/*
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Copyright (C) 2011 by Kevin Cernekee (cernekee@gmail.com)
 *
 * SMP support for BMIPS
 */

#include <linux/init.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/delay.h>
#include <linux/smp.h>
#include <linux/interrupt.h>
#include <linux/spinlock.h>
#include <linux/cpu.h>
#include <linux/cpumask.h>
#include <linux/reboot.h>
#include <linux/io.h>
#include <linux/compiler.h>
#include <linux/linkage.h>
#include <linux/bug.h>
#include <linux/kernel.h>

#include <asm/time.h>
#include <asm/pgtable.h>
#include <asm/processor.h>
#include <asm/bootinfo.h>
#include <asm/pmon.h>
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>
#include <asm/mipsregs.h>
#include <asm/bmips.h>
#include <asm/traps.h>
#include <asm/barrier.h>
#include <asm/cpu-features.h>

static int __maybe_unused max_cpus = 1;

/* these may be configured by the platform code */
int bmips_smp_enabled = 1;
int bmips_cpu_offset;
cpumask_t bmips_booted_mask;
unsigned long bmips_tp1_irqs = IE_IRQ1;

#define RESET_FROM_KSEG0                0x80080800
#define RESET_FROM_KSEG1                0xa0080800

static void bmips_set_reset_vec(int cpu, u32 val);

#ifdef CONFIG_SMP

/* initial $sp, $gp - used by arch/mips/kernel/bmips_vec.S */
unsigned long bmips_smp_boot_sp;
unsigned long bmips_smp_boot_gp;

static void bmips43xx_send_ipi_single(int cpu, unsigned int action);
static void bmips5000_send_ipi_single(int cpu, unsigned int action);
static irqreturn_t bmips43xx_ipi_interrupt(int irq, void *dev_id);
static irqreturn_t bmips5000_ipi_interrupt(int irq, void *dev_id);

/* SW interrupts 0,1 are used for interprocessor signaling */
#define IPI0_IRQ                        (MIPS_CPU_IRQ_BASE + 0)
#define IPI1_IRQ                        (MIPS_CPU_IRQ_BASE + 1)

#define CPUNUM(cpu, shift)              (((cpu) + bmips_cpu_offset) << (shift))
#define ACTION_CLR_IPI(cpu, ipi)        (0x2000 | CPUNUM(cpu, 9) | ((ipi) << 8))
#define ACTION_SET_IPI(cpu, ipi)        (0x3000 | CPUNUM(cpu, 9) | ((ipi) << 8))
#define ACTION_BOOT_THREAD(cpu)         (0x08 | CPUNUM(cpu, 0))

static void __init bmips_smp_setup(void)
{
        int i, cpu = 1, boot_cpu = 0;
        int cpu_hw_intr;

        switch (current_cpu_type()) {
        case CPU_BMIPS4350:
        case CPU_BMIPS4380:
                /* arbitration priority */
                clear_c0_brcm_cmt_ctrl(0x30);

                /* NBK and weak order flags */
                set_c0_brcm_config_0(0x30000);

                /* Find out if we are running on TP0 or TP1 */
                boot_cpu = !!(read_c0_brcm_cmt_local() & (1 << 31));

                /*
                 * MIPS interrupts 0,1 (SW INT 0,1) cross over to the other
                 * thread
                 * MIPS interrupt 2 (HW INT 0) is the CPU0 L1 controller output
                 * MIPS interrupt 3 (HW INT 1) is the CPU1 L1 controller output
                 */
                if (boot_cpu == 0)
                        cpu_hw_intr = 0x02;
                else
                        cpu_hw_intr = 0x1d;

                change_c0_brcm_cmt_intr(0xf8018000,
                                        (cpu_hw_intr << 27) | (0x03 << 15));

                /* single core, 2 threads (2 pipelines) */
                max_cpus = 2;

                break;
        case CPU_BMIPS5000:
                /* enable raceless SW interrupts */
                set_c0_brcm_config(0x03 << 22);

