1/*
2 * drivers/cpufreq/spear-cpufreq.c
3 *
4 * CPU Frequency Scaling for SPEAr platform
5 *
6 * Copyright (C) 2012 ST Microelectronics
7 * Deepak Sikri <deepak.sikri@st.com>
8 *
9 * This file is licensed under the terms of the GNU General Public
10 * License version 2. This program is licensed "as is" without any
11 * warranty of any kind, whether express or implied.
12 */
13
14#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
15
16#include <linux/clk.h>
17#include <linux/cpufreq.h>
18#include <linux/err.h>
19#include <linux/init.h>
20#include <linux/module.h>
21#include <linux/of_device.h>
22#include <linux/platform_device.h>
23#include <linux/slab.h>
24#include <linux/types.h>
25
26/* SPEAr CPUFreq driver data structure */
27static struct {
28	struct clk *clk;
29	unsigned int transition_latency;
30	struct cpufreq_frequency_table *freq_tbl;
31	u32 cnt;
32} spear_cpufreq;
33
34static struct clk *spear1340_cpu_get_possible_parent(unsigned long newfreq)
35{
36	struct clk *sys_pclk;
37	int pclk;
38	/*
39	 * In SPEAr1340, cpu clk's parent sys clk can take input from
40	 * following sources
41	 */
42	const char *sys_clk_src[] = {
43		"sys_syn_clk",
44		"pll1_clk",
45		"pll2_clk",
46		"pll3_clk",
47	};
48
49	/*
50	 * As sys clk can have multiple source with their own range
51	 * limitation so we choose possible sources accordingly
52	 */
53	if (newfreq <= 300000000)
54		pclk = 0; /* src is sys_syn_clk */
55	else if (newfreq > 300000000 && newfreq <= 500000000)
56		pclk = 3; /* src is pll3_clk */
57	else if (newfreq == 600000000)
58		pclk = 1; /* src is pll1_clk */
59	else
60		return ERR_PTR(-EINVAL);
61
62	/* Get parent to sys clock */
63	sys_pclk = clk_get(NULL, sys_clk_src[pclk]);
64	if (IS_ERR(sys_pclk))
65		pr_err("Failed to get %s clock\n", sys_clk_src[pclk]);
66
67	return sys_pclk;
68}
69
70/*
71 * In SPEAr1340, we cannot use newfreq directly because we need to actually
72 * access a source clock (clk) which might not be ancestor of cpu at present.
73 * Hence in SPEAr1340 we would operate on source clock directly before switching
74 * cpu clock to it.
75 */
76static int spear1340_set_cpu_rate(struct clk *sys_pclk, unsigned long newfreq)
77{
78	struct clk *sys_clk;
79	int ret = 0;
80
81	sys_clk = clk_get_parent(spear_cpufreq.clk);
82	if (IS_ERR(sys_clk)) {
83		pr_err("failed to get cpu's parent (sys) clock\n");
84		return PTR_ERR(sys_clk);
85	}
86
87	/* Set the rate of the source clock before changing the parent */
88	ret = clk_set_rate(sys_pclk, newfreq);
89	if (ret) {
90		pr_err("Failed to set sys clk rate to %lu\n", newfreq);
91		return ret;
92	}
93
94	ret = clk_set_parent(sys_clk, sys_pclk);
95	if (ret) {
96		pr_err("Failed to set sys clk parent\n");
97		return ret;
98	}
99
100	return 0;
101}
102
103static int spear_cpufreq_target(struct cpufreq_policy *policy,
104		unsigned int index)
105{
106	long newfreq;
107	struct clk *srcclk;
108	int ret, mult = 1;
109
110	newfreq = spear_cpufreq.freq_tbl[index].frequency * 1000;
111
112	if (of_machine_is_compatible("st,spear1340")) {
113		/*
114		 * SPEAr1340 is special in the sense that due to the possibility
115		 * of multiple clock sources for cpu clk's parent we can have
116		 * different clock source for different frequency of cpu clk.
117		 * Hence we need to choose one from amongst these possible clock
118		 * sources.
