drivers/clk/samsung/clk-cpu.c - kernel/bruno - Git at Google

 /*
  * Copyright (c) 2014 Samsung Electronics Co., Ltd.
  * Author: Thomas Abraham <thomas.ab@samsung.com>
  *
  * Copyright (c) 2015 Samsung Electronics Co., Ltd.
  * Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
  *
  * 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.
  *
  * This file contains the utility function to register CPU clock for Samsung
  * Exynos platforms. A CPU clock is defined as a clock supplied to a CPU or a
  * group of CPUs. The CPU clock is typically derived from a hierarchy of clock
  * blocks which includes mux and divider blocks. There are a number of other
  * auxiliary clocks supplied to the CPU domain such as the debug blocks and AXI
  * clock for CPU domain. The rates of these auxiliary clocks are related to the
  * CPU clock rate and this relation is usually specified in the hardware manual
  * of the SoC or supplied after the SoC characterization.
  *
  * The below implementation of the CPU clock allows the rate changes of the CPU
  * clock and the corresponding rate changes of the auxillary clocks of the CPU
  * domain. The platform clock driver provides a clock register configuration
  * for each configurable rate which is then used to program the clock hardware
  * registers to acheive a fast co-oridinated rate change for all the CPU domain
  * clocks.
  *
  * On a rate change request for the CPU clock, the rate change is propagated
  * upto the PLL supplying the clock to the CPU domain clock blocks. While the
  * CPU domain PLL is reconfigured, the CPU domain clocks are driven using an
  * alternate clock source. If required, the alternate clock source is divided
  * down in order to keep the output clock rate within the previous OPP limits.
 */

 #include <linux/errno.h>
 #include <linux/slab.h>
 #include <linux/clk.h>
 #include <linux/clk-provider.h>
 #include "clk-cpu.h"

 #define E4210_SRC_CPU		0x0
 #define E4210_STAT_CPU		0x200
 #define E4210_DIV_CPU0		0x300
 #define E4210_DIV_CPU1		0x304
 #define E4210_DIV_STAT_CPU0	0x400
 #define E4210_DIV_STAT_CPU1	0x404

 #define E4210_DIV0_RATIO0_MASK	0x7
 #define E4210_DIV1_HPM_MASK	(0x7 << 4)
 #define E4210_DIV1_COPY_MASK	(0x7 << 0)
 #define E4210_MUX_HPM_MASK	(1 << 20)
 #define E4210_DIV0_ATB_SHIFT	16
 #define E4210_DIV0_ATB_MASK	(DIV_MASK << E4210_DIV0_ATB_SHIFT)

 #define MAX_DIV			8
 #define DIV_MASK		7
 #define DIV_MASK_ALL		0xffffffff
 #define MUX_MASK		7

 /*
  * Helper function to wait until divider(s) have stabilized after the divider
  * value has changed.
  */
 static void wait_until_divider_stable(void __iomem *div_reg, unsigned long mask)
 {
 	unsigned long timeout = jiffies + msecs_to_jiffies(10);

 	do {
 		if (!(readl(div_reg) & mask))
 			return;
 	} while (time_before(jiffies, timeout));

 	if (!(readl(div_reg) & mask))
 		return;

 	pr_err("%s: timeout in divider stablization\n", __func__);
 }

 /*
  * Helper function to wait until mux has stabilized after the mux selection
  * value was changed.
  */
 static void wait_until_mux_stable(void __iomem *mux_reg, u32 mux_pos,
 					unsigned long mux_value)
 {
 	unsigned long timeout = jiffies + msecs_to_jiffies(10);

 	do {
 		if (((readl(mux_reg) >> mux_pos) & MUX_MASK) == mux_value)
 			return;
 	} while (time_before(jiffies, timeout));

 	if (((readl(mux_reg) >> mux_pos) & MUX_MASK) == mux_value)
 		return;

 	pr_err("%s: re-parenting mux timed-out\n", __func__);
 }

 /* common round rate callback useable for all types of CPU clocks */
 static long exynos_cpuclk_round_rate(struct clk_hw *hw,
 			unsigned long drate, unsigned long *prate)
 {
 	struct clk_hw *parent = clk_hw_get_parent(hw);
 	*prate = clk_hw_round_rate(parent, drate);
 	return *prate;
 }

