/*
 * apb_timer.c: Driver for Langwell APB timers
 *
 * (C) Copyright 2009 Intel Corporation
 * Author: Jacob Pan (jacob.jun.pan@intel.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; version 2
 * of the License.
 *
 * Note:
 * Langwell is the south complex of Intel Moorestown MID platform. There are
 * eight external timers in total that can be used by the operating system.
 * The timer information, such as frequency and addresses, is provided to the
 * OS via SFI tables.
 * Timer interrupts are routed via FW/HW emulated IOAPIC independently via
 * individual redirection table entries (RTE).
 * Unlike HPET, there is no master counter, therefore one of the timers are
 * used as clocksource. The overall allocation looks like:
 *  - timer 0 - NR_CPUs for per cpu timer
 *  - one timer for clocksource
 *  - one timer for watchdog driver.
 * It is also worth notice that APB timer does not support true one-shot mode,
 * free-running mode will be used here to emulate one-shot mode.
 * APB timer can also be used as broadcast timer along with per cpu local APIC
 * timer, but by default APB timer has higher rating than local APIC timers.
 */

#include <linux/delay.h>
#include <linux/dw_apb_timer.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/pm.h>
#include <linux/sfi.h>
#include <linux/interrupt.h>
#include <linux/cpu.h>
#include <linux/irq.h>

#include <asm/fixmap.h>
#include <asm/apb_timer.h>
#include <asm/intel-mid.h>
#include <asm/time.h>

#define APBT_CLOCKEVENT_RATING          110
#define APBT_CLOCKSOURCE_RATING         250

#define APBT_CLOCKEVENT0_NUM   (0)
#define APBT_CLOCKSOURCE_NUM   (2)

static phys_addr_t apbt_address;
static int apb_timer_block_enabled;
static void __iomem *apbt_virt_address;

/*
 * Common DW APB timer info
 */
static unsigned long apbt_freq;

struct apbt_dev {
        struct dw_apb_clock_event_device        *timer;
        unsigned int                            num;
        int                                     cpu;
        unsigned int                            irq;
        char                                    name[10];
};

static struct dw_apb_clocksource *clocksource_apbt;

static inline void __iomem *adev_virt_addr(struct apbt_dev *adev)
{
        return apbt_virt_address + adev->num * APBTMRS_REG_SIZE;
}

static DEFINE_PER_CPU(struct apbt_dev, cpu_apbt_dev);

#ifdef CONFIG_SMP
static unsigned int apbt_num_timers_used;
#endif

static inline void apbt_set_mapping(void)
{
        struct sfi_timer_table_entry *mtmr;
        int phy_cs_timer_id = 0;

        if (apbt_virt_address) {
                pr_debug("APBT base already mapped\n");
                return;
        }
        mtmr = sfi_get_mtmr(APBT_CLOCKEVENT0_NUM);
        if (mtmr == NULL) {
                printk(KERN_ERR "Failed to get MTMR %d from SFI\n",
                       APBT_CLOCKEVENT0_NUM);
                return;
        }
        apbt_address = (phys_addr_t)mtmr->phys_addr;
        if (!apbt_address) {
                printk(KERN_WARNING "No timer base from SFI, use default\n");
                apbt_address = APBT_DEFAULT_BASE;
        }
        apbt_virt_address = ioremap_nocache(apbt_address, APBT_MMAP_SIZE);
        if (!apbt_virt_address) {
                pr_debug("Failed mapping APBT phy address at %lu\n",\
                         (unsigned long)apbt_address);
                goto panic_noapbt;
        }
        apbt_freq = mtmr->freq_hz;
        sfi_free_mtmr(mtmr);

        /* Now figure out the physical timer id for clocksource device */
        mtmr = sfi_get_mtmr(APBT_CLOCKSOURCE_NUM);
        if (mtmr == NULL)
                goto panic_noapbt;

        /* Now figure out the physical timer id */
        pr_debug("Use timer %d for clocksource\n",
                 (int)(mtmr->phys_addr & 0xff) / APBTMRS_REG_SIZE);
        phy_cs_timer_id = (unsigned int)(mtmr->phys_addr & 0xff) /
                APBTMRS_REG_SIZE;

        clocksource_apbt = dw_apb_clocksource_init(APBT_CLOCKSOURCE_RATING,
                "apbt0", apbt_virt_address + phy_cs_timer_id *
                APBTMRS_REG_SIZE, apbt_freq);
        return;

panic_noapbt:
        panic("Failed to setup APB system timer\n");

