// SPDX-License-Identifier: GPL-2.0-or-later
/*
** SMP Support
**
** Copyright (C) 1999 Walt Drummond <drummond@valinux.com>
** Copyright (C) 1999 David Mosberger-Tang <davidm@hpl.hp.com>
** Copyright (C) 2001,2004 Grant Grundler <grundler@parisc-linux.org>
** 
** Lots of stuff stolen from arch/alpha/kernel/smp.c
** ...and then parisc stole from arch/ia64/kernel/smp.c. Thanks David! :^)
**
** Thanks to John Curry and Ullas Ponnadi. I learned a lot from their work.
** -grant (1/12/2001)
**
*/
#include <linux/types.h>
#include <linux/spinlock.h>

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/sched/mm.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/smp.h>
#include <linux/kernel_stat.h>
#include <linux/mm.h>
#include <linux/err.h>
#include <linux/delay.h>
#include <linux/bitops.h>
#include <linux/ftrace.h>
#include <linux/cpu.h>
#include <linux/kgdb.h>
#include <linux/sched/hotplug.h>

#include <linux/atomic.h>
#include <asm/current.h>
#include <asm/delay.h>
#include <asm/tlbflush.h>

#include <asm/io.h>
#include <asm/irq.h>            /* for CPU_IRQ_REGION and friends */
#include <asm/mmu_context.h>
#include <asm/page.h>
#include <asm/processor.h>
#include <asm/ptrace.h>
#include <asm/unistd.h>
#include <asm/cacheflush.h>

#undef DEBUG_SMP
#ifdef DEBUG_SMP
static int smp_debug_lvl = 0;
#define smp_debug(lvl, printargs...)            \
                if (lvl >= smp_debug_lvl)       \
                        printk(printargs);
#else
#define smp_debug(lvl, ...)     do { } while(0)
#endif /* DEBUG_SMP */

volatile struct task_struct *smp_init_current_idle_task;

/* track which CPU is booting */
static volatile int cpu_now_booting;

static DEFINE_PER_CPU(spinlock_t, ipi_lock);

enum ipi_message_type {
        IPI_NOP=0,
        IPI_RESCHEDULE=1,
        IPI_CALL_FUNC,
        IPI_CPU_START,
        IPI_CPU_STOP,
        IPI_CPU_TEST,
#ifdef CONFIG_KGDB
        IPI_ENTER_KGDB,
#endif
};


/********** SMP inter processor interrupt and communication routines */

#undef PER_CPU_IRQ_REGION
#ifdef PER_CPU_IRQ_REGION
/* XXX REVISIT Ignore for now.
**    *May* need this "hook" to register IPI handler
**    once we have perCPU ExtIntr switch tables.
*/
static void
ipi_init(int cpuid)
{
#error verify IRQ_OFFSET(IPI_IRQ) is ipi_interrupt() in new IRQ region

        if(cpu_online(cpuid) )
        {
                switch_to_idle_task(current);
        }

        return;
}
#endif


/*
** Yoink this CPU from the runnable list... 
**
*/
static void
halt_processor(void) 
{
        /* REVISIT : redirect I/O Interrupts to another CPU? */
        /* REVISIT : does PM *know* this CPU isn't available? */
        set_cpu_online(smp_processor_id(), false);
        local_irq_disable();
        __pdc_cpu_rendezvous();
        for (;;)
                ;
}


irqreturn_t __irq_entry
ipi_interrupt(int irq, void *dev_id) 
{
        int this_cpu = smp_processor_id();
        struct cpuinfo_parisc *p = &per_cpu(cpu_data, this_cpu);
        unsigned long ops;
        unsigned long flags;

        for (;;) {
                spinlock_t *lock = &per_cpu(ipi_lock, this_cpu);
                spin_lock_irqsave(lock, flags);
                ops = p->pending_ipi;
                p->pending_ipi = 0;
                spin_unlock_irqrestore(lock, flags);

                mb(); /* Order bit clearing and data access. */

                if (!ops)
                    break;

                while (ops) {
                        unsigned long which = ffz(~ops);

                        ops &= ~(1 << which);

                        switch (which) {
                        case IPI_NOP:
                                smp_debug(100, KERN_DEBUG "CPU%d IPI_NOP\n", this_cpu);
                                break;
                                
                        case IPI_RESCHEDULE:
                                smp_debug(100, KERN_DEBUG "CPU%d IPI_RESCHEDULE\n", this_cpu);
                                inc_irq_stat(irq_resched_count);
                                scheduler_ipi();
                                break;

                        case IPI_CALL_FUNC:
                                smp_debug(100, KERN_DEBUG "CPU%d IPI_CALL_FUNC\n", this_cpu);
                                inc_irq_stat(irq_call_count);
                                generic_smp_call_function_interrupt();
                                break;

