1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2019 Daniel Palmer <daniel@thingy.jp>
4 */
5
6#include <linux/clk-provider.h>
7#include <linux/device.h>
8#include <linux/kernel.h>
9#include <linux/of_address.h>
10#include <linux/platform_device.h>
11
12/*
13 * This IP is not documented outside of the messy vendor driver.
14 * Below is what we think the registers look like based on looking at
15 * the vendor code and poking at the hardware:
16 *
17 * 0x140 -- LPF low. Seems to store one half of the clock transition
18 * 0x144 /
19 * 0x148 -- LPF high. Seems to store one half of the clock transition
20 * 0x14c /
21 * 0x150 -- vendor code says "toggle lpf enable"
22 * 0x154 -- mu?
23 * 0x15c -- lpf_update_count?
24 * 0x160 -- vendor code says "switch to LPF". Clock source config? Register bank?
25 * 0x164 -- vendor code says "from low to high" which seems to mean transition from LPF low to
26 * LPF high.
27 * 0x174 -- Seems to be the PLL lock status bit
28 * 0x180 -- Seems to be the current frequency, this might need to be populated by software?
29 * 0x184 /  The vendor driver uses these to set the initial value of LPF low
30 *
31 * Frequency seems to be calculated like this:
32 * (parent clock (432mhz) / register_magic_value) * 16 * 524288
33 * Only the lower 24 bits of the resulting value will be used. In addition, the
34 * PLL doesn't seem to be able to lock on frequencies lower than 220 MHz, as
35 * divisor 0xfb586f (220 MHz) works but 0xfb7fff locks up.
36 *
37 * Vendor values:
38 * frequency - register value
39 *
40 * 400000000  - 0x0067AE14
41 * 600000000  - 0x00451EB8,
42 * 800000000  - 0x0033D70A,
43 * 1000000000 - 0x002978d4,
44 */
45
46#define REG_LPF_LOW_L		0x140
47#define REG_LPF_LOW_H		0x144
48#define REG_LPF_HIGH_BOTTOM	0x148
49#define REG_LPF_HIGH_TOP	0x14c
50#define REG_LPF_TOGGLE		0x150
51#define REG_LPF_MYSTERYTWO	0x154
52#define REG_LPF_UPDATE_COUNT	0x15c
53#define REG_LPF_MYSTERYONE	0x160
54#define REG_LPF_TRANSITIONCTRL	0x164
55#define REG_LPF_LOCK		0x174
56#define REG_CURRENT		0x180
57
58#define LPF_LOCK_TIMEOUT	100000000
59
60#define MULTIPLIER_1		16
61#define MULTIPLIER_2		524288
62#define MULTIPLIER		(MULTIPLIER_1 * MULTIPLIER_2)
63
64struct msc313_cpupll {
65	void __iomem *base;
66	struct clk_hw clk_hw;
67};
68
69#define to_cpupll(_hw) container_of(_hw, struct msc313_cpupll, clk_hw)
70
71static u32 msc313_cpupll_reg_read32(struct msc313_cpupll *cpupll, unsigned int reg)
72{
73	u32 value;
74
75	value = ioread16(cpupll->base + reg + 4) << 16;
76	value |= ioread16(cpupll->base + reg);
77
78	return value;
79}
80
81static void msc313_cpupll_reg_write32(struct msc313_cpupll *cpupll, unsigned int reg, u32 value)
82{
83	u16 l = value & 0xffff, h = (value >> 16) & 0xffff;
84
85	iowrite16(l, cpupll->base + reg);
86	iowrite16(h, cpupll->base + reg + 4);
87}
88
89static void msc313_cpupll_setfreq(struct msc313_cpupll *cpupll, u32 regvalue)
90{
91	ktime_t timeout;
92
93	msc313_cpupll_reg_write32(cpupll, REG_LPF_HIGH_BOTTOM, regvalue);
94
95	iowrite16(0x1, cpupll->base + REG_LPF_MYSTERYONE);
96	iowrite16(0x6, cpupll->base + REG_LPF_MYSTERYTWO);
97	iowrite16(0x8, cpupll->base + REG_LPF_UPDATE_COUNT);
98	iowrite16(BIT(12), cpupll->base + REG_LPF_TRANSITIONCTRL);
99
100	iowrite16(0, cpupll->base + REG_LPF_TOGGLE);
101	iowrite16(1, cpupll->base + REG_LPF_TOGGLE);
102
103	timeout = ktime_add_ns(ktime_get(), LPF_LOCK_TIMEOUT);
104	while (!(ioread16(cpupll->base + REG_LPF_LOCK))) {
105		if (ktime_after(ktime_get(), timeout)) {
