/*
 * Copyright (C) 2013 Imagination Technologies
 * Author: Paul Burton <paul.burton@imgtec.com>
 *
 * 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/delay.h>
#include <linux/io.h>
#include <linux/irqchip/mips-gic.h>
#include <linux/sched/task_stack.h>
#include <linux/sched/hotplug.h>
#include <linux/slab.h>
#include <linux/smp.h>
#include <linux/types.h>

#include <asm/bcache.h>
#include <asm/mips-cm.h>
#include <asm/mips-cpc.h>
#include <asm/mips_mt.h>
#include <asm/mipsregs.h>
#include <asm/pm-cps.h>
#include <asm/r4kcache.h>
#include <asm/smp-cps.h>
#include <asm/time.h>
#include <asm/uasm.h>

static bool threads_disabled;
static DECLARE_BITMAP(core_power, NR_CPUS);

struct core_boot_config *mips_cps_core_bootcfg;

static int __init setup_nothreads(char *s)
{
        threads_disabled = true;
        return 0;
}
early_param("nothreads", setup_nothreads);

static unsigned core_vpe_count(unsigned core)
{
        unsigned cfg;

        if (threads_disabled)
                return 1;

        if ((!IS_ENABLED(CONFIG_MIPS_MT_SMP) || !cpu_has_mipsmt)
                && (!IS_ENABLED(CONFIG_CPU_MIPSR6) || !cpu_has_vp))
                return 1;

        mips_cm_lock_other(core, 0);
        cfg = read_gcr_co_config() & CM_GCR_Cx_CONFIG_PVPE_MSK;
        mips_cm_unlock_other();
        return (cfg >> CM_GCR_Cx_CONFIG_PVPE_SHF) + 1;
}

static void __init cps_smp_setup(void)
{
        unsigned int ncores, nvpes, core_vpes;
        unsigned long core_entry;
        int c, v;

        /* Detect & record VPE topology */
        ncores = mips_cm_numcores();
        pr_info("%s topology ", cpu_has_mips_r6 ? "VP" : "VPE");
        for (c = nvpes = 0; c < ncores; c++) {
                core_vpes = core_vpe_count(c);
                pr_cont("%c%u", c ? ',' : '{', core_vpes);

                /* Use the number of VPEs in core 0 for smp_num_siblings */
                if (!c)
                        smp_num_siblings = core_vpes;

                for (v = 0; v < min_t(int, core_vpes, NR_CPUS - nvpes); v++) {
                        cpu_data[nvpes + v].core = c;
#if defined(CONFIG_MIPS_MT_SMP) || defined(CONFIG_CPU_MIPSR6)
                        cpu_data[nvpes + v].vpe_id = v;
#endif
                }

                nvpes += core_vpes;
        }
        pr_cont("} total %u\n", nvpes);

        /* Indicate present CPUs (CPU being synonymous with VPE) */
        for (v = 0; v < min_t(unsigned, nvpes, NR_CPUS); v++) {
                set_cpu_possible(v, true);
                set_cpu_present(v, true);
                __cpu_number_map[v] = v;
                __cpu_logical_map[v] = v;
        }

        /* Set a coherent default CCA (CWB) */
        change_c0_config(CONF_CM_CMASK, 0x5);

        /* Core 0 is powered up (we're running on it) */
        bitmap_set(core_power, 0, 1);

        /* Initialise core 0 */
        mips_cps_core_init();

        /* Make core 0 coherent with everything */
        write_gcr_cl_coherence(0xff);

        if (mips_cm_revision() >= CM_REV_CM3) {
                core_entry = CKSEG1ADDR((unsigned long)mips_cps_core_entry);
                write_gcr_bev_base(core_entry);
        }

#ifdef CONFIG_MIPS_MT_FPAFF
        /* If we have an FPU, enroll ourselves in the FPU-full mask */
        if (cpu_has_fpu)
                cpumask_set_cpu(0, &mt_fpu_cpumask);
#endif /* CONFIG_MIPS_MT_FPAFF */
}

static void __init cps_prepare_cpus(unsigned int max_cpus)
{
        unsigned ncores, core_vpes, c, cca;
        bool cca_unsuitable;
        u32 *entry_code;

        mips_mt_set_cpuoptions();

