LOCAL / clocksource: arm_arch_timer: Don't register clockevent for Per-CPU

[platform/kernel/linux-exynos.git] / drivers / clocksource / arm_arch_timer.c

/*
 *  linux/drivers/clocksource/arm_arch_timer.c
 *
 *  Copyright (C) 2011 ARM Ltd.
 *  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 version 2 as
 * published by the Free Software Foundation.
 */

#define pr_fmt(fmt)     "arm_arch_timer: " fmt

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/device.h>
#include <linux/smp.h>
#include <linux/cpu.h>
#include <linux/cpu_pm.h>
#include <linux/clockchips.h>
#include <linux/clocksource.h>
#include <linux/interrupt.h>
#include <linux/of_irq.h>
#include <linux/of_address.h>
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/sched/clock.h>
#include <linux/sched_clock.h>
#include <linux/acpi.h>

#include <asm/arch_timer.h>
#include <asm/virt.h>

#include <clocksource/arm_arch_timer.h>

#undef pr_fmt
#define pr_fmt(fmt) "arch_timer: " fmt

#define CNTTIDR         0x08
#define CNTTIDR_VIRT(n) (BIT(1) << ((n) * 4))

#define CNTACR(n)       (0x40 + ((n) * 4))
#define CNTACR_RPCT     BIT(0)
#define CNTACR_RVCT     BIT(1)
#define CNTACR_RFRQ     BIT(2)
#define CNTACR_RVOFF    BIT(3)
#define CNTACR_RWVT     BIT(4)
#define CNTACR_RWPT     BIT(5)

#define CNTVCT_LO       0x08
#define CNTVCT_HI       0x0c
#define CNTFRQ          0x10
#define CNTP_TVAL       0x28
#define CNTP_CTL        0x2c
#define CNTV_TVAL       0x38
#define CNTV_CTL        0x3c

static unsigned arch_timers_present __initdata;

static void __iomem *arch_counter_base;

struct arch_timer {
        void __iomem *base;
        struct clock_event_device evt;
};

#define to_arch_timer(e) container_of(e, struct arch_timer, evt)

static u32 arch_timer_rate;
static int arch_timer_ppi[ARCH_TIMER_MAX_TIMER_PPI];

static struct clock_event_device __percpu *arch_timer_evt;

static enum arch_timer_ppi_nr arch_timer_uses_ppi = ARCH_TIMER_VIRT_PPI;
static bool arch_timer_c3stop;
static bool arch_timer_mem_use_virtual;
static bool arch_counter_suspend_stop;
static bool vdso_default = true;

static bool evtstrm_enable = IS_ENABLED(CONFIG_ARM_ARCH_TIMER_EVTSTREAM);
static bool mct_enable = IS_ENABLED(CONFIG_CLKSRC_EXYNOS_MCT);

static int __init early_evtstrm_cfg(char *buf)
{
        return strtobool(buf, &evtstrm_enable);
}
early_param("clocksource.arm_arch_timer.evtstrm", early_evtstrm_cfg);

/*
 * Architected system timer support.
 */

static __always_inline
void arch_timer_reg_write(int access, enum arch_timer_reg reg, u32 val,
                          struct clock_event_device *clk)
{
        if (access == ARCH_TIMER_MEM_PHYS_ACCESS) {
                struct arch_timer *timer = to_arch_timer(clk);
                switch (reg) {
                case ARCH_TIMER_REG_CTRL:
                        writel_relaxed(val, timer->base + CNTP_CTL);
                        break;
                case ARCH_TIMER_REG_TVAL:
                        writel_relaxed(val, timer->base + CNTP_TVAL);
                        break;
                }
        } else if (access == ARCH_TIMER_MEM_VIRT_ACCESS) {
                struct arch_timer *timer = to_arch_timer(clk);
                switch (reg) {
                case ARCH_TIMER_REG_CTRL:
                        writel_relaxed(val, timer->base + CNTV_CTL);
                        break;
                case ARCH_TIMER_REG_TVAL:
                        writel_relaxed(val, timer->base + CNTV_TVAL);
                        break;
                }
        } else {
                arch_timer_reg_write_cp15(access, reg, val);
        }
}

static __always_inline
u32 arch_timer_reg_read(int access, enum arch_timer_reg reg,
                        struct clock_event_device *clk)
{
        u32 val;

        if (access == ARCH_TIMER_MEM_PHYS_ACCESS) {
                struct arch_timer *timer = to_arch_timer(clk);
                switch (reg) {
                case ARCH_TIMER_REG_CTRL:
                        val = readl_relaxed(timer->base + CNTP_CTL);
                        break;
                case ARCH_TIMER_REG_TVAL:
                        val = readl_relaxed(timer->base + CNTP_TVAL);
                        break;
                }
        } else if (access == ARCH_TIMER_MEM_VIRT_ACCESS) {
                struct arch_timer *timer = to_arch_timer(clk);
                switch (reg) {
                case ARCH_TIMER_REG_CTRL:
                        val = readl_relaxed(timer->base + CNTV_CTL);
                        break;
                case ARCH_TIMER_REG_TVAL:
                        val = readl_relaxed(timer->base + CNTV_TVAL);
                        break;
                }
        } else {
                val = arch_timer_reg_read_cp15(access, reg);
        }

        return val;
}

/*
 * Default to cp15 based access because arm64 uses this function for
 * sched_clock() before DT is probed and the cp15 method is guaranteed
 * to exist on arm64. arm doesn't use this before DT is probed so even
 * if we don't have the cp15 accessors we won't have a problem.
 */
u64 (*arch_timer_read_counter)(void) = arch_counter_get_cntvct;

static u64 arch_counter_read(struct clocksource *cs)
{
        return arch_timer_read_counter();
}

static u64 arch_counter_read_cc(const struct cyclecounter *cc)
{
        return arch_timer_read_counter();
}

static struct clocksource clocksource_counter = {
        .name   = "arch_sys_counter",
        .rating = 400,
        .read   = arch_counter_read,
        .mask   = CLOCKSOURCE_MASK(56),
        .flags  = CLOCK_SOURCE_IS_CONTINUOUS,
};

static struct cyclecounter cyclecounter __ro_after_init = {
        .read   = arch_counter_read_cc,
        .mask   = CLOCKSOURCE_MASK(56),
};

struct ate_acpi_oem_info {
        char oem_id[ACPI_OEM_ID_SIZE + 1];
        char oem_table_id[ACPI_OEM_TABLE_ID_SIZE + 1];
        u32 oem_revision;
};

