arch/powerpc/sysdev/fsl_gtm.c - kernel/skids - Git at Google

 /*
  * Freescale General-purpose Timers Module
  *
  * Copyright (c) Freescale Semicondutor, Inc. 2006.
  *               Shlomi Gridish <gridish@freescale.com>
  *               Jerry Huang <Chang-Ming.Huang@freescale.com>
  * Copyright (c) MontaVista Software, Inc. 2008.
  *               Anton Vorontsov <avorontsov@ru.mvista.com>
  *
  * 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.
  */

 #include <linux/kernel.h>
 #include <linux/errno.h>
 #include <linux/list.h>
 #include <linux/io.h>
 #include <linux/of.h>
 #include <linux/spinlock.h>
 #include <linux/bitops.h>
 #include <linux/slab.h>
 #include <asm/fsl_gtm.h>

 #define GTCFR_STP(x)		((x) & 1 ? 1 << 5 : 1 << 1)
 #define GTCFR_RST(x)		((x) & 1 ? 1 << 4 : 1 << 0)

 #define GTMDR_ICLK_MASK		(3 << 1)
 #define GTMDR_ICLK_ICAS		(0 << 1)
 #define GTMDR_ICLK_ICLK		(1 << 1)
 #define GTMDR_ICLK_SLGO		(2 << 1)
 #define GTMDR_FRR		(1 << 3)
 #define GTMDR_ORI		(1 << 4)
 #define GTMDR_SPS(x)		((x) << 8)

 struct gtm_timers_regs {
 	u8	gtcfr1;		/* Timer 1, Timer 2 global config register */
 	u8	res0[0x3];
 	u8	gtcfr2;		/* Timer 3, timer 4 global config register */
 	u8	res1[0xB];
 	__be16	gtmdr1;		/* Timer 1 mode register */
 	__be16	gtmdr2;		/* Timer 2 mode register */
 	__be16	gtrfr1;		/* Timer 1 reference register */
 	__be16	gtrfr2;		/* Timer 2 reference register */
 	__be16	gtcpr1;		/* Timer 1 capture register */
 	__be16	gtcpr2;		/* Timer 2 capture register */
 	__be16	gtcnr1;		/* Timer 1 counter */
 	__be16	gtcnr2;		/* Timer 2 counter */
 	__be16	gtmdr3;		/* Timer 3 mode register */
 	__be16	gtmdr4;		/* Timer 4 mode register */
 	__be16	gtrfr3;		/* Timer 3 reference register */
 	__be16	gtrfr4;		/* Timer 4 reference register */
 	__be16	gtcpr3;		/* Timer 3 capture register */
 	__be16	gtcpr4;		/* Timer 4 capture register */
 	__be16	gtcnr3;		/* Timer 3 counter */
 	__be16	gtcnr4;		/* Timer 4 counter */
 	__be16	gtevr1;		/* Timer 1 event register */
 	__be16	gtevr2;		/* Timer 2 event register */
 	__be16	gtevr3;		/* Timer 3 event register */
 	__be16	gtevr4;		/* Timer 4 event register */
 	__be16	gtpsr1;		/* Timer 1 prescale register */
 	__be16	gtpsr2;		/* Timer 2 prescale register */
 	__be16	gtpsr3;		/* Timer 3 prescale register */
 	__be16	gtpsr4;		/* Timer 4 prescale register */
 	u8 res2[0x40];
 } __attribute__ ((packed));

 struct gtm {
 	unsigned int clock;
 	struct gtm_timers_regs __iomem *regs;
 	struct gtm_timer timers[4];
 	spinlock_t lock;
 	struct list_head list_node;
 };

 static LIST_HEAD(gtms);

