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.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 int spear_cpufreq_verify(struct cpufreq_policy *policy)
  34 {
  35         return cpufreq_frequency_table_verify(policy, spear_cpufreq.freq_tbl);
  36 }
  37
  38 static unsigned int spear_cpufreq_get(unsigned int cpu)
  39 {
  40         return clk_get_rate(spear_cpufreq.clk) / 1000;
  41 }
  42
  43 static struct clk *spear1340_cpu_get_possible_parent(unsigned long newfreq)
  44 {
  45         struct clk *sys_pclk;
  46         int pclk;
  47         /*
  48          * In SPEAr1340, cpu clk's parent sys clk can take input from
  49          * following sources
  50          */
  51         const char *sys_clk_src[] = {
  52                 "sys_syn_clk",
  53                 "pll1_clk",
  54                 "pll2_clk",
  55                 "pll3_clk",
  56         };
  57
  58         /*
  59          * As sys clk can have multiple source with their own range
  60          * limitation so we choose possible sources accordingly
  61          */
  62         if (newfreq <= 300000000)
  63                 pclk = 0; /* src is sys_syn_clk */
  64         else if (newfreq > 300000000 && newfreq <= 500000000)
  65                 pclk = 3; /* src is pll3_clk */
  66         else if (newfreq == 600000000)
  67                 pclk = 1; /* src is pll1_clk */
  68         else
  69                 return ERR_PTR(-EINVAL);
  70
  71         /* Get parent to sys clock */
  72         sys_pclk = clk_get(NULL, sys_clk_src[pclk]);
  73         if (IS_ERR(sys_pclk))
  74                 pr_err("Failed to get %s clock\n", sys_clk_src[pclk]);
  75
  76         return sys_pclk;
  77 }
  78
  79 /*
  80  * In SPEAr1340, we cannot use newfreq directly because we need to actually
  81  * access a source clock (clk) which might not be ancestor of cpu at present.
  82  * Hence in SPEAr1340 we would operate on source clock directly before switching
  83  * cpu clock to it.
  84  */
  85 static int spear1340_set_cpu_rate(struct clk *sys_pclk, unsigned long newfreq)
  86 {
  87         struct clk *sys_clk;
  88         int ret = 0;
  89
  90         sys_clk = clk_get_parent(spear_cpufreq.clk);
  91         if (IS_ERR(sys_clk)) {
  92                 pr_err("failed to get cpu's parent (sys) clock\n");
  93                 return PTR_ERR(sys_clk);
  94         }
  95
  96         /* Set the rate of the source clock before changing the parent */
  97         ret = clk_set_rate(sys_pclk, newfreq);
  98         if (ret) {
  99                 pr_err("Failed to set sys clk rate to %lu\n", newfreq);
 100                 return ret;
 101         }
 102
 103         ret = clk_set_parent(sys_clk, sys_pclk);
 104         if (ret) {
 105                 pr_err("Failed to set sys clk parent\n");
 106                 return ret;
 107         }
 108
 109         return 0;
 110 }
 111
 112 static int spear_cpufreq_target(struct cpufreq_policy *policy,
 113                 unsigned int target_freq, unsigned int relation)
 114 {
 115         struct cpufreq_freqs freqs;
 116         unsigned long newfreq;
 117         struct clk *srcclk;
 118         int index, ret, mult = 1;
 119
 120         if (cpufreq_frequency_table_target(policy, spear_cpufreq.freq_tbl,
 121                                 target_freq, relation, &index))
 122                 return -EINVAL;
 123
 124         freqs.old = spear_cpufreq_get(0);
 125
 126         newfreq = spear_cpufreq.freq_tbl[index].frequency * 1000;
 127         if (of_machine_is_compatible("st,spear1340")) {
 128                 /*
 129                  * SPEAr1340 is special in the sense that due to the possibility
 130                  * of multiple clock sources for cpu clk's parent we can have
 131                  * different clock source for different frequency of cpu clk.
 132                  * Hence we need to choose one from amongst these possible clock
 133                  * sources.
