drivers/clocksource/cadence_ttc_timer.c - maze/linux - Git at Google

 /*
  * This file contains driver for the Cadence Triple Timer Counter Rev 06
  *
  *  Copyright (C) 2011-2013 Xilinx
  *
  * based on arch/mips/kernel/time.c timer driver
  *
  * 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/clk.h>
 #include <linux/interrupt.h>
 #include <linux/clockchips.h>
 #include <linux/of_address.h>
 #include <linux/of_irq.h>
 #include <linux/slab.h>
 #include <linux/clk-provider.h>

 /*
  * This driver configures the 2 16-bit count-up timers as follows:
  *
  * T1: Timer 1, clocksource for generic timekeeping
  * T2: Timer 2, clockevent source for hrtimers
  * T3: Timer 3, <unused>
  *
  * The input frequency to the timer module for emulation is 2.5MHz which is
  * common to all the timer channels (T1, T2, and T3). With a pre-scaler of 32,
  * the timers are clocked at 78.125KHz (12.8 us resolution).

  * The input frequency to the timer module in silicon is configurable and
  * obtained from device tree. The pre-scaler of 32 is used.
  */

 /*
  * Timer Register Offset Definitions of Timer 1, Increment base address by 4
  * and use same offsets for Timer 2
  */
 #define TTC_CLK_CNTRL_OFFSET		0x00 /* Clock Control Reg, RW */
 #define TTC_CNT_CNTRL_OFFSET		0x0C /* Counter Control Reg, RW */
 #define TTC_COUNT_VAL_OFFSET		0x18 /* Counter Value Reg, RO */
 #define TTC_INTR_VAL_OFFSET		0x24 /* Interval Count Reg, RW */
 #define TTC_ISR_OFFSET		0x54 /* Interrupt Status Reg, RO */
 #define TTC_IER_OFFSET		0x60 /* Interrupt Enable Reg, RW */

 #define TTC_CNT_CNTRL_DISABLE_MASK	0x1

 /*
  * Setup the timers to use pre-scaling, using a fixed value for now that will
  * work across most input frequency, but it may need to be more dynamic
  */
 #define PRESCALE_EXPONENT	11	/* 2 ^ PRESCALE_EXPONENT = PRESCALE */
 #define PRESCALE		2048	/* The exponent must match this */
 #define CLK_CNTRL_PRESCALE	((PRESCALE_EXPONENT - 1) << 1)
 #define CLK_CNTRL_PRESCALE_EN	1
 #define CNT_CNTRL_RESET		(1 << 4)

 /**
  * struct ttc_timer - This definition defines local timer structure
  *
  * @base_addr:	Base address of timer
  * @clk:	Associated clock source
  * @clk_rate_change_nb	Notifier block for clock rate changes
  */
 struct ttc_timer {
 	void __iomem *base_addr;
 	struct clk *clk;
 	struct notifier_block clk_rate_change_nb;
 };

 #define to_ttc_timer(x) \
 		container_of(x, struct ttc_timer, clk_rate_change_nb)

 struct ttc_timer_clocksource {
 	struct ttc_timer	ttc;
 	struct clocksource	cs;
 };

 #define to_ttc_timer_clksrc(x) \
 		container_of(x, struct ttc_timer_clocksource, cs)

 struct ttc_timer_clockevent {
 	struct ttc_timer		ttc;
 	struct clock_event_device	ce;
 };

 #define to_ttc_timer_clkevent(x) \
 		container_of(x, struct ttc_timer_clockevent, ce)

 /**
  * ttc_set_interval - Set the timer interval value
  *
  * @timer:	Pointer to the timer instance
  * @cycles:	Timer interval ticks
  **/
 static void ttc_set_interval(struct ttc_timer *timer,
 					unsigned long cycles)
 {
 	u32 ctrl_reg;

 	/* Disable the counter, set the counter value  and re-enable counter */
 	ctrl_reg = __raw_readl(timer->base_addr + TTC_CNT_CNTRL_OFFSET);
 	ctrl_reg |= TTC_CNT_CNTRL_DISABLE_MASK;
 	__raw_writel(ctrl_reg, timer->base_addr + TTC_CNT_CNTRL_OFFSET);