 /**
  * gtm_get_timer - request GTM timer to use it with the rest of GTM API
  * Context:	non-IRQ
  *
  * This function reserves GTM timer for later use. It returns gtm_timer
  * structure to use with the rest of GTM API, you should use timer->irq
  * to manage timer interrupt.
  */
 struct gtm_timer *gtm_get_timer16(void)
 {
 	struct gtm *gtm = NULL;
 	int i;

 	list_for_each_entry(gtm, &gtms, list_node) {
 		spin_lock_irq(&gtm->lock);

 		for (i = 0; i < ARRAY_SIZE(gtm->timers); i++) {
 			if (!gtm->timers[i].requested) {
 				gtm->timers[i].requested = true;
 				spin_unlock_irq(&gtm->lock);
 				return &gtm->timers[i];
 			}
 		}

 		spin_unlock_irq(&gtm->lock);
 	}

 	if (gtm)
 		return ERR_PTR(-EBUSY);
 	return ERR_PTR(-ENODEV);
 }
 EXPORT_SYMBOL(gtm_get_timer16);

 /**
  * gtm_get_specific_timer - request specific GTM timer
  * @gtm:	specific GTM, pass here GTM's device_node->data
  * @timer:	specific timer number, Timer1 is 0.
  * Context:	non-IRQ
  *
  * This function reserves GTM timer for later use. It returns gtm_timer
  * structure to use with the rest of GTM API, you should use timer->irq
  * to manage timer interrupt.
  */
 struct gtm_timer *gtm_get_specific_timer16(struct gtm *gtm,
 					   unsigned int timer)
 {
 	struct gtm_timer *ret = ERR_PTR(-EBUSY);

 	if (timer > 3)
 		return ERR_PTR(-EINVAL);

 	spin_lock_irq(&gtm->lock);

 	if (gtm->timers[timer].requested)
 		goto out;

 	ret = &gtm->timers[timer];
 	ret->requested = true;

 out:
 	spin_unlock_irq(&gtm->lock);
 	return ret;
 }
 EXPORT_SYMBOL(gtm_get_specific_timer16);

 /**
  * gtm_put_timer16 - release 16 bits GTM timer
  * @tmr:	pointer to the gtm_timer structure obtained from gtm_get_timer
  * Context:	any
  *
  * This function releases GTM timer so others may request it.
  */
 void gtm_put_timer16(struct gtm_timer *tmr)
 {
 	gtm_stop_timer16(tmr);

 	spin_lock_irq(&tmr->gtm->lock);
 	tmr->requested = false;
 	spin_unlock_irq(&tmr->gtm->lock);
 }
 EXPORT_SYMBOL(gtm_put_timer16);

 /*
  * This is back-end for the exported functions, it's used to reset single
  * timer in reference mode.
  */
 static int gtm_set_ref_timer16(struct gtm_timer *tmr, int frequency,
 			       int reference_value, bool free_run)
 {
 	struct gtm *gtm = tmr->gtm;
 	int num = tmr - &gtm->timers[0];
 	unsigned int prescaler;
 	u8 iclk = GTMDR_ICLK_ICLK;
 	u8 psr;
 	u8 sps;
 	unsigned long flags;
 	int max_prescaler = 256 * 256 * 16;

 	/* CPM2 doesn't have primary prescaler */
 	if (!tmr->gtpsr)
 		max_prescaler /= 256;

 	prescaler = gtm->clock / frequency;
 	/*
 	 * We have two 8 bit prescalers -- primary and secondary (psr, sps),
 	 * plus "slow go" mode (clk / 16). So, total prescale value is
 	 * 16 * (psr + 1) * (sps + 1). Though, for CPM2 GTMs we losing psr.
 	 */
 	if (prescaler > max_prescaler)
 		return -EINVAL;

 	if (prescaler > max_prescaler / 16) {
 		iclk = GTMDR_ICLK_SLGO;
 		prescaler /= 16;
 	}

 	if (prescaler <= 256) {
 		psr = 0;
 		sps = prescaler - 1;
 	} else {
 		psr = 256 - 1;
 		sps = prescaler / 256 - 1;
 	}

 	spin_lock_irqsave(&gtm->lock, flags);

