drivers/clocksource/timer-atmel-st.c - linux - Git at Google

 /*
  * linux/arch/arm/mach-at91/at91rm9200_time.c
  *
  *  Copyright (C) 2003 SAN People
  *  Copyright (C) 2003 ATMEL
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  * 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.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */

 #include <linux/kernel.h>
 #include <linux/interrupt.h>
 #include <linux/irq.h>
 #include <linux/clk.h>
 #include <linux/clockchips.h>
 #include <linux/export.h>
 #include <linux/mfd/syscon.h>
 #include <linux/mfd/syscon/atmel-st.h>
 #include <linux/of_irq.h>
 #include <linux/regmap.h>

 static unsigned long last_crtr;
 static u32 irqmask;
 static struct clock_event_device clkevt;
 static struct regmap *regmap_st;
 static int timer_latch;

 /*
  * The ST_CRTR is updated asynchronously to the master clock ... but
  * the updates as seen by the CPU don't seem to be strictly monotonic.
  * Waiting until we read the same value twice avoids glitching.
  */
 static inline unsigned long read_CRTR(void)
 {
 	unsigned int x1, x2;

 	regmap_read(regmap_st, AT91_ST_CRTR, &x1);
 	do {
 		regmap_read(regmap_st, AT91_ST_CRTR, &x2);
 		if (x1 == x2)
 			break;
 		x1 = x2;
 	} while (1);
 	return x1;
 }

 /*
  * IRQ handler for the timer.
  */
 static irqreturn_t at91rm9200_timer_interrupt(int irq, void *dev_id)
 {
 	u32 sr;

 	regmap_read(regmap_st, AT91_ST_SR, &sr);
 	sr &= irqmask;

 	/*
 	 * irqs should be disabled here, but as the irq is shared they are only
 	 * guaranteed to be off if the timer irq is registered first.
 	 */
 	WARN_ON_ONCE(!irqs_disabled());

 	/* simulate "oneshot" timer with alarm */
 	if (sr & AT91_ST_ALMS) {
 		clkevt.event_handler(&clkevt);
 		return IRQ_HANDLED;
 	}

 	/* periodic mode should handle delayed ticks */
 	if (sr & AT91_ST_PITS) {
 		u32	crtr = read_CRTR();

 		while (((crtr - last_crtr) & AT91_ST_CRTV) >= timer_latch) {
 			last_crtr += timer_latch;
 			clkevt.event_handler(&clkevt);
 		}
 		return IRQ_HANDLED;
 	}

 	/* this irq is shared ... */
 	return IRQ_NONE;
 }

 static cycle_t read_clk32k(struct clocksource *cs)
 {
 	return read_CRTR();
 }

 static struct clocksource clk32k = {
 	.name		= "32k_counter",
 	.rating		= 150,
 	.read		= read_clk32k,
 	.mask		= CLOCKSOURCE_MASK(20),
 	.flags		= CLOCK_SOURCE_IS_CONTINUOUS,
 };

 static void clkdev32k_disable_and_flush_irq(void)
 {
 	unsigned int val;

 	/* Disable and flush pending timer interrupts */
 	regmap_write(regmap_st, AT91_ST_IDR, AT91_ST_PITS | AT91_ST_ALMS);
 	regmap_read(regmap_st, AT91_ST_SR, &val);
 	last_crtr = read_CRTR();
 }

 static int clkevt32k_shutdown(struct clock_event_device *evt)
 {
 	clkdev32k_disable_and_flush_irq();
 	irqmask = 0;
 	regmap_write(regmap_st, AT91_ST_IER, irqmask);
 	return 0;
 }

 static int clkevt32k_set_oneshot(struct clock_event_device *dev)
 {
 	clkdev32k_disable_and_flush_irq();

 	/*
 	 * ALM for oneshot irqs, set by next_event()
 	 * before 32 seconds have passed.
 	 */
 	irqmask = AT91_ST_ALMS;
 	regmap_write(regmap_st, AT91_ST_RTAR, last_crtr);
 	regmap_write(regmap_st, AT91_ST_IER, irqmask);
 	return 0;
 }

 static int clkevt32k_set_periodic(struct clock_event_device *dev)
 {
 	clkdev32k_disable_and_flush_irq();

