xref: /linux/drivers/clk/clk-divider.c (revision 502d45774af09f1c681c754c4b7cdfb5d7f72fd9)

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2011 Sascha Hauer, Pengutronix <s.hauer@pengutronix.de>
 * Copyright (C) 2011 Richard Zhao, Linaro <richard.zhao@linaro.org>
 * Copyright (C) 2011-2012 Mike Turquette, Linaro Ltd <mturquette@linaro.org>
 *
 * Adjustable divider clock implementation
 */

#include <linux/clk-provider.h>
#include <linux/device.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/io.h>
#include <linux/err.h>
#include <linux/string.h>
#include <linux/log2.h>
#include <linux/overflow.h>

/*
 * DOC: basic adjustable divider clock that cannot gate
 *
 * Traits of this clock:
 * prepare - clk_prepare only ensures that parents are prepared
 * enable - clk_enable only ensures that parents are enabled
 * rate - rate is adjustable.  clk->rate = ceiling(parent->rate / divisor)
 * parent - fixed parent.  No clk_set_parent support
 */

static inline u32 clk_div_readl(struct clk_divider *divider)
{
	if (divider->flags & CLK_DIVIDER_BIG_ENDIAN)
		return ioread32be(divider->reg);

	return readl(divider->reg);
}

static inline void clk_div_writel(struct clk_divider *divider, u32 val)
{
	if (divider->flags & CLK_DIVIDER_BIG_ENDIAN)
		iowrite32be(val, divider->reg);
	else
		writel(val, divider->reg);
}

static unsigned int _get_table_maxdiv(const struct clk_div_table *table,
				      u8 width)
{
	unsigned int maxdiv = 0, mask = clk_div_mask(width);
	const struct clk_div_table *clkt;

	for (clkt = table; clkt->div; clkt++)
		if (clkt->div > maxdiv && clkt->val <= mask)
			maxdiv = clkt->div;
	return maxdiv;
}

static unsigned int _get_table_mindiv(const struct clk_div_table *table)
{
	unsigned int mindiv = UINT_MAX;
	const struct clk_div_table *clkt;

	for (clkt = table; clkt->div; clkt++)
		if (clkt->div < mindiv)
			mindiv = clkt->div;
	return mindiv;
}

static unsigned int _get_maxdiv(const struct clk_div_table *table, u8 width,
				unsigned long flags)
{
	if (flags & CLK_DIVIDER_ONE_BASED)
		return clk_div_mask(width);
	if (flags & CLK_DIVIDER_POWER_OF_TWO)
		return 1 << clk_div_mask(width);
	if (flags & CLK_DIVIDER_EVEN_INTEGERS)
		return 2 * (clk_div_mask(width) + 1);
	if (table)
		return _get_table_maxdiv(table, width);
	return clk_div_mask(width) + 1;
}

static unsigned int _get_table_div(const struct clk_div_table *table,
							unsigned int val)
{
	const struct clk_div_table *clkt;

	for (clkt = table; clkt->div; clkt++)
		if (clkt->val == val)
			return clkt->div;
	return 0;
}

static unsigned int _get_div(const struct clk_div_table *table,
			     unsigned int val, unsigned long flags, u8 width)
{
	if (flags & CLK_DIVIDER_ONE_BASED)
		return val;
	if (flags & CLK_DIVIDER_POWER_OF_TWO)
		return 1 << val;
	if (flags & CLK_DIVIDER_MAX_AT_ZERO)
		return val ? val : clk_div_mask(width) + 1;
	if (flags & CLK_DIVIDER_EVEN_INTEGERS)
		return 2 * (val + 1);
	if (table)
		return _get_table_div(table, val);
	return val + 1;
}

static unsigned int _get_table_val(const struct clk_div_table *table,
							unsigned int div)
{
	const struct clk_div_table *clkt;

	for (clkt = table; clkt->div; clkt++)
		if (clkt->div == div)
			return clkt->val;
	return 0;
}