 134                  */
 135                 srcclk = spear1340_cpu_get_possible_parent(newfreq);
 136                 if (IS_ERR(srcclk)) {
 137                         pr_err("Failed to get src clk\n");
 138                         return PTR_ERR(srcclk);
 139                 }
 140
 141                 /* SPEAr1340: src clk is always 2 * intended cpu clk */
 142                 mult = 2;
 143         } else {
 144                 /*
 145                  * src clock to be altered is ancestor of cpu clock. Hence we
 146                  * can directly work on cpu clk
 147                  */
 148                 srcclk = spear_cpufreq.clk;
 149         }
 150
 151         newfreq = clk_round_rate(srcclk, newfreq * mult);
 152         if (newfreq < 0) {
 153                 pr_err("clk_round_rate failed for cpu src clock\n");
 154                 return newfreq;
 155         }
 156
 157         freqs.new = newfreq / 1000;
 158         freqs.new /= mult;
 159
 160         cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE);
 161
 162         if (mult == 2)
 163                 ret = spear1340_set_cpu_rate(srcclk, newfreq);
 164         else
 165                 ret = clk_set_rate(spear_cpufreq.clk, newfreq);
 166
 167         /* Get current rate after clk_set_rate, in case of failure */
 168         if (ret) {
 169                 pr_err("CPU Freq: cpu clk_set_rate failed: %d\n", ret);
 170                 freqs.new = clk_get_rate(spear_cpufreq.clk) / 1000;
 171         }
 172
 173         cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE);
 174         return ret;
 175 }
 176
 177 static int spear_cpufreq_init(struct cpufreq_policy *policy)
 178 {
 179         int ret;
 180
 181         ret = cpufreq_frequency_table_cpuinfo(policy, spear_cpufreq.freq_tbl);
 182         if (ret) {
 183                 pr_err("cpufreq_frequency_table_cpuinfo() failed");
 184                 return ret;
 185         }
 186
 187         cpufreq_frequency_table_get_attr(spear_cpufreq.freq_tbl, policy->cpu);
 188         policy->cpuinfo.transition_latency = spear_cpufreq.transition_latency;
 189         policy->cur = spear_cpufreq_get(0);
 190
 191         cpumask_setall(policy->cpus);
 192
 193         return 0;
 194 }
 195
 196 static int spear_cpufreq_exit(struct cpufreq_policy *policy)
 197 {
 198         cpufreq_frequency_table_put_attr(policy->cpu);
 199         return 0;
 200 }
 201
 202 static struct freq_attr *spear_cpufreq_attr[] = {
 203          &cpufreq_freq_attr_scaling_available_freqs,
 204          NULL,
 205 };
 206
 207 static struct cpufreq_driver spear_cpufreq_driver = {
 208         .name           = "cpufreq-spear",
 209         .flags          = CPUFREQ_STICKY,
 210         .verify         = spear_cpufreq_verify,
 211         .target         = spear_cpufreq_target,
 212         .get            = spear_cpufreq_get,
 213         .init           = spear_cpufreq_init,
 214         .exit           = spear_cpufreq_exit,
 215         .attr           = spear_cpufreq_attr,
 216 };
 217
 218 static int spear_cpufreq_driver_init(void)
 219 {
 220         struct device_node *np;
 221         const struct property *prop;
 222         struct cpufreq_frequency_table *freq_tbl;
 223         const __be32 *val;
 224         int cnt, i, ret;
 225
 226         np = of_find_node_by_path("/cpus/cpu@0");
 227         if (!np) {
 228                 pr_err("No cpu node found");
 229                 return -ENODEV;
 230         }
 231
 232         if (of_property_read_u32(np, "clock-latency",
 233                                 &spear_cpufreq.transition_latency))
 234                 spear_cpufreq.transition_latency = CPUFREQ_ETERNAL;
 235
 236         prop = of_find_property(np, "cpufreq_tbl", NULL);
 237         if (!prop || !prop->value) {
 238                 pr_err("Invalid cpufreq_tbl");
 239                 ret = -ENODEV;
 240                 goto out_put_node;
 241         }
 242
 243         cnt = prop->length / sizeof(u32);
 244         val = prop->value;
 245
 246         freq_tbl = kmalloc(sizeof(*freq_tbl) * (cnt + 1), GFP_KERNEL);
 247         if (!freq_tbl) {
 248                 ret = -ENOMEM;
 249                 goto out_put_node;
 250         }
 251
 252         for (i = 0; i < cnt; i++) {
 253                 freq_tbl[i].index = i;
 254                 freq_tbl[i].frequency = be32_to_cpup(val++);
 255         }
 256
 257         freq_tbl[i].index = i;
 258         freq_tbl[i].frequency = CPUFREQ_TABLE_END;
 259
 260         spear_cpufreq.freq_tbl = freq_tbl;
 261
 262         of_node_put(np);
 263
 264         spear_cpufreq.clk = clk_get(NULL, "cpu_clk");
 265         if (IS_ERR(spear_cpufreq.clk)) {
 266                 pr_err("Unable to get CPU clock\n");
 267                 ret = PTR_ERR(spear_cpufreq.clk);
 268                 goto out_put_mem;
 269         }
 270
 271         ret = cpufreq_register_driver(&spear_cpufreq_driver);
 272         if (!ret)
 273                 return 0;
 274
 275         pr_err("failed register driver: %d\n", ret);
 276         clk_put(spear_cpufreq.clk);
 277
 278 out_put_mem:
 279         kfree(freq_tbl);
 280         return ret;
 281
 282 out_put_node:
 283         of_node_put(np);
 284         return ret;
 285 }
 286 late_initcall(spear_cpufreq_driver_init);
 287
 288 MODULE_AUTHOR("Deepak Sikri <deepak.sikri@st.com>");
 289 MODULE_DESCRIPTION("SPEAr CPUFreq driver");
 290 MODULE_LICENSE("GPL");