 	__raw_writel(cycles, timer->base_addr + TTC_INTR_VAL_OFFSET);

 	/*
 	 * Reset the counter (0x10) so that it starts from 0, one-shot
 	 * mode makes this needed for timing to be right.
 	 */
 	ctrl_reg |= CNT_CNTRL_RESET;
 	ctrl_reg &= ~TTC_CNT_CNTRL_DISABLE_MASK;
 	__raw_writel(ctrl_reg, timer->base_addr + TTC_CNT_CNTRL_OFFSET);
 }

 /**
  * ttc_clock_event_interrupt - Clock event timer interrupt handler
  *
  * @irq:	IRQ number of the Timer
  * @dev_id:	void pointer to the ttc_timer instance
  *
  * returns: Always IRQ_HANDLED - success
  **/
 static irqreturn_t ttc_clock_event_interrupt(int irq, void *dev_id)
 {
 	struct ttc_timer_clockevent *ttce = dev_id;
 	struct ttc_timer *timer = &ttce->ttc;

 	/* Acknowledge the interrupt and call event handler */
 	__raw_readl(timer->base_addr + TTC_ISR_OFFSET);

 	ttce->ce.event_handler(&ttce->ce);

 	return IRQ_HANDLED;
 }

 /**
  * __ttc_clocksource_read - Reads the timer counter register
  *
  * returns: Current timer counter register value
  **/
 static cycle_t __ttc_clocksource_read(struct clocksource *cs)
 {
 	struct ttc_timer *timer = &to_ttc_timer_clksrc(cs)->ttc;

 	return (cycle_t)__raw_readl(timer->base_addr +
 				TTC_COUNT_VAL_OFFSET);
 }

 /**
  * ttc_set_next_event - Sets the time interval for next event
  *
  * @cycles:	Timer interval ticks
  * @evt:	Address of clock event instance
  *
  * returns: Always 0 - success
  **/
 static int ttc_set_next_event(unsigned long cycles,
 					struct clock_event_device *evt)
 {
 	struct ttc_timer_clockevent *ttce = to_ttc_timer_clkevent(evt);
 	struct ttc_timer *timer = &ttce->ttc;

 	ttc_set_interval(timer, cycles);
 	return 0;
 }

 /**
  * ttc_set_mode - Sets the mode of timer
  *
  * @mode:	Mode to be set
  * @evt:	Address of clock event instance
  **/
 static void ttc_set_mode(enum clock_event_mode mode,
 					struct clock_event_device *evt)
 {
 	struct ttc_timer_clockevent *ttce = to_ttc_timer_clkevent(evt);
 	struct ttc_timer *timer = &ttce->ttc;
 	u32 ctrl_reg;

 	switch (mode) {
 	case CLOCK_EVT_MODE_PERIODIC:
 		ttc_set_interval(timer,
 				DIV_ROUND_CLOSEST(clk_get_rate(ttce->ttc.clk),
 					PRESCALE * HZ));
 		break;
 	case CLOCK_EVT_MODE_ONESHOT:
 	case CLOCK_EVT_MODE_UNUSED:
 	case CLOCK_EVT_MODE_SHUTDOWN:
 		ctrl_reg = __raw_readl(timer->base_addr +
 					TTC_CNT_CNTRL_OFFSET);
 		ctrl_reg |= TTC_CNT_CNTRL_DISABLE_MASK;
 		__raw_writel(ctrl_reg,
 				timer->base_addr + TTC_CNT_CNTRL_OFFSET);
 		break;
 	case CLOCK_EVT_MODE_RESUME:
 		ctrl_reg = __raw_readl(timer->base_addr +
 					TTC_CNT_CNTRL_OFFSET);
 		ctrl_reg &= ~TTC_CNT_CNTRL_DISABLE_MASK;
 		__raw_writel(ctrl_reg,
 				timer->base_addr + TTC_CNT_CNTRL_OFFSET);
 		break;
 	}
 }