        /* Detect whether the CCA is unsuited to multi-core SMP */
        cca = read_c0_config() & CONF_CM_CMASK;
        switch (cca) {
        case 0x4: /* CWBE */
        case 0x5: /* CWB */
                /* The CCA is coherent, multi-core is fine */
                cca_unsuitable = false;
                break;

        default:
                /* CCA is not coherent, multi-core is not usable */
                cca_unsuitable = true;
        }

        /* Warn the user if the CCA prevents multi-core */
        ncores = mips_cm_numcores();
        if (cca_unsuitable && ncores > 1) {
                pr_warn("Using only one core due to unsuitable CCA 0x%x\n",
                        cca);

                for_each_present_cpu(c) {
                        if (cpu_data[c].core)
                                set_cpu_present(c, false);
                }
        }

        /*
         * Patch the start of mips_cps_core_entry to provide:
         *
         * s0 = kseg0 CCA
         */
        entry_code = (u32 *)&mips_cps_core_entry;
        uasm_i_addiu(&entry_code, 16, 0, cca);
        blast_dcache_range((unsigned long)&mips_cps_core_entry,
                           (unsigned long)entry_code);
        bc_wback_inv((unsigned long)&mips_cps_core_entry,
                     (void *)entry_code - (void *)&mips_cps_core_entry);
        __sync();

        /* Allocate core boot configuration structs */
        mips_cps_core_bootcfg = kcalloc(ncores, sizeof(*mips_cps_core_bootcfg),
                                        GFP_KERNEL);
        if (!mips_cps_core_bootcfg) {
                pr_err("Failed to allocate boot config for %u cores\n", ncores);
                goto err_out;
        }

        /* Allocate VPE boot configuration structs */
        for (c = 0; c < ncores; c++) {
                core_vpes = core_vpe_count(c);
                mips_cps_core_bootcfg[c].vpe_config = kcalloc(core_vpes,
                                sizeof(*mips_cps_core_bootcfg[c].vpe_config),
                                GFP_KERNEL);
                if (!mips_cps_core_bootcfg[c].vpe_config) {
                        pr_err("Failed to allocate %u VPE boot configs\n",
                               core_vpes);
                        goto err_out;
                }
        }

        /* Mark this CPU as booted */
        atomic_set(&mips_cps_core_bootcfg[current_cpu_data.core].vpe_mask,
                   1 << cpu_vpe_id(&current_cpu_data));

        return;
err_out:
        /* Clean up allocations */
        if (mips_cps_core_bootcfg) {
                for (c = 0; c < ncores; c++)
                        kfree(mips_cps_core_bootcfg[c].vpe_config);
                kfree(mips_cps_core_bootcfg);
                mips_cps_core_bootcfg = NULL;
        }

        /* Effectively disable SMP by declaring CPUs not present */
        for_each_possible_cpu(c) {
                if (c == 0)
                        continue;
                set_cpu_present(c, false);
        }
}

static void boot_core(unsigned int core, unsigned int vpe_id)
{
        u32 access, stat, seq_state;
        unsigned timeout;

        /* Select the appropriate core */
        mips_cm_lock_other(core, 0);

        /* Set its reset vector */
        write_gcr_co_reset_base(CKSEG1ADDR((unsigned long)mips_cps_core_entry));

        /* Ensure its coherency is disabled */
        write_gcr_co_coherence(0);

        /* Start it with the legacy memory map and exception base */
        write_gcr_co_reset_ext_base(CM_GCR_RESET_EXT_BASE_UEB);

