/*
 * Octeon Watchdog driver
 *
 * Copyright (C) 2007, 2008, 2009, 2010 Cavium Networks
 *
 * Converted to use WATCHDOG_CORE by Aaro Koskinen <aaro.koskinen@iki.fi>.
 *
 * Some parts derived from wdt.c
 *
 *      (c) Copyright 1996-1997 Alan Cox <alan@lxorguk.ukuu.org.uk>,
 *                                              All Rights Reserved.
 *
 *      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.
 *
 *      Neither Alan Cox nor CymruNet Ltd. admit liability nor provide
 *      warranty for any of this software. This material is provided
 *      "AS-IS" and at no charge.
 *
 *      (c) Copyright 1995    Alan Cox <alan@lxorguk.ukuu.org.uk>
 *
 * 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.
 *
 *
 * The OCTEON watchdog has a maximum timeout of 2^32 * io_clock.
 * For most systems this is less than 10 seconds, so to allow for
 * software to request longer watchdog heartbeats, we maintain software
 * counters to count multiples of the base rate.  If the system locks
 * up in such a manner that we can not run the software counters, the
 * only result is a watchdog reset sooner than was requested.  But
 * that is OK, because in this case userspace would likely not be able
 * to do anything anyhow.
 *
 * The hardware watchdog interval we call the period.  The OCTEON
 * watchdog goes through several stages, after the first period an
 * irq is asserted, then if it is not reset, after the next period NMI
 * is asserted, then after an additional period a chip wide soft reset.
 * So for the software counters, we reset watchdog after each period
 * and decrement the counter.  But for the last two periods we need to
 * let the watchdog progress to the NMI stage so we disable the irq
 * and let it proceed.  Once in the NMI, we print the register state
 * to the serial port and then wait for the reset.
 *
 * A watchdog is maintained for each CPU in the system, that way if
 * one CPU suffers a lockup, we also get a register dump and reset.
 * The userspace ping resets the watchdog on all CPUs.
 *
 * Before userspace opens the watchdog device, we still run the
 * watchdogs to catch any lockups that may be kernel related.
 *
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/miscdevice.h>
#include <linux/interrupt.h>
#include <linux/watchdog.h>
#include <linux/cpumask.h>
#include <linux/bitops.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/string.h>
#include <linux/delay.h>
#include <linux/cpu.h>
#include <linux/smp.h>
#include <linux/fs.h>
#include <linux/irq.h>

#include <asm/mipsregs.h>
#include <asm/uasm.h>

#include <asm/octeon/octeon.h>

/* The count needed to achieve timeout_sec. */
static unsigned int timeout_cnt;

/* The maximum period supported. */
static unsigned int max_timeout_sec;

/* The current period.  */
static unsigned int timeout_sec;

/* Set to non-zero when userspace countdown mode active */
static int do_coundown;
static unsigned int countdown_reset;
static unsigned int per_cpu_countdown[NR_CPUS];

static cpumask_t irq_enabled_cpus;

#define WD_TIMO 60                      /* Default heartbeat = 60 seconds */

static int heartbeat = WD_TIMO;
module_param(heartbeat, int, S_IRUGO);
MODULE_PARM_DESC(heartbeat,
        "Watchdog heartbeat in seconds. (0 < heartbeat, default="
                                __MODULE_STRING(WD_TIMO) ")");

static bool nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, bool, S_IRUGO);
MODULE_PARM_DESC(nowayout,
        "Watchdog cannot be stopped once started (default="
                                __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");

static u32 nmi_stage1_insns[64] __initdata;
/* We need one branch and therefore one relocation per target label. */
static struct uasm_label labels[5] __initdata;
static struct uasm_reloc relocs[5] __initdata;

enum lable_id {
        label_enter_bootloader = 1
};

/* Some CP0 registers */
#define K0              26
#define C0_CVMMEMCTL 11, 7
#define C0_STATUS 12, 0
#define C0_EBASE 15, 1
#define C0_DESAVE 31, 0

void octeon_wdt_nmi_stage2(void);

static void __init octeon_wdt_build_stage1(void)
{
        int i;
        int len;
        u32 *p = nmi_stage1_insns;
#ifdef CONFIG_HOTPLUG_CPU
        struct uasm_label *l = labels;
        struct uasm_reloc *r = relocs;
#endif