 /* common recalc rate callback useable for all types of CPU clocks */
 static unsigned long exynos_cpuclk_recalc_rate(struct clk_hw *hw,
 			unsigned long parent_rate)
 {
 	/*
 	 * The CPU clock output (armclk) rate is the same as its parent
 	 * rate. Although there exist certain dividers inside the CPU
 	 * clock block that could be used to divide the parent clock,
 	 * the driver does not make use of them currently, except during
 	 * frequency transitions.
 	 */
 	return parent_rate;
 }

 static const struct clk_ops exynos_cpuclk_clk_ops = {
 	.recalc_rate = exynos_cpuclk_recalc_rate,
 	.round_rate = exynos_cpuclk_round_rate,
 };

 /*
  * Helper function to set the 'safe' dividers for the CPU clock. The parameters
  * div and mask contain the divider value and the register bit mask of the
  * dividers to be programmed.
  */
 static void exynos_set_safe_div(void __iomem *base, unsigned long div,
 					unsigned long mask)
 {
 	unsigned long div0;

 	div0 = readl(base + E4210_DIV_CPU0);
 	div0 = (div0 & ~mask) | (div & mask);
 	writel(div0, base + E4210_DIV_CPU0);
 	wait_until_divider_stable(base + E4210_DIV_STAT_CPU0, mask);
 }

 /* handler for pre-rate change notification from parent clock */
 static int exynos_cpuclk_pre_rate_change(struct clk_notifier_data *ndata,
 			struct exynos_cpuclk *cpuclk, void __iomem *base)
 {
 	const struct exynos_cpuclk_cfg_data *cfg_data = cpuclk->cfg;
 	unsigned long alt_prate = clk_get_rate(cpuclk->alt_parent);
 	unsigned long alt_div = 0, alt_div_mask = DIV_MASK;
 	unsigned long div0, div1 = 0, mux_reg;
 	unsigned long flags;

 	/* find out the divider values to use for clock data */
 	while ((cfg_data->prate * 1000) != ndata->new_rate) {
 		if (cfg_data->prate == 0)
 			return -EINVAL;
 		cfg_data++;
 	}

 	spin_lock_irqsave(cpuclk->lock, flags);

 	/*
 	 * For the selected PLL clock frequency, get the pre-defined divider
 	 * values. If the clock for sclk_hpm is not sourced from apll, then
 	 * the values for DIV_COPY and DIV_HPM dividers need not be set.
 	 */
 	div0 = cfg_data->div0;
 	if (cpuclk->flags & CLK_CPU_HAS_DIV1) {
 		div1 = cfg_data->div1;
 		if (readl(base + E4210_SRC_CPU) & E4210_MUX_HPM_MASK)
 			div1 = readl(base + E4210_DIV_CPU1) &
 				(E4210_DIV1_HPM_MASK | E4210_DIV1_COPY_MASK);
 	}

 	/*
 	 * If the old parent clock speed is less than the clock speed of
 	 * the alternate parent, then it should be ensured that at no point
 	 * the armclk speed is more than the old_prate until the dividers are
 	 * set.  Also workaround the issue of the dividers being set to lower
 	 * values before the parent clock speed is set to new lower speed
 	 * (this can result in too high speed of armclk output clocks).
 	 */
 	if (alt_prate > ndata->old_rate || ndata->old_rate > ndata->new_rate) {
 		unsigned long tmp_rate = min(ndata->old_rate, ndata->new_rate);

 		alt_div = DIV_ROUND_UP(alt_prate, tmp_rate) - 1;
 		WARN_ON(alt_div >= MAX_DIV);

 		if (cpuclk->flags & CLK_CPU_NEEDS_DEBUG_ALT_DIV) {
 			/*
 			 * In Exynos4210, ATB clock parent is also mout_core. So
 			 * ATB clock also needs to be mantained at safe speed.
 			 */
 			alt_div |= E4210_DIV0_ATB_MASK;
 			alt_div_mask |= E4210_DIV0_ATB_MASK;
 		}
 		exynos_set_safe_div(base, alt_div, alt_div_mask);
 		div0 |= alt_div;
 	}