        /* Ensure the core can access the GCRs */
        access = read_gcr_access();
        access |= 1 << (CM_GCR_ACCESS_ACCESSEN_SHF + core);
        write_gcr_access(access);

        if (mips_cpc_present()) {
                /* Reset the core */
                mips_cpc_lock_other(core);

                if (mips_cm_revision() >= CM_REV_CM3) {
                        /* Run only the requested VP following the reset */
                        write_cpc_co_vp_stop(0xf);
                        write_cpc_co_vp_run(1 << vpe_id);

                        /*
                         * Ensure that the VP_RUN register is written before the
                         * core leaves reset.
                         */
                        wmb();
                }

                write_cpc_co_cmd(CPC_Cx_CMD_RESET);

                timeout = 100;
                while (true) {
                        stat = read_cpc_co_stat_conf();
                        seq_state = stat & CPC_Cx_STAT_CONF_SEQSTATE_MSK;

                        /* U6 == coherent execution, ie. the core is up */
                        if (seq_state == CPC_Cx_STAT_CONF_SEQSTATE_U6)
                                break;

                        /* Delay a little while before we start warning */
                        if (timeout) {
                                timeout--;
                                mdelay(10);
                                continue;
                        }

                        pr_warn("Waiting for core %u to start... STAT_CONF=0x%x\n",
                                core, stat);
                        mdelay(1000);
                }

                mips_cpc_unlock_other();
        } else {
                /* Take the core out of reset */
                write_gcr_co_reset_release(0);
        }

        mips_cm_unlock_other();

        /* The core is now powered up */
        bitmap_set(core_power, core, 1);
}

static void remote_vpe_boot(void *dummy)
{
        unsigned core = current_cpu_data.core;
        struct core_boot_config *core_cfg = &mips_cps_core_bootcfg[core];

        mips_cps_boot_vpes(core_cfg, cpu_vpe_id(&current_cpu_data));
}

static void cps_boot_secondary(int cpu, struct task_struct *idle)
{
        unsigned core = cpu_data[cpu].core;
        unsigned vpe_id = cpu_vpe_id(&cpu_data[cpu]);
        struct core_boot_config *core_cfg = &mips_cps_core_bootcfg[core];
        struct vpe_boot_config *vpe_cfg = &core_cfg->vpe_config[vpe_id];
        unsigned long core_entry;
        unsigned int remote;
        int err;

        vpe_cfg->pc = (unsigned long)&smp_bootstrap;
        vpe_cfg->sp = __KSTK_TOS(idle);
        vpe_cfg->gp = (unsigned long)task_thread_info(idle);

        atomic_or(1 << cpu_vpe_id(&cpu_data[cpu]), &core_cfg->vpe_mask);

        preempt_disable();

        if (!test_bit(core, core_power)) {
                /* Boot a VPE on a powered down core */
                boot_core(core, vpe_id);
                goto out;
        }

        if (cpu_has_vp) {
                mips_cm_lock_other(core, vpe_id);
                core_entry = CKSEG1ADDR((unsigned long)mips_cps_core_entry);
                write_gcr_co_reset_base(core_entry);
                mips_cm_unlock_other();
        }

        if (core != current_cpu_data.core) {
                /* Boot a VPE on another powered up core */
                for (remote = 0; remote < NR_CPUS; remote++) {
                        if (cpu_data[remote].core != core)
                                continue;
                        if (cpu_online(remote))
                                break;
                }
                if (remote >= NR_CPUS) {
                        pr_crit("No online CPU in core %u to start CPU%d\n",
                                core, cpu);
                        goto out;
                }

                err = smp_call_function_single(remote, remote_vpe_boot,
                                               NULL, 1);
                if (err)
                        panic("Failed to call remote CPU\n");
                goto out;
        }

        BUG_ON(!cpu_has_mipsmt && !cpu_has_vp);

        /* Boot a VPE on this core */
        mips_cps_boot_vpes(core_cfg, vpe_id);
out:
        preempt_enable();
}

static void cps_init_secondary(void)
{
        /* Disable MT - we only want to run 1 TC per VPE */
        if (cpu_has_mipsmt)
                dmt();

        if (mips_cm_revision() >= CM_REV_CM3) {
                unsigned ident = gic_read_local_vp_id();