}

static inline void apbt_clear_mapping(void)
{
        iounmap(apbt_virt_address);
        apbt_virt_address = NULL;
}

static int __init apbt_clockevent_register(void)
{
        struct sfi_timer_table_entry *mtmr;
        struct apbt_dev *adev = this_cpu_ptr(&cpu_apbt_dev);

        mtmr = sfi_get_mtmr(APBT_CLOCKEVENT0_NUM);
        if (mtmr == NULL) {
                printk(KERN_ERR "Failed to get MTMR %d from SFI\n",
                       APBT_CLOCKEVENT0_NUM);
                return -ENODEV;
        }

        adev->num = smp_processor_id();
        adev->timer = dw_apb_clockevent_init(smp_processor_id(), "apbt0",
                intel_mid_timer_options == INTEL_MID_TIMER_LAPIC_APBT ?
                APBT_CLOCKEVENT_RATING - 100 : APBT_CLOCKEVENT_RATING,
                adev_virt_addr(adev), 0, apbt_freq);
        /* Firmware does EOI handling for us. */
        adev->timer->eoi = NULL;

        if (intel_mid_timer_options == INTEL_MID_TIMER_LAPIC_APBT) {
                global_clock_event = &adev->timer->ced;
                printk(KERN_DEBUG "%s clockevent registered as global\n",
                       global_clock_event->name);
        }

        dw_apb_clockevent_register(adev->timer);

        sfi_free_mtmr(mtmr);
        return 0;
}

#ifdef CONFIG_SMP

static void apbt_setup_irq(struct apbt_dev *adev)
{
        irq_modify_status(adev->irq, 0, IRQ_MOVE_PCNTXT);
        irq_set_affinity(adev->irq, cpumask_of(adev->cpu));
}

/* Should be called with per cpu */
void apbt_setup_secondary_clock(void)
{
        struct apbt_dev *adev;
        int cpu;

        /* Don't register boot CPU clockevent */
        cpu = smp_processor_id();
        if (!cpu)
                return;

        adev = this_cpu_ptr(&cpu_apbt_dev);
        if (!adev->timer) {
                adev->timer = dw_apb_clockevent_init(cpu, adev->name,
                        APBT_CLOCKEVENT_RATING, adev_virt_addr(adev),
                        adev->irq, apbt_freq);
                adev->timer->eoi = NULL;
        } else {
                dw_apb_clockevent_resume(adev->timer);
        }

        printk(KERN_INFO "Registering CPU %d clockevent device %s, cpu %08x\n",
               cpu, adev->name, adev->cpu);

        apbt_setup_irq(adev);
        dw_apb_clockevent_register(adev->timer);

        return;
}

/*
 * this notify handler process CPU hotplug events. in case of S0i3, nonboot
 * cpus are disabled/enabled frequently, for performance reasons, we keep the
 * per cpu timer irq registered so that we do need to do free_irq/request_irq.
 *
 * TODO: it might be more reliable to directly disable percpu clockevent device
 * without the notifier chain. currently, cpu 0 may get interrupts from other
 * cpu timers during the offline process due to the ordering of notification.
 * the extra interrupt is harmless.
 */
static int apbt_cpu_dead(unsigned int cpu)
{
        struct apbt_dev *adev = &per_cpu(cpu_apbt_dev, cpu);

        dw_apb_clockevent_pause(adev->timer);
        if (system_state == SYSTEM_RUNNING) {
                pr_debug("skipping APBT CPU %u offline\n", cpu);
        } else {
                pr_debug("APBT clockevent for cpu %u offline\n", cpu);
                dw_apb_clockevent_stop(adev->timer);
        }
        return 0;
}

static __init int apbt_late_init(void)
{
        if (intel_mid_timer_options == INTEL_MID_TIMER_LAPIC_APBT ||
                !apb_timer_block_enabled)
                return 0;
        return cpuhp_setup_state(CPUHP_X86_APB_DEAD, "x86/apb:dead", NULL,
                                 apbt_cpu_dead);
}
fs_initcall(apbt_late_init);
#else

void apbt_setup_secondary_clock(void) {}

#endif /* CONFIG_SMP */

static int apbt_clocksource_register(void)
{
        u64 start, now;
        u64 t1;

        /* Start the counter, use timer 2 as source, timer 0/1 for event */
        dw_apb_clocksource_start(clocksource_apbt);

        /* Verify whether apbt counter works */
        t1 = dw_apb_clocksource_read(clocksource_apbt);
        start = rdtsc();

        /*
         * We don't know the TSC frequency yet, but waiting for
         * 200000 TSC cycles is safe:
         * 4 GHz == 50us
         * 1 GHz == 200us
         */
        do {
                rep_nop();
                now = rdtsc();
        } while ((now - start) < 200000UL);

