// SPDX-License-Identifier: GPL-2.0

#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/kernel_stat.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/percpu.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/irq.h>
#include <linux/irqdomain.h>
#include <linux/of.h>
#include <linux/sched/task_stack.h>
#include <linux/sched/mm.h>
#include <linux/sched/hotplug.h>
#include <asm/irq.h>
#include <asm/traps.h>
#include <asm/sections.h>
#include <asm/mmu_context.h>
#include <asm/pgalloc.h>

struct ipi_data_struct {
        unsigned long bits ____cacheline_aligned;
};
static DEFINE_PER_CPU(struct ipi_data_struct, ipi_data);

enum ipi_message_type {
        IPI_EMPTY,
        IPI_RESCHEDULE,
        IPI_CALL_FUNC,
        IPI_MAX
};

static irqreturn_t handle_ipi(int irq, void *dev)
{
        while (true) {
                unsigned long ops;

                ops = xchg(&this_cpu_ptr(&ipi_data)->bits, 0);
                if (ops == 0)
                        return IRQ_HANDLED;

                if (ops & (1 << IPI_RESCHEDULE))
                        scheduler_ipi();

                if (ops & (1 << IPI_CALL_FUNC))
                        generic_smp_call_function_interrupt();

                BUG_ON((ops >> IPI_MAX) != 0);
        }

        return IRQ_HANDLED;
}

static void (*send_arch_ipi)(const struct cpumask *mask);

static int ipi_irq;
void __init set_send_ipi(void (*func)(const struct cpumask *mask), int irq)
{
        if (send_arch_ipi)
                return;

        send_arch_ipi = func;
        ipi_irq = irq;
}

static void
send_ipi_message(const struct cpumask *to_whom, enum ipi_message_type operation)
{
        int i;

        for_each_cpu(i, to_whom)
                set_bit(operation, &per_cpu_ptr(&ipi_data, i)->bits);

        smp_mb();
        send_arch_ipi(to_whom);
}

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

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

static void ipi_stop(void *unused)
{
        while (1);
}

void smp_send_stop(void)
{
        on_each_cpu(ipi_stop, NULL, 1);
}

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

void __init smp_prepare_boot_cpu(void)
{
}

void __init smp_prepare_cpus(unsigned int max_cpus)
{
}

static int ipi_dummy_dev;

void __init setup_smp_ipi(void)
{
        int rc;

        if (ipi_irq == 0)
                panic("%s IRQ mapping failed\n", __func__);

        rc = request_percpu_irq(ipi_irq, handle_ipi, "IPI Interrupt",
                                &ipi_dummy_dev);
        if (rc)
                panic("%s IRQ request failed\n", __func__);

        enable_percpu_irq(ipi_irq, 0);
}

void __init setup_smp(void)
{
        struct device_node *node = NULL;
        int cpu;

        for_each_of_cpu_node(node) {
                if (!of_device_is_available(node))
                        continue;

                if (of_property_read_u32(node, "reg", &cpu))
                        continue;

                if (cpu >= NR_CPUS)
                        continue;

                set_cpu_possible(cpu, true);
                set_cpu_present(cpu, true);
        }
}

extern void _start_smp_secondary(void);

volatile unsigned int secondary_hint;
volatile unsigned int secondary_ccr;
volatile unsigned int secondary_stack;

int __cpu_up(unsigned int cpu, struct task_struct *tidle)
{
        unsigned long mask = 1 << cpu;

        secondary_stack =
                (unsigned int) task_stack_page(tidle) + THREAD_SIZE - 8;
        secondary_hint = mfcr("cr31");
        secondary_ccr  = mfcr("cr18");

        /*
         * Because other CPUs are in reset status, we must flush data
         * from cache to out and secondary CPUs use them in
         * csky_start_secondary(void)
         */
        mtcr("cr17", 0x22);

        if (mask & mfcr("cr<29, 0>")) {
                send_arch_ipi(cpumask_of(cpu));
        } else {
                /* Enable cpu in SMP reset ctrl reg */
                mask |= mfcr("cr<29, 0>");
                mtcr("cr<29, 0>", mask);
        }

        /* Wait for the cpu online */
        while (!cpu_online(cpu));

        secondary_stack = 0;

        return 0;
}

void __init smp_cpus_done(unsigned int max_cpus)
{
}

int setup_profiling_timer(unsigned int multiplier)
{
        return -EINVAL;
}

void csky_start_secondary(void)
{
        struct mm_struct *mm = &init_mm;
        unsigned int cpu = smp_processor_id();

        mtcr("cr31", secondary_hint);
        mtcr("cr18", secondary_ccr);

        mtcr("vbr", vec_base);

        flush_tlb_all();
        write_mmu_pagemask(0);
        TLBMISS_HANDLER_SETUP_PGD(swapper_pg_dir);
        TLBMISS_HANDLER_SETUP_PGD_KERNEL(swapper_pg_dir);

#ifdef CONFIG_CPU_HAS_FPU
        init_fpu();
#endif

        enable_percpu_irq(ipi_irq, 0);

        mmget(mm);
        mmgrab(mm);
        current->active_mm = mm;
        cpumask_set_cpu(cpu, mm_cpumask(mm));

        notify_cpu_starting(cpu);
        set_cpu_online(cpu, true);

        pr_info("CPU%u Online: %s...\n", cpu, __func__);

        local_irq_enable();
        preempt_disable();
        cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
}

#ifdef CONFIG_HOTPLUG_CPU
int __cpu_disable(void)
{
        unsigned int cpu = smp_processor_id();

        set_cpu_online(cpu, false);

        irq_migrate_all_off_this_cpu();

        clear_tasks_mm_cpumask(cpu);

        return 0;
}

void __cpu_die(unsigned int cpu)
{
        if (!cpu_wait_death(cpu, 5)) {
                pr_crit("CPU%u: shutdown failed\n", cpu);
                return;
        }
        pr_notice("CPU%u: shutdown\n", cpu);
}

void arch_cpu_idle_dead(void)
{
        idle_task_exit();

        cpu_report_death();

        while (!secondary_stack)
                arch_cpu_idle();

        local_irq_disable();

        asm volatile(
                "mov    sp, %0\n"
                "mov    r8, %0\n"
                "jmpi   csky_start_secondary"
                :
                : "r" (secondary_stack));
}
#endif