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/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
  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         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  */
  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
 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
 153 static 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
 160 static 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
 170 static 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
 227 out_put_mem:
 228         kfree(freq_tbl);
 229         return ret;
 230
 231 out_put_node:
 232         of_node_put(np);
 233         return ret;
 234 }
 235
 236 static struct platform_driver spear_cpufreq_platdrv = {
 237         .driver = {
 238                 .name   = "spear-cpufreq",
 239         },
 240         .probe          = spear_cpufreq_probe,
 241 };
 242 module_platform_driver(spear_cpufreq_platdrv);
 243
 244 MODULE_AUTHOR("Deepak Sikri <deepak.sikri@st.com>");
 245 MODULE_DESCRIPTION("SPEAr CPUFreq driver");
 246 MODULE_LICENSE("GPL");