        /*
         * For the next few instructions running the debugger may
         * cause corruption of k0 in the saved registers. Since we're
         * about to crash, nobody probably cares.
         *
         * Save K0 into the debug scratch register
         */
        uasm_i_dmtc0(&p, K0, C0_DESAVE);

        uasm_i_mfc0(&p, K0, C0_STATUS);
#ifdef CONFIG_HOTPLUG_CPU
        if (octeon_bootloader_entry_addr)
                uasm_il_bbit0(&p, &r, K0, ilog2(ST0_NMI),
                              label_enter_bootloader);
#endif
        /* Force 64-bit addressing enabled */
        uasm_i_ori(&p, K0, K0, ST0_UX | ST0_SX | ST0_KX);
        uasm_i_mtc0(&p, K0, C0_STATUS);

#ifdef CONFIG_HOTPLUG_CPU
        if (octeon_bootloader_entry_addr) {
                uasm_i_mfc0(&p, K0, C0_EBASE);
                /* Coreid number in K0 */
                uasm_i_andi(&p, K0, K0, 0xf);
                /* 8 * coreid in bits 16-31 */
                uasm_i_dsll_safe(&p, K0, K0, 3 + 16);
                uasm_i_ori(&p, K0, K0, 0x8001);
                uasm_i_dsll_safe(&p, K0, K0, 16);
                uasm_i_ori(&p, K0, K0, 0x0700);
                uasm_i_drotr_safe(&p, K0, K0, 32);
                /*
                 * Should result in: 0x8001,0700,0000,8*coreid which is
                 * CVMX_CIU_WDOGX(coreid) - 0x0500
                 *
                 * Now ld K0, CVMX_CIU_WDOGX(coreid)
                 */
                uasm_i_ld(&p, K0, 0x500, K0);
                /*
                 * If bit one set handle the NMI as a watchdog event.
                 * otherwise transfer control to bootloader.
                 */
                uasm_il_bbit0(&p, &r, K0, 1, label_enter_bootloader);
                uasm_i_nop(&p);
        }
#endif

        /* Clear Dcache so cvmseg works right. */
        uasm_i_cache(&p, 1, 0, 0);

        /* Use K0 to do a read/modify/write of CVMMEMCTL */
        uasm_i_dmfc0(&p, K0, C0_CVMMEMCTL);
        /* Clear out the size of CVMSEG */
        uasm_i_dins(&p, K0, 0, 0, 6);
        /* Set CVMSEG to its largest value */
        uasm_i_ori(&p, K0, K0, 0x1c0 | 54);
        /* Store the CVMMEMCTL value */
        uasm_i_dmtc0(&p, K0, C0_CVMMEMCTL);

        /* Load the address of the second stage handler */
        UASM_i_LA(&p, K0, (long)octeon_wdt_nmi_stage2);
        uasm_i_jr(&p, K0);
        uasm_i_dmfc0(&p, K0, C0_DESAVE);

#ifdef CONFIG_HOTPLUG_CPU
        if (octeon_bootloader_entry_addr) {
                uasm_build_label(&l, p, label_enter_bootloader);
                /* Jump to the bootloader and restore K0 */
                UASM_i_LA(&p, K0, (long)octeon_bootloader_entry_addr);
                uasm_i_jr(&p, K0);
                uasm_i_dmfc0(&p, K0, C0_DESAVE);
        }
#endif
        uasm_resolve_relocs(relocs, labels);

        len = (int)(p - nmi_stage1_insns);
        pr_debug("Synthesized NMI stage 1 handler (%d instructions)\n", len);

        pr_debug("\t.set push\n");
        pr_debug("\t.set noreorder\n");
        for (i = 0; i < len; i++)
                pr_debug("\t.word 0x%08x\n", nmi_stage1_insns[i]);
        pr_debug("\t.set pop\n");

        if (len > 32)
                panic("NMI stage 1 handler exceeds 32 instructions, was %d\n",
                      len);
}

static int cpu2core(int cpu)
{
#ifdef CONFIG_SMP
        return cpu_logical_map(cpu);
#else
        return cvmx_get_core_num();
#endif
}

static int core2cpu(int coreid)
{
#ifdef CONFIG_SMP
        return cpu_number_map(coreid);
#else
        return 0;
#endif
}

