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.h>
22 #include <linux/platform_device.h>
23 #include <linux/slab.h>
24 #include <linux/types.h>
25 
26 /* SPEAr CPUFreq driver data structure */
27 static struct {
28 	struct clk *clk;
29 	unsigned int transition_latency;
30 	struct cpufreq_frequency_table *freq_tbl;
31 	u32 cnt;
32 } spear_cpufreq;
33 
spear1340_cpu_get_possible_parent(unsigned long newfreq)34 static 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 	static const char * const 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  */
spear1340_set_cpu_rate(struct clk * sys_pclk,unsigned long newfreq)76 static 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 
spear_cpufreq_target(struct cpufreq_policy * policy,unsigned int index)103 static 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 
spear_cpufreq_init(struct cpufreq_policy * policy)153 static int spear_cpufreq_init(struct cpufreq_policy *policy)
154 {
155 	policy->clk = spear_cpufreq.clk;
156 	cpufreq_generic_init(policy, spear_cpufreq.freq_tbl,
157 			spear_cpufreq.transition_latency);
158 	return 0;
159 }
160 
161 static struct cpufreq_driver spear_cpufreq_driver = {
162 	.name		= "cpufreq-spear",
163 	.flags		= CPUFREQ_NEED_INITIAL_FREQ_CHECK,
164 	.verify		= cpufreq_generic_frequency_table_verify,
165 	.target_index	= spear_cpufreq_target,
166 	.get		= cpufreq_generic_get,
167 	.init		= spear_cpufreq_init,
168 	.attr		= cpufreq_generic_attr,
169 };
170 
spear_cpufreq_probe(struct platform_device * pdev)171 static int spear_cpufreq_probe(struct platform_device *pdev)
172 {
173 	struct device_node *np;
174 	const struct property *prop;
175 	struct cpufreq_frequency_table *freq_tbl;
176 	const __be32 *val;
177 	int cnt, i, ret;
178 
179 	np = of_cpu_device_node_get(0);
180 	if (!np) {
181 		pr_err("No cpu node found\n");
182 		return -ENODEV;
183 	}
184 
185 	if (of_property_read_u32(np, "clock-latency",
186 				&spear_cpufreq.transition_latency))
187 		spear_cpufreq.transition_latency = CPUFREQ_ETERNAL;
188 
189 	prop = of_find_property(np, "cpufreq_tbl", NULL);
190 	if (!prop || !prop->value) {
191 		pr_err("Invalid cpufreq_tbl\n");
192 		ret = -ENODEV;
193 		goto out_put_node;
194 	}
195 
196 	cnt = prop->length / sizeof(u32);
197 	val = prop->value;
198 
199 	freq_tbl = kcalloc(cnt + 1, sizeof(*freq_tbl), GFP_KERNEL);
200 	if (!freq_tbl) {
201 		ret = -ENOMEM;
202 		goto out_put_node;
203 	}
204 
205 	for (i = 0; i < cnt; i++)
206 		freq_tbl[i].frequency = be32_to_cpup(val++);
207 
208 	freq_tbl[i].frequency = CPUFREQ_TABLE_END;
209 
210 	spear_cpufreq.freq_tbl = freq_tbl;
211 
212 	of_node_put(np);
213 
214 	spear_cpufreq.clk = clk_get(NULL, "cpu_clk");
215 	if (IS_ERR(spear_cpufreq.clk)) {
216 		pr_err("Unable to get CPU clock\n");
217 		ret = PTR_ERR(spear_cpufreq.clk);
218 		goto out_put_mem;
219 	}
220 
221 	ret = cpufreq_register_driver(&spear_cpufreq_driver);
222 	if (!ret)
223 		return 0;
224 
225 	pr_err("failed register driver: %d\n", ret);
226 	clk_put(spear_cpufreq.clk);
227 
228 out_put_mem:
229 	kfree(freq_tbl);
230 	return ret;
231 
232 out_put_node:
233 	of_node_put(np);
234 	return ret;
235 }
236 
237 static struct platform_driver spear_cpufreq_platdrv = {
238 	.driver = {
239 		.name	= "spear-cpufreq",
240 	},
241 	.probe		= spear_cpufreq_probe,
242 };
243 module_platform_driver(spear_cpufreq_platdrv);
244 
245 MODULE_AUTHOR("Deepak Sikri <deepak.sikri@st.com>");
246 MODULE_DESCRIPTION("SPEAr CPUFreq driver");
247 MODULE_LICENSE("GPL");
248