1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * Copyright 2014 Google, Inc
4  * Author: Alexandru M Stan <amstan@chromium.org>
5  */
6 
7 #include <linux/slab.h>
8 #include <linux/clk.h>
9 #include <linux/clk-provider.h>
10 #include <linux/io.h>
11 #include <linux/kernel.h>
12 #include "clk.h"
13 
14 struct rockchip_mmc_clock {
15 	struct clk_hw	hw;
16 	void __iomem	*reg;
17 	int		id;
18 	int		shift;
19 	int		cached_phase;
20 	struct notifier_block clk_rate_change_nb;
21 };
22 
23 #define to_mmc_clock(_hw) container_of(_hw, struct rockchip_mmc_clock, hw)
24 
25 #define RK3288_MMC_CLKGEN_DIV 2
26 
27 static unsigned long rockchip_mmc_recalc(struct clk_hw *hw,
28 					 unsigned long parent_rate)
29 {
30 	return parent_rate / RK3288_MMC_CLKGEN_DIV;
31 }
32 
33 #define ROCKCHIP_MMC_DELAY_SEL BIT(10)
34 #define ROCKCHIP_MMC_DEGREE_MASK 0x3
35 #define ROCKCHIP_MMC_DELAYNUM_OFFSET 2
36 #define ROCKCHIP_MMC_DELAYNUM_MASK (0xff << ROCKCHIP_MMC_DELAYNUM_OFFSET)
37 
38 #define PSECS_PER_SEC 1000000000000LL
39 
40 /*
41  * Each fine delay is between 44ps-77ps. Assume each fine delay is 60ps to
42  * simplify calculations. So 45degs could be anywhere between 33deg and 57.8deg.
43  */
44 #define ROCKCHIP_MMC_DELAY_ELEMENT_PSEC 60
45 
46 static int rockchip_mmc_get_phase(struct clk_hw *hw)
47 {
48 	struct rockchip_mmc_clock *mmc_clock = to_mmc_clock(hw);
49 	unsigned long rate = clk_hw_get_rate(hw);
50 	u32 raw_value;
51 	u16 degrees;
52 	u32 delay_num = 0;
53 
54 	/* See the comment for rockchip_mmc_set_phase below */
55 	if (!rate)
56 		return -EINVAL;
57 
58 	raw_value = readl(mmc_clock->reg) >> (mmc_clock->shift);
59 
60 	degrees = (raw_value & ROCKCHIP_MMC_DEGREE_MASK) * 90;
61 
62 	if (raw_value & ROCKCHIP_MMC_DELAY_SEL) {
63 		/* degrees/delaynum * 1000000 */
64 		unsigned long factor = (ROCKCHIP_MMC_DELAY_ELEMENT_PSEC / 10) *
65 					36 * (rate / 10000);
66 
67 		delay_num = (raw_value & ROCKCHIP_MMC_DELAYNUM_MASK);
68 		delay_num >>= ROCKCHIP_MMC_DELAYNUM_OFFSET;
69 		degrees += DIV_ROUND_CLOSEST(delay_num * factor, 1000000);
70 	}
71 
72 	return degrees % 360;
73 }
74 
75 static int rockchip_mmc_set_phase(struct clk_hw *hw, int degrees)
76 {
77 	struct rockchip_mmc_clock *mmc_clock = to_mmc_clock(hw);
78 	unsigned long rate = clk_hw_get_rate(hw);
79 	u8 nineties, remainder;
80 	u8 delay_num;
81 	u32 raw_value;
82 	u32 delay;
83 
84 	/*
85 	 * The below calculation is based on the output clock from
86 	 * MMC host to the card, which expects the phase clock inherits
87 	 * the clock rate from its parent, namely the output clock
88 	 * provider of MMC host. However, things may go wrong if
89 	 * (1) It is orphan.
90 	 * (2) It is assigned to the wrong parent.
91 	 *
92 	 * This check help debug the case (1), which seems to be the
93 	 * most likely problem we often face and which makes it difficult
94 	 * for people to debug unstable mmc tuning results.
95 	 */
96 	if (!rate) {
97 		pr_err("%s: invalid clk rate\n", __func__);
98 		return -EINVAL;
99 	}
100 
101 	nineties = degrees / 90;
102 	remainder = (degrees % 90);
103 
104 	/*
105 	 * Due to the inexact nature of the "fine" delay, we might
106 	 * actually go non-monotonic.  We don't go _too_ monotonic
107 	 * though, so we should be OK.  Here are options of how we may
108 	 * work:
109 	 *
110 	 * Ideally we end up with:
111 	 *   1.0, 2.0, ..., 69.0, 70.0, ...,  89.0, 90.0
112 	 *
113 	 * On one extreme (if delay is actually 44ps):
114 	 *   .73, 1.5, ..., 50.6, 51.3, ...,  65.3, 90.0
115 	 * The other (if delay is actually 77ps):
116 	 *   1.3, 2.6, ..., 88.6. 89.8, ..., 114.0, 90
117 	 *
118 	 * It's possible we might make a delay that is up to 25
119 	 * degrees off from what we think we're making.  That's OK
120 	 * though because we should be REALLY far from any bad range.