 	/* PIT for periodic irqs; fixed rate of 1/HZ */
 	irqmask = AT91_ST_PITS;
 	regmap_write(regmap_st, AT91_ST_PIMR, timer_latch);
 	regmap_write(regmap_st, AT91_ST_IER, irqmask);
 	return 0;
 }

 static int
 clkevt32k_next_event(unsigned long delta, struct clock_event_device *dev)
 {
 	u32		alm;
 	int		status = 0;
 	unsigned int	val;

 	BUG_ON(delta < 2);

 	/* The alarm IRQ uses absolute time (now+delta), not the relative
 	 * time (delta) in our calling convention.  Like all clockevents
 	 * using such "match" hardware, we have a race to defend against.
 	 *
 	 * Our defense here is to have set up the clockevent device so the
 	 * delta is at least two.  That way we never end up writing RTAR
 	 * with the value then held in CRTR ... which would mean the match
 	 * wouldn't trigger until 32 seconds later, after CRTR wraps.
 	 */
 	alm = read_CRTR();

 	/* Cancel any pending alarm; flush any pending IRQ */
 	regmap_write(regmap_st, AT91_ST_RTAR, alm);
 	regmap_read(regmap_st, AT91_ST_SR, &val);

 	/* Schedule alarm by writing RTAR. */
 	alm += delta;
 	regmap_write(regmap_st, AT91_ST_RTAR, alm);

 	return status;
 }

 static struct clock_event_device clkevt = {
 	.name			= "at91_tick",
 	.features		= CLOCK_EVT_FEAT_PERIODIC |
 				  CLOCK_EVT_FEAT_ONESHOT,
 	.rating			= 150,
 	.set_next_event		= clkevt32k_next_event,
 	.set_state_shutdown	= clkevt32k_shutdown,
 	.set_state_periodic	= clkevt32k_set_periodic,
 	.set_state_oneshot	= clkevt32k_set_oneshot,
 	.tick_resume		= clkevt32k_shutdown,
 };

 /*
  * ST (system timer) module supports both clockevents and clocksource.
  */
 static int __init atmel_st_timer_init(struct device_node *node)
 {
 	struct clk *sclk;
 	unsigned int sclk_rate, val;
 	int irq, ret;

 	regmap_st = syscon_node_to_regmap(node);
 	if (IS_ERR(regmap_st)) {
 		pr_err("Unable to get regmap\n");
 		return PTR_ERR(regmap_st);
 	}

 	/* Disable all timer interrupts, and clear any pending ones */
 	regmap_write(regmap_st, AT91_ST_IDR,
 		AT91_ST_PITS | AT91_ST_WDOVF | AT91_ST_RTTINC | AT91_ST_ALMS);
 	regmap_read(regmap_st, AT91_ST_SR, &val);

 	/* Get the interrupts property */
 	irq  = irq_of_parse_and_map(node, 0);
 	if (!irq) {
 		pr_err("Unable to get IRQ from DT\n");
 		return -EINVAL;
 	}

 	/* Make IRQs happen for the system timer */
 	ret = request_irq(irq, at91rm9200_timer_interrupt,
 			  IRQF_SHARED | IRQF_TIMER | IRQF_IRQPOLL,
 			  "at91_tick", regmap_st);
 	if (ret) {
 		pr_err("Unable to setup IRQ\n");
 		return ret;
 	}

 	sclk = of_clk_get(node, 0);
 	if (IS_ERR(sclk)) {
 		pr_err("Unable to get slow clock\n");
 		return PTR_ERR(sclk);
 	}

 	ret = clk_prepare_enable(sclk);
 	if (ret) {
 		pr_err("Could not enable slow clock\n");
 		return ret;
 	}

 	sclk_rate = clk_get_rate(sclk);
 	if (!sclk_rate) {
 		pr_err("Invalid slow clock rate\n");
 		return -EINVAL;
 	}
 	timer_latch = (sclk_rate + HZ / 2) / HZ;

 	/* The 32KiHz "Slow Clock" (tick every 30517.58 nanoseconds) is used
 	 * directly for the clocksource and all clockevents, after adjusting
 	 * its prescaler from the 1 Hz default.
 	 */
 	regmap_write(regmap_st, AT91_ST_RTMR, 1);

 	/* Setup timer clockevent, with minimum of two ticks (important!!) */
 	clkevt.cpumask = cpumask_of(0);
 	clockevents_config_and_register(&clkevt, sclk_rate,
 					2, AT91_ST_ALMV);

