/*
   * (C) Copyright 2009 Intel Corporation
   * Author: Jacob Pan (jacob.jun.pan@intel.com)
   *
   * Shared with ARM platforms, Jamie Iles, Picochip 2011
   *
   * 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.
   *
   * Support for the Synopsys DesignWare APB Timers.
   */
  #include <linux/dw_apb_timer.h>
  #include <linux/delay.h>
  #include <linux/kernel.h>
  #include <linux/interrupt.h>
  #include <linux/irq.h>
  #include <linux/io.h>
  #include <linux/slab.h>
  
  #define APBT_MIN_PERIOD			4
  #define APBT_MIN_DELTA_USEC		200
  
  #define APBTMR_N_LOAD_COUNT		0x00
  #define APBTMR_N_CURRENT_VALUE		0x04
  #define APBTMR_N_CONTROL		0x08
  #define APBTMR_N_EOI			0x0c
  #define APBTMR_N_INT_STATUS		0x10
  
  #define APBTMRS_INT_STATUS		0xa0
  #define APBTMRS_EOI			0xa4
  #define APBTMRS_RAW_INT_STATUS		0xa8
  #define APBTMRS_COMP_VERSION		0xac
  
  #define APBTMR_CONTROL_ENABLE		(1 << 0)
  /* 1: periodic, 0:free running. */
  #define APBTMR_CONTROL_MODE_PERIODIC	(1 << 1)
  #define APBTMR_CONTROL_INT		(1 << 2)
  
  static inline struct dw_apb_clock_event_device *
  ced_to_dw_apb_ced(struct clock_event_device *evt)
  {
  	return container_of(evt, struct dw_apb_clock_event_device, ced);
  }
  
  static inline struct dw_apb_clocksource *
  clocksource_to_dw_apb_clocksource(struct clocksource *cs)
  {
  	return container_of(cs, struct dw_apb_clocksource, cs);
  }
  
  static unsigned long apbt_readl(struct dw_apb_timer *timer, unsigned long offs)
  {
  	return readl(timer->base + offs);
  }
  
  static void apbt_writel(struct dw_apb_timer *timer, unsigned long val,
  		 unsigned long offs)
  {
  	writel(val, timer->base + offs);
  }
  
  static void apbt_disable_int(struct dw_apb_timer *timer)
  {
  	unsigned long ctrl = apbt_readl(timer, APBTMR_N_CONTROL);
  
  	ctrl |= APBTMR_CONTROL_INT;
  	apbt_writel(timer, ctrl, APBTMR_N_CONTROL);
  }
  
  /**
   * dw_apb_clockevent_pause() - stop the clock_event_device from running
   *
   * @dw_ced:	The APB clock to stop generating events.
   */
  void dw_apb_clockevent_pause(struct dw_apb_clock_event_device *dw_ced)
  {
  	disable_irq(dw_ced->timer.irq);
  	apbt_disable_int(&dw_ced->timer);
  }
  
  static void apbt_eoi(struct dw_apb_timer *timer)
  {
  	apbt_readl(timer, APBTMR_N_EOI);
  }
  
  static irqreturn_t dw_apb_clockevent_irq(int irq, void *data)
  {
  	struct clock_event_device *evt = data;
  	struct dw_apb_clock_event_device *dw_ced = ced_to_dw_apb_ced(evt);
  
  	if (!evt->event_handler) {
  		pr_info("Spurious APBT timer interrupt %d", irq);
  		return IRQ_NONE;
  	}
  
  	if (dw_ced->eoi)
  		dw_ced->eoi(&dw_ced->timer);
  
  	evt->event_handler(evt);
  	return IRQ_HANDLED;
  }
  
  static void apbt_enable_int(struct dw_apb_timer *timer)
  {
  	unsigned long ctrl = apbt_readl(timer, APBTMR_N_CONTROL);
  	/* clear pending intr */
  	apbt_readl(timer, APBTMR_N_EOI);
  	ctrl &= ~APBTMR_CONTROL_INT;
  	apbt_writel(timer, ctrl, APBTMR_N_CONTROL);
  }
  