                        case IPI_CPU_START:
                                smp_debug(100, KERN_DEBUG "CPU%d IPI_CPU_START\n", this_cpu);
                                break;

                        case IPI_CPU_STOP:
                                smp_debug(100, KERN_DEBUG "CPU%d IPI_CPU_STOP\n", this_cpu);
                                halt_processor();
                                break;

                        case IPI_CPU_TEST:
                                smp_debug(100, KERN_DEBUG "CPU%d is alive!\n", this_cpu);
                                break;
#ifdef CONFIG_KGDB
                        case IPI_ENTER_KGDB:
                                smp_debug(100, KERN_DEBUG "CPU%d ENTER_KGDB\n", this_cpu);
                                kgdb_nmicallback(raw_smp_processor_id(), get_irq_regs());
                                break;
#endif
                        default:
                                printk(KERN_CRIT "Unknown IPI num on CPU%d: %lu\n",
                                        this_cpu, which);
                                return IRQ_NONE;
                        } /* Switch */

                        /* before doing more, let in any pending interrupts */
                        if (ops) {
                                local_irq_enable();
                                local_irq_disable();
                        }
                } /* while (ops) */
        }
        return IRQ_HANDLED;
}


static inline void
ipi_send(int cpu, enum ipi_message_type op)
{
        struct cpuinfo_parisc *p = &per_cpu(cpu_data, cpu);
        spinlock_t *lock = &per_cpu(ipi_lock, cpu);
        unsigned long flags;

        spin_lock_irqsave(lock, flags);
        p->pending_ipi |= 1 << op;
        gsc_writel(IPI_IRQ - CPU_IRQ_BASE, p->hpa);
        spin_unlock_irqrestore(lock, flags);
}

static void
send_IPI_mask(const struct cpumask *mask, enum ipi_message_type op)
{
        int cpu;

        for_each_cpu(cpu, mask)
                ipi_send(cpu, op);
}

static inline void
send_IPI_single(int dest_cpu, enum ipi_message_type op)
{
        BUG_ON(dest_cpu == NO_PROC_ID);

        ipi_send(dest_cpu, op);
}

static inline void
send_IPI_allbutself(enum ipi_message_type op)
{
        int i;

        preempt_disable();
        for_each_online_cpu(i) {
                if (i != smp_processor_id())
                        send_IPI_single(i, op);
        }
        preempt_enable();
}

#ifdef CONFIG_KGDB
void kgdb_roundup_cpus(void)
{
        send_IPI_allbutself(IPI_ENTER_KGDB);
}
#endif

inline void 
smp_send_stop(void)     { send_IPI_allbutself(IPI_CPU_STOP); }

void
arch_smp_send_reschedule(int cpu) { send_IPI_single(cpu, IPI_RESCHEDULE); }

void
smp_send_all_nop(void)
{
        send_IPI_allbutself(IPI_NOP);
}

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

void arch_send_call_function_single_ipi(int cpu)
{
        send_IPI_single(cpu, IPI_CALL_FUNC);
}

/*
 * Called by secondaries to update state and initialize CPU registers.
 */
static void
smp_cpu_init(int cpunum)
{
        /* Set modes and Enable floating point coprocessor */
        init_per_cpu(cpunum);

        disable_sr_hashing();

        mb();

        /* Well, support 2.4 linux scheme as well. */
        if (cpu_online(cpunum)) {
                extern void machine_halt(void); /* arch/parisc.../process.c */

                printk(KERN_CRIT "CPU#%d already initialized!\n", cpunum);
                machine_halt();
        }

        notify_cpu_starting(cpunum);

        set_cpu_online(cpunum, true);

        /* Initialise the idle task for this CPU */
        mmgrab(&init_mm);
        current->active_mm = &init_mm;
        BUG_ON(current->mm);
        enter_lazy_tlb(&init_mm, current);

        init_IRQ();   /* make sure no IRQs are enabled or pending */
        parisc_clockevent_init();
}


/*
 * Slaves start using C here. Indirectly called from smp_slave_stext.
 * Do what start_kernel() and main() do for boot strap processor (aka monarch)
 */
void smp_callin(unsigned long pdce_proc)
{
        int slave_id = cpu_now_booting;

#ifdef CONFIG_64BIT
        WARN_ON(((unsigned long)(PAGE0->mem_pdc_hi) << 32
                        | PAGE0->mem_pdc) != pdce_proc);
#endif

        smp_cpu_init(slave_id);

        flush_cache_all_local(); /* start with known state */
        flush_tlb_all_local(NULL);

        local_irq_enable();  /* Interrupts have been off until now */

        cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);

        /* NOTREACHED */
        panic("smp_callin() AAAAaaaaahhhh....\n");
}

/*
 * Bring one cpu online.
 */
static int smp_boot_one_cpu(int cpuid, struct task_struct *idle)
{
        const struct cpuinfo_parisc *p = &per_cpu(cpu_data, cpuid);
        long timeout;

