arm/mach-omap2/clock.c

/*
 *  linux/arch/arm/mach-omap2/clock.c
 *
 *  Copyright (C) 2005-2008 Texas Instruments, Inc.
 *  Copyright (C) 2004-2010 Nokia Corporation
 *
 *  Contacts:
 *  Richard Woodruff <r-woodruff2@ti.com>
 *  Paul Walmsley
 *
 * 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.
 */
#undef DEBUG

#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/list.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/delay.h>
#include <linux/clk.h>
#include <linux/io.h>
#include <linux/bitops.h>

#include <asm/cpu.h>


#include <trace/events/power.h>

#include "soc.h"
#include "clockdomain.h"
#include "clock.h"
#include "cm.h"
#include "cm2xxx.h"
#include "cm3xxx.h"
#include "cm-regbits-24xx.h"
#include "cm-regbits-34xx.h"
#include "common.h"

/*
 * MAX_MODULE_ENABLE_WAIT: maximum of number of microseconds to wait
 * for a module to indicate that it is no longer in idle
 */
#define MAX_MODULE_ENABLE_WAIT		100000

u16 cpu_mask;

/*
 * clkdm_control: if true, then when a clock is enabled in the
 * hardware, its clockdomain will first be enabled; and when a clock
 * is disabled in the hardware, its clockdomain will be disabled
 * afterwards.
 */
static bool clkdm_control = true;

static LIST_HEAD(clocks);
static DEFINE_MUTEX(clocks_mutex);
static DEFINE_SPINLOCK(clockfw_lock);

/*
 * OMAP2+ specific clock functions
 */

/* Private functions */


/**
 * _wait_idlest_generic - wait for a module to leave the idle state
 * @reg: virtual address of module IDLEST register
 * @mask: value to mask against to determine if the module is active
 * @idlest: idle state indicator (0 or 1) for the clock
 * @name: name of the clock (for printk)
 *
 * Wait for a module to leave idle, where its idle-status register is
 * not inside the CM module.  Returns 1 if the module left idle
 * promptly, or 0 if the module did not leave idle before the timeout
 * elapsed.  XXX Deprecated - should be moved into drivers for the
 * individual IP block that the IDLEST register exists in.
 */
static int _wait_idlest_generic(void __iomem *reg, u32 mask, u8 idlest,
				const char *name)
{
	int i = 0, ena = 0;

	ena = (idlest) ? 0 : mask;

	omap_test_timeout(((__raw_readl(reg) & mask) == ena),
			  MAX_MODULE_ENABLE_WAIT, i);

	if (i < MAX_MODULE_ENABLE_WAIT)
		pr_debug("omap clock: module associated with clock %s ready after %d loops\n",
			 name, i);
	else
		pr_err("omap clock: module associated with clock %s didn't enable in %d tries\n",
		       name, MAX_MODULE_ENABLE_WAIT);

	return (i < MAX_MODULE_ENABLE_WAIT) ? 1 : 0;
};

/**
 * _omap2_module_wait_ready - wait for an OMAP module to leave IDLE
 * @clk: struct clk * belonging to the module
 *
 * If the necessary clocks for the OMAP hardware IP block that
 * corresponds to clock @clk are enabled, then wait for the module to
 * indicate readiness (i.e., to leave IDLE).  This code does not
 * belong in the clock code and will be moved in the medium term to
 * module-dependent code.  No return value.
 */
static void _omap2_module_wait_ready(struct clk *clk)
{
	void __iomem *companion_reg, *idlest_reg;
	u8 other_bit, idlest_bit, idlest_val, idlest_reg_id;
	s16 prcm_mod;
	int r;

	/* Not all modules have multiple clocks that their IDLEST depends on */
	if (clk->ops->find_companion) {
		clk->ops->find_companion(clk, &companion_reg, &other_bit);
		if (!(__raw_readl(companion_reg) & (1 << other_bit)))
			return;
	}

	clk->ops->find_idlest(clk, &idlest_reg, &idlest_bit, &idlest_val);

	r = cm_split_idlest_reg(idlest_reg, &prcm_mod, &idlest_reg_id);
	if (r) {
		/* IDLEST register not in the CM module */
		_wait_idlest_generic(idlest_reg, (1 << idlest_bit), idlest_val,
				     clk->name);
	} else {
		cm_wait_module_ready(prcm_mod, idlest_reg_id, idlest_bit);
	};
}