#ifdef CONFIG_FSL_ERRATUM_A008585
/*
 * The number of retries is an arbitrary value well beyond the highest number
 * of iterations the loop has been observed to take.
 */
#define __fsl_a008585_read_reg(reg) ({                  \
        u64 _old, _new;                                 \
        int _retries = 200;                             \
                                                        \
        do {                                            \
                _old = read_sysreg(reg);                \
                _new = read_sysreg(reg);                \
                _retries--;                             \
        } while (unlikely(_old != _new) && _retries);   \
                                                        \
        WARN_ON_ONCE(!_retries);                        \
        _new;                                           \
})

static u32 notrace fsl_a008585_read_cntp_tval_el0(void)
{
        return __fsl_a008585_read_reg(cntp_tval_el0);
}

static u32 notrace fsl_a008585_read_cntv_tval_el0(void)
{
        return __fsl_a008585_read_reg(cntv_tval_el0);
}

static u64 notrace fsl_a008585_read_cntvct_el0(void)
{
        return __fsl_a008585_read_reg(cntvct_el0);
}
#endif

#ifdef CONFIG_HISILICON_ERRATUM_161010101
/*
 * Verify whether the value of the second read is larger than the first by
 * less than 32 is the only way to confirm the value is correct, so clear the
 * lower 5 bits to check whether the difference is greater than 32 or not.
 * Theoretically the erratum should not occur more than twice in succession
 * when reading the system counter, but it is possible that some interrupts
 * may lead to more than twice read errors, triggering the warning, so setting
 * the number of retries far beyond the number of iterations the loop has been
 * observed to take.
 */
#define __hisi_161010101_read_reg(reg) ({                               \
        u64 _old, _new;                                         \
        int _retries = 50;                                      \
                                                                \
        do {                                                    \
                _old = read_sysreg(reg);                        \
                _new = read_sysreg(reg);                        \
                _retries--;                                     \
        } while (unlikely((_new - _old) >> 5) && _retries);     \
                                                                \
        WARN_ON_ONCE(!_retries);                                \
        _new;                                                   \
})

static u32 notrace hisi_161010101_read_cntp_tval_el0(void)
{
        return __hisi_161010101_read_reg(cntp_tval_el0);
}

static u32 notrace hisi_161010101_read_cntv_tval_el0(void)
{
        return __hisi_161010101_read_reg(cntv_tval_el0);
}

static u64 notrace hisi_161010101_read_cntvct_el0(void)
{
        return __hisi_161010101_read_reg(cntvct_el0);
}

static struct ate_acpi_oem_info hisi_161010101_oem_info[] = {
        /*
         * Note that trailing spaces are required to properly match
         * the OEM table information.
         */
        {
                .oem_id         = "HISI  ",
                .oem_table_id   = "HIP05   ",
                .oem_revision   = 0,
        },
        {
                .oem_id         = "HISI  ",
                .oem_table_id   = "HIP06   ",
                .oem_revision   = 0,
        },
        {
                .oem_id         = "HISI  ",
                .oem_table_id   = "HIP07   ",
                .oem_revision   = 0,
        },
        { /* Sentinel indicating the end of the OEM array */ },
};
#endif

#ifdef CONFIG_ARM64_ERRATUM_858921
static u64 notrace arm64_858921_read_cntvct_el0(void)
{
        u64 old, new;

        old = read_sysreg(cntvct_el0);
        new = read_sysreg(cntvct_el0);
        return (((old ^ new) >> 32) & 1) ? old : new;
}
#endif

#ifdef CONFIG_ARM_ARCH_TIMER_OOL_WORKAROUND
DEFINE_PER_CPU(const struct arch_timer_erratum_workaround *,
               timer_unstable_counter_workaround);
EXPORT_SYMBOL_GPL(timer_unstable_counter_workaround);

DEFINE_STATIC_KEY_FALSE(arch_timer_read_ool_enabled);
EXPORT_SYMBOL_GPL(arch_timer_read_ool_enabled);

static void erratum_set_next_event_tval_generic(const int access, unsigned long evt,
                                                struct clock_event_device *clk)
{
        unsigned long ctrl;
        u64 cval = evt + arch_counter_get_cntvct();

        ctrl = arch_timer_reg_read(access, ARCH_TIMER_REG_CTRL, clk);
        ctrl |= ARCH_TIMER_CTRL_ENABLE;
        ctrl &= ~ARCH_TIMER_CTRL_IT_MASK;

        if (access == ARCH_TIMER_PHYS_ACCESS)
                write_sysreg(cval, cntp_cval_el0);
        else
                write_sysreg(cval, cntv_cval_el0);

        arch_timer_reg_write(access, ARCH_TIMER_REG_CTRL, ctrl, clk);
}

static __maybe_unused int erratum_set_next_event_tval_virt(unsigned long evt,
                                            struct clock_event_device *clk)
{
        erratum_set_next_event_tval_generic(ARCH_TIMER_VIRT_ACCESS, evt, clk);
        return 0;
}

static __maybe_unused int erratum_set_next_event_tval_phys(unsigned long evt,
                                            struct clock_event_device *clk)
{
        erratum_set_next_event_tval_generic(ARCH_TIMER_PHYS_ACCESS, evt, clk);
        return 0;
}

static const struct arch_timer_erratum_workaround ool_workarounds[] = {
#ifdef CONFIG_FSL_ERRATUM_A008585
        {
                .match_type = ate_match_dt,
                .id = "fsl,erratum-a008585",
                .desc = "Freescale erratum a005858",
                .read_cntp_tval_el0 = fsl_a008585_read_cntp_tval_el0,
                .read_cntv_tval_el0 = fsl_a008585_read_cntv_tval_el0,
                .read_cntvct_el0 = fsl_a008585_read_cntvct_el0,
                .set_next_event_phys = erratum_set_next_event_tval_phys,
                .set_next_event_virt = erratum_set_next_event_tval_virt,
        },
#endif
#ifdef CONFIG_HISILICON_ERRATUM_161010101
        {
                .match_type = ate_match_dt,
                .id = "hisilicon,erratum-161010101",
                .desc = "HiSilicon erratum 161010101",
                .read_cntp_tval_el0 = hisi_161010101_read_cntp_tval_el0,
                .read_cntv_tval_el0 = hisi_161010101_read_cntv_tval_el0,
                .read_cntvct_el0 = hisi_161010101_read_cntvct_el0,
                .set_next_event_phys = erratum_set_next_event_tval_phys,
                .set_next_event_virt = erratum_set_next_event_tval_virt,
        },
        {
                .match_type = ate_match_acpi_oem_info,
                .id = hisi_161010101_oem_info,
                .desc = "HiSilicon erratum 161010101",
                .read_cntp_tval_el0 = hisi_161010101_read_cntp_tval_el0,
                .read_cntv_tval_el0 = hisi_161010101_read_cntv_tval_el0,
                .read_cntvct_el0 = hisi_161010101_read_cntvct_el0,
                .set_next_event_phys = erratum_set_next_event_tval_phys,
                .set_next_event_virt = erratum_set_next_event_tval_virt,
        },
#endif
#ifdef CONFIG_ARM64_ERRATUM_858921
        {
                .match_type = ate_match_local_cap_id,
                .id = (void *)ARM64_WORKAROUND_858921,
                .desc = "ARM erratum 858921",
                .read_cntvct_el0 = arm64_858921_read_cntvct_el0,
        },
#endif
};