  static int apbt_shutdown(struct clock_event_device *evt)
  {
  	struct dw_apb_clock_event_device *dw_ced = ced_to_dw_apb_ced(evt);
  	unsigned long ctrl;
  
  	pr_debug("%s CPU %d state=shutdown
  ", __func__,
  		 cpumask_first(evt->cpumask));
  
  	ctrl = apbt_readl(&dw_ced->timer, APBTMR_N_CONTROL);
  	ctrl &= ~APBTMR_CONTROL_ENABLE;
  	apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
  	return 0;
  }
  
  static int apbt_set_oneshot(struct clock_event_device *evt)
  {
  	struct dw_apb_clock_event_device *dw_ced = ced_to_dw_apb_ced(evt);
  	unsigned long ctrl;
  
  	pr_debug("%s CPU %d state=oneshot
  ", __func__,
  		 cpumask_first(evt->cpumask));
  
  	ctrl = apbt_readl(&dw_ced->timer, APBTMR_N_CONTROL);
  	/*
  	 * set free running mode, this mode will let timer reload max
  	 * timeout which will give time (3min on 25MHz clock) to rearm
  	 * the next event, therefore emulate the one-shot mode.
  	 */
  	ctrl &= ~APBTMR_CONTROL_ENABLE;
  	ctrl &= ~APBTMR_CONTROL_MODE_PERIODIC;
  
  	apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
  	/* write again to set free running mode */
  	apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
  
  	/*
  	 * DW APB p. 46, load counter with all 1s before starting free
  	 * running mode.
  	 */
  	apbt_writel(&dw_ced->timer, ~0, APBTMR_N_LOAD_COUNT);
  	ctrl &= ~APBTMR_CONTROL_INT;
  	ctrl |= APBTMR_CONTROL_ENABLE;
  	apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
  	return 0;
  }
  
  static int apbt_set_periodic(struct clock_event_device *evt)
  {
  	struct dw_apb_clock_event_device *dw_ced = ced_to_dw_apb_ced(evt);
  	unsigned long period = DIV_ROUND_UP(dw_ced->timer.freq, HZ);
  	unsigned long ctrl;
  
  	pr_debug("%s CPU %d state=periodic
  ", __func__,
  		 cpumask_first(evt->cpumask));
  
  	ctrl = apbt_readl(&dw_ced->timer, APBTMR_N_CONTROL);
  	ctrl |= APBTMR_CONTROL_MODE_PERIODIC;
  	apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
  	/*
  	 * DW APB p. 46, have to disable timer before load counter,
  	 * may cause sync problem.
  	 */
  	ctrl &= ~APBTMR_CONTROL_ENABLE;
  	apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
  	udelay(1);
  	pr_debug("Setting clock period %lu for HZ %d
  ", period, HZ);
  	apbt_writel(&dw_ced->timer, period, APBTMR_N_LOAD_COUNT);
  	ctrl |= APBTMR_CONTROL_ENABLE;
  	apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
  	return 0;
  }
  
  static int apbt_resume(struct clock_event_device *evt)
  {
  	struct dw_apb_clock_event_device *dw_ced = ced_to_dw_apb_ced(evt);
  
  	pr_debug("%s CPU %d state=resume
  ", __func__,
  		 cpumask_first(evt->cpumask));
  
  	apbt_enable_int(&dw_ced->timer);
  	return 0;
  }
  
  static int apbt_next_event(unsigned long delta,
  			   struct clock_event_device *evt)
  {
  	unsigned long ctrl;
  	struct dw_apb_clock_event_device *dw_ced = ced_to_dw_apb_ced(evt);
  
