/*
   *  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.
   */
  #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/acpi.h>
  
  #include <asm/arch_timer.h>
  #include <asm/virt.h>
  
  #include <clocksource/arm_arch_timer.h>
  
  #define CNTTIDR		0x08
  #define CNTTIDR_VIRT(n)	(BIT(1) << ((n) * 4))
  
  #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
  
  #define ARCH_CP15_TIMER	BIT(0)
  #define ARCH_MEM_TIMER	BIT(1)
  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;
  
  enum ppi_nr {
  	PHYS_SECURE_PPI,
  	PHYS_NONSECURE_PPI,
  	VIRT_PPI,
  	HYP_PPI,
  	MAX_TIMER_PPI
  };
  
  static int arch_timer_ppi[MAX_TIMER_PPI];
  
  static struct clock_event_device __percpu *arch_timer_evt;
  
  static bool arch_timer_use_virtual = true;
  static bool arch_timer_c3stop;
  static bool arch_timer_mem_use_virtual;
  
  /*
   * 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;
  }
  
  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)
  {
  	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)
  {
  	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_CP15_TIMER) {
  		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());
  		if (arch_timer_use_virtual) {
  			clk->irq = arch_timer_ppi[VIRT_PPI];
  			clk->set_state_shutdown = arch_timer_shutdown_virt;
  			clk->set_next_event = arch_timer_set_next_event_virt;
  		} else {
  			clk->irq = arch_timer_ppi[PHYS_SECURE_PPI];
  			clk->set_state_shutdown = arch_timer_shutdown_phys;
  			clk->set_next_event = arch_timer_set_next_event_phys;
  		}
  	} 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_next_event =
  				arch_timer_set_next_event_virt_mem;
  		} else {
  			clk->set_state_shutdown = 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 the physical counter */
  	/* Also disable virtual event stream */
  	cntkctl &= ~(ARCH_TIMER_USR_PT_ACCESS_EN
  			| ARCH_TIMER_USR_VT_ACCESS_EN
  			| ARCH_TIMER_VIRT_EVT_EN
  			| ARCH_TIMER_USR_PCT_ACCESS_EN);
  
  	/* Enable user access to the virtual counter */
  	cntkctl |= ARCH_TIMER_USR_VCT_ACCESS_EN;
  
  	arch_timer_set_cntkctl(cntkctl);
  }
  
  static int arch_timer_setup(struct clock_event_device *clk)
  {
  	__arch_timer_setup(ARCH_CP15_TIMER, clk);
  
  	if (arch_timer_use_virtual)
  		enable_percpu_irq(arch_timer_ppi[VIRT_PPI], 0);
  	else {
  		enable_percpu_irq(arch_timer_ppi[PHYS_SECURE_PPI], 0);
  		if (arch_timer_ppi[PHYS_NONSECURE_PPI])
  			enable_percpu_irq(arch_timer_ppi[PHYS_NONSECURE_PPI], 0);
  	}
  
  	arch_counter_set_user_access();
  	if (IS_ENABLED(CONFIG_ARM_ARCH_TIMER_EVTSTREAM))
  		arch_timer_configure_evtstream();
  
  	return 0;
  }
  
  static void
  arch_timer_detect_rate(void __iomem *cntbase, struct device_node *np)
  {
  	/* Who has more than one independent system counter? */
  	if (arch_timer_rate)
  		return;
  
  	/*
  	 * Try to determine the frequency from the device tree or CNTFRQ,
  	 * if ACPI is enabled, get the frequency from CNTFRQ ONLY.
  	 */
  	if (!acpi_disabled ||
  	    of_property_read_u32(np, "clock-frequency", &arch_timer_rate)) {
  		if (cntbase)
  			arch_timer_rate = readl_relaxed(cntbase + CNTFRQ);
  		else
  			arch_timer_rate = arch_timer_get_cntfrq();
  	}
  
  	/* Check the timer frequency. */
  	if (arch_timer_rate == 0)
  		pr_warn("Architected timer frequency not available
  ");
  }
  
  static void arch_timer_banner(unsigned type)
  {
  	pr_info("Architected %s%s%s timer(s) running at %lu.%02luMHz (%s%s%s).
  ",
  		     type & ARCH_CP15_TIMER ? "cp15" : "",
  		     type == (ARCH_CP15_TIMER | ARCH_MEM_TIMER) ?  " and " : "",
  		     type & ARCH_MEM_TIMER ? "mmio" : "",
  		     (unsigned long)arch_timer_rate / 1000000,
  		     (unsigned long)(arch_timer_rate / 10000) % 100,
  		     type & ARCH_CP15_TIMER ?
  			arch_timer_use_virtual ? "virt" : "phys" :
  			"",
  		     type == (ARCH_CP15_TIMER | ARCH_MEM_TIMER) ?  "/" : "",
  		     type & ARCH_MEM_TIMER ?
  			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;
  }
  