typedef bool (*ate_match_fn_t)(const struct arch_timer_erratum_workaround *,
                               const void *);

static
bool arch_timer_check_dt_erratum(const struct arch_timer_erratum_workaround *wa,
                                 const void *arg)
{
        const struct device_node *np = arg;

        return of_property_read_bool(np, wa->id);
}

static
bool arch_timer_check_local_cap_erratum(const struct arch_timer_erratum_workaround *wa,
                                        const void *arg)
{
        return this_cpu_has_cap((uintptr_t)wa->id);
}


static
bool arch_timer_check_acpi_oem_erratum(const struct arch_timer_erratum_workaround *wa,
                                       const void *arg)
{
        static const struct ate_acpi_oem_info empty_oem_info = {};
        const struct ate_acpi_oem_info *info = wa->id;
        const struct acpi_table_header *table = arg;

        /* Iterate over the ACPI OEM info array, looking for a match */
        while (memcmp(info, &empty_oem_info, sizeof(*info))) {
                if (!memcmp(info->oem_id, table->oem_id, ACPI_OEM_ID_SIZE) &&
                    !memcmp(info->oem_table_id, table->oem_table_id, ACPI_OEM_TABLE_ID_SIZE) &&
                    info->oem_revision == table->oem_revision)
                        return true;

                info++;
        }

        return false;
}

static const struct arch_timer_erratum_workaround *
arch_timer_iterate_errata(enum arch_timer_erratum_match_type type,
                          ate_match_fn_t match_fn,
                          void *arg)
{
        int i;

        for (i = 0; i < ARRAY_SIZE(ool_workarounds); i++) {
                if (ool_workarounds[i].match_type != type)
                        continue;

                if (match_fn(&ool_workarounds[i], arg))
                        return &ool_workarounds[i];
        }

        return NULL;
}

static
void arch_timer_enable_workaround(const struct arch_timer_erratum_workaround *wa,
                                  bool local)
{
        int i;

        if (local) {
                __this_cpu_write(timer_unstable_counter_workaround, wa);
        } else {
                for_each_possible_cpu(i)
                        per_cpu(timer_unstable_counter_workaround, i) = wa;
        }

        /*
         * Use the locked version, as we're called from the CPU
         * hotplug framework. Otherwise, we end-up in deadlock-land.
         */
        static_branch_enable_cpuslocked(&arch_timer_read_ool_enabled);

        /*
         * Don't use the vdso fastpath if errata require using the
         * out-of-line counter accessor. We may change our mind pretty
         * late in the game (with a per-CPU erratum, for example), so
         * change both the default value and the vdso itself.
         */
        if (wa->read_cntvct_el0) {
                clocksource_counter.archdata.vdso_direct = false;
                vdso_default = false;
        }
}

static void arch_timer_check_ool_workaround(enum arch_timer_erratum_match_type type,
                                            void *arg)
{
        const struct arch_timer_erratum_workaround *wa;
        ate_match_fn_t match_fn = NULL;
        bool local = false;

        switch (type) {
        case ate_match_dt:
                match_fn = arch_timer_check_dt_erratum;
                break;
        case ate_match_local_cap_id:
                match_fn = arch_timer_check_local_cap_erratum;
                local = true;
                break;
        case ate_match_acpi_oem_info:
                match_fn = arch_timer_check_acpi_oem_erratum;
                break;
        default:
                WARN_ON(1);
                return;
        }

        wa = arch_timer_iterate_errata(type, match_fn, arg);
        if (!wa)
                return;

        if (needs_unstable_timer_counter_workaround()) {
                const struct arch_timer_erratum_workaround *__wa;
                __wa = __this_cpu_read(timer_unstable_counter_workaround);
                if (__wa && wa != __wa)
                        pr_warn("Can't enable workaround for %s (clashes with %s\n)",
                                wa->desc, __wa->desc);

                if (__wa)
                        return;
        }

        arch_timer_enable_workaround(wa, local);
        pr_info("Enabling %s workaround for %s\n",
                local ? "local" : "global", wa->desc);
}

#define erratum_handler(fn, r, ...)                                     \
({                                                                      \
        bool __val;                                                     \
        if (needs_unstable_timer_counter_workaround()) {                \
                const struct arch_timer_erratum_workaround *__wa;       \
                __wa = __this_cpu_read(timer_unstable_counter_workaround); \
                if (__wa && __wa->fn) {                                 \
                        r = __wa->fn(__VA_ARGS__);                      \
                        __val = true;                                   \
                } else {                                                \
                        __val = false;                                  \
                }                                                       \
        } else {                                                        \
                __val = false;                                          \
        }                                                               \
        __val;                                                          \
})

static bool arch_timer_this_cpu_has_cntvct_wa(void)
{
        const struct arch_timer_erratum_workaround *wa;

        wa = __this_cpu_read(timer_unstable_counter_workaround);
        return wa && wa->read_cntvct_el0;
}
#else
#define arch_timer_check_ool_workaround(t,a)            do { } while(0)
#define erratum_set_next_event_tval_virt(...)           ({BUG(); 0;})
#define erratum_set_next_event_tval_phys(...)           ({BUG(); 0;})
#define erratum_handler(fn, r, ...)                     ({false;})
#define arch_timer_this_cpu_has_cntvct_wa()             ({false;})
#endif /* CONFIG_ARM_ARCH_TIMER_OOL_WORKAROUND */

static __always_inline irqreturn_t timer_handler(const int access,
                                        struct clock_event_device *evt)
{
        unsigned long ctrl;

        ctrl = arch_timer_reg_read(access, ARCH_TIMER_REG_CTRL, evt);
        if (ctrl & ARCH_TIMER_CTRL_IT_STAT) {
                ctrl |= ARCH_TIMER_CTRL_IT_MASK;
                arch_timer_reg_write(access, ARCH_TIMER_REG_CTRL, ctrl, evt);
                evt->event_handler(evt);
                return IRQ_HANDLED;
        }

        return IRQ_NONE;
}

static irqreturn_t arch_timer_handler_virt(int irq, void *dev_id)
{
        struct clock_event_device *evt = dev_id;

        return timer_handler(ARCH_TIMER_VIRT_ACCESS, evt);
}

static irqreturn_t arch_timer_handler_phys(int irq, void *dev_id)
{
        struct clock_event_device *evt = dev_id;

        return timer_handler(ARCH_TIMER_PHYS_ACCESS, evt);
}

static irqreturn_t arch_timer_handler_phys_mem(int irq, void *dev_id)
{
        struct clock_event_device *evt = dev_id;