  	/* Disable timer */
  	ctrl = apbt_readl(&dw_ced->timer, APBTMR_N_CONTROL);
  	ctrl &= ~APBTMR_CONTROL_ENABLE;
  	apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
  	/* write new count */
  	apbt_writel(&dw_ced->timer, delta, APBTMR_N_LOAD_COUNT);
  	ctrl |= APBTMR_CONTROL_ENABLE;
  	apbt_writel(&dw_ced->timer, ctrl, APBTMR_N_CONTROL);
  
  	return 0;
  }
  
  /**
   * dw_apb_clockevent_init() - use an APB timer as a clock_event_device
   *
   * @cpu:	The CPU the events will be targeted at.
   * @name:	The name used for the timer and the IRQ for it.
   * @rating:	The rating to give the timer.
   * @base:	I/O base for the timer registers.
   * @irq:	The interrupt number to use for the timer.
   * @freq:	The frequency that the timer counts at.
   *
   * This creates a clock_event_device for using with the generic clock layer
   * but does not start and register it.  This should be done with
   * dw_apb_clockevent_register() as the next step.  If this is the first time
   * it has been called for a timer then the IRQ will be requested, if not it
   * just be enabled to allow CPU hotplug to avoid repeatedly requesting and
   * releasing the IRQ.
   */
  struct dw_apb_clock_event_device *
  dw_apb_clockevent_init(int cpu, const char *name, unsigned rating,
  		       void __iomem *base, int irq, unsigned long freq)
  {
  	struct dw_apb_clock_event_device *dw_ced =
  		kzalloc(sizeof(*dw_ced), GFP_KERNEL);
  	int err;
  
  	if (!dw_ced)
  		return NULL;
  
  	dw_ced->timer.base = base;
  	dw_ced->timer.irq = irq;
  	dw_ced->timer.freq = freq;
  
  	clockevents_calc_mult_shift(&dw_ced->ced, freq, APBT_MIN_PERIOD);
  	dw_ced->ced.max_delta_ns = clockevent_delta2ns(0x7fffffff,
  						       &dw_ced->ced);
  	dw_ced->ced.min_delta_ns = clockevent_delta2ns(5000, &dw_ced->ced);
  	dw_ced->ced.cpumask = cpumask_of(cpu);
  	dw_ced->ced.features = CLOCK_EVT_FEAT_PERIODIC |
  				CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_DYNIRQ;
  	dw_ced->ced.set_state_shutdown = apbt_shutdown;
  	dw_ced->ced.set_state_periodic = apbt_set_periodic;
  	dw_ced->ced.set_state_oneshot = apbt_set_oneshot;
  	dw_ced->ced.tick_resume = apbt_resume;
  	dw_ced->ced.set_next_event = apbt_next_event;
  	dw_ced->ced.irq = dw_ced->timer.irq;
  	dw_ced->ced.rating = rating;
  	dw_ced->ced.name = name;
  
  	dw_ced->irqaction.name		= dw_ced->ced.name;
  	dw_ced->irqaction.handler	= dw_apb_clockevent_irq;
  	dw_ced->irqaction.dev_id	= &dw_ced->ced;
  	dw_ced->irqaction.irq		= irq;
  	dw_ced->irqaction.flags		= IRQF_TIMER | IRQF_IRQPOLL |
  					  IRQF_NOBALANCING;
  
  	dw_ced->eoi = apbt_eoi;
  	err = setup_irq(irq, &dw_ced->irqaction);
  	if (err) {
  		pr_err("failed to request timer irq
  ");
  		kfree(dw_ced);
  		dw_ced = NULL;
  	}
  
  	return dw_ced;
  }
  
  /**
   * dw_apb_clockevent_resume() - resume a clock that has been paused.
   *
   * @dw_ced:	The APB clock to resume.
   */
  void dw_apb_clockevent_resume(struct dw_apb_clock_event_device *dw_ced)
  {
  	enable_irq(dw_ced->timer.irq);
  }
  
  /**
   * dw_apb_clockevent_stop() - stop the clock_event_device and release the IRQ.
   *
   * @dw_ced:	The APB clock to stop generating the events.
   */
  void dw_apb_clockevent_stop(struct dw_apb_clock_event_device *dw_ced)
  {
  	free_irq(dw_ced->timer.irq, &dw_ced->ced);
  }
  
  /**
   * dw_apb_clockevent_register() - register the clock with the generic layer
   *
   * @dw_ced:	The APB clock to register as a clock_event_device.
   */
  void dw_apb_clockevent_register(struct dw_apb_clock_event_device *dw_ced)
  {
  	apbt_writel(&dw_ced->timer, 0, APBTMR_N_CONTROL);
  	clockevents_register_device(&dw_ced->ced);
  	apbt_enable_int(&dw_ced->timer);
  }
  
