// SPDX-License-Identifier: GPL-2.0-only
/*
 * SMP support for Hexagon
 *
 * Copyright (c) 2010-2012, The Linux Foundation. All rights reserved.
 */

#include <linux/err.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/percpu.h>
#include <linux/sched/mm.h>
#include <linux/smp.h>
#include <linux/spinlock.h>
#include <linux/cpu.h>
#include <linux/mm_types.h>

#include <asm/time.h>    /*  timer_interrupt  */
#include <asm/hexagon_vm.h>

#define BASE_IPI_IRQ 26

/*
 * cpu_possible_mask needs to be filled out prior to setup_per_cpu_areas
 * (which is prior to any of our smp_prepare_cpu crap), in order to set
 * up the...  per_cpu areas.
 */

struct ipi_data {
        unsigned long bits;
};

static DEFINE_PER_CPU(struct ipi_data, ipi_data);

static inline void __handle_ipi(unsigned long *ops, struct ipi_data *ipi,
                                int cpu)
{
        unsigned long msg = 0;
        do {
                msg = find_next_bit(ops, BITS_PER_LONG, msg+1);

                switch (msg) {

                case IPI_TIMER:
                        ipi_timer();
                        break;

                case IPI_CALL_FUNC:
                        generic_smp_call_function_interrupt();
                        break;

                case IPI_CPU_STOP:
                        /*
                         * call vmstop()
                         */
                        __vmstop();
                        break;

                case IPI_RESCHEDULE:
                        scheduler_ipi();
                        break;
                }
        } while (msg < BITS_PER_LONG);
}

/*  Used for IPI call from other CPU's to unmask int  */
void smp_vm_unmask_irq(void *info)
{
        __vmintop_locen((long) info);
}


/*
 * This is based on Alpha's IPI stuff.
 * Supposed to take (int, void*) as args now.
 * Specifically, first arg is irq, second is the irq_desc.
 */

static irqreturn_t handle_ipi(int irq, void *desc)
{
        int cpu = smp_processor_id();
        struct ipi_data *ipi = &per_cpu(ipi_data, cpu);
        unsigned long ops;

        while ((ops = xchg(&ipi->bits, 0)) != 0)
                __handle_ipi(&ops, ipi, cpu);
        return IRQ_HANDLED;
}

void send_ipi(const struct cpumask *cpumask, enum ipi_message_type msg)
{
        unsigned long flags;
        unsigned long cpu;
        unsigned long retval;

        local_irq_save(flags);

        for_each_cpu(cpu, cpumask) {
                struct ipi_data *ipi = &per_cpu(ipi_data, cpu);

                set_bit(msg, &ipi->bits);
                /*  Possible barrier here  */
                retval = __vmintop_post(BASE_IPI_IRQ+cpu);

                if (retval != 0) {
                        printk(KERN_ERR "interrupt %ld not configured?\n",
                                BASE_IPI_IRQ+cpu);
                }
        }

        local_irq_restore(flags);
}

/*
 * interrupts should already be disabled from the VM
 * SP should already be correct; need to set THREADINFO_REG
 * to point to current thread info
 */

static void start_secondary(void)
{
        unsigned long thread_ptr;
        unsigned int cpu, irq;

        /*  Calculate thread_info pointer from stack pointer  */
        __asm__ __volatile__(
                "%0 = SP;\n"
                : "=r" (thread_ptr)
        );

        thread_ptr = thread_ptr & ~(THREAD_SIZE-1);

        __asm__ __volatile__(
                QUOTED_THREADINFO_REG " = %0;\n"
                :
                : "r" (thread_ptr)
        );

        /*  Set the memory struct  */
        mmgrab(&init_mm);
        current->active_mm = &init_mm;

        cpu = smp_processor_id();

        irq = BASE_IPI_IRQ + cpu;
        if (request_irq(irq, handle_ipi, IRQF_TRIGGER_RISING, "ipi_handler",
                        NULL))
                pr_err("Failed to request irq %u (ipi_handler)\n", irq);

        /*  Register the clock_event dummy  */
        setup_percpu_clockdev();

        printk(KERN_INFO "%s cpu %d\n", __func__, current_thread_info()->cpu);

        notify_cpu_starting(cpu);

        set_cpu_online(cpu, true);

        local_irq_enable();

        cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
}


/*
 * called once for each present cpu
 * apparently starts up the CPU and then
 * maintains control until "cpu_online(cpu)" is set.
 */

int __cpu_up(unsigned int cpu, struct task_struct *idle)
{
        struct thread_info *thread = (struct thread_info *)idle->stack;
        void *stack_start;

        thread->cpu = cpu;

        /*  Boot to the head.  */
        stack_start =  ((void *) thread) + THREAD_SIZE;
        __vmstart(start_secondary, stack_start);

        while (!cpu_online(cpu))
                barrier();

        return 0;
}

void __init smp_cpus_done(unsigned int max_cpus)
{
}

void __init smp_prepare_cpus(unsigned int max_cpus)
{
        int i, irq = BASE_IPI_IRQ;

        /*
         * should eventually have some sort of machine
         * descriptor that has this stuff
         */

        /*  Right now, let's just fake it. */
        for (i = 0; i < max_cpus; i++)
                set_cpu_present(i, true);

        /*  Also need to register the interrupts for IPI  */
        if (max_cpus > 1) {
                if (request_irq(irq, handle_ipi, IRQF_TRIGGER_RISING,
                                "ipi_handler", NULL))
                        pr_err("Failed to request irq %d (ipi_handler)\n", irq);
        }
}

void arch_smp_send_reschedule(int cpu)
{
        send_ipi(cpumask_of(cpu), IPI_RESCHEDULE);
}

void smp_send_stop(void)
{
        struct cpumask targets;
        cpumask_copy(&targets, cpu_online_mask);
        cpumask_clear_cpu(smp_processor_id(), &targets);
        send_ipi(&targets, IPI_CPU_STOP);
}

void arch_send_call_function_single_ipi(int cpu)
{
        send_ipi(cpumask_of(cpu), IPI_CALL_FUNC);
}

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

void smp_start_cpus(void)
{
        int i;

        for (i = 0; i < NR_CPUS; i++)
                set_cpu_possible(i, true);
}