        return timer_handler(ARCH_TIMER_MEM_PHYS_ACCESS, evt);
}

static irqreturn_t arch_timer_handler_virt_mem(int irq, void *dev_id)
{
        struct clock_event_device *evt = dev_id;

        return timer_handler(ARCH_TIMER_MEM_VIRT_ACCESS, evt);
}

static __always_inline int timer_shutdown(const int access,
                                          struct clock_event_device *clk)
{
        unsigned long ctrl;

        ctrl = arch_timer_reg_read(access, ARCH_TIMER_REG_CTRL, clk);
        ctrl &= ~ARCH_TIMER_CTRL_ENABLE;
        arch_timer_reg_write(access, ARCH_TIMER_REG_CTRL, ctrl, clk);

        return 0;
}

static int arch_timer_shutdown_virt(struct clock_event_device *clk)
{
        return timer_shutdown(ARCH_TIMER_VIRT_ACCESS, clk);
}

static int arch_timer_shutdown_phys(struct clock_event_device *clk)
{
        return timer_shutdown(ARCH_TIMER_PHYS_ACCESS, clk);
}

static int arch_timer_shutdown_virt_mem(struct clock_event_device *clk)
{
        return timer_shutdown(ARCH_TIMER_MEM_VIRT_ACCESS, clk);
}

static int arch_timer_shutdown_phys_mem(struct clock_event_device *clk)
{
        return timer_shutdown(ARCH_TIMER_MEM_PHYS_ACCESS, clk);
}

static __always_inline void set_next_event(const int access, unsigned long evt,
                                           struct clock_event_device *clk)
{
        unsigned long ctrl;
        ctrl = arch_timer_reg_read(access, ARCH_TIMER_REG_CTRL, clk);
        ctrl |= ARCH_TIMER_CTRL_ENABLE;
        ctrl &= ~ARCH_TIMER_CTRL_IT_MASK;
        arch_timer_reg_write(access, ARCH_TIMER_REG_TVAL, evt, clk);
        arch_timer_reg_write(access, ARCH_TIMER_REG_CTRL, ctrl, clk);
}

static int arch_timer_set_next_event_virt(unsigned long evt,
                                          struct clock_event_device *clk)
{
        int ret;

        if (erratum_handler(set_next_event_virt, ret, evt, clk))
                return ret;

        set_next_event(ARCH_TIMER_VIRT_ACCESS, evt, clk);
        return 0;
}

static int arch_timer_set_next_event_phys(unsigned long evt,
                                          struct clock_event_device *clk)
{
        int ret;

        if (erratum_handler(set_next_event_phys, ret, evt, clk))
                return ret;

        set_next_event(ARCH_TIMER_PHYS_ACCESS, evt, clk);
        return 0;
}

static int arch_timer_set_next_event_virt_mem(unsigned long evt,
                                              struct clock_event_device *clk)
{
        set_next_event(ARCH_TIMER_MEM_VIRT_ACCESS, evt, clk);
        return 0;
}

static int arch_timer_set_next_event_phys_mem(unsigned long evt,
                                              struct clock_event_device *clk)
{
        set_next_event(ARCH_TIMER_MEM_PHYS_ACCESS, evt, clk);
        return 0;
}

static void __arch_timer_setup(unsigned type,
                               struct clock_event_device *clk)
{
        clk->features = CLOCK_EVT_FEAT_ONESHOT;

        if (type == ARCH_TIMER_TYPE_CP15) {
                if (arch_timer_c3stop)
                        clk->features |= CLOCK_EVT_FEAT_C3STOP;
                clk->name = "arch_sys_timer";
                clk->rating = 450;
                clk->cpumask = cpumask_of(smp_processor_id());
                clk->irq = arch_timer_ppi[arch_timer_uses_ppi];
                switch (arch_timer_uses_ppi) {
                case ARCH_TIMER_VIRT_PPI:
                        clk->set_state_shutdown = arch_timer_shutdown_virt;
                        clk->set_state_oneshot_stopped = arch_timer_shutdown_virt;
                        clk->set_next_event = arch_timer_set_next_event_virt;
                        break;
                case ARCH_TIMER_PHYS_SECURE_PPI:
                case ARCH_TIMER_PHYS_NONSECURE_PPI:
                case ARCH_TIMER_HYP_PPI:
                        clk->set_state_shutdown = arch_timer_shutdown_phys;
                        clk->set_state_oneshot_stopped = arch_timer_shutdown_phys;
                        clk->set_next_event = arch_timer_set_next_event_phys;
                        break;
                default:
                        BUG();
                }

                arch_timer_check_ool_workaround(ate_match_local_cap_id, NULL);
        } else {
                clk->features |= CLOCK_EVT_FEAT_DYNIRQ;
                clk->name = "arch_mem_timer";
                clk->rating = 400;
                clk->cpumask = cpu_all_mask;
                if (arch_timer_mem_use_virtual) {
                        clk->set_state_shutdown = arch_timer_shutdown_virt_mem;
                        clk->set_state_oneshot_stopped = arch_timer_shutdown_virt_mem;
                        clk->set_next_event =
                                arch_timer_set_next_event_virt_mem;
                } else {
                        clk->set_state_shutdown = arch_timer_shutdown_phys_mem;
                        clk->set_state_oneshot_stopped = arch_timer_shutdown_phys_mem;
                        clk->set_next_event =
                                arch_timer_set_next_event_phys_mem;
                }
        }

        clk->set_state_shutdown(clk);

        clockevents_config_and_register(clk, arch_timer_rate, 0xf, 0x7fffffff);
}

static void arch_timer_evtstrm_enable(int divider)
{
        u32 cntkctl = arch_timer_get_cntkctl();

        cntkctl &= ~ARCH_TIMER_EVT_TRIGGER_MASK;
        /* Set the divider and enable virtual event stream */
        cntkctl |= (divider << ARCH_TIMER_EVT_TRIGGER_SHIFT)
                        | ARCH_TIMER_VIRT_EVT_EN;
        arch_timer_set_cntkctl(cntkctl);
        elf_hwcap |= HWCAP_EVTSTRM;
#ifdef CONFIG_COMPAT
        compat_elf_hwcap |= COMPAT_HWCAP_EVTSTRM;
#endif
}

static void arch_timer_configure_evtstream(void)
{
        int evt_stream_div, pos;

        /* Find the closest power of two to the divisor */
        evt_stream_div = arch_timer_rate / ARCH_TIMER_EVT_STREAM_FREQ;
        pos = fls(evt_stream_div);
        if (pos > 1 && !(evt_stream_div & (1 << (pos - 2))))
                pos--;
        /* enable event stream */
        arch_timer_evtstrm_enable(min(pos, 15));
}

static void arch_counter_set_user_access(void)
{
        u32 cntkctl = arch_timer_get_cntkctl();