/**
 * Poke the watchdog when an interrupt is received
 *
 * @cpl:
 * @dev_id:
 *
 * Returns
 */
static irqreturn_t octeon_wdt_poke_irq(int cpl, void *dev_id)
{
        unsigned int core = cvmx_get_core_num();
        int cpu = core2cpu(core);

        if (do_coundown) {
                if (per_cpu_countdown[cpu] > 0) {
                        /* We're alive, poke the watchdog */
                        cvmx_write_csr(CVMX_CIU_PP_POKEX(core), 1);
                        per_cpu_countdown[cpu]--;
                } else {
                        /* Bad news, you are about to reboot. */
                        disable_irq_nosync(cpl);
                        cpumask_clear_cpu(cpu, &irq_enabled_cpus);
                }
        } else {
                /* Not open, just ping away... */
                cvmx_write_csr(CVMX_CIU_PP_POKEX(core), 1);
        }
        return IRQ_HANDLED;
}

/* From setup.c */
extern int prom_putchar(char c);

/**
 * Write a string to the uart
 *
 * @str:        String to write
 */
static void octeon_wdt_write_string(const char *str)
{
        /* Just loop writing one byte at a time */
        while (*str)
                prom_putchar(*str++);
}

/**
 * Write a hex number out of the uart
 *
 * @value:      Number to display
 * @digits:     Number of digits to print (1 to 16)
 */
static void octeon_wdt_write_hex(u64 value, int digits)
{
        int d;
        int v;

        for (d = 0; d < digits; d++) {
                v = (value >> ((digits - d - 1) * 4)) & 0xf;
                if (v >= 10)
                        prom_putchar('a' + v - 10);
                else
                        prom_putchar('0' + v);
        }
}

static const char reg_name[][3] = {
        "$0", "at", "v0", "v1", "a0", "a1", "a2", "a3",
        "a4", "a5", "a6", "a7", "t0", "t1", "t2", "t3",
        "s0", "s1", "s2", "s3", "s4", "s5", "s6", "s7",
        "t8", "t9", "k0", "k1", "gp", "sp", "s8", "ra"
};

/**
 * NMI stage 3 handler. NMIs are handled in the following manner:
 * 1) The first NMI handler enables CVMSEG and transfers from
 * the bootbus region into normal memory. It is careful to not
 * destroy any registers.
 * 2) The second stage handler uses CVMSEG to save the registers
 * and create a stack for C code. It then calls the third level
 * handler with one argument, a pointer to the register values.
 * 3) The third, and final, level handler is the following C
 * function that prints out some useful infomration.
 *
 * @reg:    Pointer to register state before the NMI
 */
void octeon_wdt_nmi_stage3(u64 reg[32])
{
        u64 i;

        unsigned int coreid = cvmx_get_core_num();
        /*
         * Save status and cause early to get them before any changes
         * might happen.
         */
        u64 cp0_cause = read_c0_cause();
        u64 cp0_status = read_c0_status();
        u64 cp0_error_epc = read_c0_errorepc();
        u64 cp0_epc = read_c0_epc();

        /* Delay so output from all cores output is not jumbled together. */
        __delay(100000000ull * coreid);

        octeon_wdt_write_string("\r\n*** NMI Watchdog interrupt on Core 0x");
        octeon_wdt_write_hex(coreid, 1);
        octeon_wdt_write_string(" ***\r\n");
        for (i = 0; i < 32; i++) {
                octeon_wdt_write_string("\t");
                octeon_wdt_write_string(reg_name[i]);
                octeon_wdt_write_string("\t0x");
                octeon_wdt_write_hex(reg[i], 16);
                if (i & 1)
                        octeon_wdt_write_string("\r\n");
        }
        octeon_wdt_write_string("\terr_epc\t0x");
        octeon_wdt_write_hex(cp0_error_epc, 16);

        octeon_wdt_write_string("\tepc\t0x");
        octeon_wdt_write_hex(cp0_epc, 16);
        octeon_wdt_write_string("\r\n");

        octeon_wdt_write_string("\tstatus\t0x");
        octeon_wdt_write_hex(cp0_status, 16);
        octeon_wdt_write_string("\tcause\t0x");
        octeon_wdt_write_hex(cp0_cause, 16);
        octeon_wdt_write_string("\r\n");

        octeon_wdt_write_string("\tsum0\t0x");
        octeon_wdt_write_hex(cvmx_read_csr(CVMX_CIU_INTX_SUM0(coreid * 2)), 16);
        octeon_wdt_write_string("\ten0\t0x");
        octeon_wdt_write_hex(cvmx_read_csr(CVMX_CIU_INTX_EN0(coreid * 2)), 16);
        octeon_wdt_write_string("\r\n");

        octeon_wdt_write_string("*** Chip soft reset soon ***\r\n");
}

static void octeon_wdt_disable_interrupt(int cpu)
{
        unsigned int core;
        unsigned int irq;
        union cvmx_ciu_wdogx ciu_wdog;

        core = cpu2core(cpu);

        irq = OCTEON_IRQ_WDOG0 + core;