/* Public functions */

/**
 * omap2_init_clk_clkdm - look up a clockdomain name, store pointer in clk
 * @clk: OMAP clock struct ptr to use
 *
 * Convert a clockdomain name stored in a struct clk 'clk' into a
 * clockdomain pointer, and save it into the struct clk.  Intended to be
 * called during clk_register().  No return value.
 */
void omap2_init_clk_clkdm(struct clk *clk)
{
	struct clockdomain *clkdm;
	const char *clk_name;

	if (!clk->clkdm_name)
		return;

	clk_name = __clk_get_name(clk);

	clkdm = clkdm_lookup(clk->clkdm_name);
	if (clkdm) {
		pr_debug("clock: associated clk %s to clkdm %s\n",
			 clk_name, clk->clkdm_name);
		clk->clkdm = clkdm;
	} else {
		pr_debug("clock: could not associate clk %s to clkdm %s\n",
			 clk_name, clk->clkdm_name);
	}
}

/**
 * omap2_clk_disable_clkdm_control - disable clkdm control on clk enable/disable
 *
 * Prevent the OMAP clock code from calling into the clockdomain code
 * when a hardware clock in that clockdomain is enabled or disabled.
 * Intended to be called at init time from omap*_clk_init().  No
 * return value.
 */
void __init omap2_clk_disable_clkdm_control(void)
{
	clkdm_control = false;
}

/**
 * omap2_clk_dflt_find_companion - find companion clock to @clk
 * @clk: struct clk * to find the companion clock of
 * @other_reg: void __iomem ** to return the companion clock CM_*CLKEN va in
 * @other_bit: u8 ** to return the companion clock bit shift in
 *
 * Note: We don't need special code here for INVERT_ENABLE for the
 * time being since INVERT_ENABLE only applies to clocks enabled by
 * CM_CLKEN_PLL
 *
 * Convert CM_ICLKEN* <-> CM_FCLKEN*.  This conversion assumes it's
 * just a matter of XORing the bits.
 *
 * Some clocks don't have companion clocks.  For example, modules with
 * only an interface clock (such as MAILBOXES) don't have a companion
 * clock.  Right now, this code relies on the hardware exporting a bit
 * in the correct companion register that indicates that the
 * nonexistent 'companion clock' is active.  Future patches will
 * associate this type of code with per-module data structures to
 * avoid this issue, and remove the casts.  No return value.
 */
void omap2_clk_dflt_find_companion(struct clk *clk, void __iomem **other_reg,
				   u8 *other_bit)
{
	u32 r;

	/*
	 * Convert CM_ICLKEN* <-> CM_FCLKEN*.  This conversion assumes
	 * it's just a matter of XORing the bits.
	 */
	r = ((__force u32)clk->enable_reg ^ (CM_FCLKEN ^ CM_ICLKEN));

	*other_reg = (__force void __iomem *)r;
	*other_bit = clk->enable_bit;
}

/**
 * omap2_clk_dflt_find_idlest - find CM_IDLEST reg va, bit shift for @clk
 * @clk: struct clk * to find IDLEST info for
 * @idlest_reg: void __iomem ** to return the CM_IDLEST va in
 * @idlest_bit: u8 * to return the CM_IDLEST bit shift in
 * @idlest_val: u8 * to return the idle status indicator
 *
 * Return the CM_IDLEST register address and bit shift corresponding
 * to the module that "owns" this clock.  This default code assumes
 * that the CM_IDLEST bit shift is the CM_*CLKEN bit shift, and that
 * the IDLEST register address ID corresponds to the CM_*CLKEN
 * register address ID (e.g., that CM_FCLKEN2 corresponds to
 * CM_IDLEST2).  This is not true for all modules.  No return value.
 */
void omap2_clk_dflt_find_idlest(struct clk *clk, void __iomem **idlest_reg,
				u8 *idlest_bit, u8 *idlest_val)
{
	u32 r;

	r = (((__force u32)clk->enable_reg & ~0xf0) | 0x20);
	*idlest_reg = (__force void __iomem *)r;
	*idlest_bit = clk->enable_bit;