                /* route HW interrupt 0 to CPU0, HW interrupt 1 to CPU1 */
                change_c0_brcm_mode(0x1f << 27, 0x02 << 27);

                /* N cores, 2 threads per core */
                max_cpus = (((read_c0_brcm_config() >> 6) & 0x03) + 1) << 1;

                /* clear any pending SW interrupts */
                for (i = 0; i < max_cpus; i++) {
                        write_c0_brcm_action(ACTION_CLR_IPI(i, 0));
                        write_c0_brcm_action(ACTION_CLR_IPI(i, 1));
                }

                break;
        default:
                max_cpus = 1;
        }

        if (!bmips_smp_enabled)
                max_cpus = 1;

        /* this can be overridden by the BSP */
        if (!board_ebase_setup)
                board_ebase_setup = &bmips_ebase_setup;

        __cpu_number_map[boot_cpu] = 0;
        __cpu_logical_map[0] = boot_cpu;

        for (i = 0; i < max_cpus; i++) {
                if (i != boot_cpu) {
                        __cpu_number_map[i] = cpu;
                        __cpu_logical_map[cpu] = i;
                        cpu++;
                }
                set_cpu_possible(i, 1);
                set_cpu_present(i, 1);
        }
}

/*
 * IPI IRQ setup - runs on CPU0
 */
static void bmips_prepare_cpus(unsigned int max_cpus)
{
        irqreturn_t (*bmips_ipi_interrupt)(int irq, void *dev_id);

        switch (current_cpu_type()) {
        case CPU_BMIPS4350:
        case CPU_BMIPS4380:
                bmips_ipi_interrupt = bmips43xx_ipi_interrupt;
                break;
        case CPU_BMIPS5000:
                bmips_ipi_interrupt = bmips5000_ipi_interrupt;
                break;
        default:
                return;
        }

        if (request_irq(IPI0_IRQ, bmips_ipi_interrupt, IRQF_PERCPU,
                        "smp_ipi0", NULL))
                panic("Can't request IPI0 interrupt");
        if (request_irq(IPI1_IRQ, bmips_ipi_interrupt, IRQF_PERCPU,
                        "smp_ipi1", NULL))
                panic("Can't request IPI1 interrupt");
}

/*
 * Tell the hardware to boot CPUx - runs on CPU0
 */
static void bmips_boot_secondary(int cpu, struct task_struct *idle)
{
        bmips_smp_boot_sp = __KSTK_TOS(idle);
        bmips_smp_boot_gp = (unsigned long)task_thread_info(idle);
        mb();

        /*
         * Initial boot sequence for secondary CPU:
         *   bmips_reset_nmi_vec @ a000_0000 ->
         *   bmips_smp_entry ->
         *   plat_wired_tlb_setup (cached function call; optional) ->
         *   start_secondary (cached jump)
         *
         * Warm restart sequence:
         *   play_dead WAIT loop ->
         *   bmips_smp_int_vec @ BMIPS_WARM_RESTART_VEC ->
         *   eret to play_dead ->
         *   bmips_secondary_reentry ->
         *   start_secondary
         */

        pr_info("SMP: Booting CPU%d...\n", cpu);

        if (cpumask_test_cpu(cpu, &bmips_booted_mask)) {
                /* kseg1 might not exist if this CPU enabled XKS01 */
                bmips_set_reset_vec(cpu, RESET_FROM_KSEG0);

                switch (current_cpu_type()) {
                case CPU_BMIPS4350:
                case CPU_BMIPS4380:
                        bmips43xx_send_ipi_single(cpu, 0);
                        break;
                case CPU_BMIPS5000:
                        bmips5000_send_ipi_single(cpu, 0);
                        break;
                }
        } else {
                bmips_set_reset_vec(cpu, RESET_FROM_KSEG1);

                switch (current_cpu_type()) {
                case CPU_BMIPS4350:
                case CPU_BMIPS4380:
                        /* Reset slave TP1 if booting from TP0 */
                        if (cpu_logical_map(cpu) == 1)
                                set_c0_brcm_cmt_ctrl(0x01);
                        break;
                case CPU_BMIPS5000:
                        write_c0_brcm_action(ACTION_BOOT_THREAD(cpu));
                        break;
                }
                cpumask_set_cpu(cpu, &bmips_booted_mask);
        }
}