  /*
   * 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 cycle_t arch_counter_read(struct clocksource *cs)
  {
  	return arch_timer_read_counter();
  }
  
  static cycle_t 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 | CLOCK_SOURCE_SUSPEND_NONSTOP,
  };
  
  static struct cyclecounter cyclecounter = {
  	.read	= arch_counter_read_cc,
  	.mask	= CLOCKSOURCE_MASK(56),
  };
  
  static struct timecounter timecounter;
  
  struct timecounter *arch_timer_get_timecounter(void)
  {
  	return &timecounter;
  }
  
  static void __init arch_counter_register(unsigned type)
  {
  	u64 start_count;
  
  	/* Register the CP15 based counter if we have one */
  	if (type & ARCH_CP15_TIMER) {
  		if (IS_ENABLED(CONFIG_ARM64) || arch_timer_use_virtual)
  			arch_timer_read_counter = arch_counter_get_cntvct;
  		else
  			arch_timer_read_counter = arch_counter_get_cntpct;
  	} else {
  		arch_timer_read_counter = arch_counter_get_cntvct_mem;
  
  		/* If the clocksource name is "arch_sys_counter" the
  		 * VDSO will attempt to read the CP15-based counter.
  		 * Ensure this does not happen when CP15-based
  		 * counter is not available.
  		 */
  		clocksource_counter.name = "arch_mem_counter";
  	}
  
  	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(&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("arch_timer_teardown disable IRQ%d cpu #%d
  ",
  		 clk->irq, smp_processor_id());
  
  	if (arch_timer_use_virtual)
  		disable_percpu_irq(arch_timer_ppi[VIRT_PPI]);
  	else {
  		disable_percpu_irq(arch_timer_ppi[PHYS_SECURE_PPI]);
  		if (arch_timer_ppi[PHYS_NONSECURE_PPI])
  			disable_percpu_irq(arch_timer_ppi[PHYS_NONSECURE_PPI]);
  	}
  
  	clk->set_state_shutdown(clk);
  }
  
  static int arch_timer_cpu_notify(struct notifier_block *self,
  					   unsigned long action, void *hcpu)
  {
  	/*
  	 * Grab cpu pointer in each case to avoid spurious
  	 * preemptible warnings
  	 */
  	switch (action & ~CPU_TASKS_FROZEN) {
  	case CPU_STARTING:
  		arch_timer_setup(this_cpu_ptr(arch_timer_evt));
  		break;
  	case CPU_DYING:
  		arch_timer_stop(this_cpu_ptr(arch_timer_evt));
  		break;
  	}
  
  	return NOTIFY_OK;
  }
  
  static struct notifier_block arch_timer_cpu_nb = {
  	.notifier_call = arch_timer_cpu_notify,
  };
  
  #ifdef CONFIG_CPU_PM
  static unsigned int saved_cntkctl;
  static int arch_timer_cpu_pm_notify(struct notifier_block *self,
  				    unsigned long action, void *hcpu)
  {
  	if (action == CPU_PM_ENTER)
  		saved_cntkctl = arch_timer_get_cntkctl();
  	else if (action == CPU_PM_ENTER_FAILED || action == CPU_PM_EXIT)
  		arch_timer_set_cntkctl(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);
  }
  #else
  static int __init arch_timer_cpu_pm_init(void)
  {
  	return 0;
  }
  #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;
  	}
  
  	if (arch_timer_use_virtual) {
  		ppi = arch_timer_ppi[VIRT_PPI];
  		err = request_percpu_irq(ppi, arch_timer_handler_virt,
  					 "arch_timer", arch_timer_evt);
  	} else {
  		ppi = arch_timer_ppi[PHYS_SECURE_PPI];
  		err = request_percpu_irq(ppi, arch_timer_handler_phys,
  					 "arch_timer", arch_timer_evt);
  		if (!err && arch_timer_ppi[PHYS_NONSECURE_PPI]) {
  			ppi = arch_timer_ppi[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[PHYS_SECURE_PPI],
  						arch_timer_evt);
  		}
  	}
  
  	if (err) {
  		pr_err("arch_timer: can't register interrupt %d (%d)
  ",
  		       ppi, err);
  		goto out_free;
  	}
  
  	err = register_cpu_notifier(&arch_timer_cpu_nb);
  	if (err)
  		goto out_free_irq;
  
  	err = arch_timer_cpu_pm_init();
  	if (err)
  		goto out_unreg_notify;
  