	/*
	 * 24xx uses 0 to indicate not ready, and 1 to indicate ready.
	 * 34xx reverses this, just to keep us on our toes
	 * AM35xx uses both, depending on the module.
	 */
	if (cpu_is_omap24xx())
		*idlest_val = OMAP24XX_CM_IDLEST_VAL;
	else if (cpu_is_omap34xx())
		*idlest_val = OMAP34XX_CM_IDLEST_VAL;
	else
		BUG();

}

int omap2_dflt_clk_enable(struct clk *clk)
{
	u32 v;

	if (unlikely(clk->enable_reg == NULL)) {
		pr_err("clock.c: Enable for %s without enable code\n",
		       clk->name);
		return 0; /* REVISIT: -EINVAL */
	}

	v = __raw_readl(clk->enable_reg);
	if (clk->flags & INVERT_ENABLE)
		v &= ~(1 << clk->enable_bit);
	else
		v |= (1 << clk->enable_bit);
	__raw_writel(v, clk->enable_reg);
	v = __raw_readl(clk->enable_reg); /* OCP barrier */

	if (clk->ops->find_idlest)
		_omap2_module_wait_ready(clk);

	return 0;
}

void omap2_dflt_clk_disable(struct clk *clk)
{
	u32 v;

	if (!clk->enable_reg) {
		/*
		 * 'Independent' here refers to a clock which is not
		 * controlled by its parent.
		 */
		pr_err("clock: clk_disable called on independent clock %s which has no enable_reg\n", clk->name);
		return;
	}

	v = __raw_readl(clk->enable_reg);
	if (clk->flags & INVERT_ENABLE)
		v |= (1 << clk->enable_bit);
	else
		v &= ~(1 << clk->enable_bit);
	__raw_writel(v, clk->enable_reg);
	/* No OCP barrier needed here since it is a disable operation */
}

const struct clkops clkops_omap2_dflt_wait = {
	.enable		= omap2_dflt_clk_enable,
	.disable	= omap2_dflt_clk_disable,
	.find_companion	= omap2_clk_dflt_find_companion,
	.find_idlest	= omap2_clk_dflt_find_idlest,
};

const struct clkops clkops_omap2_dflt = {
	.enable		= omap2_dflt_clk_enable,
	.disable	= omap2_dflt_clk_disable,
};

/**
 * omap2_clk_disable - disable a clock, if the system is not using it
 * @clk: struct clk * to disable
 *
 * Decrements the usecount on struct clk @clk.  If there are no users
 * left, call the clkops-specific clock disable function to disable it
 * in hardware.  If the clock is part of a clockdomain (which they all
 * should be), request that the clockdomain be disabled.  (It too has
 * a usecount, and so will not be disabled in the hardware until it no
 * longer has any users.)  If the clock has a parent clock (most of
 * them do), then call ourselves, recursing on the parent clock.  This
 * can cause an entire branch of the clock tree to be powered off by
 * simply disabling one clock.  Intended to be called with the clockfw_lock
 * spinlock held.  No return value.
 */
void omap2_clk_disable(struct clk *clk)
{
	if (clk->usecount == 0) {
		WARN(1, "clock: %s: omap2_clk_disable() called, but usecount already 0?", clk->name);
		return;
	}

	pr_debug("clock: %s: decrementing usecount\n", clk->name);

	clk->usecount--;

	if (clk->usecount > 0)
		return;

	pr_debug("clock: %s: disabling in hardware\n", clk->name);

	if (clk->ops && clk->ops->disable) {
		trace_clock_disable(clk->name, 0, smp_processor_id());
		clk->ops->disable(clk);
	}

	if (clkdm_control && clk->clkdm)
		clkdm_clk_disable(clk->clkdm, clk);