 	/* register clocksource */
 	return clocksource_register_hz(&clk32k, sclk_rate);
 }
 CLOCKSOURCE_OF_DECLARE(atmel_st_timer, "atmel,at91rm9200-st",
 		       atmel_st_timer_init);
	/*
	* linux/arch/arm/mach-at91/at91rm9200_time.c
	*
	* Copyright (C) 2003 SAN People
	* Copyright (C) 2003 ATMEL
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* 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.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	*/

	#include <linux/kernel.h>
	#include <linux/interrupt.h>
	#include <linux/irq.h>
	#include <linux/clk.h>
	#include <linux/clockchips.h>
	#include <linux/export.h>
	#include <linux/mfd/syscon.h>
	#include <linux/mfd/syscon/atmel-st.h>
	#include <linux/of_irq.h>
	#include <linux/regmap.h>

	static unsigned long last_crtr;
	static u32 irqmask;
	static struct clock_event_device clkevt;
	static struct regmap *regmap_st;
	static int timer_latch;

	/*
	* The ST_CRTR is updated asynchronously to the master clock ... but
	* the updates as seen by the CPU don't seem to be strictly monotonic.
	* Waiting until we read the same value twice avoids glitching.
	*/
	static inline unsigned long read_CRTR(void)
	{
	unsigned int x1, x2;

	regmap_read(regmap_st, AT91_ST_CRTR, &x1);
	do {
	regmap_read(regmap_st, AT91_ST_CRTR, &x2);
	if (x1 == x2)
	break;
	x1 = x2;
	} while (1);
	return x1;
	}

	/*
	* IRQ handler for the timer.
	*/
	static irqreturn_t at91rm9200_timer_interrupt(int irq, void *dev_id)
	{
	u32 sr;

	regmap_read(regmap_st, AT91_ST_SR, &sr);
	sr &= irqmask;

	/*
	* irqs should be disabled here, but as the irq is shared they are only
	* guaranteed to be off if the timer irq is registered first.
	*/
	WARN_ON_ONCE(!irqs_disabled());

	/* simulate "oneshot" timer with alarm */
	if (sr & AT91_ST_ALMS) {
	clkevt.event_handler(&clkevt);
	return IRQ_HANDLED;
	}

	/* periodic mode should handle delayed ticks */
	if (sr & AT91_ST_PITS) {
	u32 crtr = read_CRTR();

	while (((crtr - last_crtr) & AT91_ST_CRTV) >= timer_latch) {
	last_crtr += timer_latch;
	clkevt.event_handler(&clkevt);
	}
	return IRQ_HANDLED;
	}

	/* this irq is shared ... */
	return IRQ_NONE;
	}

	static cycle_t read_clk32k(struct clocksource *cs)
	{
	return read_CRTR();
	}

	static struct clocksource clk32k = {
	.name = "32k_counter",
	.rating = 150,
	.read = read_clk32k,
	.mask = CLOCKSOURCE_MASK(20),
	.flags = CLOCK_SOURCE_IS_CONTINUOUS,
	};

	static void clkdev32k_disable_and_flush_irq(void)
	{
	unsigned int val;

	/* Disable and flush pending timer interrupts */
	regmap_write(regmap_st, AT91_ST_IDR, AT91_ST_PITS \| AT91_ST_ALMS);
	regmap_read(regmap_st, AT91_ST_SR, &val);
	last_crtr = read_CRTR();
	}

	static int clkevt32k_shutdown(struct clock_event_device *evt)
	{
	clkdev32k_disable_and_flush_irq();
	irqmask = 0;
	regmap_write(regmap_st, AT91_ST_IER, irqmask);
	return 0;
	}

	static int clkevt32k_set_oneshot(struct clock_event_device *dev)
	{
	clkdev32k_disable_and_flush_irq();

	/*
	* ALM for oneshot irqs, set by next_event()
	* before 32 seconds have passed.
	*/
	irqmask = AT91_ST_ALMS;
	regmap_write(regmap_st, AT91_ST_RTAR, last_crtr);
	regmap_write(regmap_st, AT91_ST_IER, irqmask);
	return 0;
	}

	static int clkevt32k_set_periodic(struct clock_event_device *dev)
	{
	clkdev32k_disable_and_flush_irq();