  	/* Immediately configure the timer on the boot CPU */
  	arch_timer_setup(this_cpu_ptr(arch_timer_evt));
  
  	return 0;
  
  out_unreg_notify:
  	unregister_cpu_notifier(&arch_timer_cpu_nb);
  out_free_irq:
  	if (arch_timer_use_virtual)
  		free_percpu_irq(arch_timer_ppi[VIRT_PPI], arch_timer_evt);
  	else {
  		free_percpu_irq(arch_timer_ppi[PHYS_SECURE_PPI],
  				arch_timer_evt);
  		if (arch_timer_ppi[PHYS_NONSECURE_PPI])
  			free_percpu_irq(arch_timer_ppi[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_MEM_TIMER, &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("arch_timer: Failed to request mem timer irq
  ");
  		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_probing(int type, const struct of_device_id *matches)
  {
  	struct device_node *dn;
  	bool needs_probing = false;
  
  	dn = of_find_matching_node(NULL, matches);
  	if (dn && of_device_is_available(dn) && !(arch_timers_present & type))
  		needs_probing = true;
  	of_node_put(dn);
  
  	return needs_probing;
  }
  
  static void __init arch_timer_common_init(void)
  {
  	unsigned mask = ARCH_CP15_TIMER | ARCH_MEM_TIMER;
  
  	/* Wait until both nodes are probed if we have two timers */
  	if ((arch_timers_present & mask) != mask) {
  		if (arch_timer_needs_probing(ARCH_MEM_TIMER, arch_timer_mem_of_match))
  			return;
  		if (arch_timer_needs_probing(ARCH_CP15_TIMER, arch_timer_of_match))
  			return;
  	}
  
  	arch_timer_banner(arch_timers_present);
  	arch_counter_register(arch_timers_present);
  	arch_timer_arch_init();
  }
  
  static void __init arch_timer_init(void)
  {
  	/*
  	 * 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.
  	 *
  	 * If no interrupt provided for virtual timer, we'll have to
  	 * stick to the physical timer. It'd better be accessible...
  	 */
  	if (is_hyp_mode_available() || !arch_timer_ppi[VIRT_PPI]) {
  		arch_timer_use_virtual = false;
  
  		if (!arch_timer_ppi[PHYS_SECURE_PPI] ||
  		    !arch_timer_ppi[PHYS_NONSECURE_PPI]) {
  			pr_warn("arch_timer: No interrupt available, giving up
  ");
  			return;
  		}
  	}
  
  	arch_timer_register();
  	arch_timer_common_init();
  }
  
  static void __init arch_timer_of_init(struct device_node *np)
  {
  	int i;
  
  	if (arch_timers_present & ARCH_CP15_TIMER) {
  		pr_warn("arch_timer: multiple nodes in dt, skipping
  ");
  		return;
  	}
  
  	arch_timers_present |= ARCH_CP15_TIMER;
  	for (i = PHYS_SECURE_PPI; i < MAX_TIMER_PPI; i++)
  		arch_timer_ppi[i] = irq_of_parse_and_map(np, i);
  
  	arch_timer_detect_rate(NULL, np);
  
  	arch_timer_c3stop = !of_property_read_bool(np, "always-on");
  
  	/*
  	 * 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_use_virtual = false;
  
  	arch_timer_init();
  }
  CLOCKSOURCE_OF_DECLARE(armv7_arch_timer, "arm,armv7-timer", arch_timer_of_init);
  CLOCKSOURCE_OF_DECLARE(armv8_arch_timer, "arm,armv8-timer", arch_timer_of_init);
  
  static void __init arch_timer_mem_init(struct device_node *np)
  {
  	struct device_node *frame, *best_frame = NULL;
  	void __iomem *cntctlbase, *base;
  	unsigned int irq;
  	u32 cnttidr;
  
  	arch_timers_present |= ARCH_MEM_TIMER;
  	cntctlbase = of_iomap(np, 0);
  	if (!cntctlbase) {
  		pr_err("arch_timer: Can't find CNTCTLBase
  ");
  		return;
  	}
  
  	cnttidr = readl_relaxed(cntctlbase + CNTTIDR);
  	iounmap(cntctlbase);
  