	if (clk->parent)
		omap2_clk_disable(clk->parent);
}

/**
 * omap2_clk_enable - request that the system enable a clock
 * @clk: struct clk * to enable
 *
 * Increments the usecount on struct clk @clk.  If there were no users
 * previously, then recurse up the clock tree, enabling all of the
 * clock's parents and all of the parent clockdomains, and finally,
 * enabling @clk's clockdomain, and @clk itself.  Intended to be
 * called with the clockfw_lock spinlock held.  Returns 0 upon success
 * or a negative error code upon failure.
 */
int omap2_clk_enable(struct clk *clk)
{
	int ret;

	pr_debug("clock: %s: incrementing usecount\n", clk->name);

	clk->usecount++;

	if (clk->usecount > 1)
		return 0;

	pr_debug("clock: %s: enabling in hardware\n", clk->name);

	if (clk->parent) {
		ret = omap2_clk_enable(clk->parent);
		if (ret) {
			WARN(1, "clock: %s: could not enable parent %s: %d\n",
			     clk->name, clk->parent->name, ret);
			goto oce_err1;
		}
	}

	if (clkdm_control && clk->clkdm) {
		ret = clkdm_clk_enable(clk->clkdm, clk);
		if (ret) {
			WARN(1, "clock: %s: could not enable clockdomain %s: %d\n",
			     clk->name, clk->clkdm->name, ret);
			goto oce_err2;
		}
	}

	if (clk->ops && clk->ops->enable) {
		trace_clock_enable(clk->name, 1, smp_processor_id());
		ret = clk->ops->enable(clk);
		if (ret) {
			WARN(1, "clock: %s: could not enable: %d\n",
			     clk->name, ret);
			goto oce_err3;
		}
	}

	return 0;

oce_err3:
	if (clkdm_control && clk->clkdm)
		clkdm_clk_disable(clk->clkdm, clk);
oce_err2:
	if (clk->parent)
		omap2_clk_disable(clk->parent);
oce_err1:
	clk->usecount--;

	return ret;
}

/* Given a clock and a rate apply a clock specific rounding function */
long omap2_clk_round_rate(struct clk *clk, unsigned long rate)
{
	if (clk->round_rate)
		return clk->round_rate(clk, rate);

	return clk->rate;
}

/* Set the clock rate for a clock source */
int omap2_clk_set_rate(struct clk *clk, unsigned long rate)
{
	int ret = -EINVAL;

	pr_debug("clock: set_rate for clock %s to rate %ld\n", clk->name, rate);

	/* dpll_ck, core_ck, virt_prcm_set; plus all clksel clocks */
	if (clk->set_rate) {
		trace_clock_set_rate(clk->name, rate, smp_processor_id());
		ret = clk->set_rate(clk, rate);
	}

	return ret;
}

int omap2_clk_set_parent(struct clk *clk, struct clk *new_parent)
{
	if (!clk->clksel)
		return -EINVAL;

	if (clk->parent == new_parent)
		return 0;

	return omap2_clksel_set_parent(clk, new_parent);
}

/*
 * OMAP2+ clock reset and init functions
 */

#ifdef CONFIG_OMAP_RESET_CLOCKS
void omap2_clk_disable_unused(struct clk *clk)
{
	u32 regval32, v;

	v = (clk->flags & INVERT_ENABLE) ? (1 << clk->enable_bit) : 0;

	regval32 = __raw_readl(clk->enable_reg);
	if ((regval32 & (1 << clk->enable_bit)) == v)
		return;

	pr_debug("Disabling unused clock \"%s\"\n", clk->name);
	if (cpu_is_omap34xx()) {
		omap2_clk_enable(clk);
		omap2_clk_disable(clk);
	} else {
		clk->ops->disable(clk);
	}
	if (clk->clkdm != NULL)
		pwrdm_state_switch(clk->clkdm->pwrdm.ptr);
}
#endif