 	/*
 	 * Properly reset timers: stop, reset, set up prescalers, reference
 	 * value and clear event register.
 	 */
 	clrsetbits_8(tmr->gtcfr, ~(GTCFR_STP(num) | GTCFR_RST(num)),
 				 GTCFR_STP(num) | GTCFR_RST(num));

 	setbits8(tmr->gtcfr, GTCFR_STP(num));

 	if (tmr->gtpsr)
 		out_be16(tmr->gtpsr, psr);
 	clrsetbits_be16(tmr->gtmdr, 0xFFFF, iclk | GTMDR_SPS(sps) |
 			GTMDR_ORI | (free_run ? GTMDR_FRR : 0));
 	out_be16(tmr->gtcnr, 0);
 	out_be16(tmr->gtrfr, reference_value);
 	out_be16(tmr->gtevr, 0xFFFF);

 	/* Let it be. */
 	clrbits8(tmr->gtcfr, GTCFR_STP(num));

 	spin_unlock_irqrestore(&gtm->lock, flags);

 	return 0;
 }

 /**
  * gtm_set_timer16 - (re)set 16 bit timer with arbitrary precision
  * @tmr:	pointer to the gtm_timer structure obtained from gtm_get_timer
  * @usec:	timer interval in microseconds
  * @reload:	if set, the timer will reset upon expiry rather than
  *         	continue running free.
  * Context:	any
  *
  * This function (re)sets the GTM timer so that it counts up to the requested
  * interval value, and fires the interrupt when the value is reached. This
  * function will reduce the precision of the timer as needed in order for the
  * requested timeout to fit in a 16-bit register.
  */
 int gtm_set_timer16(struct gtm_timer *tmr, unsigned long usec, bool reload)
 {
 	/* quite obvious, frequency which is enough for µSec precision */
 	int freq = 1000000;
 	unsigned int bit;

 	bit = fls_long(usec);
 	if (bit > 15) {
 		freq >>= bit - 15;
 		usec >>= bit - 15;
 	}

 	if (!freq)
 		return -EINVAL;

 	return gtm_set_ref_timer16(tmr, freq, usec, reload);
 }
 EXPORT_SYMBOL(gtm_set_timer16);

 /**
  * gtm_set_exact_utimer16 - (re)set 16 bits timer
  * @tmr:	pointer to the gtm_timer structure obtained from gtm_get_timer
  * @usec:	timer interval in microseconds
  * @reload:	if set, the timer will reset upon expiry rather than
  *         	continue running free.
  * Context:	any
  *
  * This function (re)sets GTM timer so that it counts up to the requested
  * interval value, and fires the interrupt when the value is reached. If reload
  * flag was set, timer will also reset itself upon reference value, otherwise
  * it continues to increment.
  *
  * The _exact_ bit in the function name states that this function will not
  * crop precision of the "usec" argument, thus usec is limited to 16 bits
  * (single timer width).
  */
 int gtm_set_exact_timer16(struct gtm_timer *tmr, u16 usec, bool reload)
 {
 	/* quite obvious, frequency which is enough for µSec precision */
 	const int freq = 1000000;

 	/*
 	 * We can lower the frequency (and probably power consumption) by
 	 * dividing both frequency and usec by 2 until there is no remainder.
 	 * But we won't bother with this unless savings are measured, so just
 	 * run the timer as is.
 	 */

 	return gtm_set_ref_timer16(tmr, freq, usec, reload);
 }
 EXPORT_SYMBOL(gtm_set_exact_timer16);

 /**
  * gtm_stop_timer16 - stop single timer
  * @tmr:	pointer to the gtm_timer structure obtained from gtm_get_timer
  * Context:	any
  *
  * This function simply stops the GTM timer.
  */
 void gtm_stop_timer16(struct gtm_timer *tmr)
 {
 	struct gtm *gtm = tmr->gtm;
 	int num = tmr - &gtm->timers[0];
 	unsigned long flags;

 	spin_lock_irqsave(&gtm->lock, flags);

 	setbits8(tmr->gtcfr, GTCFR_STP(num));
 	out_be16(tmr->gtevr, 0xFFFF);

 	spin_unlock_irqrestore(&gtm->lock, flags);
 }
 EXPORT_SYMBOL(gtm_stop_timer16);