        /* Disable user access to the timers and both counters */
        /* Also disable virtual event stream */
        cntkctl &= ~(ARCH_TIMER_USR_PT_ACCESS_EN
                        | ARCH_TIMER_USR_VT_ACCESS_EN
                        | ARCH_TIMER_USR_VCT_ACCESS_EN
                        | ARCH_TIMER_VIRT_EVT_EN
                        | ARCH_TIMER_USR_PCT_ACCESS_EN);

        /*
         * Enable user access to the virtual counter if it doesn't
         * need to be workaround. The vdso may have been already
         * disabled though.
         */
        if (arch_timer_this_cpu_has_cntvct_wa())
                pr_info("CPU%d: Trapping CNTVCT access\n", smp_processor_id());
        else
                cntkctl |= ARCH_TIMER_USR_VCT_ACCESS_EN;

        arch_timer_set_cntkctl(cntkctl);
}

static bool arch_timer_has_nonsecure_ppi(void)
{
        return (arch_timer_uses_ppi == ARCH_TIMER_PHYS_SECURE_PPI &&
                arch_timer_ppi[ARCH_TIMER_PHYS_NONSECURE_PPI]);
}

static u32 check_ppi_trigger(int irq)
{
        u32 flags = irq_get_trigger_type(irq);

        if (flags != IRQF_TRIGGER_HIGH && flags != IRQF_TRIGGER_LOW) {
                pr_warn("WARNING: Invalid trigger for IRQ%d, assuming level low\n", irq);
                pr_warn("WARNING: Please fix your firmware\n");
                flags = IRQF_TRIGGER_LOW;
        }

        return flags;
}

static int arch_timer_starting_cpu(unsigned int cpu)
{
        struct clock_event_device *clk = this_cpu_ptr(arch_timer_evt);
        u32 flags;

        __arch_timer_setup(ARCH_TIMER_TYPE_CP15, clk);

        flags = check_ppi_trigger(arch_timer_ppi[arch_timer_uses_ppi]);
        enable_percpu_irq(arch_timer_ppi[arch_timer_uses_ppi], flags);

        if (arch_timer_has_nonsecure_ppi()) {
                flags = check_ppi_trigger(arch_timer_ppi[ARCH_TIMER_PHYS_NONSECURE_PPI]);
                enable_percpu_irq(arch_timer_ppi[ARCH_TIMER_PHYS_NONSECURE_PPI],
                                  flags);
        }

        arch_counter_set_user_access();
        if (evtstrm_enable)
                arch_timer_configure_evtstream();

        return 0;
}

/*
 * For historical reasons, when probing with DT we use whichever (non-zero)
 * rate was probed first, and don't verify that others match. If the first node
 * probed has a clock-frequency property, this overrides the HW register.
 */
static void arch_timer_of_configure_rate(u32 rate, struct device_node *np)
{
        /* Who has more than one independent system counter? */
        if (arch_timer_rate)
                return;

        if (of_property_read_u32(np, "clock-frequency", &arch_timer_rate))
                arch_timer_rate = rate;

        /* Check the timer frequency. */
        if (arch_timer_rate == 0)
                pr_warn("frequency not available\n");
}

static void arch_timer_banner(unsigned type)
{
        pr_info("%s%s%s timer(s) running at %lu.%02luMHz (%s%s%s).\n",
                type & ARCH_TIMER_TYPE_CP15 ? "cp15" : "",
                type == (ARCH_TIMER_TYPE_CP15 | ARCH_TIMER_TYPE_MEM) ?
                        " and " : "",
                type & ARCH_TIMER_TYPE_MEM ? "mmio" : "",
                (unsigned long)arch_timer_rate / 1000000,
                (unsigned long)(arch_timer_rate / 10000) % 100,
                type & ARCH_TIMER_TYPE_CP15 ?
                        (arch_timer_uses_ppi == ARCH_TIMER_VIRT_PPI) ? "virt" : "phys" :
                        "",
                type == (ARCH_TIMER_TYPE_CP15 | ARCH_TIMER_TYPE_MEM) ? "/" : "",
                type & ARCH_TIMER_TYPE_MEM ?
                        arch_timer_mem_use_virtual ? "virt" : "phys" :
                        "");
}

u32 arch_timer_get_rate(void)
{
        return arch_timer_rate;
}

static u64 arch_counter_get_cntvct_mem(void)
{
        u32 vct_lo, vct_hi, tmp_hi;

        do {
                vct_hi = readl_relaxed(arch_counter_base + CNTVCT_HI);
                vct_lo = readl_relaxed(arch_counter_base + CNTVCT_LO);
                tmp_hi = readl_relaxed(arch_counter_base + CNTVCT_HI);
        } while (vct_hi != tmp_hi);

        return ((u64) vct_hi << 32) | vct_lo;
}

static struct arch_timer_kvm_info arch_timer_kvm_info;

struct arch_timer_kvm_info *arch_timer_get_kvm_info(void)
{
        return &arch_timer_kvm_info;
}

static void __init arch_counter_register(unsigned type)
{
        u64 start_count;

        /* Register the CP15 based counter if we have one */
        if (type & ARCH_TIMER_TYPE_CP15) {
                if (IS_ENABLED(CONFIG_ARM64) ||
                    arch_timer_uses_ppi == ARCH_TIMER_VIRT_PPI)
                        arch_timer_read_counter = arch_counter_get_cntpct;
                else
                        arch_timer_read_counter = arch_counter_get_cntpct;

                clocksource_counter.archdata.vdso_direct = vdso_default;
        } else {
                arch_timer_read_counter = arch_counter_get_cntvct_mem;
        }

        if (!arch_counter_suspend_stop)
                clocksource_counter.flags |= CLOCK_SOURCE_SUSPEND_NONSTOP;
        start_count = arch_timer_read_counter();
        clocksource_register_hz(&clocksource_counter, arch_timer_rate);
        cyclecounter.mult = clocksource_counter.mult;
        cyclecounter.shift = clocksource_counter.shift;
        timecounter_init(&arch_timer_kvm_info.timecounter,
                         &cyclecounter, start_count);