/**
 * omap2_clk_switch_mpurate_at_boot - switch ARM MPU rate by boot-time argument
 * @mpurate_ck_name: clk name of the clock to change rate
 *
 * Change the ARM MPU clock rate to the rate specified on the command
 * line, if one was specified.  @mpurate_ck_name should be
 * "virt_prcm_set" on OMAP2xxx and "dpll1_ck" on OMAP34xx/OMAP36xx.
 * XXX Does not handle voltage scaling - on OMAP2xxx this is currently
 * handled by the virt_prcm_set clock, but this should be handled by
 * the OPP layer.  XXX This is intended to be handled by the OPP layer
 * code in the near future and should be removed from the clock code.
 * Returns -EINVAL if 'mpurate' is zero or if clk_set_rate() rejects
 * the rate, -ENOENT if the struct clk referred to by @mpurate_ck_name
 * cannot be found, or 0 upon success.
 */
int __init omap2_clk_switch_mpurate_at_boot(const char *mpurate_ck_name)
{
	struct clk *mpurate_ck;
	int r;

	if (!mpurate)
		return -EINVAL;

	mpurate_ck = clk_get(NULL, mpurate_ck_name);
	if (WARN(IS_ERR(mpurate_ck), "Failed to get %s.\n", mpurate_ck_name))
		return -ENOENT;

	r = clk_set_rate(mpurate_ck, mpurate);
	if (IS_ERR_VALUE(r)) {
		WARN(1, "clock: %s: unable to set MPU rate to %d: %d\n",
		     mpurate_ck->name, mpurate, r);
		clk_put(mpurate_ck);
		return -EINVAL;
	}

	calibrate_delay();
	recalculate_root_clocks();

	clk_put(mpurate_ck);

	return 0;
}

/**
 * omap2_clk_print_new_rates - print summary of current clock tree rates
 * @hfclkin_ck_name: clk name for the off-chip HF oscillator
 * @core_ck_name: clk name for the on-chip CORE_CLK
 * @mpu_ck_name: clk name for the ARM MPU clock
 *
 * Prints a short message to the console with the HFCLKIN oscillator
 * rate, the rate of the CORE clock, and the rate of the ARM MPU clock.
 * Called by the boot-time MPU rate switching code.   XXX This is intended
 * to be handled by the OPP layer code in the near future and should be
 * removed from the clock code.  No return value.
 */
void __init omap2_clk_print_new_rates(const char *hfclkin_ck_name,
				      const char *core_ck_name,
				      const char *mpu_ck_name)
{
	struct clk *hfclkin_ck, *core_ck, *mpu_ck;
	unsigned long hfclkin_rate;

	mpu_ck = clk_get(NULL, mpu_ck_name);
	if (WARN(IS_ERR(mpu_ck), "clock: failed to get %s.\n", mpu_ck_name))
		return;

	core_ck = clk_get(NULL, core_ck_name);
	if (WARN(IS_ERR(core_ck), "clock: failed to get %s.\n", core_ck_name))
		return;

	hfclkin_ck = clk_get(NULL, hfclkin_ck_name);
	if (WARN(IS_ERR(hfclkin_ck), "Failed to get %s.\n", hfclkin_ck_name))
		return;

	hfclkin_rate = clk_get_rate(hfclkin_ck);

	pr_info("Switched to new clocking rate (Crystal/Core/MPU): %ld.%01ld/%ld/%ld MHz\n",
		(hfclkin_rate / 1000000), ((hfclkin_rate / 100000) % 10),
		(clk_get_rate(core_ck) / 1000000),
		(clk_get_rate(mpu_ck) / 1000000));
}