119		 */
120		srcclk = spear1340_cpu_get_possible_parent(newfreq);
121		if (IS_ERR(srcclk)) {
122			pr_err("Failed to get src clk\n");
123			return PTR_ERR(srcclk);
124		}
125
126		/* SPEAr1340: src clk is always 2 * intended cpu clk */
127		mult = 2;
128	} else {
129		/*
130		 * src clock to be altered is ancestor of cpu clock. Hence we
131		 * can directly work on cpu clk
132		 */
133		srcclk = spear_cpufreq.clk;
134	}
135
136	newfreq = clk_round_rate(srcclk, newfreq * mult);
137	if (newfreq <= 0) {
138		pr_err("clk_round_rate failed for cpu src clock\n");
139		return newfreq;
140	}
141
142	if (mult == 2)
143		ret = spear1340_set_cpu_rate(srcclk, newfreq);
144	else
145		ret = clk_set_rate(spear_cpufreq.clk, newfreq);
146
147	if (ret)
148		pr_err("CPU Freq: cpu clk_set_rate failed: %d\n", ret);
149
150	return ret;
151}
152
153static int spear_cpufreq_init(struct cpufreq_policy *policy)
154{
155	policy->clk = spear_cpufreq.clk;
156	return cpufreq_generic_init(policy, spear_cpufreq.freq_tbl,
157			spear_cpufreq.transition_latency);
158}
159
160static struct cpufreq_driver spear_cpufreq_driver = {
161	.name		= "cpufreq-spear",
162	.flags		= CPUFREQ_STICKY | CPUFREQ_NEED_INITIAL_FREQ_CHECK,
163	.verify		= cpufreq_generic_frequency_table_verify,
164	.target_index	= spear_cpufreq_target,
165	.get		= cpufreq_generic_get,
166	.init		= spear_cpufreq_init,
167	.attr		= cpufreq_generic_attr,
168};
169
170static int spear_cpufreq_probe(struct platform_device *pdev)
171{
172	struct device_node *np;
173	const struct property *prop;
174	struct cpufreq_frequency_table *freq_tbl;
175	const __be32 *val;
176	int cnt, i, ret;
177
178	np = of_cpu_device_node_get(0);
179	if (!np) {
180		pr_err("No cpu node found");
181		return -ENODEV;
182	}
183
184	if (of_property_read_u32(np, "clock-latency",
185				&spear_cpufreq.transition_latency))
186		spear_cpufreq.transition_latency = CPUFREQ_ETERNAL;
187
188	prop = of_find_property(np, "cpufreq_tbl", NULL);
189	if (!prop || !prop->value) {
190		pr_err("Invalid cpufreq_tbl");
191		ret = -ENODEV;
192		goto out_put_node;
193	}
194
195	cnt = prop->length / sizeof(u32);
196	val = prop->value;
197
198	freq_tbl = kzalloc(sizeof(*freq_tbl) * (cnt + 1), GFP_KERNEL);
199	if (!freq_tbl) {
200		ret = -ENOMEM;
201		goto out_put_node;
202	}
203
204	for (i = 0; i < cnt; i++)
205		freq_tbl[i].frequency = be32_to_cpup(val++);
206
207	freq_tbl[i].frequency = CPUFREQ_TABLE_END;
208
209	spear_cpufreq.freq_tbl = freq_tbl;
210
211	of_node_put(np);
212
213	spear_cpufreq.clk = clk_get(NULL, "cpu_clk");
214	if (IS_ERR(spear_cpufreq.clk)) {
215		pr_err("Unable to get CPU clock\n");
216		ret = PTR_ERR(spear_cpufreq.clk);
217		goto out_put_mem;
218	}
219
220	ret = cpufreq_register_driver(&spear_cpufreq_driver);
221	if (!ret)
222		return 0;
223
224	pr_err("failed register driver: %d\n", ret);
225	clk_put(spear_cpufreq.clk);
226
227out_put_mem:
228	kfree(freq_tbl);
229	return ret;
230
231out_put_node:
232	of_node_put(np);
233	return ret;
234}
235
236static struct platform_driver spear_cpufreq_platdrv = {
237	.driver = {
238		.name	= "spear-cpufreq",
239	},
240	.probe		= spear_cpufreq_probe,
241};
242module_platform_driver(spear_cpufreq_platdrv);
243
244MODULE_AUTHOR("Deepak Sikri <deepak.sikri@st.com>");
245MODULE_DESCRIPTION("SPEAr CPUFreq driver");
246MODULE_LICENSE("GPL");
247