static unsigned int _get_val(const struct clk_div_table *table,
			     unsigned int div, unsigned long flags, u8 width)
{
	if (flags & CLK_DIVIDER_ONE_BASED)
		return div;
	if (flags & CLK_DIVIDER_POWER_OF_TWO)
		return __ffs(div);
	if (flags & CLK_DIVIDER_MAX_AT_ZERO)
		return (div == clk_div_mask(width) + 1) ? 0 : div;
	if (flags & CLK_DIVIDER_EVEN_INTEGERS)
		return (div >> 1) - 1;
	if (table)
		return  _get_table_val(table, div);
	return div - 1;
}

unsigned long divider_recalc_rate(struct clk_hw *hw, unsigned long parent_rate,
				  unsigned int val,
				  const struct clk_div_table *table,
				  unsigned long flags, unsigned long width)
{
	unsigned int div;

	div = _get_div(table, val, flags, width);
	if (!div) {
		WARN(!(flags & CLK_DIVIDER_ALLOW_ZERO),
			"%s: Zero divisor and CLK_DIVIDER_ALLOW_ZERO not set\n",
			clk_hw_get_name(hw));
		return parent_rate;
	}

	return DIV_ROUND_UP_ULL((u64)parent_rate, div);
}
EXPORT_SYMBOL_GPL(divider_recalc_rate);

static unsigned long clk_divider_recalc_rate(struct clk_hw *hw,
		unsigned long parent_rate)
{
	struct clk_divider *divider = to_clk_divider(hw);
	unsigned int val;

	val = clk_div_readl(divider) >> divider->shift;
	val &= clk_div_mask(divider->width);

	return divider_recalc_rate(hw, parent_rate, val, divider->table,
				   divider->flags, divider->width);
}

static bool _is_valid_table_div(const struct clk_div_table *table,
							 unsigned int div)
{
	const struct clk_div_table *clkt;

	for (clkt = table; clkt->div; clkt++)
		if (clkt->div == div)
			return true;
	return false;
}

static bool _is_valid_div(const struct clk_div_table *table, unsigned int div,
			  unsigned long flags)
{
	if (flags & CLK_DIVIDER_POWER_OF_TWO)
		return is_power_of_2(div);
	if (table)
		return _is_valid_table_div(table, div);
	return true;
}

static int _round_up_table(const struct clk_div_table *table, int div)
{
	const struct clk_div_table *clkt;
	int up = INT_MAX;

	for (clkt = table; clkt->div; clkt++) {
		if (clkt->div == div)
			return clkt->div;
		else if (clkt->div < div)
			continue;

		if ((clkt->div - div) < (up - div))
			up = clkt->div;
	}

	return up;
}

static int _round_down_table(const struct clk_div_table *table, int div)
{
	const struct clk_div_table *clkt;
	int down = _get_table_mindiv(table);

	for (clkt = table; clkt->div; clkt++) {
		if (clkt->div == div)
			return clkt->div;
		else if (clkt->div > div)
			continue;

		if ((div - clkt->div) < (div - down))
			down = clkt->div;
	}

	return down;
}

static int _div_round_up(const struct clk_div_table *table,
			 unsigned long parent_rate, unsigned long rate,
			 unsigned long flags)
{
	int div = DIV_ROUND_UP_ULL((u64)parent_rate, rate);

	if (flags & CLK_DIVIDER_POWER_OF_TWO)
		div = __roundup_pow_of_two(div);
	if (table)
		div = _round_up_table(table, div);

	return div;
}

static int _div_round_closest(const struct clk_div_table *table,
			      unsigned long parent_rate, unsigned long rate,
			      unsigned long flags)
{
	int up, down;
	unsigned long up_rate, down_rate;

	up = DIV_ROUND_UP_ULL((u64)parent_rate, rate);
	down = parent_rate / rate;

	if (flags & CLK_DIVIDER_POWER_OF_TWO) {
		up = __roundup_pow_of_two(up);
		down = __rounddown_pow_of_two(down);
	} else if (table) {
		up = _round_up_table(table, up);
		down = _round_down_table(table, down);
	}

	up_rate = DIV_ROUND_UP_ULL((u64)parent_rate, up);
	down_rate = DIV_ROUND_UP_ULL((u64)parent_rate, down);

