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