        /* 56 bits minimum, so we assume worst case rollover */
        sched_clock_register(arch_timer_read_counter, 56, arch_timer_rate);
}

static void arch_timer_stop(struct clock_event_device *clk)
{
        pr_debug("disable IRQ%d cpu #%d\n", clk->irq, smp_processor_id());

        disable_percpu_irq(arch_timer_ppi[arch_timer_uses_ppi]);
        if (arch_timer_has_nonsecure_ppi())
                disable_percpu_irq(arch_timer_ppi[ARCH_TIMER_PHYS_NONSECURE_PPI]);

        clk->set_state_shutdown(clk);
}

static int arch_timer_dying_cpu(unsigned int cpu)
{
        struct clock_event_device *clk = this_cpu_ptr(arch_timer_evt);

        arch_timer_stop(clk);
        return 0;
}

#ifdef CONFIG_CPU_PM
static DEFINE_PER_CPU(unsigned long, saved_cntkctl);
static int arch_timer_cpu_pm_notify(struct notifier_block *self,
                                    unsigned long action, void *hcpu)
{
        if (action == CPU_PM_ENTER)
                __this_cpu_write(saved_cntkctl, arch_timer_get_cntkctl());
        else if (action == CPU_PM_ENTER_FAILED || action == CPU_PM_EXIT)
                arch_timer_set_cntkctl(__this_cpu_read(saved_cntkctl));
        return NOTIFY_OK;
}

static struct notifier_block arch_timer_cpu_pm_notifier = {
        .notifier_call = arch_timer_cpu_pm_notify,
};

static int __init arch_timer_cpu_pm_init(void)
{
        return cpu_pm_register_notifier(&arch_timer_cpu_pm_notifier);
}

static void __init arch_timer_cpu_pm_deinit(void)
{
        WARN_ON(cpu_pm_unregister_notifier(&arch_timer_cpu_pm_notifier));
}

#else
static int __init arch_timer_cpu_pm_init(void)
{
        return 0;
}

static void __init arch_timer_cpu_pm_deinit(void)
{
}
#endif

static int __init arch_timer_register(void)
{
        int err;
        int ppi;

        arch_timer_evt = alloc_percpu(struct clock_event_device);
        if (!arch_timer_evt) {
                err = -ENOMEM;
                goto out;
        }

        ppi = arch_timer_ppi[arch_timer_uses_ppi];
        switch (arch_timer_uses_ppi) {
        case ARCH_TIMER_VIRT_PPI:
                err = request_percpu_irq(ppi, arch_timer_handler_virt,
                                         "arch_timer", arch_timer_evt);
                break;
        case ARCH_TIMER_PHYS_SECURE_PPI:
        case ARCH_TIMER_PHYS_NONSECURE_PPI:
                err = request_percpu_irq(ppi, arch_timer_handler_phys,
                                         "arch_timer", arch_timer_evt);
                if (!err && arch_timer_has_nonsecure_ppi()) {
                        ppi = arch_timer_ppi[ARCH_TIMER_PHYS_NONSECURE_PPI];
                        err = request_percpu_irq(ppi, arch_timer_handler_phys,
                                                 "arch_timer", arch_timer_evt);
                        if (err)
                                free_percpu_irq(arch_timer_ppi[ARCH_TIMER_PHYS_SECURE_PPI],
                                                arch_timer_evt);
                }
                break;
        case ARCH_TIMER_HYP_PPI:
                err = request_percpu_irq(ppi, arch_timer_handler_phys,
                                         "arch_timer", arch_timer_evt);
                break;
        default:
                BUG();
        }

        if (err) {
                pr_err("can't register interrupt %d (%d)\n", ppi, err);
                goto out_free;
        }

        err = arch_timer_cpu_pm_init();
        if (err)
                goto out_unreg_notify;


        if (mct_enable) {
                /*
                 * FIXME: The arm64 architecture enables the arm_arch_timer always
                 * even if arm_arch_timer is not stable. When Exynos5433 uses the
                 * arm_arch_timer, it fails to enable/disble the secondary cpu.
                 * To fix the hotplug issue of secondary cpu, if Exynos's MCT timer
                 * is enabled, arm_arch_timer doesn't register the clockevent
                 * for Per-CPU.
                 */
                return 0;
        } else {
                /* Register and immediately configure the timer on the boot CPU */
                err = cpuhp_setup_state(CPUHP_AP_ARM_ARCH_TIMER_STARTING,
                                        "clockevents/arm/arch_timer:starting",
                                        arch_timer_starting_cpu, arch_timer_dying_cpu);
                if (err)
                        goto out_unreg_cpupm;
        }

        return 0;

out_unreg_cpupm:
        arch_timer_cpu_pm_deinit();

out_unreg_notify:
        free_percpu_irq(arch_timer_ppi[arch_timer_uses_ppi], arch_timer_evt);
        if (arch_timer_has_nonsecure_ppi())
                free_percpu_irq(arch_timer_ppi[ARCH_TIMER_PHYS_NONSECURE_PPI],
                                arch_timer_evt);

out_free:
        free_percpu(arch_timer_evt);
out:
        return err;
}

static int __init arch_timer_mem_register(void __iomem *base, unsigned int irq)
{
        int ret;
        irq_handler_t func;
        struct arch_timer *t;

        t = kzalloc(sizeof(*t), GFP_KERNEL);
        if (!t)
                return -ENOMEM;

        t->base = base;
        t->evt.irq = irq;
        __arch_timer_setup(ARCH_TIMER_TYPE_MEM, &t->evt);

        if (arch_timer_mem_use_virtual)
                func = arch_timer_handler_virt_mem;
        else
                func = arch_timer_handler_phys_mem;

        ret = request_irq(irq, func, IRQF_TIMER, "arch_mem_timer", &t->evt);
        if (ret) {
                pr_err("Failed to request mem timer irq\n");
                kfree(t);
        }

        return ret;
}

static const struct of_device_id arch_timer_of_match[] __initconst = {
        { .compatible   = "arm,armv7-timer",    },
        { .compatible   = "arm,armv8-timer",    },
        {},
};

static const struct of_device_id arch_timer_mem_of_match[] __initconst = {
        { .compatible   = "arm,armv7-timer-mem", },
        {},
};

static bool __init arch_timer_needs_of_probing(void)
{
        struct device_node *dn;
        bool needs_probing = false;
        unsigned int mask = ARCH_TIMER_TYPE_CP15 | ARCH_TIMER_TYPE_MEM;

        /* We have two timers, and both device-tree nodes are probed. */
        if ((arch_timers_present & mask) == mask)
                return false;

        /*
         * Only one type of timer is probed,
         * check if we have another type of timer node in device-tree.
         */
        if (arch_timers_present & ARCH_TIMER_TYPE_CP15)
                dn = of_find_matching_node(NULL, arch_timer_mem_of_match);
        else
                dn = of_find_matching_node(NULL, arch_timer_of_match);

        if (dn && of_device_is_available(dn))
                needs_probing = true;

        of_node_put(dn);

        return needs_probing;
}

static int __init arch_timer_common_init(void)
{
        arch_timer_banner(arch_timers_present);
        arch_counter_register(arch_timers_present);
        return arch_timer_arch_init();
}