 static int ttc_rate_change_clocksource_cb(struct notifier_block *nb,
 		unsigned long event, void *data)
 {
 	struct clk_notifier_data *ndata = data;
 	struct ttc_timer *ttc = to_ttc_timer(nb);
 	struct ttc_timer_clocksource *ttccs = container_of(ttc,
 			struct ttc_timer_clocksource, ttc);

 	switch (event) {
 	case POST_RATE_CHANGE:
 		/*
 		 * Do whatever is necessary to maintain a proper time base
 		 *
 		 * I cannot find a way to adjust the currently used clocksource
 		 * to the new frequency. __clocksource_updatefreq_hz() sounds
 		 * good, but does not work. Not sure what's that missing.
 		 *
 		 * This approach works, but triggers two clocksource switches.
 		 * The first after unregister to clocksource jiffies. And
 		 * another one after the register to the newly registered timer.
 		 *
 		 * Alternatively we could 'waste' another HW timer to ping pong
 		 * between clock sources. That would also use one register and
 		 * one unregister call, but only trigger one clocksource switch
 		 * for the cost of another HW timer used by the OS.
 		 */
 		clocksource_unregister(&ttccs->cs);
 		clocksource_register_hz(&ttccs->cs,
 				ndata->new_rate / PRESCALE);
 		/* fall through */
 	case PRE_RATE_CHANGE:
 	case ABORT_RATE_CHANGE:
 	default:
 		return NOTIFY_DONE;
 	}
 }

 static void __init ttc_setup_clocksource(struct clk *clk, void __iomem *base)
 {
 	struct ttc_timer_clocksource *ttccs;
 	int err;

 	ttccs = kzalloc(sizeof(*ttccs), GFP_KERNEL);
 	if (WARN_ON(!ttccs))
 		return;

 	ttccs->ttc.clk = clk;

 	err = clk_prepare_enable(ttccs->ttc.clk);
 	if (WARN_ON(err)) {
 		kfree(ttccs);
 		return;
 	}

 	ttccs->ttc.clk_rate_change_nb.notifier_call =
 		ttc_rate_change_clocksource_cb;
 	ttccs->ttc.clk_rate_change_nb.next = NULL;
 	if (clk_notifier_register(ttccs->ttc.clk,
 				&ttccs->ttc.clk_rate_change_nb))
 		pr_warn("Unable to register clock notifier.\n");

 	ttccs->ttc.base_addr = base;
 	ttccs->cs.name = "ttc_clocksource";
 	ttccs->cs.rating = 200;
 	ttccs->cs.read = __ttc_clocksource_read;
 	ttccs->cs.mask = CLOCKSOURCE_MASK(16);
 	ttccs->cs.flags = CLOCK_SOURCE_IS_CONTINUOUS;

 	/*
 	 * Setup the clock source counter to be an incrementing counter
 	 * with no interrupt and it rolls over at 0xFFFF. Pre-scale
 	 * it by 32 also. Let it start running now.
 	 */
 	__raw_writel(0x0,  ttccs->ttc.base_addr + TTC_IER_OFFSET);
 	__raw_writel(CLK_CNTRL_PRESCALE | CLK_CNTRL_PRESCALE_EN,
 		     ttccs->ttc.base_addr + TTC_CLK_CNTRL_OFFSET);
 	__raw_writel(CNT_CNTRL_RESET,
 		     ttccs->ttc.base_addr + TTC_CNT_CNTRL_OFFSET);

 	err = clocksource_register_hz(&ttccs->cs,
 			clk_get_rate(ttccs->ttc.clk) / PRESCALE);
 	if (WARN_ON(err)) {
 		kfree(ttccs);
 		return;
 	}
 }

 static int ttc_rate_change_clockevent_cb(struct notifier_block *nb,
 		unsigned long event, void *data)
 {
 	struct clk_notifier_data *ndata = data;
 	struct ttc_timer *ttc = to_ttc_timer(nb);
 	struct ttc_timer_clockevent *ttcce = container_of(ttc,
 			struct ttc_timer_clockevent, ttc);

 	switch (event) {
 	case POST_RATE_CHANGE:
 	{
 		unsigned long flags;

