/*
   * Copyright (C) 2010 Google, Inc.
   *
   * Author:
   *	Colin Cross <ccross@google.com>
   *
   * This software is licensed under the terms of the GNU General Public
   * License version 2, as published by the Free Software Foundation, and
   * may be copied, distributed, and modified under those terms.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   */
  
  #include <linux/init.h>
  #include <linux/err.h>
  #include <linux/time.h>
  #include <linux/interrupt.h>
  #include <linux/irq.h>
  #include <linux/clockchips.h>
  #include <linux/clocksource.h>
  #include <linux/clk.h>
  #include <linux/io.h>
  #include <linux/of_address.h>
  #include <linux/of_irq.h>
  #include <linux/sched_clock.h>
  #include <linux/delay.h>
  
  #include <asm/mach/time.h>
  #include <asm/smp_twd.h>
  
  #define RTC_SECONDS            0x08
  #define RTC_SHADOW_SECONDS     0x0c
  #define RTC_MILLISECONDS       0x10
  
  #define TIMERUS_CNTR_1US 0x10
  #define TIMERUS_USEC_CFG 0x14
  #define TIMERUS_CNTR_FREEZE 0x4c
  
  #define TIMER1_BASE 0x0
  #define TIMER2_BASE 0x8
  #define TIMER3_BASE 0x50
  #define TIMER4_BASE 0x58
  
  #define TIMER_PTV 0x0
  #define TIMER_PCR 0x4
  
  static void __iomem *timer_reg_base;
  static void __iomem *rtc_base;
  
  static struct timespec64 persistent_ts;
  static u64 persistent_ms, last_persistent_ms;
  
  static struct delay_timer tegra_delay_timer;
  
  #define timer_writel(value, reg) \
  	writel_relaxed(value, timer_reg_base + (reg))
  #define timer_readl(reg) \
  	readl_relaxed(timer_reg_base + (reg))
  
  static int tegra_timer_set_next_event(unsigned long cycles,
  					 struct clock_event_device *evt)
  {
  	u32 reg;
  
  	reg = 0x80000000 | ((cycles > 1) ? (cycles-1) : 0);
  	timer_writel(reg, TIMER3_BASE + TIMER_PTV);
  
  	return 0;
  }
  
  static inline void timer_shutdown(struct clock_event_device *evt)
  {
  	timer_writel(0, TIMER3_BASE + TIMER_PTV);
  }
  
  static int tegra_timer_shutdown(struct clock_event_device *evt)
  {
  	timer_shutdown(evt);
  	return 0;
  }
  
  static int tegra_timer_set_periodic(struct clock_event_device *evt)
  {
  	u32 reg = 0xC0000000 | ((1000000 / HZ) - 1);
  
  	timer_shutdown(evt);
  	timer_writel(reg, TIMER3_BASE + TIMER_PTV);
  	return 0;
  }
  
  static struct clock_event_device tegra_clockevent = {
  	.name			= "timer0",
  	.rating			= 300,
  	.features		= CLOCK_EVT_FEAT_ONESHOT |
  				  CLOCK_EVT_FEAT_PERIODIC,
  	.set_next_event		= tegra_timer_set_next_event,
  	.set_state_shutdown	= tegra_timer_shutdown,
  	.set_state_periodic	= tegra_timer_set_periodic,
  	.set_state_oneshot	= tegra_timer_shutdown,
  	.tick_resume		= tegra_timer_shutdown,
  };
  
  static u64 notrace tegra_read_sched_clock(void)
  {
  	return timer_readl(TIMERUS_CNTR_1US);
  }
  
  /*
   * tegra_rtc_read - Reads the Tegra RTC registers
   * Care must be taken that this funciton is not called while the
   * tegra_rtc driver could be executing to avoid race conditions
   * on the RTC shadow register
   */
  static u64 tegra_rtc_read_ms(void)
  {
  	u32 ms = readl(rtc_base + RTC_MILLISECONDS);
  	u32 s = readl(rtc_base + RTC_SHADOW_SECONDS);
  	return (u64)s * MSEC_PER_SEC + ms;
  }
  