                /*
                 * Ensure that our calculation of the VP ID matches up with
                 * what the GIC reports, otherwise we'll have configured
                 * interrupts incorrectly.
                 */
                BUG_ON(ident != mips_cm_vp_id(smp_processor_id()));
        }

        if (cpu_has_veic)
                clear_c0_status(ST0_IM);
        else
                change_c0_status(ST0_IM, STATUSF_IP2 | STATUSF_IP3 |
                                         STATUSF_IP4 | STATUSF_IP5 |
                                         STATUSF_IP6 | STATUSF_IP7);
}

static void cps_smp_finish(void)
{
        write_c0_compare(read_c0_count() + (8 * mips_hpt_frequency / HZ));

#ifdef CONFIG_MIPS_MT_FPAFF
        /* If we have an FPU, enroll ourselves in the FPU-full mask */
        if (cpu_has_fpu)
                cpumask_set_cpu(smp_processor_id(), &mt_fpu_cpumask);
#endif /* CONFIG_MIPS_MT_FPAFF */

        local_irq_enable();
}

#ifdef CONFIG_HOTPLUG_CPU

static int cps_cpu_disable(void)
{
        unsigned cpu = smp_processor_id();
        struct core_boot_config *core_cfg;

        if (!cpu)
                return -EBUSY;

        if (!cps_pm_support_state(CPS_PM_POWER_GATED))
                return -EINVAL;

        core_cfg = &mips_cps_core_bootcfg[current_cpu_data.core];
        atomic_sub(1 << cpu_vpe_id(&current_cpu_data), &core_cfg->vpe_mask);
        smp_mb__after_atomic();
        set_cpu_online(cpu, false);
        calculate_cpu_foreign_map();

        return 0;
}

static DECLARE_COMPLETION(cpu_death_chosen);
static unsigned cpu_death_sibling;
static enum {
        CPU_DEATH_HALT,
        CPU_DEATH_POWER,
} cpu_death;

void play_dead(void)
{
        unsigned int cpu, core, vpe_id;

        local_irq_disable();
        idle_task_exit();
        cpu = smp_processor_id();
        core = cpu_data[cpu].core;
        cpu_death = CPU_DEATH_POWER;

        pr_debug("CPU%d going offline\n", cpu);

        if (cpu_has_mipsmt || cpu_has_vp) {
                /* Look for another online VPE within the core */
                for_each_online_cpu(cpu_death_sibling) {
                        if (cpu_data[cpu_death_sibling].core != core)
                                continue;

                        /*
                         * There is an online VPE within the core. Just halt
                         * this TC and leave the core alone.
                         */
                        cpu_death = CPU_DEATH_HALT;
                        break;
                }
        }

        /* This CPU has chosen its way out */
        complete(&cpu_death_chosen);

        if (cpu_death == CPU_DEATH_HALT) {
                vpe_id = cpu_vpe_id(&cpu_data[cpu]);

                pr_debug("Halting core %d VP%d\n", core, vpe_id);
                if (cpu_has_mipsmt) {
                        /* Halt this TC */
                        write_c0_tchalt(TCHALT_H);
                        instruction_hazard();
                } else if (cpu_has_vp) {
                        write_cpc_cl_vp_stop(1 << vpe_id);

                        /* Ensure that the VP_STOP register is written */
                        wmb();
                }
        } else {
                pr_debug("Gating power to core %d\n", core);
                /* Power down the core */
                cps_pm_enter_state(CPS_PM_POWER_GATED);
        }

