r.t.
         * in-kernel synchronisation, try to get the firwmare to help us to
         * verify that it has really left the kernel before we consider
         * clobbering anything it might still be using.
         */
        if (!op_cpu_kill(cpu))
                pr_warn("CPU%d may not have shut down cleanly\n", cpu);
}

/*
 * Called from the idle thread for the CPU which has been shutdown.
 *
 * Note that we disable IRQs here, but do not re-enable them
 * before returning to the caller. This is also the behaviour
 * of the other hotplug-cpu capable cores, so presumably coming
 * out of idle fixes this.
 */
void cpu_die(void)
{
        unsigned int cpu = smp_processor_id();

        idle_task_exit();

        local_irq_disable();

        /* Tell __cpu_die() that this CPU is now safe to dispose of */
        complete(&cpu_died);

        /*
         * Actually shutdown the CPU. This must never fail. The specific hotplug
         * mechanism must perform all required cache maintenance to ensure that
         * no dirty lines are lost in the process of shutting down the CPU.
         */
        cpu_ops[cpu]->cpu_die(cpu);

        BUG();
}
#endif

void __init smp_cpus_done(unsigned int max_cpus)
{
        pr_info("SMP: Total of %d processors activated.\n", num_online_cpus());
        apply_alternatives_all();
}

void __init smp_prepare_boot_cpu(void)
{
        set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
}

/*
 * Enumerate the possible CPU set from the device tree and build the
 * cpu logical map array containing MPIDR values related to logical
 * cpus. Assumes that cpu_logical_map(0) has already been initialized.
 */
void __init smp_init_cpus(void)
{
        struct device_node *dn = NULL;
        unsigned int i, cpu = 1;
        bool bootcpu_valid = false;

        while ((dn = of_find_node_by_type(dn, "cpu"))) {
                const u32 *cell;
                u64 hwid;

                /*
                 * A cpu node with missing "reg" property is
                 * considered invalid to build a cpu_logical_map
                 * entry.
                 */
                cell = of_get_property(dn, "reg", NULL);
                if (!cell) {
                        pr_err("%s: missing reg property\n", dn->full_name);
                        goto next;
                }
                hwid = of_read_number(cell, of_n_addr_cells(dn));

                /*
                 * Non affinity bits must be set to 0 in the DT
                 */
                if (hwid & ~MPIDR_HWID_BITMASK) {
                        pr_err("%s: invalid reg property\n", dn->full_name);
                        goto next;
                }

                /*
                 * Duplicate MPIDRs are a recipe for disaster. Scan
                 * all initialized entries and check for
                 * duplicates. If any is found just ignore the cpu.
                 * cpu_logical_map was initialized to INVALID_HWID to
                 * avoid matching valid MPIDR values.
                 */
                for (i = 1; (i < cpu) && (i < NR_CPUS); i++) {
                        if (cpu_logical_map(i) == hwid) {
                                pr_err("%s: duplicate cpu reg properties in the DT\n",
                                        dn->full_name);
                                goto next;
                        }
                }

                /*
                 * The numbering scheme requires that the boot CPU
                 * must be assigned logical id 0. Record it so that
                 * the logical map built from DT is validated and can
                 * be used.
                 */
                if (hwid == cpu_logical_map(0)) {
                        if (bootcpu_valid) {
                                pr_err("%s: duplicate boot cpu reg property in DT\n",
                                        dn->full_name);
                                goto next;
                        }

                        bootcpu_valid = true;

                        /*
                         * cpu_logical_map has already been
                         * initialized and the boot cpu doesn't need
                         * the enable-method so continue without
                         * incrementing cpu.
                         */
                        continue;
                }

                if (cpu >= NR_CPUS)
                        goto next;

                if (cpu_read_ops(dn, cpu) != 0)
                        goto next;

                if (cpu_ops[cpu]->cpu_init(dn, cpu))
                        goto next;

                pr_debug("cpu logical map 0x%llx\n", hwid);
                cpu_logical_map(cpu) = hwid;
next:
                cpu++;
        }

        /* sanity check */
        if (cpu > NR_CPUS)
                pr_warning("no. of cores (%d) greater than configured maximum of %d - clipping\n",
                           cpu, NR_CPUS);

        if (!bootcpu_valid) {
                pr_err("DT missing boot CPU MPIDR, not enabling secondaries\n");
                return;
        }

        /*
         * All the cpus that made it to the cpu_logical_map have been
         * validated so set them as possible cpus.
         */
        for (i = 0; i < NR_CPUS; i++)
                if (cpu_logical_map(i) != INVALID_HWID)
                        set_cpu_possible(i, true);
}

void __init smp_prepare_cpus(unsigned int max_cpus)
{
        int err;
        unsigned int cpu, ncores = num_possible_cpus();

        init_cpu_topology();

        smp_store_cpu_info(smp_processor_id());

        /*
         * are we trying to boot more cores than exist?
         */
        if (max_cpus > ncores)
                max_cpus = ncores;

        /* Don't bother if we're effectively UP */
        if (max_cpus <= 1)
                return;