  /*
   * tegra_read_persistent_clock64 -  Return time from a persistent clock.
   *
   * Reads the time from a source which isn't disabled during PM, the
   * 32k sync timer.  Convert the cycles elapsed since last read into
   * nsecs and adds to a monotonically increasing timespec64.
   * Care must be taken that this funciton is not called while the
   * tegra_rtc driver could be executing to avoid race conditions
   * on the RTC shadow register
   */
  static void tegra_read_persistent_clock64(struct timespec64 *ts)
  {
  	u64 delta;
  
  	last_persistent_ms = persistent_ms;
  	persistent_ms = tegra_rtc_read_ms();
  	delta = persistent_ms - last_persistent_ms;
  
  	timespec64_add_ns(&persistent_ts, delta * NSEC_PER_MSEC);
  	*ts = persistent_ts;
  }
  
  static unsigned long tegra_delay_timer_read_counter_long(void)
  {
  	return readl(timer_reg_base + TIMERUS_CNTR_1US);
  }
  
  static irqreturn_t tegra_timer_interrupt(int irq, void *dev_id)
  {
  	struct clock_event_device *evt = (struct clock_event_device *)dev_id;
  	timer_writel(1<<30, TIMER3_BASE + TIMER_PCR);
  	evt->event_handler(evt);
  	return IRQ_HANDLED;
  }
  
  static struct irqaction tegra_timer_irq = {
  	.name		= "timer0",
  	.flags		= IRQF_TIMER | IRQF_TRIGGER_HIGH,
  	.handler	= tegra_timer_interrupt,
  	.dev_id		= &tegra_clockevent,
  };
  
  static void __init tegra20_init_timer(struct device_node *np)
  {
  	struct clk *clk;
  	unsigned long rate;
  	int ret;
  
  	timer_reg_base = of_iomap(np, 0);
  	if (!timer_reg_base) {
  		pr_err("Can't map timer registers
  ");
  		BUG();
  	}
  
  	tegra_timer_irq.irq = irq_of_parse_and_map(np, 2);
  	if (tegra_timer_irq.irq <= 0) {
  		pr_err("Failed to map timer IRQ
  ");
  		BUG();
  	}
  
  	clk = of_clk_get(np, 0);
  	if (IS_ERR(clk)) {
  		pr_warn("Unable to get timer clock. Assuming 12Mhz input clock.
  ");
  		rate = 12000000;
  	} else {
  		clk_prepare_enable(clk);
  		rate = clk_get_rate(clk);
  	}
  
  	switch (rate) {
  	case 12000000:
  		timer_writel(0x000b, TIMERUS_USEC_CFG);
  		break;
  	case 13000000:
  		timer_writel(0x000c, TIMERUS_USEC_CFG);
  		break;
  	case 19200000:
  		timer_writel(0x045f, TIMERUS_USEC_CFG);
  		break;
  	case 26000000:
  		timer_writel(0x0019, TIMERUS_USEC_CFG);
  		break;
  	default:
  		WARN(1, "Unknown clock rate");
  	}
  
  	sched_clock_register(tegra_read_sched_clock, 32, 1000000);
  
  	if (clocksource_mmio_init(timer_reg_base + TIMERUS_CNTR_1US,
  		"timer_us", 1000000, 300, 32, clocksource_mmio_readl_up)) {
  		pr_err("Failed to register clocksource
  ");
  		BUG();
  	}
  
  	tegra_delay_timer.read_current_timer =
  			tegra_delay_timer_read_counter_long;
  	tegra_delay_timer.freq = 1000000;
  	register_current_timer_delay(&tegra_delay_timer);
  
  	ret = setup_irq(tegra_timer_irq.irq, &tegra_timer_irq);
  	if (ret) {
  		pr_err("Failed to register timer IRQ: %d
  ", ret);
  		BUG();
  	}
  
  	tegra_clockevent.cpumask = cpu_all_mask;
  	tegra_clockevent.irq = tegra_timer_irq.irq;
  	clockevents_config_and_register(&tegra_clockevent, 1000000,
  					0x1, 0x1fffffff);
  }
  CLOCKSOURCE_OF_DECLARE(tegra20_timer, "nvidia,tegra20-timer", tegra20_init_timer);
  
  static void __init tegra20_init_rtc(struct device_node *np)
  {
  	struct clk *clk;
  
  	rtc_base = of_iomap(np, 0);
  	if (!rtc_base) {
  		pr_err("Can't map RTC registers");
  		BUG();
  	}
  
  	/*
  	 * rtc registers are used by read_persistent_clock, keep the rtc clock
  	 * enabled
  	 */
  	clk = of_clk_get(np, 0);
  	if (IS_ERR(clk))
  		pr_warn("Unable to get rtc-tegra clock
  ");
  	else
  		clk_prepare_enable(clk);
  
  	register_persistent_clock(NULL, tegra_read_persistent_clock64);
  }
  CLOCKSOURCE_OF_DECLARE(tegra20_rtc, "nvidia,tegra20-rtc", tegra20_init_rtc);
  
  #ifdef CONFIG_PM
  static u32 usec_config;
  
  void tegra_timer_suspend(void)
  {
  	usec_config = timer_readl(TIMERUS_USEC_CFG);
  }
  
  void tegra_timer_resume(void)
  {
  	timer_writel(usec_config, TIMERUS_USEC_CFG);
  }
  #endif