        /* Poke the watchdog to clear out its state */
        cvmx_write_csr(CVMX_CIU_PP_POKEX(core), 1);

        /* Disable the hardware. */
        ciu_wdog.u64 = 0;
        cvmx_write_csr(CVMX_CIU_WDOGX(core), ciu_wdog.u64);

        free_irq(irq, octeon_wdt_poke_irq);
}

static void octeon_wdt_setup_interrupt(int cpu)
{
        unsigned int core;
        unsigned int irq;
        union cvmx_ciu_wdogx ciu_wdog;

        core = cpu2core(cpu);

        /* Disable it before doing anything with the interrupts. */
        ciu_wdog.u64 = 0;
        cvmx_write_csr(CVMX_CIU_WDOGX(core), ciu_wdog.u64);

        per_cpu_countdown[cpu] = countdown_reset;

        irq = OCTEON_IRQ_WDOG0 + core;

        if (request_irq(irq, octeon_wdt_poke_irq,
                        IRQF_NO_THREAD, "octeon_wdt", octeon_wdt_poke_irq))
                panic("octeon_wdt: Couldn't obtain irq %d", irq);

        cpumask_set_cpu(cpu, &irq_enabled_cpus);

        /* Poke the watchdog to clear out its state */
        cvmx_write_csr(CVMX_CIU_PP_POKEX(core), 1);

        /* Finally enable the watchdog now that all handlers are installed */
        ciu_wdog.u64 = 0;
        ciu_wdog.s.len = timeout_cnt;
        ciu_wdog.s.mode = 3;    /* 3 = Interrupt + NMI + Soft-Reset */
        cvmx_write_csr(CVMX_CIU_WDOGX(core), ciu_wdog.u64);
}

static int octeon_wdt_cpu_callback(struct notifier_block *nfb,
                                           unsigned long action, void *hcpu)
{
        unsigned int cpu = (unsigned long)hcpu;

        switch (action) {
        case CPU_DOWN_PREPARE:
                octeon_wdt_disable_interrupt(cpu);
                break;
        case CPU_ONLINE:
        case CPU_DOWN_FAILED:
                octeon_wdt_setup_interrupt(cpu);
                break;
        default:
                break;
        }
        return NOTIFY_OK;
}

static int octeon_wdt_ping(struct watchdog_device __always_unused *wdog)
{
        int cpu;
        int coreid;

        for_each_online_cpu(cpu) {
                coreid = cpu2core(cpu);
                cvmx_write_csr(CVMX_CIU_PP_POKEX(coreid), 1);
                per_cpu_countdown[cpu] = countdown_reset;
                if ((countdown_reset || !do_coundown) &&
                    !cpumask_test_cpu(cpu, &irq_enabled_cpus)) {
                        /* We have to enable the irq */
                        int irq = OCTEON_IRQ_WDOG0 + coreid;

                        enable_irq(irq);
                        cpumask_set_cpu(cpu, &irq_enabled_cpus);
                }
        }
        return 0;
}

static void octeon_wdt_calc_parameters(int t)
{
        unsigned int periods;

        timeout_sec = max_timeout_sec;


        /*
         * Find the largest interrupt period, that can evenly divide
         * the requested heartbeat time.
         */
        while ((t % timeout_sec) != 0)
                timeout_sec--;

        periods = t / timeout_sec;

        /*
         * The last two periods are after the irq is disabled, and
         * then to the nmi, so we subtract them off.
         */

        countdown_reset = periods > 2 ? periods - 2 : 0;
        heartbeat = t;
        timeout_cnt = ((octeon_get_io_clock_rate() >> 8) * timeout_sec) >> 8;
}

static int octeon_wdt_set_timeout(struct watchdog_device *wdog,
                                  unsigned int t)
{
        int cpu;
        int coreid;
        union cvmx_ciu_wdogx ciu_wdog;

        if (t <= 0)
                return -1;

        octeon_wdt_calc_parameters(t);

        for_each_online_cpu(cpu) {
                coreid = cpu2core(cpu);
                cvmx_write_csr(CVMX_CIU_PP_POKEX(coreid), 1);
                ciu_wdog.u64 = 0;
                ciu_wdog.s.len = timeout_cnt;
                ciu_wdog.s.mode = 3;    /* 3 = Interrupt + NMI + Soft-Reset */
                cvmx_write_csr(CVMX_CIU_WDOGX(coreid), ciu_wdog.u64);
                cvmx_write_csr(CVMX_CIU_PP_POKEX(coreid), 1);
        }
        octeon_wdt_ping(wdog); /* Get the irqs back on. */
        return 0;
}

