Root/drivers/clk/clk-divider.c

1/*
2 * Copyright (C) 2011 Sascha Hauer, Pengutronix <s.hauer@pengutronix.de>
3 * Copyright (C) 2011 Richard Zhao, Linaro <richard.zhao@linaro.org>
4 * Copyright (C) 2011-2012 Mike Turquette, Linaro Ltd <mturquette@linaro.org>
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 *
10 * Adjustable divider clock implementation
11 */
12
13#include <linux/clk-provider.h>
14#include <linux/module.h>
15#include <linux/slab.h>
16#include <linux/io.h>
17#include <linux/err.h>
18#include <linux/string.h>
19
20/*
21 * DOC: basic adjustable divider clock that cannot gate
22 *
23 * Traits of this clock:
24 * prepare - clk_prepare only ensures that parents are prepared
25 * enable - clk_enable only ensures that parents are enabled
26 * rate - rate is adjustable. clk->rate = parent->rate / divisor
27 * parent - fixed parent. No clk_set_parent support
28 */
29
30#define to_clk_divider(_hw) container_of(_hw, struct clk_divider, hw)
31
32#define div_mask(d) ((1 << (d->width)) - 1)
33#define is_power_of_two(i) !(i & ~i)
34
35static unsigned int _get_table_maxdiv(const struct clk_div_table *table)
36{
37    unsigned int maxdiv = 0;
38    const struct clk_div_table *clkt;
39
40    for (clkt = table; clkt->div; clkt++)
41        if (clkt->div > maxdiv)
42            maxdiv = clkt->div;
43    return maxdiv;
44}
45
46static unsigned int _get_maxdiv(struct clk_divider *divider)
47{
48    if (divider->flags & CLK_DIVIDER_ONE_BASED)
49        return div_mask(divider);
50    if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
51        return 1 << div_mask(divider);
52    if (divider->table)
53        return _get_table_maxdiv(divider->table);
54    return div_mask(divider) + 1;
55}
56
57static unsigned int _get_table_div(const struct clk_div_table *table,
58                            unsigned int val)
59{
60    const struct clk_div_table *clkt;
61
62    for (clkt = table; clkt->div; clkt++)
63        if (clkt->val == val)
64            return clkt->div;
65    return 0;
66}
67
68static unsigned int _get_div(struct clk_divider *divider, unsigned int val)
69{
70    if (divider->flags & CLK_DIVIDER_ONE_BASED)
71        return val;
72    if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
73        return 1 << val;
74    if (divider->table)
75        return _get_table_div(divider->table, val);
76    return val + 1;
77}
78
79static unsigned int _get_table_val(const struct clk_div_table *table,
80                            unsigned int div)
81{
82    const struct clk_div_table *clkt;
83
84    for (clkt = table; clkt->div; clkt++)
85        if (clkt->div == div)
86            return clkt->val;
87    return 0;
88}
89
90static unsigned int _get_val(struct clk_divider *divider, u8 div)
91{
92    if (divider->flags & CLK_DIVIDER_ONE_BASED)
93        return div;
94    if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
95        return __ffs(div);
96    if (divider->table)
97        return _get_table_val(divider->table, div);
98    return div - 1;
99}
100
101static unsigned long clk_divider_recalc_rate(struct clk_hw *hw,
102        unsigned long parent_rate)
103{
104    struct clk_divider *divider = to_clk_divider(hw);
105    unsigned int div, val;
106
107    val = readl(divider->reg) >> divider->shift;
108    val &= div_mask(divider);
109
110    div = _get_div(divider, val);
111    if (!div) {
112        WARN(1, "%s: Invalid divisor for clock %s\n", __func__,
113                        __clk_get_name(hw->clk));
114        return parent_rate;
115    }
116
117    return parent_rate / div;
118}
119
120/*
121 * The reverse of DIV_ROUND_UP: The maximum number which
122 * divided by m is r
123 */
124#define MULT_ROUND_UP(r, m) ((r) * (m) + (m) - 1)
125
126static bool _is_valid_table_div(const struct clk_div_table *table,
127                             unsigned int div)
128{
129    const struct clk_div_table *clkt;
130
131    for (clkt = table; clkt->div; clkt++)
132        if (clkt->div == div)
133            return true;
134    return false;
135}
136
137static bool _is_valid_div(struct clk_divider *divider, unsigned int div)
138{
139    if (divider->flags & CLK_DIVIDER_POWER_OF_TWO)
140        return is_power_of_two(div);
141    if (divider->table)
142        return _is_valid_table_div(divider->table, div);
143    return true;
144}
145
146static int clk_divider_bestdiv(struct clk_hw *hw, unsigned long rate,
147        unsigned long *best_parent_rate)
148{
149    struct clk_divider *divider = to_clk_divider(hw);
150    int i, bestdiv = 0;
151    unsigned long parent_rate, best = 0, now, maxdiv;
152
153    if (!rate)
154        rate = 1;
155
156    maxdiv = _get_maxdiv(divider);
157
158    if (!(__clk_get_flags(hw->clk) & CLK_SET_RATE_PARENT)) {
159        parent_rate = *best_parent_rate;
160        bestdiv = DIV_ROUND_UP(parent_rate, rate);
161        bestdiv = bestdiv == 0 ? 1 : bestdiv;
162        bestdiv = bestdiv > maxdiv ? maxdiv : bestdiv;
163        return bestdiv;
164    }
165
166    /*
167     * The maximum divider we can use without overflowing
168     * unsigned long in rate * i below