 		/*
 		 * clockevents_update_freq should be called with IRQ disabled on
 		 * the CPU the timer provides events for. The timer we use is
 		 * common to both CPUs, not sure if we need to run on both
 		 * cores.
 		 */
 		local_irq_save(flags);
 		clockevents_update_freq(&ttcce->ce,
 				ndata->new_rate / PRESCALE);
 		local_irq_restore(flags);

 		/* fall through */
 	}
 	case PRE_RATE_CHANGE:
 	case ABORT_RATE_CHANGE:
 	default:
 		return NOTIFY_DONE;
 	}
 }

 static void __init ttc_setup_clockevent(struct clk *clk,
 						void __iomem *base, u32 irq)
 {
 	struct ttc_timer_clockevent *ttcce;
 	int err;

 	ttcce = kzalloc(sizeof(*ttcce), GFP_KERNEL);
 	if (WARN_ON(!ttcce))
 		return;

 	ttcce->ttc.clk = clk;

 	err = clk_prepare_enable(ttcce->ttc.clk);
 	if (WARN_ON(err)) {
 		kfree(ttcce);
 		return;
 	}

 	ttcce->ttc.clk_rate_change_nb.notifier_call =
 		ttc_rate_change_clockevent_cb;
 	ttcce->ttc.clk_rate_change_nb.next = NULL;
 	if (clk_notifier_register(ttcce->ttc.clk,
 				&ttcce->ttc.clk_rate_change_nb))
 		pr_warn("Unable to register clock notifier.\n");

 	ttcce->ttc.base_addr = base;
 	ttcce->ce.name = "ttc_clockevent";
 	ttcce->ce.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
 	ttcce->ce.set_next_event = ttc_set_next_event;
 	ttcce->ce.set_mode = ttc_set_mode;
 	ttcce->ce.rating = 200;
 	ttcce->ce.irq = irq;
 	ttcce->ce.cpumask = cpu_possible_mask;

 	/*
 	 * Setup the clock event timer to be an interval timer which
 	 * is prescaled by 32 using the interval interrupt. Leave it
 	 * disabled for now.
 	 */
 	__raw_writel(0x23, ttcce->ttc.base_addr + TTC_CNT_CNTRL_OFFSET);
 	__raw_writel(CLK_CNTRL_PRESCALE | CLK_CNTRL_PRESCALE_EN,
 		     ttcce->ttc.base_addr + TTC_CLK_CNTRL_OFFSET);
 	__raw_writel(0x1,  ttcce->ttc.base_addr + TTC_IER_OFFSET);

 	err = request_irq(irq, ttc_clock_event_interrupt,
 			  IRQF_DISABLED | IRQF_TIMER,
 			  ttcce->ce.name, ttcce);
 	if (WARN_ON(err)) {
 		kfree(ttcce);
 		return;
 	}

 	clockevents_config_and_register(&ttcce->ce,
 			clk_get_rate(ttcce->ttc.clk) / PRESCALE, 1, 0xfffe);
 }

 /**
  * ttc_timer_init - Initialize the timer
  *
  * Initializes the timer hardware and register the clock source and clock event
  * timers with Linux kernal timer framework
  */
 static void __init ttc_timer_init(struct device_node *timer)
 {
 	unsigned int irq;
 	void __iomem *timer_baseaddr;
 	struct clk *clk;
 	static int initialized;

 	if (initialized)
 		return;

 	initialized = 1;

 	/*
 	 * Get the 1st Triple Timer Counter (TTC) block from the device tree
 	 * and use it. Note that the event timer uses the interrupt and it's the
 	 * 2nd TTC hence the irq_of_parse_and_map(,1)
 	 */
 	timer_baseaddr = of_iomap(timer, 0);
 	if (!timer_baseaddr) {
 		pr_err("ERROR: invalid timer base address\n");
 		BUG();
 	}

 	irq = irq_of_parse_and_map(timer, 1);
 	if (irq <= 0) {
 		pr_err("ERROR: invalid interrupt number\n");
 		BUG();
 	}

 	clk = of_clk_get_by_name(timer, "cpu_1x");
 	if (IS_ERR(clk)) {
 		pr_err("ERROR: timer input clock not found\n");
 		BUG();
 	}