 	/* select sclk_mpll as the alternate parent */
 	mux_reg = readl(base + E4210_SRC_CPU);
 	writel(mux_reg | (1 << 16), base + E4210_SRC_CPU);
 	wait_until_mux_stable(base + E4210_STAT_CPU, 16, 2);

 	/* alternate parent is active now. set the dividers */
 	writel(div0, base + E4210_DIV_CPU0);
 	wait_until_divider_stable(base + E4210_DIV_STAT_CPU0, DIV_MASK_ALL);

 	if (cpuclk->flags & CLK_CPU_HAS_DIV1) {
 		writel(div1, base + E4210_DIV_CPU1);
 		wait_until_divider_stable(base + E4210_DIV_STAT_CPU1,
 				DIV_MASK_ALL);
 	}

 	spin_unlock_irqrestore(cpuclk->lock, flags);
 	return 0;
 }

 /* handler for post-rate change notification from parent clock */
 static int exynos_cpuclk_post_rate_change(struct clk_notifier_data *ndata,
 			struct exynos_cpuclk *cpuclk, void __iomem *base)
 {
 	const struct exynos_cpuclk_cfg_data *cfg_data = cpuclk->cfg;
 	unsigned long div = 0, div_mask = DIV_MASK;
 	unsigned long mux_reg;
 	unsigned long flags;

 	/* find out the divider values to use for clock data */
 	if (cpuclk->flags & CLK_CPU_NEEDS_DEBUG_ALT_DIV) {
 		while ((cfg_data->prate * 1000) != ndata->new_rate) {
 			if (cfg_data->prate == 0)
 				return -EINVAL;
 			cfg_data++;
 		}
 	}

 	spin_lock_irqsave(cpuclk->lock, flags);

 	/* select mout_apll as the alternate parent */
 	mux_reg = readl(base + E4210_SRC_CPU);
 	writel(mux_reg & ~(1 << 16), base + E4210_SRC_CPU);
 	wait_until_mux_stable(base + E4210_STAT_CPU, 16, 1);

 	if (cpuclk->flags & CLK_CPU_NEEDS_DEBUG_ALT_DIV) {
 		div |= (cfg_data->div0 & E4210_DIV0_ATB_MASK);
 		div_mask |= E4210_DIV0_ATB_MASK;
 	}

 	exynos_set_safe_div(base, div, div_mask);
 	spin_unlock_irqrestore(cpuclk->lock, flags);
 	return 0;
 }

 /*
  * This notifier function is called for the pre-rate and post-rate change
  * notifications of the parent clock of cpuclk.
  */
 static int exynos_cpuclk_notifier_cb(struct notifier_block *nb,
 				unsigned long event, void *data)
 {
 	struct clk_notifier_data *ndata = data;
 	struct exynos_cpuclk *cpuclk;
 	void __iomem *base;
 	int err = 0;

 	cpuclk = container_of(nb, struct exynos_cpuclk, clk_nb);
 	base = cpuclk->ctrl_base;

 	if (event == PRE_RATE_CHANGE)
 		err = exynos_cpuclk_pre_rate_change(ndata, cpuclk, base);
 	else if (event == POST_RATE_CHANGE)
 		err = exynos_cpuclk_post_rate_change(ndata, cpuclk, base);

 	return notifier_from_errno(err);
 }

 /* helper function to register a CPU clock */
 int __init exynos_register_cpu_clock(struct samsung_clk_provider *ctx,
 		unsigned int lookup_id, const char *name, const char *parent,
 		const char *alt_parent, unsigned long offset,
 		const struct exynos_cpuclk_cfg_data *cfg,
 		unsigned long num_cfgs, unsigned long flags)
 {
 	struct exynos_cpuclk *cpuclk;
 	struct clk_init_data init;
 	struct clk *clk;
 	int ret = 0;