	return (rate - up_rate) <= (down_rate - rate) ? up : down;
}

static int _div_round(const struct clk_div_table *table,
		      unsigned long parent_rate, unsigned long rate,
		      unsigned long flags)
{
	if (flags & CLK_DIVIDER_ROUND_CLOSEST)
		return _div_round_closest(table, parent_rate, rate, flags);

	return _div_round_up(table, parent_rate, rate, flags);
}

static bool _is_best_div(unsigned long rate, unsigned long now,
			 unsigned long best, unsigned long flags)
{
	if (flags & CLK_DIVIDER_ROUND_CLOSEST)
		return abs(rate - now) < abs(rate - best);

	return now <= rate && now > best;
}

static int _next_div(const struct clk_div_table *table, int div,
		     unsigned long flags)
{
	div++;

	if (flags & CLK_DIVIDER_POWER_OF_TWO)
		return __roundup_pow_of_two(div);
	if (table)
		return _round_up_table(table, div);

	return div;
}

static int clk_divider_bestdiv(struct clk_hw *hw, struct clk_hw *parent,
			       unsigned long rate,
			       unsigned long *best_parent_rate,
			       const struct clk_div_table *table, u8 width,
			       unsigned long flags)
{
	int i, bestdiv = 0;
	unsigned long parent_rate, best = 0, now, maxdiv;
	unsigned long parent_rate_saved = *best_parent_rate;
	unsigned long target_parent_rate;

	if (!rate)
		rate = 1;

	maxdiv = _get_maxdiv(table, width, flags);

	if (!(clk_hw_get_flags(hw) & CLK_SET_RATE_PARENT)) {
		parent_rate = *best_parent_rate;
		bestdiv = _div_round(table, parent_rate, rate, flags);
		bestdiv = bestdiv == 0 ? 1 : bestdiv;
		bestdiv = bestdiv > maxdiv ? maxdiv : bestdiv;
		return bestdiv;
	}

	for (i = _next_div(table, 0, flags); i <= maxdiv;
					     i = _next_div(table, i, flags)) {
		bool overflow = check_mul_overflow(rate, (unsigned long)i, &target_parent_rate);

		if (!overflow && target_parent_rate == parent_rate_saved) {
			/*
			 * It's the most ideal case if the requested rate can be
			 * divided from parent clock without needing to change
			 * parent rate, so return the divider immediately.
			 */
			*best_parent_rate = parent_rate_saved;
			return i;
		}
		/*
		 * Clamp target_parent_rate to ULONG_MAX on overflow. The true
		 * required parent rate exceeds what can be represented, so ask
		 * the parent for the highest rate it can produce. There is no
		 * point continuing the loop past this since larger dividers
		 * only move further from the requested rate.
		 */
		if (overflow)
			target_parent_rate = ULONG_MAX;
		parent_rate = clk_hw_round_rate(parent, target_parent_rate);
		now = DIV_ROUND_UP_ULL((u64)parent_rate, i);
		if (_is_best_div(rate, now, best, flags)) {
			bestdiv = i;
			best = now;
			*best_parent_rate = parent_rate;
		}
		if (overflow)
			break;
	}

	if (!bestdiv) {
		bestdiv = _get_maxdiv(table, width, flags);
		*best_parent_rate = clk_hw_round_rate(parent, 1);
	}

	return bestdiv;
}

int divider_determine_rate(struct clk_hw *hw, struct clk_rate_request *req,
			   const struct clk_div_table *table, u8 width,
			   unsigned long flags)
{
	int div;

	div = clk_divider_bestdiv(hw, req->best_parent_hw, req->rate,
				  &req->best_parent_rate, table, width, flags);

	req->rate = DIV_ROUND_UP_ULL((u64)req->best_parent_rate, div);

	return 0;
}
EXPORT_SYMBOL_GPL(divider_determine_rate);

int divider_ro_determine_rate(struct clk_hw *hw, struct clk_rate_request *req,
			      const struct clk_div_table *table, u8 width,
			      unsigned long flags, unsigned int val)
{
	int div;

	div = _get_div(table, val, flags, width);