 	ttc_setup_clocksource(clk, timer_baseaddr);
 	ttc_setup_clockevent(clk, timer_baseaddr + 4, irq);

 	pr_info("%s #0 at %p, irq=%d\n", timer->name, timer_baseaddr, irq);
 }

 CLOCKSOURCE_OF_DECLARE(ttc, "cdns,ttc", ttc_timer_init);
	/*
	* This file contains driver for the Cadence Triple Timer Counter Rev 06
	*
	* Copyright (C) 2011-2013 Xilinx
	*
	* based on arch/mips/kernel/time.c timer driver
	*
	* 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/clk.h>
	#include <linux/interrupt.h>
	#include <linux/clockchips.h>
	#include <linux/of_address.h>
	#include <linux/of_irq.h>
	#include <linux/slab.h>
	#include <linux/clk-provider.h>

	/*
	* This driver configures the 2 16-bit count-up timers as follows:
	*
	* T1: Timer 1, clocksource for generic timekeeping
	* T2: Timer 2, clockevent source for hrtimers
	* T3: Timer 3, <unused>
	*
	* The input frequency to the timer module for emulation is 2.5MHz which is
	* common to all the timer channels (T1, T2, and T3). With a pre-scaler of 32,
	* the timers are clocked at 78.125KHz (12.8 us resolution).

	* The input frequency to the timer module in silicon is configurable and
	* obtained from device tree. The pre-scaler of 32 is used.
	*/

	/*
	* Timer Register Offset Definitions of Timer 1, Increment base address by 4
	* and use same offsets for Timer 2
	*/
	#define TTC_CLK_CNTRL_OFFSET 0x00 /* Clock Control Reg, RW */
	#define TTC_CNT_CNTRL_OFFSET 0x0C /* Counter Control Reg, RW */
	#define TTC_COUNT_VAL_OFFSET 0x18 /* Counter Value Reg, RO */
	#define TTC_INTR_VAL_OFFSET 0x24 /* Interval Count Reg, RW */
	#define TTC_ISR_OFFSET 0x54 /* Interrupt Status Reg, RO */
	#define TTC_IER_OFFSET 0x60 /* Interrupt Enable Reg, RW */

	#define TTC_CNT_CNTRL_DISABLE_MASK 0x1

	/*
	* Setup the timers to use pre-scaling, using a fixed value for now that will
	* work across most input frequency, but it may need to be more dynamic
	*/
	#define PRESCALE_EXPONENT 11 /* 2 ^ PRESCALE_EXPONENT = PRESCALE */
	#define PRESCALE 2048 /* The exponent must match this */
	#define CLK_CNTRL_PRESCALE ((PRESCALE_EXPONENT - 1) << 1)
	#define CLK_CNTRL_PRESCALE_EN 1
	#define CNT_CNTRL_RESET (1 << 4)

	/**
	* struct ttc_timer - This definition defines local timer structure
	*
	* @base_addr: Base address of timer
	* @clk: Associated clock source
	* @clk_rate_change_nb Notifier block for clock rate changes
	*/
	struct ttc_timer {
	void __iomem *base_addr;
	struct clk *clk;
	struct notifier_block clk_rate_change_nb;
	};

	#define to_ttc_timer(x) \
	container_of(x, struct ttc_timer, clk_rate_change_nb)

	struct ttc_timer_clocksource {
	struct ttc_timer ttc;
	struct clocksource cs;
	};

	#define to_ttc_timer_clksrc(x) \
	container_of(x, struct ttc_timer_clocksource, cs)

	struct ttc_timer_clockevent {
	struct ttc_timer ttc;
	struct clock_event_device ce;
	};

	#define to_ttc_timer_clkevent(x) \
	container_of(x, struct ttc_timer_clockevent, ce)

	/**
	* ttc_set_interval - Set the timer interval value
	*
	* @timer: Pointer to the timer instance
	* @cycles: Timer interval ticks
	**/
	static void ttc_set_interval(struct ttc_timer *timer,
	unsigned long cycles)
	{
	u32 ctrl_reg;

