1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (c) 2024 SpacemiT Technology Co. Ltd
4 * Copyright (c) 2024-2025 Haylen Chu <heylenay@4d2.org>
5 *
6 * DDN stands for "Divider Denominator Numerator", it's M/N clock with a
7 * constant x2 factor. This clock hardware follows the equation below,
8 *
9 * numerator Fin
10 * 2 * ------------- = -------
11 * denominator Fout
12 *
13 * Thus, Fout could be calculated with,
14 *
15 * Fin denominator
16 * Fout = ----- * -------------
17 * 2 numerator
18 */
19
20 #include <linux/clk-provider.h>
21 #include <linux/rational.h>
22
23 #include "ccu_ddn.h"
24
ccu_ddn_calc_rate(unsigned long prate,unsigned long num,unsigned long den)25 static unsigned long ccu_ddn_calc_rate(unsigned long prate,
26 unsigned long num, unsigned long den)
27 {
28 return prate * den / 2 / num;
29 }
30
ccu_ddn_calc_best_rate(struct ccu_ddn * ddn,unsigned long rate,unsigned long prate,unsigned long * num,unsigned long * den)31 static unsigned long ccu_ddn_calc_best_rate(struct ccu_ddn *ddn,
32 unsigned long rate, unsigned long prate,
33 unsigned long *num, unsigned long *den)
34 {
35 rational_best_approximation(rate, prate / 2,
36 ddn->den_mask >> ddn->den_shift,
37 ddn->num_mask >> ddn->num_shift,
38 den, num);
39 return ccu_ddn_calc_rate(prate, *num, *den);
40 }
41
ccu_ddn_round_rate(struct clk_hw * hw,unsigned long rate,unsigned long * prate)42 static long ccu_ddn_round_rate(struct clk_hw *hw, unsigned long rate,
43 unsigned long *prate)
44 {
45 struct ccu_ddn *ddn = hw_to_ccu_ddn(hw);
46 unsigned long num, den;
47
48 return ccu_ddn_calc_best_rate(ddn, rate, *prate, &num, &den);
49 }
50
ccu_ddn_recalc_rate(struct clk_hw * hw,unsigned long prate)51 static unsigned long ccu_ddn_recalc_rate(struct clk_hw *hw, unsigned long prate)
52 {
53 struct ccu_ddn *ddn = hw_to_ccu_ddn(hw);
54 unsigned int val, num, den;
55
56 val = ccu_read(&ddn->common, ctrl);
57
58 num = (val & ddn->num_mask) >> ddn->num_shift;
59 den = (val & ddn->den_mask) >> ddn->den_shift;
60
61 return ccu_ddn_calc_rate(prate, num, den);
62 }
63
ccu_ddn_set_rate(struct clk_hw * hw,unsigned long rate,unsigned long prate)64 static int ccu_ddn_set_rate(struct clk_hw *hw, unsigned long rate,
65 unsigned long prate)
66 {
67 struct ccu_ddn *ddn = hw_to_ccu_ddn(hw);
68 unsigned long num, den;
69
70 ccu_ddn_calc_best_rate(ddn, rate, prate, &num, &den);
71
72 ccu_update(&ddn->common, ctrl,
73 ddn->num_mask | ddn->den_mask,
74 (num << ddn->num_shift) | (den << ddn->den_shift));
75
76 return 0;
77 }
78
79 const struct clk_ops spacemit_ccu_ddn_ops = {
80 .recalc_rate = ccu_ddn_recalc_rate,
81 .round_rate = ccu_ddn_round_rate,
82 .set_rate = ccu_ddn_set_rate,
83 };
84