/* Common data */

int clk_enable(struct clk *clk)
{
	unsigned long flags;
	int ret;

	if (clk == NULL || IS_ERR(clk))
		return -EINVAL;

	spin_lock_irqsave(&clockfw_lock, flags);
	ret = omap2_clk_enable(clk);
	spin_unlock_irqrestore(&clockfw_lock, flags);

	return ret;
}
EXPORT_SYMBOL(clk_enable);

void clk_disable(struct clk *clk)
{
	unsigned long flags;

	if (clk == NULL || IS_ERR(clk))
		return;

	spin_lock_irqsave(&clockfw_lock, flags);
	if (clk->usecount == 0) {
		pr_err("Trying disable clock %s with 0 usecount\n",
		       clk->name);
		WARN_ON(1);
		goto out;
	}

	omap2_clk_disable(clk);

out:
	spin_unlock_irqrestore(&clockfw_lock, flags);
}
EXPORT_SYMBOL(clk_disable);

unsigned long clk_get_rate(struct clk *clk)
{
	unsigned long flags;
	unsigned long ret;

	if (clk == NULL || IS_ERR(clk))
		return 0;

	spin_lock_irqsave(&clockfw_lock, flags);
	ret = clk->rate;
	spin_unlock_irqrestore(&clockfw_lock, flags);

	return ret;
}
EXPORT_SYMBOL(clk_get_rate);

/*
 * Optional clock functions defined in include/linux/clk.h
 */

long clk_round_rate(struct clk *clk, unsigned long rate)
{
	unsigned long flags;
	long ret;

	if (clk == NULL || IS_ERR(clk))
		return 0;

	spin_lock_irqsave(&clockfw_lock, flags);
	ret = omap2_clk_round_rate(clk, rate);
	spin_unlock_irqrestore(&clockfw_lock, flags);

	return ret;
}
EXPORT_SYMBOL(clk_round_rate);

int clk_set_rate(struct clk *clk, unsigned long rate)
{
	unsigned long flags;
	int ret = -EINVAL;

	if (clk == NULL || IS_ERR(clk))
		return ret;

	spin_lock_irqsave(&clockfw_lock, flags);
	ret = omap2_clk_set_rate(clk, rate);
	if (ret == 0)
		propagate_rate(clk);
	spin_unlock_irqrestore(&clockfw_lock, flags);

	return ret;
}
EXPORT_SYMBOL(clk_set_rate);

int clk_set_parent(struct clk *clk, struct clk *parent)
{
	unsigned long flags;
	int ret = -EINVAL;

	if (clk == NULL || IS_ERR(clk) || parent == NULL || IS_ERR(parent))
		return ret;

	spin_lock_irqsave(&clockfw_lock, flags);
	if (clk->usecount == 0) {
		ret = omap2_clk_set_parent(clk, parent);
		if (ret == 0)
			propagate_rate(clk);
	} else {
		ret = -EBUSY;
	}
	spin_unlock_irqrestore(&clockfw_lock, flags);

	return ret;
}
EXPORT_SYMBOL(clk_set_parent);

struct clk *clk_get_parent(struct clk *clk)
{
	return clk->parent;
}
EXPORT_SYMBOL(clk_get_parent);

/*
 * OMAP specific clock functions shared between omap1 and omap2
 */

int __initdata mpurate;

/*
 * By default we use the rate set by the bootloader.
 * You can override this with mpurate= cmdline option.
 */
static int __init omap_clk_setup(char *str)
{
	get_option(&str, &mpurate);

	if (!mpurate)
		return 1;

	if (mpurate < 1000)
		mpurate *= 1000000;

	return 1;
}
__setup("mpurate=", omap_clk_setup);

/* Used for clocks that always have same value as the parent clock */
unsigned long followparent_recalc(struct clk *clk)
{
	return clk->parent->rate;
}

/*
 * Used for clocks that have the same value as the parent clock,
 * divided by some factor
 */
unsigned long omap_fixed_divisor_recalc(struct clk *clk)
{
	WARN_ON(!clk->fixed_div);

	return clk->parent->rate / clk->fixed_div;
}

void clk_reparent(struct clk *child, struct clk *parent)
{
	list_del_init(&child->sibling);
	if (parent)
		list_add(&child->sibling, &parent->children);
	child->parent = parent;

	/* now do the debugfs renaming to reattach the child
	   to the proper parent */
}

/* Propagate rate to children */
void propagate_rate(struct clk *tclk)
{
	struct clk *clkp;

	list_for_each_entry(clkp, &tclk->children, sibling) {
		if (clkp->recalc)
			clkp->rate = clkp->recalc(clkp);
		propagate_rate(clkp);
	}
}

static LIST_HEAD(root_clks);