	/* Disable the counter, set the counter value and re-enable counter */
	ctrl_reg = __raw_readl(timer->base_addr + TTC_CNT_CNTRL_OFFSET);
	ctrl_reg \|= TTC_CNT_CNTRL_DISABLE_MASK;
	__raw_writel(ctrl_reg, timer->base_addr + TTC_CNT_CNTRL_OFFSET);

	__raw_writel(cycles, timer->base_addr + TTC_INTR_VAL_OFFSET);

	/*
	* Reset the counter (0x10) so that it starts from 0, one-shot
	* mode makes this needed for timing to be right.
	*/
	ctrl_reg \|= CNT_CNTRL_RESET;
	ctrl_reg &= ~TTC_CNT_CNTRL_DISABLE_MASK;
	__raw_writel(ctrl_reg, timer->base_addr + TTC_CNT_CNTRL_OFFSET);
	}

	/**
	* ttc_clock_event_interrupt - Clock event timer interrupt handler
	*
	* @irq: IRQ number of the Timer
	* @dev_id: void pointer to the ttc_timer instance
	*
	* returns: Always IRQ_HANDLED - success
	**/
	static irqreturn_t ttc_clock_event_interrupt(int irq, void *dev_id)
	{
	struct ttc_timer_clockevent *ttce = dev_id;
	struct ttc_timer *timer = &ttce->ttc;

	/* Acknowledge the interrupt and call event handler */
	__raw_readl(timer->base_addr + TTC_ISR_OFFSET);

	ttce->ce.event_handler(&ttce->ce);

	return IRQ_HANDLED;
	}

	/**
	* __ttc_clocksource_read - Reads the timer counter register
	*
	* returns: Current timer counter register value
	**/
	static cycle_t __ttc_clocksource_read(struct clocksource *cs)
	{
	struct ttc_timer *timer = &to_ttc_timer_clksrc(cs)->ttc;

	return (cycle_t)__raw_readl(timer->base_addr +
	TTC_COUNT_VAL_OFFSET);
	}

	/**
	* ttc_set_next_event - Sets the time interval for next event
	*
	* @cycles: Timer interval ticks
	* @evt: Address of clock event instance
	*
	* returns: Always 0 - success
	**/
	static int ttc_set_next_event(unsigned long cycles,
	struct clock_event_device *evt)
	{
	struct ttc_timer_clockevent *ttce = to_ttc_timer_clkevent(evt);
	struct ttc_timer *timer = &ttce->ttc;

	ttc_set_interval(timer, cycles);
	return 0;
	}

	/**
	* ttc_set_mode - Sets the mode of timer
	*
	* @mode: Mode to be set
	* @evt: Address of clock event instance
	**/
	static void ttc_set_mode(enum clock_event_mode mode,
	struct clock_event_device *evt)
	{
	struct ttc_timer_clockevent *ttce = to_ttc_timer_clkevent(evt);
	struct ttc_timer *timer = &ttce->ttc;
	u32 ctrl_reg;

	switch (mode) {
	case CLOCK_EVT_MODE_PERIODIC:
	ttc_set_interval(timer,
	DIV_ROUND_CLOSEST(clk_get_rate(ttce->ttc.clk),
	PRESCALE * HZ));
	break;
	case CLOCK_EVT_MODE_ONESHOT:
	case CLOCK_EVT_MODE_UNUSED:
	case CLOCK_EVT_MODE_SHUTDOWN:
	ctrl_reg = __raw_readl(timer->base_addr +
	TTC_CNT_CNTRL_OFFSET);
	ctrl_reg \|= TTC_CNT_CNTRL_DISABLE_MASK;
	__raw_writel(ctrl_reg,
	timer->base_addr + TTC_CNT_CNTRL_OFFSET);
	break;
	case CLOCK_EVT_MODE_RESUME:
	ctrl_reg = __raw_readl(timer->base_addr +
	TTC_CNT_CNTRL_OFFSET);
	ctrl_reg &= ~TTC_CNT_CNTRL_DISABLE_MASK;
	__raw_writel(ctrl_reg,
	timer->base_addr + TTC_CNT_CNTRL_OFFSET);
	break;
	}
	}