169     */
170    maxdiv = min(ULONG_MAX / rate, maxdiv);
171
172    for (i = 1; i <= maxdiv; i++) {
173        if (!_is_valid_div(divider, i))
174            continue;
175        parent_rate = __clk_round_rate(__clk_get_parent(hw->clk),
176                MULT_ROUND_UP(rate, i));
177        now = parent_rate / i;
178        if (now <= rate && now > best) {
179            bestdiv = i;
180            best = now;
181            *best_parent_rate = parent_rate;
182        }
183    }
184
185    if (!bestdiv) {
186        bestdiv = _get_maxdiv(divider);
187        *best_parent_rate = __clk_round_rate(__clk_get_parent(hw->clk), 1);
188    }
189
190    return bestdiv;
191}
192
193static long clk_divider_round_rate(struct clk_hw *hw, unsigned long rate,
194                unsigned long *prate)
195{
196    int div;
197    div = clk_divider_bestdiv(hw, rate, prate);
198
199    return *prate / div;
200}
201
202static int clk_divider_set_rate(struct clk_hw *hw, unsigned long rate,
203                unsigned long parent_rate)
204{
205    struct clk_divider *divider = to_clk_divider(hw);
206    unsigned int div, value;
207    unsigned long flags = 0;
208    u32 val;
209
210    div = parent_rate / rate;
211    value = _get_val(divider, div);
212
213    if (value > div_mask(divider))
214        value = div_mask(divider);
215
216    if (divider->lock)
217        spin_lock_irqsave(divider->lock, flags);
218
219    val = readl(divider->reg);
220    val &= ~(div_mask(divider) << divider->shift);
221    val |= value << divider->shift;
222    writel(val, divider->reg);
223
224    if (divider->lock)
225        spin_unlock_irqrestore(divider->lock, flags);
226
227    return 0;
228}
229
230const struct clk_ops clk_divider_ops = {
231    .recalc_rate = clk_divider_recalc_rate,
232    .round_rate = clk_divider_round_rate,
233    .set_rate = clk_divider_set_rate,
234};
235EXPORT_SYMBOL_GPL(clk_divider_ops);
236
237static struct clk *_register_divider(struct device *dev, const char *name,
238        const char *parent_name, unsigned long flags,
239        void __iomem *reg, u8 shift, u8 width,
240        u8 clk_divider_flags, const struct clk_div_table *table,
241        spinlock_t *lock)
242{
243    struct clk_divider *div;
244    struct clk *clk;
245    struct clk_init_data init;
246
247    /* allocate the divider */
248    div = kzalloc(sizeof(struct clk_divider), GFP_KERNEL);
249    if (!div) {
250        pr_err("%s: could not allocate divider clk\n", __func__);
251        return ERR_PTR(-ENOMEM);
252    }
253
254    init.name = name;
255    init.ops = &clk_divider_ops;
256    init.flags = flags | CLK_IS_BASIC;
257    init.parent_names = (parent_name ? &parent_name: NULL);
258    init.num_parents = (parent_name ? 1 : 0);
259
260    /* struct clk_divider assignments */
261    div->reg = reg;
262    div->shift = shift;
263    div->width = width;
264    div->flags = clk_divider_flags;
265    div->lock = lock;
266    div->hw.init = &init;
267    div->table = table;
268
269    /* register the clock */
270    clk = clk_register(dev, &div->hw);
271
272    if (IS_ERR(clk))
273        kfree(div);
274
275    return clk;
276}
277
278/**
279 * clk_register_divider - register a divider clock with the clock framework
280 * @dev: device registering this clock
281 * @name: name of this clock
282 * @parent_name: name of clock's parent
283 * @flags: framework-specific flags
284 * @reg: register address to adjust divider
285 * @shift: number of bits to shift the bitfield
286 * @width: width of the bitfield
287 * @clk_divider_flags: divider-specific flags for this clock
288 * @lock: shared register lock for this clock
289 */
290struct clk *clk_register_divider(struct device *dev, const char *name,
291        const char *parent_name, unsigned long flags,
292        void __iomem *reg, u8 shift, u8 width,
293        u8 clk_divider_flags, spinlock_t *lock)
294{
295    return _register_divider(dev, name, parent_name, flags, reg, shift,
296            width, clk_divider_flags, NULL, lock);
297}
298
299/**
300 * clk_register_divider_table - register a table based divider clock with
301 * the clock framework
302 * @dev: device registering this clock
303 * @name: name of this clock
304 * @parent_name: name of clock's parent
305 * @flags: framework-specific flags
306 * @reg: register address to adjust divider
307 * @shift: number of bits to shift the bitfield
308 * @width: width of the bitfield
309 * @clk_divider_flags: divider-specific flags for this clock
310 * @table: array of divider/value pairs ending with a div set to 0
311 * @lock: shared register lock for this clock
312 */
313struct clk *clk_register_divider_table(struct device *dev, const char *name,
314        const char *parent_name, unsigned long flags,
315        void __iomem *reg, u8 shift, u8 width,
316        u8 clk_divider_flags, const struct clk_div_table *table,
317        spinlock_t *lock)
318{
319    return _register_divider(dev, name, parent_name, flags, reg, shift,
320            width, clk_divider_flags, table, lock);
321}
322

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