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/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         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  */
  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         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
 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");