  /**
   * dw_apb_clocksource_start() - start the clocksource counting.
   *
   * @dw_cs:	The clocksource to start.
   *
   * This is used to start the clocksource before registration and can be used
   * to enable calibration of timers.
   */
  void dw_apb_clocksource_start(struct dw_apb_clocksource *dw_cs)
  {
  	/*
  	 * start count down from 0xffff_ffff. this is done by toggling the
  	 * enable bit then load initial load count to ~0.
  	 */
  	unsigned long ctrl = apbt_readl(&dw_cs->timer, APBTMR_N_CONTROL);
  
  	ctrl &= ~APBTMR_CONTROL_ENABLE;
  	apbt_writel(&dw_cs->timer, ctrl, APBTMR_N_CONTROL);
  	apbt_writel(&dw_cs->timer, ~0, APBTMR_N_LOAD_COUNT);
  	/* enable, mask interrupt */
  	ctrl &= ~APBTMR_CONTROL_MODE_PERIODIC;
  	ctrl |= (APBTMR_CONTROL_ENABLE | APBTMR_CONTROL_INT);
  	apbt_writel(&dw_cs->timer, ctrl, APBTMR_N_CONTROL);
  	/* read it once to get cached counter value initialized */
  	dw_apb_clocksource_read(dw_cs);
  }
  
  static cycle_t __apbt_read_clocksource(struct clocksource *cs)
  {
  	unsigned long current_count;
  	struct dw_apb_clocksource *dw_cs =
  		clocksource_to_dw_apb_clocksource(cs);
  
  	current_count = apbt_readl(&dw_cs->timer, APBTMR_N_CURRENT_VALUE);
  
  	return (cycle_t)~current_count;
  }
  
  static void apbt_restart_clocksource(struct clocksource *cs)
  {
  	struct dw_apb_clocksource *dw_cs =
  		clocksource_to_dw_apb_clocksource(cs);
  
  	dw_apb_clocksource_start(dw_cs);
  }
  
  /**
   * dw_apb_clocksource_init() - use an APB timer as a clocksource.
   *
   * @rating:	The rating to give the clocksource.
   * @name:	The name for the clocksource.
   * @base:	The I/O base for the timer registers.
   * @freq:	The frequency that the timer counts at.
   *
   * This creates a clocksource using an APB timer but does not yet register it
   * with the clocksource system.  This should be done with
   * dw_apb_clocksource_register() as the next step.
   */
  struct dw_apb_clocksource *
  dw_apb_clocksource_init(unsigned rating, const char *name, void __iomem *base,
  			unsigned long freq)
  {
  	struct dw_apb_clocksource *dw_cs = kzalloc(sizeof(*dw_cs), GFP_KERNEL);
  
  	if (!dw_cs)
  		return NULL;
  
  	dw_cs->timer.base = base;
  	dw_cs->timer.freq = freq;
  	dw_cs->cs.name = name;
  	dw_cs->cs.rating = rating;
  	dw_cs->cs.read = __apbt_read_clocksource;
  	dw_cs->cs.mask = CLOCKSOURCE_MASK(32);
  	dw_cs->cs.flags = CLOCK_SOURCE_IS_CONTINUOUS;
  	dw_cs->cs.resume = apbt_restart_clocksource;
  
  	return dw_cs;
  }
  
  /**
   * dw_apb_clocksource_register() - register the APB clocksource.
   *
   * @dw_cs:	The clocksource to register.
   */
  void dw_apb_clocksource_register(struct dw_apb_clocksource *dw_cs)
  {
  	clocksource_register_hz(&dw_cs->cs, dw_cs->timer.freq);
  }
  
  /**
   * dw_apb_clocksource_read() - read the current value of a clocksource.
   *
   * @dw_cs:	The clocksource to read.
   */
  cycle_t dw_apb_clocksource_read(struct dw_apb_clocksource *dw_cs)
  {
  	return (cycle_t)~apbt_readl(&dw_cs->timer, APBTMR_N_CURRENT_VALUE);
  }