linux/drivers/cpufreq/spear-cpufreq.c
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   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 */
  26static struct {
  27        struct clk *clk;
  28        unsigned int transition_latency;
  29        struct cpufreq_frequency_table *freq_tbl;
  30        u32 cnt;
  31} spear_cpufreq;
  32
  33static int spear_cpufreq_verify(struct cpufreq_policy *policy)
  34{
  35        return cpufreq_frequency_table_verify(policy, spear_cpufreq.freq_tbl);
  36}
  37
  38static unsigned int spear_cpufreq_get(unsigned int cpu)
  39{
  40        return clk_get_rate(spear_cpufreq.clk) / 1000;
  41}
  42
  43static 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 */
  85static 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
 112static 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
 177static 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
 196static int spear_cpufreq_exit(struct cpufreq_policy *policy)
 197{
 198        cpufreq_frequency_table_put_attr(policy->cpu);
 199        return 0;
 200}
 201
 202static struct freq_attr *spear_cpufreq_attr[] = {
 203         &cpufreq_freq_attr_scaling_available_freqs,
 204         NULL,
 205};
 206
 207static 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
 218static 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].driver_data = i;
 254                freq_tbl[i].frequency = be32_to_cpup(val++);
 255        }
 256
 257        freq_tbl[i].driver_data = 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
 278out_put_mem:
 279        kfree(freq_tbl);
 280        return ret;
 281
 282out_put_node:
 283        of_node_put(np);
 284        return ret;
 285}
 286late_initcall(spear_cpufreq_driver_init);
 287
 288MODULE_AUTHOR("Deepak Sikri <deepak.sikri@st.com>");
 289MODULE_DESCRIPTION("SPEAr CPUFreq driver");
 290MODULE_LICENSE("GPL");
 291
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