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// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (c) 2024 SpacemiT Technology Co. Ltd
* Copyright (c) 2024-2025 Haylen Chu <heylenay@4d2.org>
*
* DDN stands for "Divider Denominator Numerator", it's M/N clock with a
* constant x2 factor. This clock hardware follows the equation below,
*
* numerator Fin
* 2 * ------------- = -------
* denominator Fout
*
* Thus, Fout could be calculated with,
*
* Fin denominator
* Fout = ----- * -------------
* 2 numerator
*/
#include <linux/clk-provider.h>
#include <linux/rational.h>
#include "ccu_ddn.h"
static unsigned long ccu_ddn_calc_rate(unsigned long prate,
unsigned long num, unsigned long den)
{
return prate * den / 2 / num;
}
static unsigned long ccu_ddn_calc_best_rate(struct ccu_ddn *ddn,
unsigned long rate, unsigned long prate,
unsigned long *num, unsigned long *den)
{
rational_best_approximation(rate, prate / 2,
ddn->den_mask >> ddn->den_shift,
ddn->num_mask >> ddn->num_shift,
den, num);
return ccu_ddn_calc_rate(prate, *num, *den);
}
static long ccu_ddn_round_rate(struct clk_hw *hw, unsigned long rate,
unsigned long *prate)
{
struct ccu_ddn *ddn = hw_to_ccu_ddn(hw);
unsigned long num, den;
return ccu_ddn_calc_best_rate(ddn, rate, *prate, &num, &den);
}
static unsigned long ccu_ddn_recalc_rate(struct clk_hw *hw, unsigned long prate)
{
struct ccu_ddn *ddn = hw_to_ccu_ddn(hw);
unsigned int val, num, den;
val = ccu_read(&ddn->common, ctrl);
num = (val & ddn->num_mask) >> ddn->num_shift;
den = (val & ddn->den_mask) >> ddn->den_shift;
return ccu_ddn_calc_rate(prate, num, den);
}
static int ccu_ddn_set_rate(struct clk_hw *hw, unsigned long rate,
unsigned long prate)
{
struct ccu_ddn *ddn = hw_to_ccu_ddn(hw);
unsigned long num, den;
ccu_ddn_calc_best_rate(ddn, rate, prate, &num, &den);
ccu_update(&ddn->common, ctrl,
ddn->num_mask | ddn->den_mask,
(num << ddn->num_shift) | (den << ddn->den_shift));
return 0;
}
const struct clk_ops spacemit_ccu_ddn_ops = {
.recalc_rate = ccu_ddn_recalc_rate,
.round_rate = ccu_ddn_round_rate,
.set_rate = ccu_ddn_set_rate,
};
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