        /* This should never be reached */
        panic("Failed to offline CPU %u", cpu);
}

static void wait_for_sibling_halt(void *ptr_cpu)
{
        unsigned cpu = (unsigned long)ptr_cpu;
        unsigned vpe_id = cpu_vpe_id(&cpu_data[cpu]);
        unsigned halted;
        unsigned long flags;

        do {
                local_irq_save(flags);
                settc(vpe_id);
                halted = read_tc_c0_tchalt();
                local_irq_restore(flags);
        } while (!(halted & TCHALT_H));
}

static void cps_cpu_die(unsigned int cpu)
{
        unsigned core = cpu_data[cpu].core;
        unsigned int vpe_id = cpu_vpe_id(&cpu_data[cpu]);
        unsigned stat;
        int err;

        /* Wait for the cpu to choose its way out */
        if (!wait_for_completion_timeout(&cpu_death_chosen,
                                         msecs_to_jiffies(5000))) {
                pr_err("CPU%u: didn't offline\n", cpu);
                return;
        }

        /*
         * Now wait for the CPU to actually offline. Without doing this that
         * offlining may race with one or more of:
         *
         *   - Onlining the CPU again.
         *   - Powering down the core if another VPE within it is offlined.
         *   - A sibling VPE entering a non-coherent state.
         *
         * In the non-MT halt case (ie. infinite loop) the CPU is doing nothing
         * with which we could race, so do nothing.
         */
        if (cpu_death == CPU_DEATH_POWER) {
                /*
                 * Wait for the core to enter a powered down or clock gated
                 * state, the latter happening when a JTAG probe is connected
                 * in which case the CPC will refuse to power down the core.
                 */
                do {
                        mips_cm_lock_other(core, 0);
                        mips_cpc_lock_other(core);
                        stat = read_cpc_co_stat_conf();
                        stat &= CPC_Cx_STAT_CONF_SEQSTATE_MSK;
                        mips_cpc_unlock_other();
                        mips_cm_unlock_other();
                } while (stat != CPC_Cx_STAT_CONF_SEQSTATE_D0 &&
                         stat != CPC_Cx_STAT_CONF_SEQSTATE_D2 &&
                         stat != CPC_Cx_STAT_CONF_SEQSTATE_U2);

                /* Indicate the core is powered off */
                bitmap_clear(core_power, core, 1);
        } else if (cpu_has_mipsmt) {
                /*
                 * Have a CPU with access to the offlined CPUs registers wait
                 * for its TC to halt.
                 */
                err = smp_call_function_single(cpu_death_sibling,
                                               wait_for_sibling_halt,
                                               (void *)(unsigned long)cpu, 1);
                if (err)
                        panic("Failed to call remote sibling CPU\n");
        } else if (cpu_has_vp) {
                do {
                        mips_cm_lock_other(core, vpe_id);
                        stat = read_cpc_co_vp_running();
                        mips_cm_unlock_other();
                } while (stat & (1 << vpe_id));
        }
}

#endif /* CONFIG_HOTPLUG_CPU */

static struct plat_smp_ops cps_smp_ops = {
        .smp_setup              = cps_smp_setup,
        .prepare_cpus           = cps_prepare_cpus,
        .boot_secondary         = cps_boot_secondary,
        .init_secondary         = cps_init_secondary,
        .smp_finish             = cps_smp_finish,
        .send_ipi_single        = mips_smp_send_ipi_single,
        .send_ipi_mask          = mips_smp_send_ipi_mask,
#ifdef CONFIG_HOTPLUG_CPU
        .cpu_disable            = cps_cpu_disable,
        .cpu_die                = cps_cpu_die,
#endif
};

bool mips_cps_smp_in_use(void)
{
        extern struct plat_smp_ops *mp_ops;
        return mp_ops == &cps_smp_ops;
}

int register_cps_smp_ops(void)
{
        if (!mips_cm_present()) {
                pr_warn("MIPS CPS SMP unable to proceed without a CM\n");
                return -ENODEV;
        }

        /* check we have a GIC - we need one for IPIs */
        if (!(read_gcr_gic_status() & CM_GCR_GIC_STATUS_EX_MSK)) {
                pr_warn("MIPS CPS SMP unable to proceed without a GIC\n");
                return -ENODEV;
        }

        register_smp_ops(&cps_smp_ops);
        return 0;
}