/*
 * Architecture specific (PPC64) functions for kexec based crash dumps.
 *
 * Copyright (C) 2005, IBM Corp.
 *
 * Created by: Haren Myneni
 *
 * This source code is licensed under the GNU General Public License,
 * Version 2.  See the file COPYING for more details.
 *
 */

#include <linux/kernel.h>
#include <linux/smp.h>
#include <linux/reboot.h>
#include <linux/kexec.h>
#include <linux/export.h>
#include <linux/crash_dump.h>
#include <linux/delay.h>
#include <linux/irq.h>
#include <linux/types.h>

#include <asm/processor.h>
#include <asm/machdep.h>
#include <asm/kexec.h>
#include <asm/kdump.h>
#include <asm/prom.h>
#include <asm/smp.h>
#include <asm/setjmp.h>
#include <asm/debug.h>

/*
 * The primary CPU waits a while for all secondary CPUs to enter. This is to
 * avoid sending an IPI if the secondary CPUs are entering
 * crash_kexec_secondary on their own (eg via a system reset).
 *
 * The secondary timeout has to be longer than the primary. Both timeouts are
 * in milliseconds.
 */
#define PRIMARY_TIMEOUT         500
#define SECONDARY_TIMEOUT       1000

#define IPI_TIMEOUT             10000
#define REAL_MODE_TIMEOUT       10000

/* This keeps a track of which one is the crashing cpu. */
int crashing_cpu = -1;
static int time_to_dump;

#define CRASH_HANDLER_MAX 3
/* List of shutdown handles */
static crash_shutdown_t crash_shutdown_handles[CRASH_HANDLER_MAX];
static DEFINE_SPINLOCK(crash_handlers_lock);

static unsigned long crash_shutdown_buf[JMP_BUF_LEN];
static int crash_shutdown_cpu = -1;

static int handle_fault(struct pt_regs *regs)
{
        if (crash_shutdown_cpu == smp_processor_id())
                longjmp(crash_shutdown_buf, 1);
        return 0;
}

#ifdef CONFIG_SMP

static atomic_t cpus_in_crash;
static void crash_ipi_callback(struct pt_regs *regs)
{
        static cpumask_t cpus_state_saved = CPU_MASK_NONE;

        int cpu = smp_processor_id();

        if (!cpu_online(cpu))
                return;

        hard_irq_disable();
        if (!cpumask_test_cpu(cpu, &cpus_state_saved)) {
                crash_save_cpu(regs, cpu);
                cpumask_set_cpu(cpu, &cpus_state_saved);
        }

        atomic_inc(&cpus_in_crash);
        smp_mb__after_atomic();

        /*
         * Starting the kdump boot.
         * This barrier is needed to make sure that all CPUs are stopped.
         */
        while (!time_to_dump)
                cpu_relax();

        if (ppc_md.kexec_cpu_down)
                ppc_md.kexec_cpu_down(1, 1);

#ifdef CONFIG_PPC64
        kexec_smp_wait();
#else
        for (;;);       /* FIXME */
#endif

        /* NOTREACHED */
}

static void crash_kexec_prepare_cpus(int cpu)
{
        unsigned int msecs;
        unsigned int ncpus = num_online_cpus() - 1;/* Excluding the panic cpu */
        int tries = 0;
        int (*old_handler)(struct pt_regs *regs);

        printk(KERN_EMERG "Sending IPI to other CPUs\n");

        crash_send_ipi(crash_ipi_callback);
        smp_wmb();

again:
        /*
         * FIXME: Until we will have the way to stop other CPUs reliably,
         * the crash CPU will send an IPI and wait for other CPUs to
         * respond.
         */
        msecs = IPI_TIMEOUT;
        while ((atomic_read(&cpus_in_crash) < ncpus) && (--msecs > 0))
                mdelay(1);

        /* Would it be better to replace the trap vector here? */

        if (atomic_read(&cpus_in_crash) >= ncpus) {
                printk(KERN_EMERG "IPI complete\n");
                return;
        }

        printk(KERN_EMERG "ERROR: %d cpu(s) not responding\n",
                ncpus - atomic_read(&cpus_in_crash));

        /*
         * If we have a panic timeout set then we can't wait indefinitely
         * for someone to activate system reset. We also give up on the
         * second time through if system reset fail to work.
         */
        if ((panic_timeout > 0) || (tries > 0))
                return;

        /*
         * A system reset will cause all CPUs to take an 0x100 exception.
         * The primary CPU returns here via setjmp, and the secondary
         * CPUs reexecute the crash_kexec_secondary path.
         */
        old_handler = __debugger;
        __debugger = handle_fault;
        crash_shutdown_cpu = smp_processor_id();

        if (setjmp(crash_shutdown_buf) == 0) {
                printk(KERN_EMERG "Activate system reset (dumprestart) "
                                  "to stop other cpu(s)\n");

                /*
                 * A system reset will force all CPUs to execute the
                 * crash code again. We need to reset cpus_in_crash so we
                 * wait for everyone to do this.
                 */
                atomic_set(&cpus_in_crash, 0);
                smp_mb();

                while (atomic_read(&cpus_in_crash) < ncpus)
                        cpu_relax();
        }

        crash_shutdown_cpu = -1;
        __debugger = old_handler;

        tries++;
        goto again;
}

/*
 * This function will be called by secondary cpus.
 */
void crash_kexec_secondary(struct pt_regs *regs)
{
        unsigned long flags;
        int msecs = SECONDARY_TIMEOUT;

        local_irq_save(flags);

