/*
 * SMP support for pSeries machines.
 *
 * Dave Engebretsen, Peter Bergner, and
 * Mike Corrigan {engebret|bergner|mikec}@us.ibm.com
 *
 * Plus various changes from other IBM teams...
 *
 *      This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 */


#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/smp.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/cache.h>
#include <linux/err.h>
#include <linux/device.h>
#include <linux/cpu.h>

#include <asm/ptrace.h>
#include <linux/atomic.h>
#include <asm/irq.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/io.h>
#include <asm/prom.h>
#include <asm/smp.h>
#include <asm/paca.h>
#include <asm/machdep.h>
#include <asm/cputable.h>
#include <asm/firmware.h>
#include <asm/rtas.h>
#include <asm/vdso_datapage.h>
#include <asm/cputhreads.h>
#include <asm/xics.h>
#include <asm/xive.h>
#include <asm/dbell.h>
#include <asm/plpar_wrappers.h>
#include <asm/code-patching.h>
#include <asm/svm.h>

#include "pseries.h"
#include "offline_states.h"


/*
 * The Primary thread of each non-boot processor was started from the OF client
 * interface by prom_hold_cpus and is spinning on secondary_hold_spinloop.
 */
static cpumask_var_t of_spin_mask;

/* Query where a cpu is now.  Return codes #defined in plpar_wrappers.h */
int smp_query_cpu_stopped(unsigned int pcpu)
{
        int cpu_status, status;
        int qcss_tok = rtas_token("query-cpu-stopped-state");

        if (qcss_tok == RTAS_UNKNOWN_SERVICE) {
                printk_once(KERN_INFO
                        "Firmware doesn't support query-cpu-stopped-state\n");
                return QCSS_HARDWARE_ERROR;
        }

        status = rtas_call(qcss_tok, 1, 2, &cpu_status, pcpu);
        if (status != 0) {
                printk(KERN_ERR
                       "RTAS query-cpu-stopped-state failed: %i\n", status);
                return status;
        }

        return cpu_status;
}

/**
 * smp_startup_cpu() - start the given cpu
 *
 * At boot time, there is nothing to do for primary threads which were
 * started from Open Firmware.  For anything else, call RTAS with the
 * appropriate start location.
 *
 * Returns:
 *      0       - failure
 *      1       - success
 */
static inline int smp_startup_cpu(unsigned int lcpu)
{
        int status;
        unsigned long start_here =
                        __pa(ppc_function_entry(generic_secondary_smp_init));
        unsigned int pcpu;
        int start_cpu;

        if (cpumask_test_cpu(lcpu, of_spin_mask))
                /* Already started by OF and sitting in spin loop */
                return 1;

        pcpu = get_hard_smp_processor_id(lcpu);

        /* Check to see if the CPU out of FW already for kexec */
        if (smp_query_cpu_stopped(pcpu) == QCSS_NOT_STOPPED){
                cpumask_set_cpu(lcpu, of_spin_mask);
                return 1;
        }

        /* Fixup atomic count: it exited inside IRQ handler. */
        task_thread_info(paca_ptrs[lcpu]->__current)->preempt_count     = 0;
#ifdef CONFIG_HOTPLUG_CPU
        if (get_cpu_current_state(lcpu) == CPU_STATE_INACTIVE)
                goto out;
#endif
        /* 
         * If the RTAS start-cpu token does not exist then presume the
         * cpu is already spinning.
         */
        start_cpu = rtas_token("start-cpu");
        if (start_cpu == RTAS_UNKNOWN_SERVICE)
                return 1;

        status = rtas_call(start_cpu, 3, 1, NULL, pcpu, start_here, pcpu);
        if (status != 0) {
                printk(KERN_ERR "start-cpu failed: %i\n", status);
                return 0;
        }

#ifdef CONFIG_HOTPLUG_CPU
out:
#endif
        return 1;
}

static void smp_setup_cpu(int cpu)
{
        if (xive_enabled())
                xive_smp_setup_cpu();
        else if (cpu != boot_cpuid)
                xics_setup_cpu();

        if (firmware_has_feature(FW_FEATURE_SPLPAR))
                vpa_init(cpu);

        cpumask_clear_cpu(cpu, of_spin_mask);
#ifdef CONFIG_HOTPLUG_CPU
        set_cpu_current_state(cpu, CPU_STATE_ONLINE);
        set_default_offline_state(cpu);
#endif
}

static int smp_pSeries_kick_cpu(int nr)
{
        if (nr < 0 || nr >= nr_cpu_ids)
                return -EINVAL;

        if (!smp_startup_cpu(nr))
                return -ENOENT;