	/* PIT for periodic irqs; fixed rate of 1/HZ */
	irqmask = AT91_ST_PITS;
	regmap_write(regmap_st, AT91_ST_PIMR, timer_latch);
	regmap_write(regmap_st, AT91_ST_IER, irqmask);
	return 0;
	}

	static int
	clkevt32k_next_event(unsigned long delta, struct clock_event_device *dev)
	{
	u32 alm;
	int status = 0;
	unsigned int val;

	BUG_ON(delta < 2);

	/* The alarm IRQ uses absolute time (now+delta), not the relative
	* time (delta) in our calling convention. Like all clockevents
	* using such "match" hardware, we have a race to defend against.
	*
	* Our defense here is to have set up the clockevent device so the
	* delta is at least two. That way we never end up writing RTAR
	* with the value then held in CRTR ... which would mean the match
	* wouldn't trigger until 32 seconds later, after CRTR wraps.
	*/
	alm = read_CRTR();

	/* Cancel any pending alarm; flush any pending IRQ */
	regmap_write(regmap_st, AT91_ST_RTAR, alm);
	regmap_read(regmap_st, AT91_ST_SR, &val);

	/* Schedule alarm by writing RTAR. */
	alm += delta;
	regmap_write(regmap_st, AT91_ST_RTAR, alm);

	return status;
	}

	static struct clock_event_device clkevt = {
	.name = "at91_tick",
	.features = CLOCK_EVT_FEAT_PERIODIC \|
	CLOCK_EVT_FEAT_ONESHOT,
	.rating = 150,
	.set_next_event = clkevt32k_next_event,
	.set_state_shutdown = clkevt32k_shutdown,
	.set_state_periodic = clkevt32k_set_periodic,
	.set_state_oneshot = clkevt32k_set_oneshot,
	.tick_resume = clkevt32k_shutdown,
	};

	/*
	* ST (system timer) module supports both clockevents and clocksource.
	*/
	static int __init atmel_st_timer_init(struct device_node *node)
	{
	struct clk *sclk;
	unsigned int sclk_rate, val;
	int irq, ret;

	regmap_st = syscon_node_to_regmap(node);
	if (IS_ERR(regmap_st)) {
	pr_err("Unable to get regmap\n");
	return PTR_ERR(regmap_st);
	}

	/* Disable all timer interrupts, and clear any pending ones */
	regmap_write(regmap_st, AT91_ST_IDR,
	AT91_ST_PITS \| AT91_ST_WDOVF \| AT91_ST_RTTINC \| AT91_ST_ALMS);
	regmap_read(regmap_st, AT91_ST_SR, &val);

	/* Get the interrupts property */
	irq = irq_of_parse_and_map(node, 0);
	if (!irq) {
	pr_err("Unable to get IRQ from DT\n");
	return -EINVAL;
	}

	/* Make IRQs happen for the system timer */
	ret = request_irq(irq, at91rm9200_timer_interrupt,
	IRQF_SHARED \| IRQF_TIMER \| IRQF_IRQPOLL,
	"at91_tick", regmap_st);
	if (ret) {
	pr_err("Unable to setup IRQ\n");
	return ret;
	}

	sclk = of_clk_get(node, 0);
	if (IS_ERR(sclk)) {
	pr_err("Unable to get slow clock\n");
	return PTR_ERR(sclk);
	}

	ret = clk_prepare_enable(sclk);
	if (ret) {
	pr_err("Could not enable slow clock\n");
	return ret;
	}

	sclk_rate = clk_get_rate(sclk);
	if (!sclk_rate) {
	pr_err("Invalid slow clock rate\n");
	return -EINVAL;
	}
	timer_latch = (sclk_rate + HZ / 2) / HZ;

	/* The 32KiHz "Slow Clock" (tick every 30517.58 nanoseconds) is used
	* directly for the clocksource and all clockevents, after adjusting
	* its prescaler from the 1 Hz default.
	*/
	regmap_write(regmap_st, AT91_ST_RTMR, 1);

	/* Setup timer clockevent, with minimum of two ticks (important!!) */
	clkevt.cpumask = cpumask_of(0);
	clockevents_config_and_register(&clkevt, sclk_rate,
	2, AT91_ST_ALMV);

	/* register clocksource */
	return clocksource_register_hz(&clk32k, sclk_rate);
	}
	CLOCKSOURCE_OF_DECLARE(atmel_st_timer, "atmel,at91rm9200-st",
	atmel_st_timer_init);