121 	 */
122 
123 	/*
124 	 * Convert to delay; do a little extra work to make sure we
125 	 * don't overflow 32-bit / 64-bit numbers.
126 	 */
127 	delay = 10000000; /* PSECS_PER_SEC / 10000 / 10 */
128 	delay *= remainder;
129 	delay = DIV_ROUND_CLOSEST(delay,
130 			(rate / 1000) * 36 *
131 				(ROCKCHIP_MMC_DELAY_ELEMENT_PSEC / 10));
132 
133 	delay_num = (u8) min_t(u32, delay, 255);
134 
135 	raw_value = delay_num ? ROCKCHIP_MMC_DELAY_SEL : 0;
136 	raw_value |= delay_num << ROCKCHIP_MMC_DELAYNUM_OFFSET;
137 	raw_value |= nineties;
138 	writel(HIWORD_UPDATE(raw_value, 0x07ff, mmc_clock->shift),
139 	       mmc_clock->reg);
140 
141 	pr_debug("%s->set_phase(%d) delay_nums=%u reg[0x%p]=0x%03x actual_degrees=%d\n",
142 		clk_hw_get_name(hw), degrees, delay_num,
143 		mmc_clock->reg, raw_value>>(mmc_clock->shift),
144 		rockchip_mmc_get_phase(hw)
145 	);
146 
147 	return 0;
148 }
149 
150 static const struct clk_ops rockchip_mmc_clk_ops = {
151 	.recalc_rate	= rockchip_mmc_recalc,
152 	.get_phase	= rockchip_mmc_get_phase,
153 	.set_phase	= rockchip_mmc_set_phase,
154 };
155 
156 #define to_rockchip_mmc_clock(x) \
157 	container_of(x, struct rockchip_mmc_clock, clk_rate_change_nb)
158 static int rockchip_mmc_clk_rate_notify(struct notifier_block *nb,
159 					unsigned long event, void *data)
160 {
161 	struct rockchip_mmc_clock *mmc_clock = to_rockchip_mmc_clock(nb);
162 	struct clk_notifier_data *ndata = data;
163 
164 	/*
165 	 * rockchip_mmc_clk is mostly used by mmc controllers to sample
166 	 * the intput data, which expects the fixed phase after the tuning
167 	 * process. However if the clock rate is changed, the phase is stale
168 	 * and may break the data sampling. So here we try to restore the phase
169 	 * for that case, except that
170 	 * (1) cached_phase is invaild since we inevitably cached it when the
171 	 * clock provider be reparented from orphan to its real parent in the
172 	 * first place. Otherwise we may mess up the initialization of MMC cards
173 	 * since we only set the default sample phase and drive phase later on.
174 	 * (2) the new coming rate is higher than the older one since mmc driver
175 	 * set the max-frequency to match the boards' ability but we can't go
176 	 * over the heads of that, otherwise the tests smoke out the issue.
177 	 */
178 	if (ndata->old_rate <= ndata->new_rate)
179 		return NOTIFY_DONE;
180 
181 	if (event == PRE_RATE_CHANGE)
182 		mmc_clock->cached_phase =
183 			rockchip_mmc_get_phase(&mmc_clock->hw);
184 	else if (mmc_clock->cached_phase != -EINVAL &&
185 		 event == POST_RATE_CHANGE)
186 		rockchip_mmc_set_phase(&mmc_clock->hw, mmc_clock->cached_phase);
187 
188 	return NOTIFY_DONE;
189 }
190 
191 struct clk *rockchip_clk_register_mmc(const char *name,
192 				const char *const *parent_names, u8 num_parents,
193 				void __iomem *reg, int shift)
194 {
195 	struct clk_init_data init;
196 	struct rockchip_mmc_clock *mmc_clock;
197 	struct clk *clk;
198 	int ret;
199 
200 	mmc_clock = kmalloc(sizeof(*mmc_clock), GFP_KERNEL);
201 	if (!mmc_clock)
202 		return ERR_PTR(-ENOMEM);
203 
204 	init.name = name;
205 	init.flags = 0;
206 	init.num_parents = num_parents;
207 	init.parent_names = parent_names;
208 	init.ops = &rockchip_mmc_clk_ops;
209 
210 	mmc_clock->hw.init = &init;
211 	mmc_clock->reg = reg;
212 	mmc_clock->shift = shift;
213 
214 	clk = clk_register(NULL, &mmc_clock->hw);
215 	if (IS_ERR(clk)) {
216 		ret = PTR_ERR(clk);
217 		goto err_register;
218 	}
219 
220 	mmc_clock->clk_rate_change_nb.notifier_call =
221 				&rockchip_mmc_clk_rate_notify;
222 	ret = clk_notifier_register(clk, &mmc_clock->clk_rate_change_nb);
223 	if (ret)
224 		goto err_notifier;
225 
226 	return clk;
227 err_notifier:
228 	clk_unregister(clk);
229 err_register:
230 	kfree(mmc_clock);
231 	return ERR_PTR(ret);
232 }
233