1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * Copyright (C) 2017 Chen-Yu Tsai <wens@csie.org>
4 */
5
6#include <linux/clk-provider.h>
7#include <linux/io.h>
8#include <linux/spinlock.h>
9
10#include "ccu_sdm.h"
11
12bool ccu_sdm_helper_is_enabled(struct ccu_common *common,
13			       struct ccu_sdm_internal *sdm)
14{
15	if (!(common->features & CCU_FEATURE_SIGMA_DELTA_MOD))
16		return false;
17
18	if (sdm->enable && !(readl(common->base + common->reg) & sdm->enable))
19		return false;
20
21	return !!(readl(common->base + sdm->tuning_reg) & sdm->tuning_enable);
22}
23
24void ccu_sdm_helper_enable(struct ccu_common *common,
25			   struct ccu_sdm_internal *sdm,
26			   unsigned long rate)
27{
28	unsigned long flags;
29	unsigned int i;
30	u32 reg;
31
32	if (!(common->features & CCU_FEATURE_SIGMA_DELTA_MOD))
33		return;
34
35	/* Set the pattern */
36	for (i = 0; i < sdm->table_size; i++)
37		if (sdm->table[i].rate == rate)
38			writel(sdm->table[i].pattern,
39			       common->base + sdm->tuning_reg);
40
41	/* Make sure SDM is enabled */
42	spin_lock_irqsave(common->lock, flags);
43	reg = readl(common->base + sdm->tuning_reg);
44	writel(reg | sdm->tuning_enable, common->base + sdm->tuning_reg);
45	spin_unlock_irqrestore(common->lock, flags);
46
47	spin_lock_irqsave(common->lock, flags);
48	reg = readl(common->base + common->reg);
49	writel(reg | sdm->enable, common->base + common->reg);
50	spin_unlock_irqrestore(common->lock, flags);
51}
52
53void ccu_sdm_helper_disable(struct ccu_common *common,
54			    struct ccu_sdm_internal *sdm)
55{
56	unsigned long flags;
57	u32 reg;
58
59	if (!(common->features & CCU_FEATURE_SIGMA_DELTA_MOD))
60		return;
61
62	spin_lock_irqsave(common->lock, flags);
63	reg = readl(common->base + common->reg);
64	writel(reg & ~sdm->enable, common->base + common->reg);
65	spin_unlock_irqrestore(common->lock, flags);
66
67	spin_lock_irqsave(common->lock, flags);
68	reg = readl(common->base + sdm->tuning_reg);
69	writel(reg & ~sdm->tuning_enable, common->base + sdm->tuning_reg);
70	spin_unlock_irqrestore(common->lock, flags);
71}
72
73/*
74 * Sigma delta modulation provides a way to do fractional-N frequency
75 * synthesis, in essence allowing the PLL to output any frequency
76 * within its operational range. On earlier SoCs such as the A10/A20,
77 * some PLLs support this. On later SoCs, all PLLs support this.
78 *
79 * The datasheets do not explain what the "wave top" and "wave bottom"
80 * parameters mean or do, nor how to calculate the effective output
81 * frequency. The only examples (and real world usage) are for the audio
82 * PLL to generate 24.576 and 22.5792 MHz clock rates used by the audio
83 * peripherals. The author lacks the underlying domain knowledge to
84 * pursue this.
85 *
86 * The goal and function of the following code is to support the two
87 * clock rates used by the audio subsystem, allowing for proper audio
88 * playback and capture without any pitch or speed changes.
89 */
90bool ccu_sdm_helper_has_rate(struct ccu_common *common,
91			     struct ccu_sdm_internal *sdm,
92			     unsigned long rate)
93{
94	unsigned int i;
95
96	if (!(common->features & CCU_FEATURE_SIGMA_DELTA_MOD))
97		return false;
98
99	for (i = 0; i < sdm->table_size; i++)
100		if (sdm->table[i].rate == rate)
101			return true;
102
103	return false;
104}
105
106unsigned long ccu_sdm_helper_read_rate(struct ccu_common *common,
107				       struct ccu_sdm_internal *sdm,
108				       u32 m, u32 n)
109{
110	unsigned int i;
111	u32 reg;
112
113	pr_debug("%s: Read sigma-delta modulation setting\n",
114		 clk_hw_get_name(&common->hw));
115
116	if (!(common->features & CCU_FEATURE_SIGMA_DELTA_MOD))
117		return 0;
118
119	pr_debug("%s: clock is sigma-delta modulated\n",
120		 clk_hw_get_name(&common->hw));
121
122	reg = readl(common->base + sdm->tuning_reg);
123
124	pr_debug("%s: pattern reg is 0x%x",
125		 clk_hw_get_name(&common->hw), reg);
126
127	for (i = 0; i < sdm->table_size; i++)
128		if (sdm->table[i].pattern == reg &&
129		    sdm->table[i].m == m && sdm->table[i].n == n)
130			return sdm->table[i].rate;
131
132	/* We can't calculate the effective clock rate, so just fail. */
133	return 0;
134}
135
136int ccu_sdm_helper_get_factors(struct ccu_common *common,
137			       struct ccu_sdm_internal *sdm,
138			       unsigned long rate,
139			       unsigned long *m, unsigned long *n)
140{
141	unsigned int i;
142
143	if (!(common->features & CCU_FEATURE_SIGMA_DELTA_MOD))
144		return -EINVAL;
145
146	for (i = 0; i < sdm->table_size; i++)
147		if (sdm->table[i].rate == rate) {
148			*m = sdm->table[i].m;
149			*n = sdm->table[i].n;
150			return 0;
151		}
152
153	/* nothing found */
154	return -EINVAL;
155}
156