        /*
         * The processor is currently spinning, waiting for the
         * cpu_start field to become non-zero After we set cpu_start,
         * the processor will continue on to secondary_start
         */
        paca_ptrs[nr]->cpu_start = 1;
#ifdef CONFIG_HOTPLUG_CPU
        set_preferred_offline_state(nr, CPU_STATE_ONLINE);

        if (get_cpu_current_state(nr) == CPU_STATE_INACTIVE) {
                long rc;
                unsigned long hcpuid;

                hcpuid = get_hard_smp_processor_id(nr);
                rc = plpar_hcall_norets(H_PROD, hcpuid);
                if (rc != H_SUCCESS)
                        printk(KERN_ERR "Error: Prod to wake up processor %d "
                                                "Ret= %ld\n", nr, rc);
        }
#endif

        return 0;
}

static int pseries_smp_prepare_cpu(int cpu)
{
        if (xive_enabled())
                return xive_smp_prepare_cpu(cpu);
        return 0;
}

/* Cause IPI as setup by the interrupt controller (xics or xive) */
static void (*ic_cause_ipi)(int cpu) __ro_after_init;

/* Use msgsndp doorbells target is a sibling, else use interrupt controller */
static void dbell_or_ic_cause_ipi(int cpu)
{
        if (doorbell_try_core_ipi(cpu))
                return;

        ic_cause_ipi(cpu);
}

static int pseries_cause_nmi_ipi(int cpu)
{
        int hwcpu;

        if (cpu == NMI_IPI_ALL_OTHERS) {
                hwcpu = H_SIGNAL_SYS_RESET_ALL_OTHERS;
        } else {
                if (cpu < 0) {
                        WARN_ONCE(true, "incorrect cpu parameter %d", cpu);
                        return 0;
                }

                hwcpu = get_hard_smp_processor_id(cpu);
        }

        if (plpar_signal_sys_reset(hwcpu) == H_SUCCESS)
                return 1;

        return 0;
}

static __init void pSeries_smp_probe(void)
{
        if (xive_enabled())
                xive_smp_probe();
        else
                xics_smp_probe();

        /* No doorbell facility, must use the interrupt controller for IPIs */
        if (!cpu_has_feature(CPU_FTR_DBELL))
                return;

        /* Doorbells can only be used for IPIs between SMT siblings */
        if (!cpu_has_feature(CPU_FTR_SMT))
                return;

        if (is_kvm_guest()) {
                /*
                 * KVM emulates doorbells by disabling FSCR[MSGP] so msgsndp
                 * faults to the hypervisor which then reads the instruction
                 * from guest memory, which tends to be slower than using XIVE.
                 */
                if (xive_enabled())
                        return;

                /*
                 * XICS hcalls aren't as fast, so we can use msgsndp (which
                 * also helps exercise KVM emulation), however KVM can't
                 * emulate secure guests because it can't read the instruction
                 * out of their memory.
                 */
                if (is_secure_guest())
                        return;
        }

        /*
         * Under PowerVM, FSCR[MSGP] is enabled as guest vCPU siblings are
         * gang scheduled on the same physical core, so doorbells are always
         * faster than the interrupt controller, and they can be used by
         * secure guests.
         */

        ic_cause_ipi = smp_ops->cause_ipi;
        smp_ops->cause_ipi = dbell_or_ic_cause_ipi;
}

static struct smp_ops_t pseries_smp_ops = {
        .message_pass   = NULL, /* Use smp_muxed_ipi_message_pass */
        .cause_ipi      = NULL, /* Filled at runtime by pSeries_smp_probe() */
        .cause_nmi_ipi  = pseries_cause_nmi_ipi,
        .probe          = pSeries_smp_probe,
        .prepare_cpu    = pseries_smp_prepare_cpu,
        .kick_cpu       = smp_pSeries_kick_cpu,
        .setup_cpu      = smp_setup_cpu,
        .cpu_bootable   = smp_generic_cpu_bootable,
};

/* This is called very early */
void __init smp_init_pseries(void)
{
        int i;

        pr_debug(" -> smp_init_pSeries()\n");
        smp_ops = &pseries_smp_ops;

        alloc_bootmem_cpumask_var(&of_spin_mask);

        /*
         * Mark threads which are still spinning in hold loops
         *
         * We know prom_init will not have started them if RTAS supports
         * query-cpu-stopped-state.
         */
        if (rtas_token("query-cpu-stopped-state") == RTAS_UNKNOWN_SERVICE) {
                if (cpu_has_feature(CPU_FTR_SMT)) {
                        for_each_present_cpu(i) {
                                if (cpu_thread_in_core(i) == 0)
                                        cpumask_set_cpu(i, of_spin_mask);
                        }
                } else
                        cpumask_copy(of_spin_mask, cpu_present_mask);

                cpumask_clear_cpu(boot_cpuid, of_spin_mask);
        }

        /* Non-lpar has additional take/give timebase */
        if (rtas_token("freeze-time-base") != RTAS_UNKNOWN_SERVICE) {
                smp_ops->give_timebase = rtas_give_timebase;
                smp_ops->take_timebase = rtas_take_timebase;
        }

        pr_debug(" <- smp_init_pSeries()\n");
}