 	cpuclk = kzalloc(sizeof(*cpuclk), GFP_KERNEL);
 	if (!cpuclk)
 		return -ENOMEM;

 	init.name = name;
 	init.flags = CLK_SET_RATE_PARENT;
 	init.parent_names = &parent;
 	init.num_parents = 1;
 	init.ops = &exynos_cpuclk_clk_ops;

 	cpuclk->hw.init = &init;
 	cpuclk->ctrl_base = ctx->reg_base + offset;
 	cpuclk->lock = &ctx->lock;
 	cpuclk->flags = flags;
 	cpuclk->clk_nb.notifier_call = exynos_cpuclk_notifier_cb;

 	cpuclk->alt_parent = __clk_lookup(alt_parent);
 	if (!cpuclk->alt_parent) {
 		pr_err("%s: could not lookup alternate parent %s\n",
 				__func__, alt_parent);
 		ret = -EINVAL;
 		goto free_cpuclk;
 	}

 	clk = __clk_lookup(parent);
 	if (!clk) {
 		pr_err("%s: could not lookup parent clock %s\n",
 				__func__, parent);
 		ret = -EINVAL;
 		goto free_cpuclk;
 	}

 	ret = clk_notifier_register(clk, &cpuclk->clk_nb);
 	if (ret) {
 		pr_err("%s: failed to register clock notifier for %s\n",
 				__func__, name);
 		goto free_cpuclk;
 	}

 	cpuclk->cfg = kmemdup(cfg, sizeof(*cfg) * num_cfgs, GFP_KERNEL);
 	if (!cpuclk->cfg) {
 		pr_err("%s: could not allocate memory for cpuclk data\n",
 				__func__);
 		ret = -ENOMEM;
 		goto unregister_clk_nb;
 	}

 	clk = clk_register(NULL, &cpuclk->hw);
 	if (IS_ERR(clk)) {
 		pr_err("%s: could not register cpuclk %s\n", __func__,	name);
 		ret = PTR_ERR(clk);
 		goto free_cpuclk_data;
 	}

 	samsung_clk_add_lookup(ctx, clk, lookup_id);
 	return 0;

 free_cpuclk_data:
 	kfree(cpuclk->cfg);
 unregister_clk_nb:
 	clk_notifier_unregister(__clk_lookup(parent), &cpuclk->clk_nb);
 free_cpuclk:
 	kfree(cpuclk);
 	return ret;
 }
	/*
	* Copyright (c) 2014 Samsung Electronics Co., Ltd.
	* Author: Thomas Abraham <thomas.ab@samsung.com>
	*
	* Copyright (c) 2015 Samsung Electronics Co., Ltd.
	* Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
	*
	* 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.
	*
	* This file contains the utility function to register CPU clock for Samsung
	* Exynos platforms. A CPU clock is defined as a clock supplied to a CPU or a
	* group of CPUs. The CPU clock is typically derived from a hierarchy of clock
	* blocks which includes mux and divider blocks. There are a number of other
	* auxiliary clocks supplied to the CPU domain such as the debug blocks and AXI
	* clock for CPU domain. The rates of these auxiliary clocks are related to the
	* CPU clock rate and this relation is usually specified in the hardware manual
	* of the SoC or supplied after the SoC characterization.
	*
	* The below implementation of the CPU clock allows the rate changes of the CPU
	* clock and the corresponding rate changes of the auxillary clocks of the CPU
	* domain. The platform clock driver provides a clock register configuration
	* for each configurable rate which is then used to program the clock hardware
	* registers to acheive a fast co-oridinated rate change for all the CPU domain
	* clocks.
	*
	* On a rate change request for the CPU clock, the rate change is propagated
	* upto the PLL supplying the clock to the CPU domain clock blocks. While the
	* CPU domain PLL is reconfigured, the CPU domain clocks are driven using an
	* alternate clock source. If required, the alternate clock source is divided
	* down in order to keep the output clock rate within the previous OPP limits.
	*/

	#include <linux/errno.h>
	#include <linux/slab.h>
	#include <linux/clk.h>
	#include <linux/clk-provider.h>
	#include "clk-cpu.h"