        /* Wait for the primary crash CPU to signal its progress */
        while (crashing_cpu < 0) {
                if (--msecs < 0) {
                        /* No response, kdump image may not have been loaded */
                        local_irq_restore(flags);
                        return;
                }

                mdelay(1);
        }

        crash_ipi_callback(regs);
}

#else   /* ! CONFIG_SMP */

static void crash_kexec_prepare_cpus(int cpu)
{
        /*
         * move the secondaries to us so that we can copy
         * the new kernel 0-0x100 safely
         *
         * do this if kexec in setup.c ?
         */
#ifdef CONFIG_PPC64
        smp_release_cpus();
#else
        /* FIXME */
#endif
}

void crash_kexec_secondary(struct pt_regs *regs)
{
}
#endif  /* CONFIG_SMP */

/* wait for all the CPUs to hit real mode but timeout if they don't come in */
#if defined(CONFIG_SMP) && defined(CONFIG_PPC64)
static void __maybe_unused crash_kexec_wait_realmode(int cpu)
{
        unsigned int msecs;
        int i;

        msecs = REAL_MODE_TIMEOUT;
        for (i=0; i < nr_cpu_ids && msecs > 0; i++) {
                if (i == cpu)
                        continue;

                while (paca[i].kexec_state < KEXEC_STATE_REAL_MODE) {
                        barrier();
                        if (!cpu_possible(i) || !cpu_online(i) || (msecs <= 0))
                                break;
                        msecs--;
                        mdelay(1);
                }
        }
        mb();
}
#else
static inline void crash_kexec_wait_realmode(int cpu) {}
#endif  /* CONFIG_SMP && CONFIG_PPC64 */

/*
 * Register a function to be called on shutdown.  Only use this if you
 * can't reset your device in the second kernel.
 */
int crash_shutdown_register(crash_shutdown_t handler)
{
        unsigned int i, rc;

        spin_lock(&crash_handlers_lock);
        for (i = 0 ; i < CRASH_HANDLER_MAX; i++)
                if (!crash_shutdown_handles[i]) {
                        /* Insert handle at first empty entry */
                        crash_shutdown_handles[i] = handler;
                        rc = 0;
                        break;
                }

        if (i == CRASH_HANDLER_MAX) {
                printk(KERN_ERR "Crash shutdown handles full, "
                       "not registered.\n");
                rc = 1;
        }

        spin_unlock(&crash_handlers_lock);
        return rc;
}
EXPORT_SYMBOL(crash_shutdown_register);

int crash_shutdown_unregister(crash_shutdown_t handler)
{
        unsigned int i, rc;

        spin_lock(&crash_handlers_lock);
        for (i = 0 ; i < CRASH_HANDLER_MAX; i++)
                if (crash_shutdown_handles[i] == handler)
                        break;

        if (i == CRASH_HANDLER_MAX) {
                printk(KERN_ERR "Crash shutdown handle not found\n");
                rc = 1;
        } else {
                /* Shift handles down */
                for (; i < (CRASH_HANDLER_MAX - 1); i++)
                        crash_shutdown_handles[i] =
                                crash_shutdown_handles[i+1];
                /*
                 * Reset last entry to NULL now that it has been shifted down,
                 * this will allow new handles to be added here.
                 */
                crash_shutdown_handles[i] = NULL;
                rc = 0;
        }

        spin_unlock(&crash_handlers_lock);
        return rc;
}
EXPORT_SYMBOL(crash_shutdown_unregister);

void default_machine_crash_shutdown(struct pt_regs *regs)
{
        unsigned int i;
        int (*old_handler)(struct pt_regs *regs);

        /*
         * This function is only called after the system
         * has panicked or is otherwise in a critical state.
         * The minimum amount of code to allow a kexec'd kernel
         * to run successfully needs to happen here.
         *
         * In practice this means stopping other cpus in
         * an SMP system.
         * The kernel is broken so disable interrupts.
         */
        hard_irq_disable();

        /*
         * Make a note of crashing cpu. Will be used in machine_kexec
         * such that another IPI will not be sent.
         */
        crashing_cpu = smp_processor_id();

        /*
         * If we came in via system reset, wait a while for the secondary
         * CPUs to enter.
         */
        if (TRAP(regs) == 0x100)
                mdelay(PRIMARY_TIMEOUT);

        crash_kexec_prepare_cpus(crashing_cpu);

        crash_save_cpu(regs, crashing_cpu);

        time_to_dump = 1;

        crash_kexec_wait_realmode(crashing_cpu);

        machine_kexec_mask_interrupts();

        /*
         * Call registered shutdown routines safely.  Swap out
         * __debugger_fault_handler, and replace on exit.
         */
        old_handler = __debugger_fault_handler;
        __debugger_fault_handler = handle_fault;
        crash_shutdown_cpu = smp_processor_id();
        for (i = 0; i < CRASH_HANDLER_MAX && crash_shutdown_handles[i]; i++) {
                if (setjmp(crash_shutdown_buf) == 0) {
                        /*
                         * Insert syncs and delay to ensure
                         * instructions in the dangerous region don't
                         * leak away from this protected region.
                         */
                        asm volatile("sync; isync");
                        /* dangerous region */
                        crash_shutdown_handles[i]();
                        asm volatile("sync; isync");
                }
        }
        crash_shutdown_cpu = -1;
        __debugger_fault_handler = old_handler;

        if (ppc_md.kexec_cpu_down)
                ppc_md.kexec_cpu_down(1, 0);
}