/*
 * Early setup - runs on secondary CPU after cache probe
 */
static void bmips_init_secondary(void)
{
        switch (current_cpu_type()) {
        case CPU_BMIPS4350:
        case CPU_BMIPS4380:
                clear_c0_cause(smp_processor_id() ? C_SW1 : C_SW0);
                break;
        case CPU_BMIPS5000:
                write_c0_brcm_action(ACTION_CLR_IPI(smp_processor_id(), 0));
                break;
        }
}

/*
 * Late setup - runs on secondary CPU before entering the idle loop
 */
static void bmips_smp_finish(void)
{
        pr_info("SMP: CPU%d is running\n", smp_processor_id());

        /* make sure there won't be a timer interrupt for a little while */
        write_c0_compare(read_c0_count() + mips_hpt_frequency / HZ);

        irq_enable_hazard();
        set_c0_status(IE_SW0 | IE_SW1 | bmips_tp1_irqs | IE_IRQ5 | ST0_IE);
        irq_enable_hazard();
}

/*
 * BMIPS5000 raceless IPIs
 *
 * Each CPU has two inbound SW IRQs which are independent of all other CPUs.
 * IPI0 is used for SMP_RESCHEDULE_YOURSELF
 * IPI1 is used for SMP_CALL_FUNCTION
 */

static void bmips5000_send_ipi_single(int cpu, unsigned int action)
{
        write_c0_brcm_action(ACTION_SET_IPI(cpu, action == SMP_CALL_FUNCTION));
}

static irqreturn_t bmips5000_ipi_interrupt(int irq, void *dev_id)
{
        int action = irq - IPI0_IRQ;

        write_c0_brcm_action(ACTION_CLR_IPI(smp_processor_id(), action));

        if (action == 0)
                scheduler_ipi();
        else
                generic_smp_call_function_interrupt();

        return IRQ_HANDLED;
}

static void bmips5000_send_ipi_mask(const struct cpumask *mask,
        unsigned int action)
{
        unsigned int i;

        for_each_cpu(i, mask)
                bmips5000_send_ipi_single(i, action);
}

/*
 * BMIPS43xx racey IPIs
 *
 * We use one inbound SW IRQ for each CPU.
 *
 * A spinlock must be held in order to keep CPUx from accidentally clearing
 * an incoming IPI when it writes CP0 CAUSE to raise an IPI on CPUy.  The
 * same spinlock is used to protect the action masks.
 */

static DEFINE_SPINLOCK(ipi_lock);
static DEFINE_PER_CPU(int, ipi_action_mask);

static void bmips43xx_send_ipi_single(int cpu, unsigned int action)
{
        unsigned long flags;

        spin_lock_irqsave(&ipi_lock, flags);
        set_c0_cause(cpu ? C_SW1 : C_SW0);
        per_cpu(ipi_action_mask, cpu) |= action;
        irq_enable_hazard();
        spin_unlock_irqrestore(&ipi_lock, flags);
}

static irqreturn_t bmips43xx_ipi_interrupt(int irq, void *dev_id)
{
        unsigned long flags;
        int action, cpu = irq - IPI0_IRQ;

        spin_lock_irqsave(&ipi_lock, flags);
        action = __this_cpu_read(ipi_action_mask);
        per_cpu(ipi_action_mask, cpu) = 0;
        clear_c0_cause(cpu ? C_SW1 : C_SW0);
        spin_unlock_irqrestore(&ipi_lock, flags);