	static int ttc_rate_change_clocksource_cb(struct notifier_block *nb,
	unsigned long event, void *data)
	{
	struct clk_notifier_data *ndata = data;
	struct ttc_timer *ttc = to_ttc_timer(nb);
	struct ttc_timer_clocksource *ttccs = container_of(ttc,
	struct ttc_timer_clocksource, ttc);

	switch (event) {
	case POST_RATE_CHANGE:
	/*
	* Do whatever is necessary to maintain a proper time base
	*
	* I cannot find a way to adjust the currently used clocksource
	* to the new frequency. __clocksource_updatefreq_hz() sounds
	* good, but does not work. Not sure what's that missing.
	*
	* This approach works, but triggers two clocksource switches.
	* The first after unregister to clocksource jiffies. And
	* another one after the register to the newly registered timer.
	*
	* Alternatively we could 'waste' another HW timer to ping pong
	* between clock sources. That would also use one register and
	* one unregister call, but only trigger one clocksource switch
	* for the cost of another HW timer used by the OS.
	*/
	clocksource_unregister(&ttccs->cs);
	clocksource_register_hz(&ttccs->cs,
	ndata->new_rate / PRESCALE);
	/* fall through */
	case PRE_RATE_CHANGE:
	case ABORT_RATE_CHANGE:
	default:
	return NOTIFY_DONE;
	}
	}

	static void __init ttc_setup_clocksource(struct clk clk, void __iomem base)
	{
	struct ttc_timer_clocksource *ttccs;
	int err;

	ttccs = kzalloc(sizeof(*ttccs), GFP_KERNEL);
	if (WARN_ON(!ttccs))
	return;

	ttccs->ttc.clk = clk;

	err = clk_prepare_enable(ttccs->ttc.clk);
	if (WARN_ON(err)) {
	kfree(ttccs);
	return;
	}

	ttccs->ttc.clk_rate_change_nb.notifier_call =
	ttc_rate_change_clocksource_cb;
	ttccs->ttc.clk_rate_change_nb.next = NULL;
	if (clk_notifier_register(ttccs->ttc.clk,
	&ttccs->ttc.clk_rate_change_nb))
	pr_warn("Unable to register clock notifier.\n");

	ttccs->ttc.base_addr = base;
	ttccs->cs.name = "ttc_clocksource";
	ttccs->cs.rating = 200;
	ttccs->cs.read = __ttc_clocksource_read;
	ttccs->cs.mask = CLOCKSOURCE_MASK(16);
	ttccs->cs.flags = CLOCK_SOURCE_IS_CONTINUOUS;

	/*
	* Setup the clock source counter to be an incrementing counter
	* with no interrupt and it rolls over at 0xFFFF. Pre-scale
	* it by 32 also. Let it start running now.
	*/
	__raw_writel(0x0, ttccs->ttc.base_addr + TTC_IER_OFFSET);
	__raw_writel(CLK_CNTRL_PRESCALE \| CLK_CNTRL_PRESCALE_EN,
	ttccs->ttc.base_addr + TTC_CLK_CNTRL_OFFSET);
	__raw_writel(CNT_CNTRL_RESET,
	ttccs->ttc.base_addr + TTC_CNT_CNTRL_OFFSET);

	err = clocksource_register_hz(&ttccs->cs,
	clk_get_rate(ttccs->ttc.clk) / PRESCALE);
	if (WARN_ON(err)) {
	kfree(ttccs);
	return;
	}
	}

	static int ttc_rate_change_clockevent_cb(struct notifier_block *nb,
	unsigned long event, void *data)
	{
	struct clk_notifier_data *ndata = data;
	struct ttc_timer *ttc = to_ttc_timer(nb);
	struct ttc_timer_clockevent *ttcce = container_of(ttc,
	struct ttc_timer_clockevent, ttc);

	switch (event) {
	case POST_RATE_CHANGE:
	{
	unsigned long flags;

	/*
	* clockevents_update_freq should be called with IRQ disabled on
	* the CPU the timer provides events for. The timer we use is
	* common to both CPUs, not sure if we need to run on both
	* cores.
	*/
	local_irq_save(flags);
	clockevents_update_freq(&ttcce->ce,
	ndata->new_rate / PRESCALE);
	local_irq_restore(flags);

