drivers/cpufreq/spear-cpufreq.c

   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/slab.h>
  23 #include <linux/types.h>
  24
  25 /* SPEAr CPUFreq driver data structure */
  26 static struct {
  27         struct clk *clk;
  28         unsigned int transition_latency;
  29         struct cpufreq_frequency_table *freq_tbl;
  30         u32 cnt;
  31 } spear_cpufreq;
  32
  33 static struct clk *spear1340_cpu_get_possible_parent(unsigned long newfreq)
  34 {
  35         struct clk *sys_pclk;
  36         int pclk;
  37         /*
  38          * In SPEAr1340, cpu clk's parent sys clk can take input from
  39          * following sources
  40          */
  41         const char *sys_clk_src[] = {
  42                 "sys_syn_clk",
  43                 "pll1_clk",
  44                 "pll2_clk",
  45                 "pll3_clk",
  46         };
  47
  48         /*
  49          * As sys clk can have multiple source with their own range
  50          * limitation so we choose possible sources accordingly
  51          */
  52         if (newfreq <= 300000000)
  53                 pclk = 0; /* src is sys_syn_clk */
  54         else if (newfreq > 300000000 && newfreq <= 500000000)
  55                 pclk = 3; /* src is pll3_clk */
  56         else if (newfreq == 600000000)
  57                 pclk = 1; /* src is pll1_clk */
  58         else
  59                 return ERR_PTR(-EINVAL);
  60
  61         /* Get parent to sys clock */
  62         sys_pclk = clk_get(NULL, sys_clk_src[pclk]);
  63         if (IS_ERR(sys_pclk))
  64                 pr_err("Failed to get %s clock\n", sys_clk_src[pclk]);
  65
  66         return sys_pclk;
  67 }
  68
  69 /*
  70  * In SPEAr1340, we cannot use newfreq directly because we need to actually
  71  * access a source clock (clk) which might not be ancestor of cpu at present.
  72  * Hence in SPEAr1340 we would operate on source clock directly before switching
  73  * cpu clock to it.
  74  */
  75 static int spear1340_set_cpu_rate(struct clk *sys_pclk, unsigned long newfreq)
  76 {
  77         struct clk *sys_clk;
  78         int ret = 0;
  79
  80         sys_clk = clk_get_parent(spear_cpufreq.clk);
  81         if (IS_ERR(sys_clk)) {
  82                 pr_err("failed to get cpu's parent (sys) clock\n");
  83                 return PTR_ERR(sys_clk);
  84         }
  85
  86         /* Set the rate of the source clock before changing the parent */
  87         ret = clk_set_rate(sys_pclk, newfreq);
  88         if (ret) {
  89                 pr_err("Failed to set sys clk rate to %lu\n", newfreq);
  90                 return ret;
  91         }
  92
  93         ret = clk_set_parent(sys_clk, sys_pclk);
  94         if (ret) {
  95                 pr_err("Failed to set sys clk parent\n");
  96                 return ret;
  97         }
  98
  99         return 0;
 100 }
 101
 102 static int spear_cpufreq_target(struct cpufreq_policy *policy,
 103                 unsigned int index)
 104 {
 105         long newfreq;
 106         struct clk *srcclk;
 107         int ret, mult = 1;
 108
 109         newfreq = spear_cpufreq.freq_tbl[index].frequency * 1000;
 110
 111         if (of_machine_is_compatible("st,spear1340")) {
 112                 /*
 113                  * SPEAr1340 is special in the sense that due to the possibility
 114                  * of multiple clock sources for cpu clk's parent we can have
 115                  * different clock source for different frequency of cpu clk.
 116                  * Hence we need to choose one from amongst these possible clock
 117                  * sources.
 118                  */
 119                 srcclk = spear1340_cpu_get_possible_parent(newfreq);
 120                 if (IS_ERR(srcclk)) {
 121                         pr_err("Failed to get src clk\n");
 122                         return PTR_ERR(srcclk);
 123                 }
 124
 125                 /* SPEAr1340: src clk is always 2 * intended cpu clk */
 126                 mult = 2;
 127         } else {
 128                 /*
 129                  * src clock to be altered is ancestor of cpu clock. Hence we
 130                  * can directly work on cpu clk
 131                  */
 132                 srcclk = spear_cpufreq.clk;
 133         }
 134
 135         newfreq = clk_round_rate(srcclk, newfreq * mult);
 136         if (newfreq <= 0) {
 137                 pr_err("clk_round_rate failed for cpu src clock\n");
 138                 return newfreq;
 139         }
 140
 141         if (mult == 2)
 142                 ret = spear1340_set_cpu_rate(srcclk, newfreq);
 143         else
 144                 ret = clk_set_rate(spear_cpufreq.clk, newfreq);
 145
 146         if (ret)
 147                 pr_err("CPU Freq: cpu clk_set_rate failed: %d\n", ret);
 148
 149         return ret;
 150 }
 151
 152 static int spear_cpufreq_init(struct cpufreq_policy *policy)
 153 {
 154         policy->clk = spear_cpufreq.clk;
 155         return cpufreq_generic_init(policy, spear_cpufreq.freq_tbl,
 156                         spear_cpufreq.transition_latency);
 157 }
 158
 159 static struct cpufreq_driver spear_cpufreq_driver = {
 160         .name           = "cpufreq-spear",
 161         .flags          = CPUFREQ_STICKY | CPUFREQ_NEED_INITIAL_FREQ_CHECK,
 162         .verify         = cpufreq_generic_frequency_table_verify,
 163         .target_index   = spear_cpufreq_target,
 164         .get            = cpufreq_generic_get,
 165         .init           = spear_cpufreq_init,
 166         .exit           = cpufreq_generic_exit,
 167         .attr           = cpufreq_generic_attr,
 168 };
 169
 170 static int spear_cpufreq_driver_init(void)
 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 = kmalloc(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].driver_data = i;
 206                 freq_tbl[i].frequency = be32_to_cpup(val++);
 207         }
 208
 209         freq_tbl[i].driver_data = i;
 210         freq_tbl[i].frequency = CPUFREQ_TABLE_END;
 211
 212         spear_cpufreq.freq_tbl = freq_tbl;
 213
 214         of_node_put(np);
 215
 216         spear_cpufreq.clk = clk_get(NULL, "cpu_clk");
 217         if (IS_ERR(spear_cpufreq.clk)) {
 218                 pr_err("Unable to get CPU clock\n");
 219                 ret = PTR_ERR(spear_cpufreq.clk);
 220                 goto out_put_mem;
 221         }
 222
 223         ret = cpufreq_register_driver(&spear_cpufreq_driver);
 224         if (!ret)
 225                 return 0;
 226
 227         pr_err("failed register driver: %d\n", ret);
 228         clk_put(spear_cpufreq.clk);
 229
 230 out_put_mem:
 231         kfree(freq_tbl);
 232         return ret;
 233
 234 out_put_node:
 235         of_node_put(np);
 236         return ret;
 237 }
 238 late_initcall(spear_cpufreq_driver_init);
 239
 240 MODULE_AUTHOR("Deepak Sikri <deepak.sikri@st.com>");
 241 MODULE_DESCRIPTION("SPEAr CPUFreq driver");
 242 MODULE_LICENSE("GPL");