#ifdef CONFIG_HOTPLUG_CPU
        int i;

        /* reset irq statistics for this CPU */
        memset(&per_cpu(irq_stat, cpuid), 0, sizeof(irq_cpustat_t));
        for (i = 0; i < NR_IRQS; i++) {
                struct irq_desc *desc = irq_to_desc(i);

                if (desc && desc->kstat_irqs)
                        *per_cpu_ptr(desc->kstat_irqs, cpuid) = (struct irqstat) { };
        }
#endif

        /* wait until last booting CPU has started. */
        while (cpu_now_booting)
                ;

        /* Let _start know what logical CPU we're booting
        ** (offset into init_tasks[],cpu_data[])
        */
        cpu_now_booting = cpuid;

        /* 
        ** boot strap code needs to know the task address since
        ** it also contains the process stack.
        */
        smp_init_current_idle_task = idle ;
        mb();

        printk(KERN_INFO "Releasing cpu %d now, hpa=%lx\n", cpuid, p->hpa);

        /*
        ** This gets PDC to release the CPU from a very tight loop.
        **
        ** From the PA-RISC 2.0 Firmware Architecture Reference Specification:
        ** "The MEM_RENDEZ vector specifies the location of OS_RENDEZ which 
        ** is executed after receiving the rendezvous signal (an interrupt to 
        ** EIR{0}). MEM_RENDEZ is valid only when it is nonzero and the 
        ** contents of memory are valid."
        */
        gsc_writel(TIMER_IRQ - CPU_IRQ_BASE, p->hpa);
        mb();

        /* 
         * OK, wait a bit for that CPU to finish staggering about. 
         * Slave will set a bit when it reaches smp_cpu_init().
         * Once the "monarch CPU" sees the bit change, it can move on.
         */
        for (timeout = 0; timeout < 10000; timeout++) {
                if(cpu_online(cpuid)) {
                        /* Which implies Slave has started up */
                        cpu_now_booting = 0;
                        goto alive ;
                }
                udelay(100);
                barrier();
        }
        printk(KERN_CRIT "SMP: CPU:%d is stuck.\n", cpuid);
        return -1;

alive:
        /* Remember the Slave data */
        smp_debug(100, KERN_DEBUG "SMP: CPU:%d came alive after %ld _us\n",
                cpuid, timeout * 100);
        return 0;
}

void __init smp_prepare_boot_cpu(void)
{
        pr_info("SMP: bootstrap CPU ID is 0\n");
}



/*
** inventory.c:do_inventory() hasn't yet been run and thus we
** don't 'discover' the additional CPUs until later.
*/
void __init smp_prepare_cpus(unsigned int max_cpus)
{
        int cpu;

        for_each_possible_cpu(cpu)
                spin_lock_init(&per_cpu(ipi_lock, cpu));

        init_cpu_present(cpumask_of(0));
}


void __init smp_cpus_done(unsigned int cpu_max)
{
}


int __cpu_up(unsigned int cpu, struct task_struct *tidle)
{
        if (cpu_online(cpu))
                return 0;

        if (num_online_cpus() < nr_cpu_ids &&
                num_online_cpus() < setup_max_cpus &&
                smp_boot_one_cpu(cpu, tidle))
                return -EIO;

        return cpu_online(cpu) ? 0 : -EIO;
}

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

        remove_cpu_topology(cpu);

        /*
         * 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);

        /* Find a new timesync master */
        if (cpu == time_keeper_id) {
                time_keeper_id = cpumask_first(cpu_online_mask);
                pr_info("CPU %d is now promoted to time-keeper master\n", time_keeper_id);
        }

        disable_percpu_irq(IPI_IRQ);

        irq_migrate_all_off_this_cpu();

        flush_cache_all_local();
        flush_tlb_all_local(NULL);

        /* disable all irqs, including timer irq */
        local_irq_disable();

        /* wait for next timer irq ... */
        mdelay(1000/HZ+100);

        /* ... and then clear all pending external irqs */
        set_eiem(0);
        mtctl(~0UL, CR_EIRR);
        mfctl(CR_EIRR);
        mtctl(0, CR_EIRR);
#endif
        return 0;
}

/*
 * 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)
{
        pdc_cpu_rendezvous_lock();
}

void arch_cpuhp_cleanup_dead_cpu(unsigned int cpu)
{
        pr_info("CPU%u: is shutting down\n", cpu);

        /* set task's state to interruptible sleep */
        set_current_state(TASK_INTERRUPTIBLE);
        schedule_timeout((IS_ENABLED(CONFIG_64BIT) ? 8:2) * HZ);

        pdc_cpu_rendezvous_unlock();
}