	/* fall through */
	}
	case PRE_RATE_CHANGE:
	case ABORT_RATE_CHANGE:
	default:
	return NOTIFY_DONE;
	}
	}

	static void __init ttc_setup_clockevent(struct clk *clk,
	void __iomem *base, u32 irq)
	{
	struct ttc_timer_clockevent *ttcce;
	int err;

	ttcce = kzalloc(sizeof(*ttcce), GFP_KERNEL);
	if (WARN_ON(!ttcce))
	return;

	ttcce->ttc.clk = clk;

	err = clk_prepare_enable(ttcce->ttc.clk);
	if (WARN_ON(err)) {
	kfree(ttcce);
	return;
	}

	ttcce->ttc.clk_rate_change_nb.notifier_call =
	ttc_rate_change_clockevent_cb;
	ttcce->ttc.clk_rate_change_nb.next = NULL;
	if (clk_notifier_register(ttcce->ttc.clk,
	&ttcce->ttc.clk_rate_change_nb))
	pr_warn("Unable to register clock notifier.\n");

	ttcce->ttc.base_addr = base;
	ttcce->ce.name = "ttc_clockevent";
	ttcce->ce.features = CLOCK_EVT_FEAT_PERIODIC \| CLOCK_EVT_FEAT_ONESHOT;
	ttcce->ce.set_next_event = ttc_set_next_event;
	ttcce->ce.set_mode = ttc_set_mode;
	ttcce->ce.rating = 200;
	ttcce->ce.irq = irq;
	ttcce->ce.cpumask = cpu_possible_mask;

	/*
	* Setup the clock event timer to be an interval timer which
	* is prescaled by 32 using the interval interrupt. Leave it
	* disabled for now.
	*/
	__raw_writel(0x23, ttcce->ttc.base_addr + TTC_CNT_CNTRL_OFFSET);
	__raw_writel(CLK_CNTRL_PRESCALE \| CLK_CNTRL_PRESCALE_EN,
	ttcce->ttc.base_addr + TTC_CLK_CNTRL_OFFSET);
	__raw_writel(0x1, ttcce->ttc.base_addr + TTC_IER_OFFSET);

	err = request_irq(irq, ttc_clock_event_interrupt,
	IRQF_DISABLED \| IRQF_TIMER,
	ttcce->ce.name, ttcce);
	if (WARN_ON(err)) {
	kfree(ttcce);
	return;
	}

	clockevents_config_and_register(&ttcce->ce,
	clk_get_rate(ttcce->ttc.clk) / PRESCALE, 1, 0xfffe);
	}

	/**
	* ttc_timer_init - Initialize the timer
	*
	* Initializes the timer hardware and register the clock source and clock event
	* timers with Linux kernal timer framework
	*/
	static void __init ttc_timer_init(struct device_node *timer)
	{
	unsigned int irq;
	void __iomem *timer_baseaddr;
	struct clk *clk;
	static int initialized;

	if (initialized)
	return;

	initialized = 1;

	/*
	* Get the 1st Triple Timer Counter (TTC) block from the device tree
	* and use it. Note that the event timer uses the interrupt and it's the
	* 2nd TTC hence the irq_of_parse_and_map(,1)
	*/
	timer_baseaddr = of_iomap(timer, 0);
	if (!timer_baseaddr) {
	pr_err("ERROR: invalid timer base address\n");
	BUG();
	}

	irq = irq_of_parse_and_map(timer, 1);
	if (irq <= 0) {
	pr_err("ERROR: invalid interrupt number\n");
	BUG();
	}

	clk = of_clk_get_by_name(timer, "cpu_1x");
	if (IS_ERR(clk)) {
	pr_err("ERROR: timer input clock not found\n");
	BUG();
	}

	ttc_setup_clocksource(clk, timer_baseaddr);
	ttc_setup_clockevent(clk, timer_baseaddr + 4, irq);

	pr_info("%s #0 at %p, irq=%d\n", timer->name, timer_baseaddr, irq);
	}

	CLOCKSOURCE_OF_DECLARE(ttc, "cdns,ttc", ttc_timer_init);