/**
 * arch_timer_select_ppi() - Select suitable PPI for the current system.
 *
 * If HYP mode is available, we know that the physical timer
 * has been configured to be accessible from PL1. Use it, so
 * that a guest can use the virtual timer instead.
 *
 * On ARMv8.1 with VH extensions, the kernel runs in HYP. VHE
 * accesses to CNTP_*_EL1 registers are silently redirected to
 * their CNTHP_*_EL2 counterparts, and use a different PPI
 * number.
 *
 * If no interrupt provided for virtual timer, we'll have to
 * stick to the physical timer. It'd better be accessible...
 * For arm64 we never use the secure interrupt.
 *
 * Return: a suitable PPI type for the current system.
 */
static enum arch_timer_ppi_nr __init arch_timer_select_ppi(void)
{
        if (is_kernel_in_hyp_mode())
                return ARCH_TIMER_HYP_PPI;

        if (!is_hyp_mode_available() && arch_timer_ppi[ARCH_TIMER_VIRT_PPI])
                return ARCH_TIMER_VIRT_PPI;

        if (IS_ENABLED(CONFIG_ARM64))
                return ARCH_TIMER_PHYS_NONSECURE_PPI;

        return ARCH_TIMER_PHYS_SECURE_PPI;
}

static int __init arch_timer_of_init(struct device_node *np)
{
        int i, ret;
        u32 rate;

        if (arch_timers_present & ARCH_TIMER_TYPE_CP15) {
                pr_warn("multiple nodes in dt, skipping\n");
                return 0;
        }

        arch_timers_present |= ARCH_TIMER_TYPE_CP15;
        for (i = ARCH_TIMER_PHYS_SECURE_PPI; i < ARCH_TIMER_MAX_TIMER_PPI; i++)
                arch_timer_ppi[i] = irq_of_parse_and_map(np, i);

        arch_timer_kvm_info.virtual_irq = arch_timer_ppi[ARCH_TIMER_VIRT_PPI];

        rate = arch_timer_get_cntfrq();
        arch_timer_of_configure_rate(rate, np);

        arch_timer_c3stop = !of_property_read_bool(np, "always-on");

        /* Check for globally applicable workarounds */
        arch_timer_check_ool_workaround(ate_match_dt, np);

        /*
         * If we cannot rely on firmware initializing the timer registers then
         * we should use the physical timers instead.
         */
        if (IS_ENABLED(CONFIG_ARM) &&
            of_property_read_bool(np, "arm,cpu-registers-not-fw-configured"))
                arch_timer_uses_ppi = ARCH_TIMER_PHYS_SECURE_PPI;
        else
                arch_timer_uses_ppi = arch_timer_select_ppi();

        if (!arch_timer_ppi[arch_timer_uses_ppi]) {
                pr_err("No interrupt available, giving up\n");
                return -EINVAL;
        }

        /* On some systems, the counter stops ticking when in suspend. */
        arch_counter_suspend_stop = of_property_read_bool(np,
                                                         "arm,no-tick-in-suspend");

        ret = arch_timer_register();
        if (ret)
                return ret;

        if (arch_timer_needs_of_probing())
                return 0;

        return arch_timer_common_init();
}
TIMER_OF_DECLARE(armv7_arch_timer, "arm,armv7-timer", arch_timer_of_init);
TIMER_OF_DECLARE(armv8_arch_timer, "arm,armv8-timer", arch_timer_of_init);

static u32 __init
arch_timer_mem_frame_get_cntfrq(struct arch_timer_mem_frame *frame)
{
        void __iomem *base;
        u32 rate;

        base = ioremap(frame->cntbase, frame->size);
        if (!base) {
                pr_err("Unable to map frame @ %pa\n", &frame->cntbase);
                return 0;
        }

        rate = readl_relaxed(base + CNTFRQ);

        iounmap(base);

        return rate;
}

static struct arch_timer_mem_frame * __init
arch_timer_mem_find_best_frame(struct arch_timer_mem *timer_mem)
{
        struct arch_timer_mem_frame *frame, *best_frame = NULL;
        void __iomem *cntctlbase;
        u32 cnttidr;
        int i;

        cntctlbase = ioremap(timer_mem->cntctlbase, timer_mem->size);
        if (!cntctlbase) {
                pr_err("Can't map CNTCTLBase @ %pa\n",
                        &timer_mem->cntctlbase);
                return NULL;
        }

        cnttidr = readl_relaxed(cntctlbase + CNTTIDR);

        /*
         * Try to find a virtual capable frame. Otherwise fall back to a
         * physical capable frame.
         */
        for (i = 0; i < ARCH_TIMER_MEM_MAX_FRAMES; i++) {
                u32 cntacr = CNTACR_RFRQ | CNTACR_RWPT | CNTACR_RPCT |
                             CNTACR_RWVT | CNTACR_RVOFF | CNTACR_RVCT;

                frame = &timer_mem->frame[i];
                if (!frame->valid)
                        continue;

                /* Try enabling everything, and see what sticks */
                writel_relaxed(cntacr, cntctlbase + CNTACR(i));
                cntacr = readl_relaxed(cntctlbase + CNTACR(i));

                if ((cnttidr & CNTTIDR_VIRT(i)) &&
                    !(~cntacr & (CNTACR_RWVT | CNTACR_RVCT))) {
                        best_frame = frame;
                        arch_timer_mem_use_virtual = true;
                        break;
                }

                if (~cntacr & (CNTACR_RWPT | CNTACR_RPCT))
                        continue;

                best_frame = frame;
        }

        iounmap(cntctlbase);

        return best_frame;
}

static int __init
arch_timer_mem_frame_register(struct arch_timer_mem_frame *frame)
{
        void __iomem *base;
        int ret, irq = 0;

        if (arch_timer_mem_use_virtual)
                irq = frame->virt_irq;
        else
                irq = frame->phys_irq;

        if (!irq) {
                pr_err("Frame missing %s irq.\n",
                       arch_timer_mem_use_virtual ? "virt" : "phys");
                return -EINVAL;
        }

        if (!request_mem_region(frame->cntbase, frame->size,
                                "arch_mem_timer"))
                return -EBUSY;

        base = ioremap(frame->cntbase, frame->size);
        if (!base) {
                pr_err("Can't map frame's registers\n");
                return -ENXIO;
        }

        ret = arch_timer_mem_register(base, irq);
        if (ret) {
                iounmap(base);
                return ret;
        }

        arch_counter_base = base;
        arch_timers_present |= ARCH_TIMER_TYPE_MEM;

        return 0;
}

static int __init arch_timer_mem_of_init(struct device_node *np)
{
        struct arch_timer_mem *timer_mem;
        struct arch_timer_mem_frame *frame;
        struct device_node *frame_node;
        struct resource res;
        int ret = -EINVAL;
        u32 rate;

        timer_mem = kzalloc(sizeof(*timer_mem), GFP_KERNEL);
        if (!timer_mem)
                return -ENOMEM;

        if (of_address_to_resource(np, 0, &res))
                goto out;
        timer_mem->cntctlbase = res.start;
        timer_mem->size = resource_size(&res);