        /*
         * Initialise the present map (which describes the set of CPUs
         * actually populated at the present time) and release the
         * secondaries from the bootloader.
         *
         * Make sure we online at most (max_cpus - 1) additional CPUs.
         */
        max_cpus--;
        for_each_possible_cpu(cpu) {
                if (max_cpus == 0)
                        break;

                if (cpu == smp_processor_id())
                        continue;

                if (!cpu_ops[cpu])
                        continue;

                err = cpu_ops[cpu]->cpu_prepare(cpu);
                if (err)
                        continue;

                set_cpu_present(cpu, true);
                max_cpus--;
        }
}

void (*__smp_cross_call)(const struct cpumask *, unsigned int);

void __init set_smp_cross_call(void (*fn)(const struct cpumask *, unsigned int))
{
        __smp_cross_call = fn;
}

static const char *ipi_types[NR_IPI] __tracepoint_string = {
#define S(x,s)  [x] = s
        S(IPI_RESCHEDULE, "Rescheduling interrupts"),
        S(IPI_CALL_FUNC, "Function call interrupts"),
        S(IPI_CALL_FUNC_SINGLE, "Single function call interrupts"),
        S(IPI_CPU_STOP, "CPU stop interrupts"),
        S(IPI_TIMER, "Timer broadcast interrupts"),
        S(IPI_IRQ_WORK, "IRQ work interrupts"),
};

static void smp_cross_call(const struct cpumask *target, unsigned int ipinr)
{
        trace_ipi_raise(target, ipi_types[ipinr]);
        __smp_cross_call(target, ipinr);
}

void show_ipi_list(struct seq_file *p, int prec)
{
        unsigned int cpu, i;

        for (i = 0; i < NR_IPI; i++) {
                seq_printf(p, "%*s%u:%s", prec - 1, "IPI", i,
                           prec >= 4 ? " " : "");
                for_each_online_cpu(cpu)
                        seq_printf(p, "%10u ",
                                   __get_irq_stat(cpu, ipi_irqs[i]));
                seq_printf(p, "      %s\n", ipi_types[i]);
        }
}

u64 smp_irq_stat_cpu(unsigned int cpu)
{
        u64 sum = 0;
        int i;

        for (i = 0; i < NR_IPI; i++)
                sum += __get_irq_stat(cpu, ipi_irqs[i]);

        return sum;
}

void arch_send_call_function_ipi_mask(const struct cpumask *mask)
{
        smp_cross_call(mask, IPI_CALL_FUNC);
}

void arch_send_call_function_single_ipi(int cpu)
{
        smp_cross_call(cpumask_of(cpu), IPI_CALL_FUNC_SINGLE);
}

#ifdef CONFIG_IRQ_WORK
void arch_irq_work_raise(void)
{
        if (__smp_cross_call)
                smp_cross_call(cpumask_of(smp_processor_id()), IPI_IRQ_WORK);
}
#endif

static DEFINE_RAW_SPINLOCK(stop_lock);

/*
 * ipi_cpu_stop - handle IPI from smp_send_stop()
 */
static void ipi_cpu_stop(unsigned int cpu)
{
        if (system_state == SYSTEM_BOOTING ||
            system_state == SYSTEM_RUNNING) {
                raw_spin_lock(&stop_lock);
                pr_crit("CPU%u: stopping\n", cpu);
                dump_stack();
                raw_spin_unlock(&stop_lock);
        }

        set_cpu_online(cpu, false);

        local_irq_disable();

        while (1)
                cpu_relax();
}

/*
 * Main handler for inter-processor interrupts
 */
void handle_IPI(int ipinr, struct pt_regs *regs)
{
        unsigned int cpu = smp_processor_id();
        struct pt_regs *old_regs = set_irq_regs(regs);

        if ((unsigned)ipinr < NR_IPI) {
                trace_ipi_entry(ipi_types[ipinr]);
                __inc_irq_stat(cpu, ipi_irqs[ipinr]);
        }

        switch (ipinr) {
        case IPI_RESCHEDULE:
                scheduler_ipi();
                break;

        case IPI_CALL_FUNC:
                irq_enter();
                generic_smp_call_function_interrupt();
                irq_exit();
                break;

        case IPI_CALL_FUNC_SINGLE:
                irq_enter();
                generic_smp_call_function_single_interrupt();
                irq_exit();
                break;

        case IPI_CPU_STOP:
                irq_enter();
                ipi_cpu_stop(cpu);
                irq_exit();
                break;

#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
        case IPI_TIMER:
                irq_enter();
                tick_receive_broadcast();
                irq_exit();
                break;
#endif

#ifdef CONFIG_IRQ_WORK
        case IPI_IRQ_WORK:
                irq_enter();
                irq_work_run();
                irq_exit();
                break;
#endif

        default:
                pr_crit("CPU%u: Unknown IPI message 0x%x\n", cpu, ipinr);
                break;
        }

        if ((unsigned)ipinr < NR_IPI)
                trace_ipi_exit(ipi_types[ipinr]);
        set_irq_regs(old_regs);
}

void smp_send_reschedule(int cpu)
{
        smp_cross_call(cpumask_of(cpu), IPI_RESCHEDULE);
}

#ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
void tick_broadcast(const struct cpumask *mask)
{
        smp_cross_call(mask, IPI_TIMER);
}
#endif

void smp_send_stop(void)
{
        unsigned long timeout;

        if (num_online_cpus() > 1) {
                cpumask_t mask;

                cpumask_copy(&mask, cpu_online_mask);
                cpu_clear(smp_processor_id(), mask);

                smp_cross_call(&mask, IPI_CPU_STOP);
        }

        /* Wait up to one second for other CPUs to stop */
        timeout = USEC_PER_SEC;
        while (num_online_cpus() > 1 && timeout--)
                udelay(1);

        if (num_online_cpus() > 1)
                pr_warning("SMP: failed to stop secondary CPUs\n");
}

/*
 * not supported here
 */
int setup_profiling_timer(unsigned int multiplier)
{
        return -EINVAL;
}