 /**
  * gtm_ack_timer16 - acknowledge timer event (free-run timers only)
  * @tmr:	pointer to the gtm_timer structure obtained from gtm_get_timer
  * @events:	events mask to ack
  * Context:	any
  *
  * Thus function used to acknowledge timer interrupt event, use it inside the
  * interrupt handler.
  */
 void gtm_ack_timer16(struct gtm_timer *tmr, u16 events)
 {
 	out_be16(tmr->gtevr, events);
 }
 EXPORT_SYMBOL(gtm_ack_timer16);

 static void __init gtm_set_shortcuts(struct device_node *np,
 				     struct gtm_timer *timers,
 				     struct gtm_timers_regs __iomem *regs)
 {
 	/*
 	 * Yeah, I don't like this either, but timers' registers a bit messed,
 	 * so we have to provide shortcuts to write timer independent code.
 	 * Alternative option is to create gt*() accessors, but that will be
 	 * even uglier and cryptic.
 	 */
 	timers[0].gtcfr = &regs->gtcfr1;
 	timers[0].gtmdr = &regs->gtmdr1;
 	timers[0].gtcnr = &regs->gtcnr1;
 	timers[0].gtrfr = &regs->gtrfr1;
 	timers[0].gtevr = &regs->gtevr1;

 	timers[1].gtcfr = &regs->gtcfr1;
 	timers[1].gtmdr = &regs->gtmdr2;
 	timers[1].gtcnr = &regs->gtcnr2;
 	timers[1].gtrfr = &regs->gtrfr2;
 	timers[1].gtevr = &regs->gtevr2;

 	timers[2].gtcfr = &regs->gtcfr2;
 	timers[2].gtmdr = &regs->gtmdr3;
 	timers[2].gtcnr = &regs->gtcnr3;
 	timers[2].gtrfr = &regs->gtrfr3;
 	timers[2].gtevr = &regs->gtevr3;

 	timers[3].gtcfr = &regs->gtcfr2;
 	timers[3].gtmdr = &regs->gtmdr4;
 	timers[3].gtcnr = &regs->gtcnr4;
 	timers[3].gtrfr = &regs->gtrfr4;
 	timers[3].gtevr = &regs->gtevr4;

 	/* CPM2 doesn't have primary prescaler */
 	if (!of_device_is_compatible(np, "fsl,cpm2-gtm")) {
 		timers[0].gtpsr = &regs->gtpsr1;
 		timers[1].gtpsr = &regs->gtpsr2;
 		timers[2].gtpsr = &regs->gtpsr3;
 		timers[3].gtpsr = &regs->gtpsr4;
 	}
 }

 static int __init fsl_gtm_init(void)
 {
 	struct device_node *np;

 	for_each_compatible_node(np, NULL, "fsl,gtm") {
 		int i;
 		struct gtm *gtm;
 		const u32 *clock;
 		int size;

 		gtm = kzalloc(sizeof(*gtm), GFP_KERNEL);
 		if (!gtm) {
 			pr_err("%s: unable to allocate memory\n",
 				np->full_name);
 			continue;
 		}

 		spin_lock_init(&gtm->lock);

 		clock = of_get_property(np, "clock-frequency", &size);
 		if (!clock || size != sizeof(*clock)) {
 			pr_err("%s: no clock-frequency\n", np->full_name);
 			goto err;
 		}
 		gtm->clock = *clock;

 		for (i = 0; i < ARRAY_SIZE(gtm->timers); i++) {
 			int ret;
 			struct resource irq;

 			ret = of_irq_to_resource(np, i, &irq);
 			if (ret == NO_IRQ) {
 				pr_err("%s: not enough interrupts specified\n",
 				       np->full_name);
 				goto err;
 			}
 			gtm->timers[i].irq = irq.start;
 			gtm->timers[i].gtm = gtm;
 		}

 		gtm->regs = of_iomap(np, 0);
 		if (!gtm->regs) {
 			pr_err("%s: unable to iomap registers\n",
 			       np->full_name);
 			goto err;
 		}

 		gtm_set_shortcuts(np, gtm->timers, gtm->regs);
 		list_add(&gtm->list_node, &gtms);