106			pr_err("timeout waiting for LPF_LOCK\n");
107			return;
108		}
109		cpu_relax();
110	}
111
112	iowrite16(0, cpupll->base + REG_LPF_TOGGLE);
113
114	msc313_cpupll_reg_write32(cpupll, REG_LPF_LOW_L, regvalue);
115}
116
117static unsigned long msc313_cpupll_frequencyforreg(u32 reg, unsigned long parent_rate)
118{
119	unsigned long long prescaled = ((unsigned long long)parent_rate) * MULTIPLIER;
120
121	if (prescaled == 0 || reg == 0)
122		return 0;
123	return DIV_ROUND_DOWN_ULL(prescaled, reg);
124}
125
126static u32 msc313_cpupll_regforfrequecy(unsigned long rate, unsigned long parent_rate)
127{
128	unsigned long long prescaled = ((unsigned long long)parent_rate) * MULTIPLIER;
129
130	if (prescaled == 0 || rate == 0)
131		return 0;
132	return DIV_ROUND_UP_ULL(prescaled, rate);
133}
134
135static unsigned long msc313_cpupll_recalc_rate(struct clk_hw *hw, unsigned long parent_rate)
136{
137	struct msc313_cpupll *cpupll = to_cpupll(hw);
138
139	return msc313_cpupll_frequencyforreg(msc313_cpupll_reg_read32(cpupll, REG_LPF_LOW_L),
140					     parent_rate);
141}
142
143static long msc313_cpupll_round_rate(struct clk_hw *hw, unsigned long rate,
144				     unsigned long *parent_rate)
145{
146	u32 reg = msc313_cpupll_regforfrequecy(rate, *parent_rate);
147	long rounded = msc313_cpupll_frequencyforreg(reg, *parent_rate);
148
149	/*
150	 * This is my poor attempt at making sure the resulting
151	 * rate doesn't overshoot the requested rate.
152	 */
153	for (; rounded >= rate && reg > 0; reg--)
154		rounded = msc313_cpupll_frequencyforreg(reg, *parent_rate);
155
156	return rounded;
157}
158
159static int msc313_cpupll_set_rate(struct clk_hw *hw, unsigned long rate, unsigned long parent_rate)
160{
161	struct msc313_cpupll *cpupll = to_cpupll(hw);
162	u32 reg = msc313_cpupll_regforfrequecy(rate, parent_rate);
163
164	msc313_cpupll_setfreq(cpupll, reg);
165
166	return 0;
167}
168
169static const struct clk_ops msc313_cpupll_ops = {
170	.recalc_rate	= msc313_cpupll_recalc_rate,
171	.round_rate	= msc313_cpupll_round_rate,
172	.set_rate	= msc313_cpupll_set_rate,
173};
174
175static const struct of_device_id msc313_cpupll_of_match[] = {
176	{ .compatible = "mstar,msc313-cpupll" },
177	{}
178};
179
180static int msc313_cpupll_probe(struct platform_device *pdev)
181{
182	struct clk_init_data clk_init = {};
183	struct clk_parent_data cpupll_parent = { .index	= 0 };
184	struct device *dev = &pdev->dev;
185	struct msc313_cpupll *cpupll;
186	int ret;
187
188	cpupll = devm_kzalloc(&pdev->dev, sizeof(*cpupll), GFP_KERNEL);
189	if (!cpupll)
190		return -ENOMEM;
191
192	cpupll->base = devm_platform_ioremap_resource(pdev, 0);
193	if (IS_ERR(cpupll->base))
194		return PTR_ERR(cpupll->base);
195
196	/* LPF might not contain the current frequency so fix that up */
197	msc313_cpupll_reg_write32(cpupll, REG_LPF_LOW_L,
198				  msc313_cpupll_reg_read32(cpupll, REG_CURRENT));
199
200	clk_init.name = dev_name(dev);
201	clk_init.ops = &msc313_cpupll_ops;
202	clk_init.parent_data = &cpupll_parent;
203	clk_init.num_parents = 1;
204	cpupll->clk_hw.init = &clk_init;
205
206	ret = devm_clk_hw_register(dev, &cpupll->clk_hw);
207	if (ret)
208		return ret;
209
210	return devm_of_clk_add_hw_provider(&pdev->dev, of_clk_hw_simple_get, &cpupll->clk_hw);
211}
212
213static struct platform_driver msc313_cpupll_driver = {
214	.driver = {
215		.name = "mstar-msc313-cpupll",
216		.of_match_table = msc313_cpupll_of_match,
217	},
218	.probe = msc313_cpupll_probe,
219};
220builtin_platform_driver(msc313_cpupll_driver);
221