	/* Even a read-only clock can propagate a rate change */
	if (clk_hw_get_flags(hw) & CLK_SET_RATE_PARENT) {
		if (!req->best_parent_hw)
			return -EINVAL;

		req->best_parent_rate = clk_hw_round_rate(req->best_parent_hw,
							  req->rate * div);
	}

	req->rate = DIV_ROUND_UP_ULL((u64)req->best_parent_rate, div);

	return 0;
}
EXPORT_SYMBOL_GPL(divider_ro_determine_rate);

static int clk_divider_determine_rate(struct clk_hw *hw,
				      struct clk_rate_request *req)
{
	struct clk_divider *divider = to_clk_divider(hw);

	/* if read only, just return current value */
	if (divider->flags & CLK_DIVIDER_READ_ONLY) {
		u32 val;

		val = clk_div_readl(divider) >> divider->shift;
		val &= clk_div_mask(divider->width);

		return divider_ro_determine_rate(hw, req, divider->table,
						 divider->width,
						 divider->flags, val);
	}

	return divider_determine_rate(hw, req, divider->table, divider->width,
				      divider->flags);
}

int divider_get_val(unsigned long rate, unsigned long parent_rate,
		    const struct clk_div_table *table, u8 width,
		    unsigned long flags)
{
	unsigned int div, value;

	div = DIV_ROUND_UP_ULL((u64)parent_rate, rate);

	if (!_is_valid_div(table, div, flags))
		return -EINVAL;

	value = _get_val(table, div, flags, width);

	return min_t(unsigned int, value, clk_div_mask(width));
}
EXPORT_SYMBOL_GPL(divider_get_val);

static int clk_divider_set_rate(struct clk_hw *hw, unsigned long rate,
				unsigned long parent_rate)
{
	struct clk_divider *divider = to_clk_divider(hw);
	int value;
	unsigned long flags = 0;
	u32 val;

	value = divider_get_val(rate, parent_rate, divider->table,
				divider->width, divider->flags);
	if (value < 0)
		return value;

	if (divider->lock)
		spin_lock_irqsave(divider->lock, flags);
	else
		__acquire(divider->lock);

	if (divider->flags & CLK_DIVIDER_HIWORD_MASK) {
		val = clk_div_mask(divider->width) << (divider->shift + 16);
	} else {
		val = clk_div_readl(divider);
		val &= ~(clk_div_mask(divider->width) << divider->shift);
	}
	val |= (u32)value << divider->shift;
	clk_div_writel(divider, val);

	if (divider->lock)
		spin_unlock_irqrestore(divider->lock, flags);
	else
		__release(divider->lock);

	return 0;
}

const struct clk_ops clk_divider_ops = {
	.recalc_rate = clk_divider_recalc_rate,
	.determine_rate = clk_divider_determine_rate,
	.set_rate = clk_divider_set_rate,
};
EXPORT_SYMBOL_GPL(clk_divider_ops);

const struct clk_ops clk_divider_ro_ops = {
	.recalc_rate = clk_divider_recalc_rate,
	.determine_rate = clk_divider_determine_rate,
};
EXPORT_SYMBOL_GPL(clk_divider_ro_ops);

struct clk_hw *__clk_hw_register_divider(struct device *dev,
		struct device_node *np, const char *name,
		const char *parent_name, const struct clk_hw *parent_hw,
		const struct clk_parent_data *parent_data, unsigned long flags,
		void __iomem *reg, u8 shift, u8 width,
		unsigned long clk_divider_flags,
		const struct clk_div_table *table, spinlock_t *lock)
{
	struct clk_divider *div;
	struct clk_hw *hw;
	struct clk_init_data init = {};
	int ret;

	if (clk_divider_flags & CLK_DIVIDER_HIWORD_MASK) {
		if (width + shift > 16) {
			pr_warn("divider value exceeds LOWORD field\n");
			return ERR_PTR(-EINVAL);
		}
	}