 		/* We don't want to lose the node and its ->data */
 		np->data = gtm;
 		of_node_get(np);

 		continue;
 err:
 		kfree(gtm);
 	}
 	return 0;
 }
 arch_initcall(fsl_gtm_init);
	/*
	* Freescale General-purpose Timers Module
	*
	* Copyright (c) Freescale Semicondutor, Inc. 2006.
	* Shlomi Gridish <gridish@freescale.com>
	* Jerry Huang <Chang-Ming.Huang@freescale.com>
	* Copyright (c) MontaVista Software, Inc. 2008.
	* Anton Vorontsov <avorontsov@ru.mvista.com>
	*
	* 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.
	*/

	#include <linux/kernel.h>
	#include <linux/errno.h>
	#include <linux/list.h>
	#include <linux/io.h>
	#include <linux/of.h>
	#include <linux/spinlock.h>
	#include <linux/bitops.h>
	#include <linux/slab.h>
	#include <asm/fsl_gtm.h>

	#define GTCFR_STP(x) ((x) & 1 ? 1 << 5 : 1 << 1)
	#define GTCFR_RST(x) ((x) & 1 ? 1 << 4 : 1 << 0)

	#define GTMDR_ICLK_MASK (3 << 1)
	#define GTMDR_ICLK_ICAS (0 << 1)
	#define GTMDR_ICLK_ICLK (1 << 1)
	#define GTMDR_ICLK_SLGO (2 << 1)
	#define GTMDR_FRR (1 << 3)
	#define GTMDR_ORI (1 << 4)
	#define GTMDR_SPS(x) ((x) << 8)

	struct gtm_timers_regs {
	u8 gtcfr1; /* Timer 1, Timer 2 global config register */
	u8 res0[0x3];
	u8 gtcfr2; /* Timer 3, timer 4 global config register */
	u8 res1[0xB];
	__be16 gtmdr1; /* Timer 1 mode register */
	__be16 gtmdr2; /* Timer 2 mode register */
	__be16 gtrfr1; /* Timer 1 reference register */
	__be16 gtrfr2; /* Timer 2 reference register */
	__be16 gtcpr1; /* Timer 1 capture register */
	__be16 gtcpr2; /* Timer 2 capture register */
	__be16 gtcnr1; /* Timer 1 counter */
	__be16 gtcnr2; /* Timer 2 counter */
	__be16 gtmdr3; /* Timer 3 mode register */
	__be16 gtmdr4; /* Timer 4 mode register */
	__be16 gtrfr3; /* Timer 3 reference register */
	__be16 gtrfr4; /* Timer 4 reference register */
	__be16 gtcpr3; /* Timer 3 capture register */
	__be16 gtcpr4; /* Timer 4 capture register */
	__be16 gtcnr3; /* Timer 3 counter */
	__be16 gtcnr4; /* Timer 4 counter */
	__be16 gtevr1; /* Timer 1 event register */
	__be16 gtevr2; /* Timer 2 event register */
	__be16 gtevr3; /* Timer 3 event register */
	__be16 gtevr4; /* Timer 4 event register */
	__be16 gtpsr1; /* Timer 1 prescale register */
	__be16 gtpsr2; /* Timer 2 prescale register */
	__be16 gtpsr3; /* Timer 3 prescale register */
	__be16 gtpsr4; /* Timer 4 prescale register */
	u8 res2[0x40];
	} __attribute__ ((packed));

	struct gtm {
	unsigned int clock;
	struct gtm_timers_regs __iomem *regs;
	struct gtm_timer timers[4];
	spinlock_t lock;
	struct list_head list_node;
	};

	static LIST_HEAD(gtms);