        if (action & SMP_RESCHEDULE_YOURSELF)
                scheduler_ipi();
        if (action & SMP_CALL_FUNCTION)
                generic_smp_call_function_interrupt();

        return IRQ_HANDLED;
}

static void bmips43xx_send_ipi_mask(const struct cpumask *mask,
        unsigned int action)
{
        unsigned int i;

        for_each_cpu(i, mask)
                bmips43xx_send_ipi_single(i, action);
}

#ifdef CONFIG_HOTPLUG_CPU

static int bmips_cpu_disable(void)
{
        unsigned int cpu = smp_processor_id();

        if (cpu == 0)
                return -EBUSY;

        pr_info("SMP: CPU%d is offline\n", cpu);

        set_cpu_online(cpu, false);
        cpumask_clear_cpu(cpu, &cpu_callin_map);
        clear_c0_status(IE_IRQ5);

        local_flush_tlb_all();
        local_flush_icache_range(0, ~0);

        return 0;
}

static void bmips_cpu_die(unsigned int cpu)
{
}

void __ref play_dead(void)
{
        idle_task_exit();

        /* flush data cache */
        _dma_cache_wback_inv(0, ~0);

        /*
         * Wakeup is on SW0 or SW1; disable everything else
         * Use BEV !IV (BMIPS_WARM_RESTART_VEC) to avoid the regular Linux
         * IRQ handlers; this clears ST0_IE and returns immediately.
         */
        clear_c0_cause(CAUSEF_IV | C_SW0 | C_SW1);
        change_c0_status(
                IE_IRQ5 | bmips_tp1_irqs | IE_SW0 | IE_SW1 | ST0_IE | ST0_BEV,
                IE_SW0 | IE_SW1 | ST0_IE | ST0_BEV);
        irq_disable_hazard();

        /*
         * wait for SW interrupt from bmips_boot_secondary(), then jump
         * back to start_secondary()
         */
        __asm__ __volatile__(
        "       wait\n"
        "       j       bmips_secondary_reentry\n"
        : : : "memory");
}

#endif /* CONFIG_HOTPLUG_CPU */

struct plat_smp_ops bmips43xx_smp_ops = {
        .smp_setup              = bmips_smp_setup,
        .prepare_cpus           = bmips_prepare_cpus,
        .boot_secondary         = bmips_boot_secondary,
        .smp_finish             = bmips_smp_finish,
        .init_secondary         = bmips_init_secondary,
        .send_ipi_single        = bmips43xx_send_ipi_single,
        .send_ipi_mask          = bmips43xx_send_ipi_mask,
#ifdef CONFIG_HOTPLUG_CPU
        .cpu_disable            = bmips_cpu_disable,
        .cpu_die                = bmips_cpu_die,
#endif
};

struct plat_smp_ops bmips5000_smp_ops = {
        .smp_setup              = bmips_smp_setup,
        .prepare_cpus           = bmips_prepare_cpus,
        .boot_secondary         = bmips_boot_secondary,
        .smp_finish             = bmips_smp_finish,
        .init_secondary         = bmips_init_secondary,
        .send_ipi_single        = bmips5000_send_ipi_single,
        .send_ipi_mask          = bmips5000_send_ipi_mask,
#ifdef CONFIG_HOTPLUG_CPU
        .cpu_disable            = bmips_cpu_disable,
        .cpu_die                = bmips_cpu_die,
#endif
};