	/* allocate the divider */
	div = kzalloc_obj(*div);
	if (!div)
		return ERR_PTR(-ENOMEM);

	init.name = name;
	if (clk_divider_flags & CLK_DIVIDER_READ_ONLY)
		init.ops = &clk_divider_ro_ops;
	else
		init.ops = &clk_divider_ops;
	init.flags = flags;
	init.parent_names = parent_name ? &parent_name : NULL;
	init.parent_hws = parent_hw ? &parent_hw : NULL;
	init.parent_data = parent_data;
	if (parent_name || parent_hw || parent_data)
		init.num_parents = 1;
	else
		init.num_parents = 0;

	/* struct clk_divider assignments */
	div->reg = reg;
	div->shift = shift;
	div->width = width;
	div->flags = clk_divider_flags;
	div->lock = lock;
	div->hw.init = &init;
	div->table = table;

	/* register the clock */
	hw = &div->hw;
	ret = clk_hw_register(dev, hw);
	if (ret) {
		kfree(div);
		hw = ERR_PTR(ret);
	}

	return hw;
}
EXPORT_SYMBOL_GPL(__clk_hw_register_divider);

/**
 * clk_register_divider_table - register a table based divider clock with
 * the clock framework
 * @dev: device registering this clock
 * @name: name of this clock
 * @parent_name: name of clock's parent
 * @flags: framework-specific flags
 * @reg: register address to adjust divider
 * @shift: number of bits to shift the bitfield
 * @width: width of the bitfield
 * @clk_divider_flags: divider-specific flags for this clock
 * @table: array of divider/value pairs ending with a div set to 0
 * @lock: shared register lock for this clock
 */
struct clk *clk_register_divider_table(struct device *dev, const char *name,
		const char *parent_name, unsigned long flags,
		void __iomem *reg, u8 shift, u8 width,
		unsigned long clk_divider_flags,
		const struct clk_div_table *table, spinlock_t *lock)
{
	struct clk_hw *hw;

	hw =  __clk_hw_register_divider(dev, NULL, name, parent_name, NULL,
			NULL, flags, reg, shift, width, clk_divider_flags,
			table, lock);
	if (IS_ERR(hw))
		return ERR_CAST(hw);
	return hw->clk;
}
EXPORT_SYMBOL_GPL(clk_register_divider_table);

void clk_unregister_divider(struct clk *clk)
{
	struct clk_divider *div;
	struct clk_hw *hw;

	hw = __clk_get_hw(clk);
	if (!hw)
		return;

	div = to_clk_divider(hw);

	clk_unregister(clk);
	kfree(div);
}
EXPORT_SYMBOL_GPL(clk_unregister_divider);

/**
 * clk_hw_unregister_divider - unregister a clk divider
 * @hw: hardware-specific clock data to unregister
 */
void clk_hw_unregister_divider(struct clk_hw *hw)
{
	struct clk_divider *div;

	div = to_clk_divider(hw);

	clk_hw_unregister(hw);
	kfree(div);
}
EXPORT_SYMBOL_GPL(clk_hw_unregister_divider);

static void devm_clk_hw_release_divider(struct device *dev, void *res)
{
	clk_hw_unregister_divider(*(struct clk_hw **)res);
}

struct clk_hw *__devm_clk_hw_register_divider(struct device *dev,
		struct device_node *np, const char *name,
		const char *parent_name, const struct clk_hw *parent_hw,
		const struct clk_parent_data *parent_data, unsigned long flags,
		void __iomem *reg, u8 shift, u8 width,
		unsigned long clk_divider_flags,
		const struct clk_div_table *table, spinlock_t *lock)
{
	struct clk_hw **ptr, *hw;

	ptr = devres_alloc(devm_clk_hw_release_divider, sizeof(*ptr), GFP_KERNEL);
	if (!ptr)
		return ERR_PTR(-ENOMEM);

	hw = __clk_hw_register_divider(dev, np, name, parent_name, parent_hw,
				       parent_data, flags, reg, shift, width,
				       clk_divider_flags, table, lock);

	if (!IS_ERR(hw)) {
		*ptr = hw;
		devres_add(dev, ptr);
	} else {
		devres_free(ptr);
	}

	return hw;
}
EXPORT_SYMBOL_GPL(__devm_clk_hw_register_divider);