	/**
	* gtm_get_timer - request GTM timer to use it with the rest of GTM API
	* Context: non-IRQ
	*
	* This function reserves GTM timer for later use. It returns gtm_timer
	* structure to use with the rest of GTM API, you should use timer->irq
	* to manage timer interrupt.
	*/
	struct gtm_timer *gtm_get_timer16(void)
	{
	struct gtm *gtm = NULL;
	int i;

	list_for_each_entry(gtm, &gtms, list_node) {
	spin_lock_irq(&gtm->lock);

	for (i = 0; i < ARRAY_SIZE(gtm->timers); i++) {
	if (!gtm->timers[i].requested) {
	gtm->timers[i].requested = true;
	spin_unlock_irq(&gtm->lock);
	return &gtm->timers[i];
	}
	}

	spin_unlock_irq(&gtm->lock);
	}

	if (gtm)
	return ERR_PTR(-EBUSY);
	return ERR_PTR(-ENODEV);
	}
	EXPORT_SYMBOL(gtm_get_timer16);

	/**
	* gtm_get_specific_timer - request specific GTM timer
	* @gtm: specific GTM, pass here GTM's device_node->data
	* @timer: specific timer number, Timer1 is 0.
	* Context: non-IRQ
	*
	* This function reserves GTM timer for later use. It returns gtm_timer
	* structure to use with the rest of GTM API, you should use timer->irq
	* to manage timer interrupt.
	*/
	struct gtm_timer gtm_get_specific_timer16(struct gtm gtm,
	unsigned int timer)
	{
	struct gtm_timer *ret = ERR_PTR(-EBUSY);

	if (timer > 3)
	return ERR_PTR(-EINVAL);

	spin_lock_irq(&gtm->lock);

	if (gtm->timers[timer].requested)
	goto out;

	ret = &gtm->timers[timer];
	ret->requested = true;

	out:
	spin_unlock_irq(&gtm->lock);
	return ret;
	}
	EXPORT_SYMBOL(gtm_get_specific_timer16);

	/**
	* gtm_put_timer16 - release 16 bits GTM timer
	* @tmr: pointer to the gtm_timer structure obtained from gtm_get_timer
	* Context: any
	*
	* This function releases GTM timer so others may request it.
	*/
	void gtm_put_timer16(struct gtm_timer *tmr)
	{
	gtm_stop_timer16(tmr);

	spin_lock_irq(&tmr->gtm->lock);
	tmr->requested = false;
	spin_unlock_irq(&tmr->gtm->lock);
	}
	EXPORT_SYMBOL(gtm_put_timer16);

	/*
	* This is back-end for the exported functions, it's used to reset single
	* timer in reference mode.
	*/
	static int gtm_set_ref_timer16(struct gtm_timer *tmr, int frequency,
	int reference_value, bool free_run)
	{
	struct gtm *gtm = tmr->gtm;
	int num = tmr - &gtm->timers[0];
	unsigned int prescaler;
	u8 iclk = GTMDR_ICLK_ICLK;
	u8 psr;
	u8 sps;
	unsigned long flags;
	int max_prescaler = 256 * 256 * 16;

	/* CPM2 doesn't have primary prescaler */
	if (!tmr->gtpsr)
	max_prescaler /= 256;

	prescaler = gtm->clock / frequency;
	/*
	* We have two 8 bit prescalers -- primary and secondary (psr, sps),
	* plus "slow go" mode (clk / 16). So, total prescale value is
	* 16 * (psr + 1) * (sps + 1). Though, for CPM2 GTMs we losing psr.
	*/
	if (prescaler > max_prescaler)
	return -EINVAL;

	if (prescaler > max_prescaler / 16) {
	iclk = GTMDR_ICLK_SLGO;
	prescaler /= 16;
	}

	if (prescaler <= 256) {
	psr = 0;
	sps = prescaler - 1;
	} else {
	psr = 256 - 1;
	sps = prescaler / 256 - 1;
	}

	spin_lock_irqsave(&gtm->lock, flags);