	#define E4210_SRC_CPU 0x0
	#define E4210_STAT_CPU 0x200
	#define E4210_DIV_CPU0 0x300
	#define E4210_DIV_CPU1 0x304
	#define E4210_DIV_STAT_CPU0 0x400
	#define E4210_DIV_STAT_CPU1 0x404

	#define E4210_DIV0_RATIO0_MASK 0x7
	#define E4210_DIV1_HPM_MASK (0x7 << 4)
	#define E4210_DIV1_COPY_MASK (0x7 << 0)
	#define E4210_MUX_HPM_MASK (1 << 20)
	#define E4210_DIV0_ATB_SHIFT 16
	#define E4210_DIV0_ATB_MASK (DIV_MASK << E4210_DIV0_ATB_SHIFT)

	#define MAX_DIV 8
	#define DIV_MASK 7
	#define DIV_MASK_ALL 0xffffffff
	#define MUX_MASK 7

	/*
	* Helper function to wait until divider(s) have stabilized after the divider
	* value has changed.
	*/
	static void wait_until_divider_stable(void __iomem *div_reg, unsigned long mask)
	{
	unsigned long timeout = jiffies + msecs_to_jiffies(10);

	do {
	if (!(readl(div_reg) & mask))
	return;
	} while (time_before(jiffies, timeout));

	if (!(readl(div_reg) & mask))
	return;

	pr_err("%s: timeout in divider stablization\n", __func__);
	}

	/*
	* Helper function to wait until mux has stabilized after the mux selection
	* value was changed.
	*/
	static void wait_until_mux_stable(void __iomem *mux_reg, u32 mux_pos,
	unsigned long mux_value)
	{
	unsigned long timeout = jiffies + msecs_to_jiffies(10);

	do {
	if (((readl(mux_reg) >> mux_pos) & MUX_MASK) == mux_value)
	return;
	} while (time_before(jiffies, timeout));

	if (((readl(mux_reg) >> mux_pos) & MUX_MASK) == mux_value)
	return;

	pr_err("%s: re-parenting mux timed-out\n", __func__);
	}

	/* common round rate callback useable for all types of CPU clocks */
	static long exynos_cpuclk_round_rate(struct clk_hw *hw,
	unsigned long drate, unsigned long *prate)
	{
	struct clk_hw *parent = clk_hw_get_parent(hw);
	*prate = clk_hw_round_rate(parent, drate);
	return *prate;
	}

	/* common recalc rate callback useable for all types of CPU clocks */
	static unsigned long exynos_cpuclk_recalc_rate(struct clk_hw *hw,
	unsigned long parent_rate)
	{
	/*
	* The CPU clock output (armclk) rate is the same as its parent
	* rate. Although there exist certain dividers inside the CPU
	* clock block that could be used to divide the parent clock,
	* the driver does not make use of them currently, except during
	* frequency transitions.
	*/
	return parent_rate;
	}

	static const struct clk_ops exynos_cpuclk_clk_ops = {
	.recalc_rate = exynos_cpuclk_recalc_rate,
	.round_rate = exynos_cpuclk_round_rate,
	};

	/*
	* Helper function to set the 'safe' dividers for the CPU clock. The parameters
	* div and mask contain the divider value and the register bit mask of the
	* dividers to be programmed.
	*/
	static void exynos_set_safe_div(void __iomem *base, unsigned long div,
	unsigned long mask)
	{
	unsigned long div0;

	div0 = readl(base + E4210_DIV_CPU0);
	div0 = (div0 & ~mask) \| (div & mask);
	writel(div0, base + E4210_DIV_CPU0);
	wait_until_divider_stable(base + E4210_DIV_STAT_CPU0, mask);
	}

	/* handler for pre-rate change notification from parent clock */
	static int exynos_cpuclk_pre_rate_change(struct clk_notifier_data *ndata,
	struct exynos_cpuclk cpuclk, void __iomem base)
	{
	const struct exynos_cpuclk_cfg_data *cfg_data = cpuclk->cfg;
	unsigned long alt_prate = clk_get_rate(cpuclk->alt_parent);
	unsigned long alt_div = 0, alt_div_mask = DIV_MASK;
	unsigned long div0, div1 = 0, mux_reg;
	unsigned long flags;

