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_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 */
  27static struct {
  28        struct clk *clk;
  29        unsigned int transition_latency;
  30        struct cpufreq_frequency_table *freq_tbl;
  31        u32 cnt;
  32} spear_cpufreq;
  33
  34static 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 */
  76static 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
 103static 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
 153static 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
 160static 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
 170static 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
 227out_put_mem:
 228        kfree(freq_tbl);
 229        return ret;
 230
 231out_put_node:
 232        of_node_put(np);
 233        return ret;
 234}
 235
 236static struct platform_driver spear_cpufreq_platdrv = {
 237        .driver = {
 238                .name   = "spear-cpufreq",
 239        },
 240        .probe          = spear_cpufreq_probe,
 241};
 242module_platform_driver(spear_cpufreq_platdrv);
 243
 244MODULE_AUTHOR("Deepak Sikri <deepak.sikri@st.com>");
 245MODULE_DESCRIPTION("SPEAr CPUFreq driver");
 246MODULE_LICENSE("GPL");
 247
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