	/*
	* Properly reset timers: stop, reset, set up prescalers, reference
	* value and clear event register.
	*/
	clrsetbits_8(tmr->gtcfr, ~(GTCFR_STP(num) \| GTCFR_RST(num)),
	GTCFR_STP(num) \| GTCFR_RST(num));

	setbits8(tmr->gtcfr, GTCFR_STP(num));

	if (tmr->gtpsr)
	out_be16(tmr->gtpsr, psr);
	clrsetbits_be16(tmr->gtmdr, 0xFFFF, iclk \| GTMDR_SPS(sps) \|
	GTMDR_ORI \| (free_run ? GTMDR_FRR : 0));
	out_be16(tmr->gtcnr, 0);
	out_be16(tmr->gtrfr, reference_value);
	out_be16(tmr->gtevr, 0xFFFF);

	/* Let it be. */
	clrbits8(tmr->gtcfr, GTCFR_STP(num));

	spin_unlock_irqrestore(&gtm->lock, flags);

	return 0;
	}

	/**
	* gtm_set_timer16 - (re)set 16 bit timer with arbitrary precision
	* @tmr: pointer to the gtm_timer structure obtained from gtm_get_timer
	* @usec: timer interval in microseconds
	* @reload: if set, the timer will reset upon expiry rather than
	* continue running free.
	* Context: any
	*
	* This function (re)sets the GTM timer so that it counts up to the requested
	* interval value, and fires the interrupt when the value is reached. This
	* function will reduce the precision of the timer as needed in order for the
	* requested timeout to fit in a 16-bit register.
	*/
	int gtm_set_timer16(struct gtm_timer *tmr, unsigned long usec, bool reload)
	{
	/* quite obvious, frequency which is enough for µSec precision */
	int freq = 1000000;
	unsigned int bit;

	bit = fls_long(usec);
	if (bit > 15) {
	freq >>= bit - 15;
	usec >>= bit - 15;
	}

	if (!freq)
	return -EINVAL;

	return gtm_set_ref_timer16(tmr, freq, usec, reload);
	}
	EXPORT_SYMBOL(gtm_set_timer16);

	/**
	* gtm_set_exact_utimer16 - (re)set 16 bits timer
	* @tmr: pointer to the gtm_timer structure obtained from gtm_get_timer
	* @usec: timer interval in microseconds
	* @reload: if set, the timer will reset upon expiry rather than
	* continue running free.
	* Context: any
	*
	* This function (re)sets GTM timer so that it counts up to the requested
	* interval value, and fires the interrupt when the value is reached. If reload
	* flag was set, timer will also reset itself upon reference value, otherwise
	* it continues to increment.
	*
	* The _exact_ bit in the function name states that this function will not
	* crop precision of the "usec" argument, thus usec is limited to 16 bits
	* (single timer width).
	*/
	int gtm_set_exact_timer16(struct gtm_timer *tmr, u16 usec, bool reload)
	{
	/* quite obvious, frequency which is enough for µSec precision */
	const int freq = 1000000;

	/*
	* We can lower the frequency (and probably power consumption) by
	* dividing both frequency and usec by 2 until there is no remainder.
	* But we won't bother with this unless savings are measured, so just
	* run the timer as is.
	*/

	return gtm_set_ref_timer16(tmr, freq, usec, reload);
	}
	EXPORT_SYMBOL(gtm_set_exact_timer16);

	/**
	* gtm_stop_timer16 - stop single timer
	* @tmr: pointer to the gtm_timer structure obtained from gtm_get_timer
	* Context: any
	*
	* This function simply stops the GTM timer.
	*/
	void gtm_stop_timer16(struct gtm_timer *tmr)
	{
	struct gtm *gtm = tmr->gtm;
	int num = tmr - &gtm->timers[0];
	unsigned long flags;

	spin_lock_irqsave(&gtm->lock, flags);

	setbits8(tmr->gtcfr, GTCFR_STP(num));
	out_be16(tmr->gtevr, 0xFFFF);

	spin_unlock_irqrestore(&gtm->lock, flags);
	}
	EXPORT_SYMBOL(gtm_stop_timer16);