	/* find out the divider values to use for clock data */
	while ((cfg_data->prate * 1000) != ndata->new_rate) {
	if (cfg_data->prate == 0)
	return -EINVAL;
	cfg_data++;
	}

	spin_lock_irqsave(cpuclk->lock, flags);

	/*
	* For the selected PLL clock frequency, get the pre-defined divider
	* values. If the clock for sclk_hpm is not sourced from apll, then
	* the values for DIV_COPY and DIV_HPM dividers need not be set.
	*/
	div0 = cfg_data->div0;
	if (cpuclk->flags & CLK_CPU_HAS_DIV1) {
	div1 = cfg_data->div1;
	if (readl(base + E4210_SRC_CPU) & E4210_MUX_HPM_MASK)
	div1 = readl(base + E4210_DIV_CPU1) &
	(E4210_DIV1_HPM_MASK \| E4210_DIV1_COPY_MASK);
	}

	/*
	* If the old parent clock speed is less than the clock speed of
	* the alternate parent, then it should be ensured that at no point
	* the armclk speed is more than the old_prate until the dividers are
	* set. Also workaround the issue of the dividers being set to lower
	* values before the parent clock speed is set to new lower speed
	* (this can result in too high speed of armclk output clocks).
	*/
	if (alt_prate > ndata->old_rate \|\| ndata->old_rate > ndata->new_rate) {
	unsigned long tmp_rate = min(ndata->old_rate, ndata->new_rate);

	alt_div = DIV_ROUND_UP(alt_prate, tmp_rate) - 1;
	WARN_ON(alt_div >= MAX_DIV);

	if (cpuclk->flags & CLK_CPU_NEEDS_DEBUG_ALT_DIV) {
	/*
	* In Exynos4210, ATB clock parent is also mout_core. So
	* ATB clock also needs to be mantained at safe speed.
	*/
	alt_div \|= E4210_DIV0_ATB_MASK;
	alt_div_mask \|= E4210_DIV0_ATB_MASK;
	}
	exynos_set_safe_div(base, alt_div, alt_div_mask);
	div0 \|= alt_div;
	}

	/* select sclk_mpll as the alternate parent */
	mux_reg = readl(base + E4210_SRC_CPU);
	writel(mux_reg \| (1 << 16), base + E4210_SRC_CPU);
	wait_until_mux_stable(base + E4210_STAT_CPU, 16, 2);

	/* alternate parent is active now. set the dividers */
	writel(div0, base + E4210_DIV_CPU0);
	wait_until_divider_stable(base + E4210_DIV_STAT_CPU0, DIV_MASK_ALL);

	if (cpuclk->flags & CLK_CPU_HAS_DIV1) {
	writel(div1, base + E4210_DIV_CPU1);
	wait_until_divider_stable(base + E4210_DIV_STAT_CPU1,
	DIV_MASK_ALL);
	}

	spin_unlock_irqrestore(cpuclk->lock, flags);
	return 0;
	}

	/* handler for post-rate change notification from parent clock */
	static int exynos_cpuclk_post_rate_change(struct clk_notifier_data *ndata,
	struct exynos_cpuclk cpuclk, void __iomem base)
	{
	const struct exynos_cpuclk_cfg_data *cfg_data = cpuclk->cfg;
	unsigned long div = 0, div_mask = DIV_MASK;
	unsigned long mux_reg;
	unsigned long flags;

	/* find out the divider values to use for clock data */
	if (cpuclk->flags & CLK_CPU_NEEDS_DEBUG_ALT_DIV) {
	while ((cfg_data->prate * 1000) != ndata->new_rate) {
	if (cfg_data->prate == 0)
	return -EINVAL;
	cfg_data++;
	}
	}

	spin_lock_irqsave(cpuclk->lock, flags);