/**
 * recalculate_root_clocks - recalculate and propagate all root clocks
 *
 * Recalculates all root clocks (clocks with no parent), which if the
 * clock's .recalc is set correctly, should also propagate their rates.
 * Called at init.
 */
void recalculate_root_clocks(void)
{
	struct clk *clkp;

	list_for_each_entry(clkp, &root_clks, sibling) {
		if (clkp->recalc)
			clkp->rate = clkp->recalc(clkp);
		propagate_rate(clkp);
	}
}

/**
 * clk_preinit - initialize any fields in the struct clk before clk init
 * @clk: struct clk * to initialize
 *
 * Initialize any struct clk fields needed before normal clk initialization
 * can run.  No return value.
 */
void clk_preinit(struct clk *clk)
{
	INIT_LIST_HEAD(&clk->children);
}

int clk_register(struct clk *clk)
{
	if (clk == NULL || IS_ERR(clk))
		return -EINVAL;

	/*
	 * trap out already registered clocks
	 */
	if (clk->node.next || clk->node.prev)
		return 0;

	mutex_lock(&clocks_mutex);
	if (clk->parent)
		list_add(&clk->sibling, &clk->parent->children);
	else
		list_add(&clk->sibling, &root_clks);

	list_add(&clk->node, &clocks);
	if (clk->init)
		clk->init(clk);
	mutex_unlock(&clocks_mutex);

	return 0;
}
EXPORT_SYMBOL(clk_register);

void clk_unregister(struct clk *clk)
{
	if (clk == NULL || IS_ERR(clk))
		return;

	mutex_lock(&clocks_mutex);
	list_del(&clk->sibling);
	list_del(&clk->node);
	mutex_unlock(&clocks_mutex);
}
EXPORT_SYMBOL(clk_unregister);

void clk_enable_init_clocks(void)
{
	struct clk *clkp;

	list_for_each_entry(clkp, &clocks, node)
		if (clkp->flags & ENABLE_ON_INIT)
			clk_enable(clkp);
}

/**
 * omap_clk_get_by_name - locate OMAP struct clk by its name
 * @name: name of the struct clk to locate
 *
 * Locate an OMAP struct clk by its name.  Assumes that struct clk
 * names are unique.  Returns NULL if not found or a pointer to the
 * struct clk if found.
 */
struct clk *omap_clk_get_by_name(const char *name)
{
	struct clk *c;
	struct clk *ret = NULL;

	mutex_lock(&clocks_mutex);

	list_for_each_entry(c, &clocks, node) {
		if (!strcmp(c->name, name)) {
			ret = c;
			break;
		}
	}

	mutex_unlock(&clocks_mutex);

	return ret;
}

int omap_clk_enable_autoidle_all(void)
{
	struct clk *c;
	unsigned long flags;

	spin_lock_irqsave(&clockfw_lock, flags);

	list_for_each_entry(c, &clocks, node)
		if (c->ops->allow_idle)
			c->ops->allow_idle(c);

	spin_unlock_irqrestore(&clockfw_lock, flags);

	return 0;
}

int omap_clk_disable_autoidle_all(void)
{
	struct clk *c;
	unsigned long flags;

	spin_lock_irqsave(&clockfw_lock, flags);

	list_for_each_entry(c, &clocks, node)
		if (c->ops->deny_idle)
			c->ops->deny_idle(c);

	spin_unlock_irqrestore(&clockfw_lock, flags);

	return 0;
}

/*
 * Low level helpers
 */
static int clkll_enable_null(struct clk *clk)
{
	return 0;
}

static void clkll_disable_null(struct clk *clk)
{
}

const struct clkops clkops_null = {
	.enable		= clkll_enable_null,
	.disable	= clkll_disable_null,
};

/*
 * Dummy clock
 *
 * Used for clock aliases that are needed on some OMAPs, but not others
 */
struct clk dummy_ck = {
	.name	= "dummy",
	.ops	= &clkops_null,
};