#endif /* CONFIG_SMP */

/***********************************************************************
 * BMIPS vector relocation
 * This is primarily used for SMP boot, but it is applicable to some
 * UP BMIPS systems as well.
 ***********************************************************************/

static void bmips_wr_vec(unsigned long dst, char *start, char *end)
{
        memcpy((void *)dst, start, end - start);
        dma_cache_wback(dst, end - start);
        local_flush_icache_range(dst, dst + (end - start));
        instruction_hazard();
}

static inline void bmips_nmi_handler_setup(void)
{
        bmips_wr_vec(BMIPS_NMI_RESET_VEC, &bmips_reset_nmi_vec,
                &bmips_reset_nmi_vec_end);
        bmips_wr_vec(BMIPS_WARM_RESTART_VEC, &bmips_smp_int_vec,
                &bmips_smp_int_vec_end);
}

struct reset_vec_info {
        int cpu;
        u32 val;
};

static void bmips_set_reset_vec_remote(void *vinfo)
{
        struct reset_vec_info *info = vinfo;
        int shift = info->cpu & 0x01 ? 16 : 0;
        u32 mask = ~(0xffff << shift), val = info->val >> 16;

        preempt_disable();
        if (smp_processor_id() > 0) {
                smp_call_function_single(0, &bmips_set_reset_vec_remote,
                                         info, 1);
        } else {
                if (info->cpu & 0x02) {
                        /* BMIPS5200 "should" use mask/shift, but it's buggy */
                        bmips_write_zscm_reg(0xa0, (val << 16) | val);
                        bmips_read_zscm_reg(0xa0);
                } else {
                        write_c0_brcm_bootvec((read_c0_brcm_bootvec() & mask) |
                                              (val << shift));
                }
        }
        preempt_enable();
}

static void bmips_set_reset_vec(int cpu, u32 val)
{
        struct reset_vec_info info;

        if (current_cpu_type() == CPU_BMIPS5000) {
                /* this needs to run from CPU0 (which is always online) */
                info.cpu = cpu;
                info.val = val;
                bmips_set_reset_vec_remote(&info);
        } else {
                void __iomem *cbr = BMIPS_GET_CBR();

                if (cpu == 0)
                        __raw_writel(val, cbr + BMIPS_RELO_VECTOR_CONTROL_0);
                else {
                        if (current_cpu_type() != CPU_BMIPS4380)
                                return;
                        __raw_writel(val, cbr + BMIPS_RELO_VECTOR_CONTROL_1);
                }
        }
        __sync();
        back_to_back_c0_hazard();
}

void bmips_ebase_setup(void)
{
        unsigned long new_ebase = ebase;

        BUG_ON(ebase != CKSEG0);

        switch (current_cpu_type()) {
        case CPU_BMIPS4350:
                /*
                 * BMIPS4350 cannot relocate the normal vectors, but it
                 * can relocate the BEV=1 vectors.  So CPU1 starts up at
                 * the relocated BEV=1, IV=0 general exception vector @
                 * 0xa000_0380.
                 *
                 * set_uncached_handler() is used here because:
                 *  - CPU1 will run this from uncached space
                 *  - None of the cacheflush functions are set up yet
                 */
                set_uncached_handler(BMIPS_WARM_RESTART_VEC - CKSEG0,
                        &bmips_smp_int_vec, 0x80);
                __sync();
                return;
        case CPU_BMIPS3300:
        case CPU_BMIPS4380:
                /*
                 * 0x8000_0000: reset/NMI (initially in kseg1)
                 * 0x8000_0400: normal vectors
                 */
                new_ebase = 0x80000400;
                bmips_set_reset_vec(0, RESET_FROM_KSEG0);
                break;
        case CPU_BMIPS5000:
                /*
                 * 0x8000_0000: reset/NMI (initially in kseg1)
                 * 0x8000_1000: normal vectors
                 */
                new_ebase = 0x80001000;
                bmips_set_reset_vec(0, RESET_FROM_KSEG0);
                write_c0_ebase(new_ebase);
                break;
        default:
                return;
        }

        board_nmi_handler_setup = &bmips_nmi_handler_setup;
        ebase = new_ebase;
}

asmlinkage void __weak plat_wired_tlb_setup(void)
{
        /*
         * Called when starting/restarting a secondary CPU.
         * Kernel stacks and other important data might only be accessible
         * once the wired entries are present.
         */
}