	/* select mout_apll as the alternate parent */
	mux_reg = readl(base + E4210_SRC_CPU);
	writel(mux_reg & ~(1 << 16), base + E4210_SRC_CPU);
	wait_until_mux_stable(base + E4210_STAT_CPU, 16, 1);

	if (cpuclk->flags & CLK_CPU_NEEDS_DEBUG_ALT_DIV) {
	div \|= (cfg_data->div0 & E4210_DIV0_ATB_MASK);
	div_mask \|= E4210_DIV0_ATB_MASK;
	}

	exynos_set_safe_div(base, div, div_mask);
	spin_unlock_irqrestore(cpuclk->lock, flags);
	return 0;
	}

	/*
	* This notifier function is called for the pre-rate and post-rate change
	* notifications of the parent clock of cpuclk.
	*/
	static int exynos_cpuclk_notifier_cb(struct notifier_block *nb,
	unsigned long event, void *data)
	{
	struct clk_notifier_data *ndata = data;
	struct exynos_cpuclk *cpuclk;
	void __iomem *base;
	int err = 0;

	cpuclk = container_of(nb, struct exynos_cpuclk, clk_nb);
	base = cpuclk->ctrl_base;

	if (event == PRE_RATE_CHANGE)
	err = exynos_cpuclk_pre_rate_change(ndata, cpuclk, base);
	else if (event == POST_RATE_CHANGE)
	err = exynos_cpuclk_post_rate_change(ndata, cpuclk, base);

	return notifier_from_errno(err);
	}

	/* helper function to register a CPU clock */
	int __init exynos_register_cpu_clock(struct samsung_clk_provider *ctx,
	unsigned int lookup_id, const char name, const char parent,
	const char *alt_parent, unsigned long offset,
	const struct exynos_cpuclk_cfg_data *cfg,
	unsigned long num_cfgs, unsigned long flags)
	{
	struct exynos_cpuclk *cpuclk;
	struct clk_init_data init;
	struct clk *clk;
	int ret = 0;

	cpuclk = kzalloc(sizeof(*cpuclk), GFP_KERNEL);
	if (!cpuclk)
	return -ENOMEM;

	init.name = name;
	init.flags = CLK_SET_RATE_PARENT;
	init.parent_names = &parent;
	init.num_parents = 1;
	init.ops = &exynos_cpuclk_clk_ops;

	cpuclk->hw.init = &init;
	cpuclk->ctrl_base = ctx->reg_base + offset;
	cpuclk->lock = &ctx->lock;
	cpuclk->flags = flags;
	cpuclk->clk_nb.notifier_call = exynos_cpuclk_notifier_cb;

	cpuclk->alt_parent = __clk_lookup(alt_parent);
	if (!cpuclk->alt_parent) {
	pr_err("%s: could not lookup alternate parent %s\n",
	__func__, alt_parent);
	ret = -EINVAL;
	goto free_cpuclk;
	}

	clk = __clk_lookup(parent);
	if (!clk) {
	pr_err("%s: could not lookup parent clock %s\n",
	__func__, parent);
	ret = -EINVAL;
	goto free_cpuclk;
	}

	ret = clk_notifier_register(clk, &cpuclk->clk_nb);
	if (ret) {
	pr_err("%s: failed to register clock notifier for %s\n",
	__func__, name);
	goto free_cpuclk;
	}

	cpuclk->cfg = kmemdup(cfg, sizeof(cfg) num_cfgs, GFP_KERNEL);
	if (!cpuclk->cfg) {
	pr_err("%s: could not allocate memory for cpuclk data\n",
	__func__);
	ret = -ENOMEM;
	goto unregister_clk_nb;
	}

	clk = clk_register(NULL, &cpuclk->hw);
	if (IS_ERR(clk)) {
	pr_err("%s: could not register cpuclk %s\n", __func__, name);
	ret = PTR_ERR(clk);
	goto free_cpuclk_data;
	}

	samsung_clk_add_lookup(ctx, clk, lookup_id);
	return 0;

	free_cpuclk_data:
	kfree(cpuclk->cfg);
	unregister_clk_nb:
	clk_notifier_unregister(__clk_lookup(parent), &cpuclk->clk_nb);
	free_cpuclk:
	kfree(cpuclk);
	return ret;
	}