static int octeon_wdt_start(struct watchdog_device *wdog)
{
        octeon_wdt_ping(wdog);
        do_coundown = 1;
        return 0;
}

static int octeon_wdt_stop(struct watchdog_device *wdog)
{
        do_coundown = 0;
        octeon_wdt_ping(wdog);
        return 0;
}

static struct notifier_block octeon_wdt_cpu_notifier = {
        .notifier_call = octeon_wdt_cpu_callback,
};

static const struct watchdog_info octeon_wdt_info = {
        .options = WDIOF_SETTIMEOUT | WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING,
        .identity = "OCTEON",
};

static const struct watchdog_ops octeon_wdt_ops = {
        .owner          = THIS_MODULE,
        .start          = octeon_wdt_start,
        .stop           = octeon_wdt_stop,
        .ping           = octeon_wdt_ping,
        .set_timeout    = octeon_wdt_set_timeout,
};

static struct watchdog_device octeon_wdt = {
        .info   = &octeon_wdt_info,
        .ops    = &octeon_wdt_ops,
};

/**
 * Module/ driver initialization.
 *
 * Returns Zero on success
 */
static int __init octeon_wdt_init(void)
{
        int i;
        int ret;
        int cpu;
        u64 *ptr;

        /*
         * Watchdog time expiration length = The 16 bits of LEN
         * represent the most significant bits of a 24 bit decrementer
         * that decrements every 256 cycles.
         *
         * Try for a timeout of 5 sec, if that fails a smaller number
         * of even seconds,
         */
        max_timeout_sec = 6;
        do {
                max_timeout_sec--;
                timeout_cnt = ((octeon_get_io_clock_rate() >> 8) *
                              max_timeout_sec) >> 8;
        } while (timeout_cnt > 65535);

        BUG_ON(timeout_cnt == 0);

        octeon_wdt_calc_parameters(heartbeat);

        pr_info("Initial granularity %d Sec\n", timeout_sec);

        octeon_wdt.timeout      = timeout_sec;
        octeon_wdt.max_timeout  = UINT_MAX;

        watchdog_set_nowayout(&octeon_wdt, nowayout);

        ret = watchdog_register_device(&octeon_wdt);
        if (ret) {
                pr_err("watchdog_register_device() failed: %d\n", ret);
                return ret;
        }

        /* Build the NMI handler ... */
        octeon_wdt_build_stage1();

        /* ... and install it. */
        ptr = (u64 *) nmi_stage1_insns;
        for (i = 0; i < 16; i++) {
                cvmx_write_csr(CVMX_MIO_BOOT_LOC_ADR, i * 8);
                cvmx_write_csr(CVMX_MIO_BOOT_LOC_DAT, ptr[i]);
        }
        cvmx_write_csr(CVMX_MIO_BOOT_LOC_CFGX(0), 0x81fc0000);

        cpumask_clear(&irq_enabled_cpus);

        cpu_notifier_register_begin();
        for_each_online_cpu(cpu)
                octeon_wdt_setup_interrupt(cpu);

        __register_hotcpu_notifier(&octeon_wdt_cpu_notifier);
        cpu_notifier_register_done();

        return 0;
}

/**
 * Module / driver shutdown
 */
static void __exit octeon_wdt_cleanup(void)
{
        int cpu;

        watchdog_unregister_device(&octeon_wdt);

        cpu_notifier_register_begin();
        __unregister_hotcpu_notifier(&octeon_wdt_cpu_notifier);

        for_each_online_cpu(cpu) {
                int core = cpu2core(cpu);
                /* Disable the watchdog */
                cvmx_write_csr(CVMX_CIU_WDOGX(core), 0);
                /* Free the interrupt handler */
                free_irq(OCTEON_IRQ_WDOG0 + core, octeon_wdt_poke_irq);
        }

        cpu_notifier_register_done();

        /*
         * Disable the boot-bus memory, the code it points to is soon
         * to go missing.
         */
        cvmx_write_csr(CVMX_MIO_BOOT_LOC_CFGX(0), 0);
}

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Cavium Networks <support@caviumnetworks.com>");
MODULE_DESCRIPTION("Cavium Networks Octeon Watchdog driver.");
module_init(octeon_wdt_init);
module_exit(octeon_wdt_cleanup);