        for_each_available_child_of_node(np, frame_node) {
                u32 n;
                struct arch_timer_mem_frame *frame;

                if (of_property_read_u32(frame_node, "frame-number", &n)) {
                        pr_err(FW_BUG "Missing frame-number.\n");
                        of_node_put(frame_node);
                        goto out;
                }
                if (n >= ARCH_TIMER_MEM_MAX_FRAMES) {
                        pr_err(FW_BUG "Wrong frame-number, only 0-%u are permitted.\n",
                               ARCH_TIMER_MEM_MAX_FRAMES - 1);
                        of_node_put(frame_node);
                        goto out;
                }
                frame = &timer_mem->frame[n];

                if (frame->valid) {
                        pr_err(FW_BUG "Duplicated frame-number.\n");
                        of_node_put(frame_node);
                        goto out;
                }

                if (of_address_to_resource(frame_node, 0, &res)) {
                        of_node_put(frame_node);
                        goto out;
                }
                frame->cntbase = res.start;
                frame->size = resource_size(&res);

                frame->virt_irq = irq_of_parse_and_map(frame_node,
                                                       ARCH_TIMER_VIRT_SPI);
                frame->phys_irq = irq_of_parse_and_map(frame_node,
                                                       ARCH_TIMER_PHYS_SPI);

                frame->valid = true;
        }

        frame = arch_timer_mem_find_best_frame(timer_mem);
        if (!frame) {
                pr_err("Unable to find a suitable frame in timer @ %pa\n",
                        &timer_mem->cntctlbase);
                ret = -EINVAL;
                goto out;
        }

        rate = arch_timer_mem_frame_get_cntfrq(frame);
        arch_timer_of_configure_rate(rate, np);

        ret = arch_timer_mem_frame_register(frame);
        if (!ret && !arch_timer_needs_of_probing())
                ret = arch_timer_common_init();
out:
        kfree(timer_mem);
        return ret;
}
TIMER_OF_DECLARE(armv7_arch_timer_mem, "arm,armv7-timer-mem",
                       arch_timer_mem_of_init);

#ifdef CONFIG_ACPI_GTDT
static int __init
arch_timer_mem_verify_cntfrq(struct arch_timer_mem *timer_mem)
{
        struct arch_timer_mem_frame *frame;
        u32 rate;
        int i;

        for (i = 0; i < ARCH_TIMER_MEM_MAX_FRAMES; i++) {
                frame = &timer_mem->frame[i];

                if (!frame->valid)
                        continue;

                rate = arch_timer_mem_frame_get_cntfrq(frame);
                if (rate == arch_timer_rate)
                        continue;

                pr_err(FW_BUG "CNTFRQ mismatch: frame @ %pa: (0x%08lx), CPU: (0x%08lx)\n",
                        &frame->cntbase,
                        (unsigned long)rate, (unsigned long)arch_timer_rate);

                return -EINVAL;
        }

        return 0;
}

static int __init arch_timer_mem_acpi_init(int platform_timer_count)
{
        struct arch_timer_mem *timers, *timer;
        struct arch_timer_mem_frame *frame, *best_frame = NULL;
        int timer_count, i, ret = 0;

        timers = kcalloc(platform_timer_count, sizeof(*timers),
                            GFP_KERNEL);
        if (!timers)
                return -ENOMEM;

        ret = acpi_arch_timer_mem_init(timers, &timer_count);
        if (ret || !timer_count)
                goto out;

        /*
         * While unlikely, it's theoretically possible that none of the frames
         * in a timer expose the combination of feature we want.
         */
        for (i = 0; i < timer_count; i++) {
                timer = &timers[i];

                frame = arch_timer_mem_find_best_frame(timer);
                if (!best_frame)
                        best_frame = frame;

                ret = arch_timer_mem_verify_cntfrq(timer);
                if (ret) {
                        pr_err("Disabling MMIO timers due to CNTFRQ mismatch\n");
                        goto out;
                }

                if (!best_frame) /* implies !frame */
                        /*
                         * Only complain about missing suitable frames if we
                         * haven't already found one in a previous iteration.
                         */
                        pr_err("Unable to find a suitable frame in timer @ %pa\n",
                                &timer->cntctlbase);
        }

        if (best_frame)
                ret = arch_timer_mem_frame_register(best_frame);
out:
        kfree(timers);
        return ret;
}

/* Initialize per-processor generic timer and memory-mapped timer(if present) */
static int __init arch_timer_acpi_init(struct acpi_table_header *table)
{
        int ret, platform_timer_count;

        if (arch_timers_present & ARCH_TIMER_TYPE_CP15) {
                pr_warn("already initialized, skipping\n");
                return -EINVAL;
        }

        arch_timers_present |= ARCH_TIMER_TYPE_CP15;

        ret = acpi_gtdt_init(table, &platform_timer_count);
        if (ret) {
                pr_err("Failed to init GTDT table.\n");
                return ret;
        }

        arch_timer_ppi[ARCH_TIMER_PHYS_NONSECURE_PPI] =
                acpi_gtdt_map_ppi(ARCH_TIMER_PHYS_NONSECURE_PPI);

        arch_timer_ppi[ARCH_TIMER_VIRT_PPI] =
                acpi_gtdt_map_ppi(ARCH_TIMER_VIRT_PPI);

        arch_timer_ppi[ARCH_TIMER_HYP_PPI] =
                acpi_gtdt_map_ppi(ARCH_TIMER_HYP_PPI);

        arch_timer_kvm_info.virtual_irq = arch_timer_ppi[ARCH_TIMER_VIRT_PPI];

        /*
         * When probing via ACPI, we have no mechanism to override the sysreg
         * CNTFRQ value. This *must* be correct.
         */
        arch_timer_rate = arch_timer_get_cntfrq();
        if (!arch_timer_rate) {
                pr_err(FW_BUG "frequency not available.\n");
                return -EINVAL;
        }

        arch_timer_uses_ppi = arch_timer_select_ppi();
        if (!arch_timer_ppi[arch_timer_uses_ppi]) {
                pr_err("No interrupt available, giving up\n");
                return -EINVAL;
        }

        /* Always-on capability */
        arch_timer_c3stop = acpi_gtdt_c3stop(arch_timer_uses_ppi);

        /* Check for globally applicable workarounds */
        arch_timer_check_ool_workaround(ate_match_acpi_oem_info, table);

        ret = arch_timer_register();
        if (ret)
                return ret;

        if (platform_timer_count &&
            arch_timer_mem_acpi_init(platform_timer_count))
                pr_err("Failed to initialize memory-mapped timer.\n");

        return arch_timer_common_init();
}
TIMER_ACPI_DECLARE(arch_timer, ACPI_SIG_GTDT, arch_timer_acpi_init);
#endif