/*
 *
 */

#ifdef CONFIG_OMAP_RESET_CLOCKS
/*
 * Disable any unused clocks left on by the bootloader
 */
static int __init clk_disable_unused(void)
{
	struct clk *ck;
	unsigned long flags;

	pr_info("clock: disabling unused clocks to save power\n");

	spin_lock_irqsave(&clockfw_lock, flags);
	list_for_each_entry(ck, &clocks, node) {
		if (ck->ops == &clkops_null)
			continue;

		if (ck->usecount > 0 || !ck->enable_reg)
			continue;

		omap2_clk_disable_unused(ck);
	}
	spin_unlock_irqrestore(&clockfw_lock, flags);

	return 0;
}
late_initcall(clk_disable_unused);
late_initcall(omap_clk_enable_autoidle_all);
#endif

#if defined(CONFIG_PM_DEBUG) && defined(CONFIG_DEBUG_FS)
/*
 *	debugfs support to trace clock tree hierarchy and attributes
 */

#include <linux/debugfs.h>
#include <linux/seq_file.h>

static struct dentry *clk_debugfs_root;

static int clk_dbg_show_summary(struct seq_file *s, void *unused)
{
	struct clk *c;
	struct clk *pa;

	mutex_lock(&clocks_mutex);
	seq_printf(s, "%-30s %-30s %-10s %s\n",
		   "clock-name", "parent-name", "rate", "use-count");

	list_for_each_entry(c, &clocks, node) {
		pa = c->parent;
		seq_printf(s, "%-30s %-30s %-10lu %d\n",
			   c->name, pa ? pa->name : "none", c->rate,
			   c->usecount);
	}
	mutex_unlock(&clocks_mutex);

	return 0;
}

static int clk_dbg_open(struct inode *inode, struct file *file)
{
	return single_open(file, clk_dbg_show_summary, inode->i_private);
}

static const struct file_operations debug_clock_fops = {
	.open           = clk_dbg_open,
	.read           = seq_read,
	.llseek         = seq_lseek,
	.release        = single_release,
};

static int clk_debugfs_register_one(struct clk *c)
{
	int err;
	struct dentry *d;
	struct clk *pa = c->parent;

	d = debugfs_create_dir(c->name, pa ? pa->dent : clk_debugfs_root);
	if (!d)
		return -ENOMEM;
	c->dent = d;

	d = debugfs_create_u8("usecount", S_IRUGO, c->dent, (u8 *)&c->usecount);
	if (!d) {
		err = -ENOMEM;
		goto err_out;
	}
	d = debugfs_create_u32("rate", S_IRUGO, c->dent, (u32 *)&c->rate);
	if (!d) {
		err = -ENOMEM;
		goto err_out;
	}
	d = debugfs_create_x32("flags", S_IRUGO, c->dent, (u32 *)&c->flags);
	if (!d) {
		err = -ENOMEM;
		goto err_out;
	}
	return 0;

err_out:
	debugfs_remove_recursive(c->dent);
	return err;
}

static int clk_debugfs_register(struct clk *c)
{
	int err;
	struct clk *pa = c->parent;

	if (pa && !pa->dent) {
		err = clk_debugfs_register(pa);
		if (err)
			return err;
	}

	if (!c->dent) {
		err = clk_debugfs_register_one(c);
		if (err)
			return err;
	}
	return 0;
}

static int __init clk_debugfs_init(void)
{
	struct clk *c;
	struct dentry *d;
	int err;

	d = debugfs_create_dir("clock", NULL);
	if (!d)
		return -ENOMEM;
	clk_debugfs_root = d;

	list_for_each_entry(c, &clocks, node) {
		err = clk_debugfs_register(c);
		if (err)
			goto err_out;
	}

	d = debugfs_create_file("summary", S_IRUGO,
		d, NULL, &debug_clock_fops);
	if (!d)
		return -ENOMEM;

	return 0;
err_out:
	debugfs_remove_recursive(clk_debugfs_root);
	return err;
}
late_initcall(clk_debugfs_init);

#endif /* defined(CONFIG_PM_DEBUG) && defined(CONFIG_DEBUG_FS) */