        /* APBT is the only always on clocksource, it has to work! */
        if (t1 == dw_apb_clocksource_read(clocksource_apbt))
                panic("APBT counter not counting. APBT disabled\n");

        dw_apb_clocksource_register(clocksource_apbt);

        return 0;
}

/*
 * Early setup the APBT timer, only use timer 0 for booting then switch to
 * per CPU timer if possible.
 * returns 1 if per cpu apbt is setup
 * returns 0 if no per cpu apbt is chosen
 * panic if set up failed, this is the only platform timer on Moorestown.
 */
void __init apbt_time_init(void)
{
#ifdef CONFIG_SMP
        int i;
        struct sfi_timer_table_entry *p_mtmr;
        struct apbt_dev *adev;
#endif

        if (apb_timer_block_enabled)
                return;
        apbt_set_mapping();
        if (!apbt_virt_address)
                goto out_noapbt;
        /*
         * Read the frequency and check for a sane value, for ESL model
         * we extend the possible clock range to allow time scaling.
         */

        if (apbt_freq < APBT_MIN_FREQ || apbt_freq > APBT_MAX_FREQ) {
                pr_debug("APBT has invalid freq 0x%lx\n", apbt_freq);
                goto out_noapbt;
        }
        if (apbt_clocksource_register()) {
                pr_debug("APBT has failed to register clocksource\n");
                goto out_noapbt;
        }
        if (!apbt_clockevent_register())
                apb_timer_block_enabled = 1;
        else {
                pr_debug("APBT has failed to register clockevent\n");
                goto out_noapbt;
        }
#ifdef CONFIG_SMP
        /* kernel cmdline disable apb timer, so we will use lapic timers */
        if (intel_mid_timer_options == INTEL_MID_TIMER_LAPIC_APBT) {
                printk(KERN_INFO "apbt: disabled per cpu timer\n");
                return;
        }
        pr_debug("%s: %d CPUs online\n", __func__, num_online_cpus());
        if (num_possible_cpus() <= sfi_mtimer_num)
                apbt_num_timers_used = num_possible_cpus();
        else
                apbt_num_timers_used = 1;
        pr_debug("%s: %d APB timers used\n", __func__, apbt_num_timers_used);

        /* here we set up per CPU timer data structure */
        for (i = 0; i < apbt_num_timers_used; i++) {
                adev = &per_cpu(cpu_apbt_dev, i);
                adev->num = i;
                adev->cpu = i;
                p_mtmr = sfi_get_mtmr(i);
                if (p_mtmr)
                        adev->irq = p_mtmr->irq;
                else
                        printk(KERN_ERR "Failed to get timer for cpu %d\n", i);
                snprintf(adev->name, sizeof(adev->name) - 1, "apbt%d", i);
        }
#endif

        return;

out_noapbt:
        apbt_clear_mapping();
        apb_timer_block_enabled = 0;
        panic("failed to enable APB timer\n");
}

/* called before apb_timer_enable, use early map */
unsigned long apbt_quick_calibrate(void)
{
        int i, scale;
        u64 old, new;
        u64 t1, t2;
        unsigned long khz = 0;
        u32 loop, shift;

        apbt_set_mapping();
        dw_apb_clocksource_start(clocksource_apbt);

        /* check if the timer can count down, otherwise return */
        old = dw_apb_clocksource_read(clocksource_apbt);
        i = 10000;
        while (--i) {
                if (old != dw_apb_clocksource_read(clocksource_apbt))
                        break;
        }
        if (!i)
                goto failed;

        /* count 16 ms */
        loop = (apbt_freq / 1000) << 4;

        /* restart the timer to ensure it won't get to 0 in the calibration */
        dw_apb_clocksource_start(clocksource_apbt);

        old = dw_apb_clocksource_read(clocksource_apbt);
        old += loop;

        t1 = rdtsc();

        do {
                new = dw_apb_clocksource_read(clocksource_apbt);
        } while (new < old);

        t2 = rdtsc();

        shift = 5;
        if (unlikely(loop >> shift == 0)) {
                printk(KERN_INFO
                       "APBT TSC calibration failed, not enough resolution\n");
                return 0;
        }
        scale = (int)div_u64((t2 - t1), loop >> shift);
        khz = (scale * (apbt_freq / 1000)) >> shift;
        printk(KERN_INFO "TSC freq calculated by APB timer is %lu khz\n", khz);
        return khz;
failed:
        return 0;
}