	/**
	* gtm_ack_timer16 - acknowledge timer event (free-run timers only)
	* @tmr: pointer to the gtm_timer structure obtained from gtm_get_timer
	* @events: events mask to ack
	* Context: any
	*
	* Thus function used to acknowledge timer interrupt event, use it inside the
	* interrupt handler.
	*/
	void gtm_ack_timer16(struct gtm_timer *tmr, u16 events)
	{
	out_be16(tmr->gtevr, events);
	}
	EXPORT_SYMBOL(gtm_ack_timer16);

	static void __init gtm_set_shortcuts(struct device_node *np,
	struct gtm_timer *timers,
	struct gtm_timers_regs __iomem *regs)
	{
	/*
	* Yeah, I don't like this either, but timers' registers a bit messed,
	* so we have to provide shortcuts to write timer independent code.
	* Alternative option is to create gt*() accessors, but that will be
	* even uglier and cryptic.
	*/
	timers[0].gtcfr = &regs->gtcfr1;
	timers[0].gtmdr = &regs->gtmdr1;
	timers[0].gtcnr = &regs->gtcnr1;
	timers[0].gtrfr = &regs->gtrfr1;
	timers[0].gtevr = &regs->gtevr1;

	timers[1].gtcfr = &regs->gtcfr1;
	timers[1].gtmdr = &regs->gtmdr2;
	timers[1].gtcnr = &regs->gtcnr2;
	timers[1].gtrfr = &regs->gtrfr2;
	timers[1].gtevr = &regs->gtevr2;

	timers[2].gtcfr = &regs->gtcfr2;
	timers[2].gtmdr = &regs->gtmdr3;
	timers[2].gtcnr = &regs->gtcnr3;
	timers[2].gtrfr = &regs->gtrfr3;
	timers[2].gtevr = &regs->gtevr3;

	timers[3].gtcfr = &regs->gtcfr2;
	timers[3].gtmdr = &regs->gtmdr4;
	timers[3].gtcnr = &regs->gtcnr4;
	timers[3].gtrfr = &regs->gtrfr4;
	timers[3].gtevr = &regs->gtevr4;

	/* CPM2 doesn't have primary prescaler */
	if (!of_device_is_compatible(np, "fsl,cpm2-gtm")) {
	timers[0].gtpsr = &regs->gtpsr1;
	timers[1].gtpsr = &regs->gtpsr2;
	timers[2].gtpsr = &regs->gtpsr3;
	timers[3].gtpsr = &regs->gtpsr4;
	}
	}

	static int __init fsl_gtm_init(void)
	{
	struct device_node *np;

	for_each_compatible_node(np, NULL, "fsl,gtm") {
	int i;
	struct gtm *gtm;
	const u32 *clock;
	int size;

	gtm = kzalloc(sizeof(*gtm), GFP_KERNEL);
	if (!gtm) {
	pr_err("%s: unable to allocate memory\n",
	np->full_name);
	continue;
	}

	spin_lock_init(&gtm->lock);

	clock = of_get_property(np, "clock-frequency", &size);
	if (!clock \|\| size != sizeof(*clock)) {
	pr_err("%s: no clock-frequency\n", np->full_name);
	goto err;
	}
	gtm->clock = *clock;

	for (i = 0; i < ARRAY_SIZE(gtm->timers); i++) {
	int ret;
	struct resource irq;

	ret = of_irq_to_resource(np, i, &irq);
	if (ret == NO_IRQ) {
	pr_err("%s: not enough interrupts specified\n",
	np->full_name);
	goto err;
	}
	gtm->timers[i].irq = irq.start;
	gtm->timers[i].gtm = gtm;
	}

	gtm->regs = of_iomap(np, 0);
	if (!gtm->regs) {
	pr_err("%s: unable to iomap registers\n",
	np->full_name);
	goto err;
	}

	gtm_set_shortcuts(np, gtm->timers, gtm->regs);
	list_add(&gtm->list_node, &gtms);

	/* We don't want to lose the node and its ->data */
	np->data = gtm;
	of_node_get(np);

	continue;
	err:
	kfree(gtm);
	}
	return 0;
	}
	arch_initcall(fsl_gtm_init);