  	/*
  	 * Try to find a virtual capable frame. Otherwise fall back to a
  	 * physical capable frame.
  	 */
  	for_each_available_child_of_node(np, frame) {
  		int n;
  
  		if (of_property_read_u32(frame, "frame-number", &n)) {
  			pr_err("arch_timer: Missing frame-number
  ");
  			of_node_put(best_frame);
  			of_node_put(frame);
  			return;
  		}
  
  		if (cnttidr & CNTTIDR_VIRT(n)) {
  			of_node_put(best_frame);
  			best_frame = frame;
  			arch_timer_mem_use_virtual = true;
  			break;
  		}
  		of_node_put(best_frame);
  		best_frame = of_node_get(frame);
  	}
  
  	base = arch_counter_base = of_iomap(best_frame, 0);
  	if (!base) {
  		pr_err("arch_timer: Can't map frame's registers
  ");
  		of_node_put(best_frame);
  		return;
  	}
  
  	if (arch_timer_mem_use_virtual)
  		irq = irq_of_parse_and_map(best_frame, 1);
  	else
  		irq = irq_of_parse_and_map(best_frame, 0);
  	of_node_put(best_frame);
  	if (!irq) {
  		pr_err("arch_timer: Frame missing %s irq",
  		       arch_timer_mem_use_virtual ? "virt" : "phys");
  		return;
  	}
  
  	arch_timer_detect_rate(base, np);
  	arch_timer_mem_register(base, irq);
  	arch_timer_common_init();
  }
  CLOCKSOURCE_OF_DECLARE(armv7_arch_timer_mem, "arm,armv7-timer-mem",
  		       arch_timer_mem_init);
  
  #ifdef CONFIG_ACPI
  static int __init map_generic_timer_interrupt(u32 interrupt, u32 flags)
  {
  	int trigger, polarity;
  
  	if (!interrupt)
  		return 0;
  
  	trigger = (flags & ACPI_GTDT_INTERRUPT_MODE) ? ACPI_EDGE_SENSITIVE
  			: ACPI_LEVEL_SENSITIVE;
  
  	polarity = (flags & ACPI_GTDT_INTERRUPT_POLARITY) ? ACPI_ACTIVE_LOW
  			: ACPI_ACTIVE_HIGH;
  
  	return acpi_register_gsi(NULL, interrupt, trigger, polarity);
  }
  
  /* Initialize per-processor generic timer */
  static int __init arch_timer_acpi_init(struct acpi_table_header *table)
  {
  	struct acpi_table_gtdt *gtdt;
  
  	if (arch_timers_present & ARCH_CP15_TIMER) {
  		pr_warn("arch_timer: already initialized, skipping
  ");
  		return -EINVAL;
  	}
  
  	gtdt = container_of(table, struct acpi_table_gtdt, header);
  
  	arch_timers_present |= ARCH_CP15_TIMER;
  
  	arch_timer_ppi[PHYS_SECURE_PPI] =
  		map_generic_timer_interrupt(gtdt->secure_el1_interrupt,
  		gtdt->secure_el1_flags);
  
  	arch_timer_ppi[PHYS_NONSECURE_PPI] =
  		map_generic_timer_interrupt(gtdt->non_secure_el1_interrupt,
  		gtdt->non_secure_el1_flags);
  
  	arch_timer_ppi[VIRT_PPI] =
  		map_generic_timer_interrupt(gtdt->virtual_timer_interrupt,
  		gtdt->virtual_timer_flags);
  
  	arch_timer_ppi[HYP_PPI] =
  		map_generic_timer_interrupt(gtdt->non_secure_el2_interrupt,
  		gtdt->non_secure_el2_flags);
  
  	/* Get the frequency from CNTFRQ */
  	arch_timer_detect_rate(NULL, NULL);
  
  	/* Always-on capability */
  	arch_timer_c3stop = !(gtdt->non_secure_el1_flags & ACPI_GTDT_ALWAYS_ON);
  
  	arch_timer_init();
  	return 0;
  }
  CLOCKSOURCE_ACPI_DECLARE(arch_timer, ACPI_SIG_GTDT, arch_timer_acpi_init);
  #endif