2 * drivers/cpufreq/spear-cpufreq.c
4 * CPU Frequency Scaling for SPEAr platform
6 * Copyright (C) 2012 ST Microelectronics
7 * Deepak Sikri <deepak.sikri@st.com>
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.
14 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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/slab.h>
23 #include <linux/types.h>
25 /* SPEAr CPUFreq driver data structure */
28 unsigned int transition_latency;
29 struct cpufreq_frequency_table *freq_tbl;
33 static unsigned int spear_cpufreq_get(unsigned int cpu)
35 return clk_get_rate(spear_cpufreq.clk) / 1000;
38 static struct clk *spear1340_cpu_get_possible_parent(unsigned long newfreq)
43 * In SPEAr1340, cpu clk's parent sys clk can take input from
46 const char *sys_clk_src[] = {
54 * As sys clk can have multiple source with their own range
55 * limitation so we choose possible sources accordingly
57 if (newfreq <= 300000000)
58 pclk = 0; /* src is sys_syn_clk */
59 else if (newfreq > 300000000 && newfreq <= 500000000)
60 pclk = 3; /* src is pll3_clk */
61 else if (newfreq == 600000000)
62 pclk = 1; /* src is pll1_clk */
64 return ERR_PTR(-EINVAL);
66 /* Get parent to sys clock */
67 sys_pclk = clk_get(NULL, sys_clk_src[pclk]);
69 pr_err("Failed to get %s clock\n", sys_clk_src[pclk]);
75 * In SPEAr1340, we cannot use newfreq directly because we need to actually
76 * access a source clock (clk) which might not be ancestor of cpu at present.
77 * Hence in SPEAr1340 we would operate on source clock directly before switching
80 static int spear1340_set_cpu_rate(struct clk *sys_pclk, unsigned long newfreq)
85 sys_clk = clk_get_parent(spear_cpufreq.clk);
86 if (IS_ERR(sys_clk)) {
87 pr_err("failed to get cpu's parent (sys) clock\n");
88 return PTR_ERR(sys_clk);
91 /* Set the rate of the source clock before changing the parent */
92 ret = clk_set_rate(sys_pclk, newfreq);
94 pr_err("Failed to set sys clk rate to %lu\n", newfreq);
98 ret = clk_set_parent(sys_clk, sys_pclk);
100 pr_err("Failed to set sys clk parent\n");
107 static int spear_cpufreq_target(struct cpufreq_policy *policy,
108 unsigned int target_freq, unsigned int relation)
110 struct cpufreq_freqs freqs;
113 int index, ret, mult = 1;
115 if (cpufreq_frequency_table_target(policy, spear_cpufreq.freq_tbl,
116 target_freq, relation, &index))
119 freqs.old = spear_cpufreq_get(0);
121 newfreq = spear_cpufreq.freq_tbl[index].frequency * 1000;
122 if (of_machine_is_compatible("st,spear1340")) {
124 * SPEAr1340 is special in the sense that due to the possibility
125 * of multiple clock sources for cpu clk's parent we can have
126 * different clock source for different frequency of cpu clk.
127 * Hence we need to choose one from amongst these possible clock
130 srcclk = spear1340_cpu_get_possible_parent(newfreq);
131 if (IS_ERR(srcclk)) {
132 pr_err("Failed to get src clk\n");
133 return PTR_ERR(srcclk);
136 /* SPEAr1340: src clk is always 2 * intended cpu clk */
140 * src clock to be altered is ancestor of cpu clock. Hence we
141 * can directly work on cpu clk
143 srcclk = spear_cpufreq.clk;
146 newfreq = clk_round_rate(srcclk, newfreq * mult);
148 pr_err("clk_round_rate failed for cpu src clock\n");
152 freqs.new = newfreq / 1000;
155 cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE);
158 ret = spear1340_set_cpu_rate(srcclk, newfreq);
160 ret = clk_set_rate(spear_cpufreq.clk, newfreq);
162 /* Get current rate after clk_set_rate, in case of failure */
164 pr_err("CPU Freq: cpu clk_set_rate failed: %d\n", ret);
165 freqs.new = clk_get_rate(spear_cpufreq.clk) / 1000;
168 cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE);
172 static int spear_cpufreq_init(struct cpufreq_policy *policy)
174 return cpufreq_generic_init(policy, spear_cpufreq.freq_tbl,
175 spear_cpufreq.transition_latency);
178 static struct cpufreq_driver spear_cpufreq_driver = {
179 .name = "cpufreq-spear",
180 .flags = CPUFREQ_STICKY,
181 .verify = cpufreq_generic_frequency_table_verify,
182 .target = spear_cpufreq_target,
183 .get = spear_cpufreq_get,
184 .init = spear_cpufreq_init,
185 .exit = cpufreq_generic_exit,
186 .attr = cpufreq_generic_attr,
189 static int spear_cpufreq_driver_init(void)
191 struct device_node *np;
192 const struct property *prop;
193 struct cpufreq_frequency_table *freq_tbl;
197 np = of_cpu_device_node_get(0);
199 pr_err("No cpu node found");
203 if (of_property_read_u32(np, "clock-latency",
204 &spear_cpufreq.transition_latency))
205 spear_cpufreq.transition_latency = CPUFREQ_ETERNAL;
207 prop = of_find_property(np, "cpufreq_tbl", NULL);
208 if (!prop || !prop->value) {
209 pr_err("Invalid cpufreq_tbl");
214 cnt = prop->length / sizeof(u32);
217 freq_tbl = kmalloc(sizeof(*freq_tbl) * (cnt + 1), GFP_KERNEL);
223 for (i = 0; i < cnt; i++) {
224 freq_tbl[i].driver_data = i;
225 freq_tbl[i].frequency = be32_to_cpup(val++);
228 freq_tbl[i].driver_data = i;
229 freq_tbl[i].frequency = CPUFREQ_TABLE_END;
231 spear_cpufreq.freq_tbl = freq_tbl;
235 spear_cpufreq.clk = clk_get(NULL, "cpu_clk");
236 if (IS_ERR(spear_cpufreq.clk)) {
237 pr_err("Unable to get CPU clock\n");
238 ret = PTR_ERR(spear_cpufreq.clk);
242 ret = cpufreq_register_driver(&spear_cpufreq_driver);
246 pr_err("failed register driver: %d\n", ret);
247 clk_put(spear_cpufreq.clk);
257 late_initcall(spear_cpufreq_driver_init);
259 MODULE_AUTHOR("Deepak Sikri <deepak.sikri@st.com>");
260 MODULE_DESCRIPTION("SPEAr CPUFreq driver");
261 MODULE_LICENSE("GPL");