linux/drivers/cpufreq/scpi-cpufreq.c
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   1/*
   2 * System Control and Power Interface (SCPI) based CPUFreq Interface driver
   3 *
   4 * Copyright (C) 2015 ARM Ltd.
   5 * Sudeep Holla <sudeep.holla@arm.com>
   6 *
   7 * This program is free software; you can redistribute it and/or modify
   8 * it under the terms of the GNU General Public License version 2 as
   9 * published by the Free Software Foundation.
  10 *
  11 * This program is distributed "as is" WITHOUT ANY WARRANTY of any
  12 * kind, whether express or implied; without even the implied warranty
  13 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14 * GNU General Public License for more details.
  15 */
  16
  17#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  18
  19#include <linux/clk.h>
  20#include <linux/cpu.h>
  21#include <linux/cpufreq.h>
  22#include <linux/cpumask.h>
  23#include <linux/export.h>
  24#include <linux/module.h>
  25#include <linux/of_platform.h>
  26#include <linux/pm_opp.h>
  27#include <linux/scpi_protocol.h>
  28#include <linux/slab.h>
  29#include <linux/types.h>
  30
  31struct scpi_data {
  32        struct clk *clk;
  33        struct device *cpu_dev;
  34};
  35
  36static struct scpi_ops *scpi_ops;
  37
  38static unsigned int scpi_cpufreq_get_rate(unsigned int cpu)
  39{
  40        struct cpufreq_policy *policy = cpufreq_cpu_get_raw(cpu);
  41        struct scpi_data *priv = policy->driver_data;
  42        unsigned long rate = clk_get_rate(priv->clk);
  43
  44        return rate / 1000;
  45}
  46
  47static int
  48scpi_cpufreq_set_target(struct cpufreq_policy *policy, unsigned int index)
  49{
  50        u64 rate = policy->freq_table[index].frequency * 1000;
  51        struct scpi_data *priv = policy->driver_data;
  52        int ret;
  53
  54        ret = clk_set_rate(priv->clk, rate);
  55
  56        if (ret)
  57                return ret;
  58
  59        if (clk_get_rate(priv->clk) != rate)
  60                return -EIO;
  61
  62        return 0;
  63}
  64
  65static int
  66scpi_get_sharing_cpus(struct device *cpu_dev, struct cpumask *cpumask)
  67{
  68        int cpu, domain, tdomain;
  69        struct device *tcpu_dev;
  70
  71        domain = scpi_ops->device_domain_id(cpu_dev);
  72        if (domain < 0)
  73                return domain;
  74
  75        for_each_possible_cpu(cpu) {
  76                if (cpu == cpu_dev->id)
  77                        continue;
  78
  79                tcpu_dev = get_cpu_device(cpu);
  80                if (!tcpu_dev)
  81                        continue;
  82
  83                tdomain = scpi_ops->device_domain_id(tcpu_dev);
  84                if (tdomain == domain)
  85                        cpumask_set_cpu(cpu, cpumask);
  86        }
  87
  88        return 0;
  89}
  90
  91static int scpi_cpufreq_init(struct cpufreq_policy *policy)
  92{
  93        int ret;
  94        unsigned int latency;
  95        struct device *cpu_dev;
  96        struct scpi_data *priv;
  97        struct cpufreq_frequency_table *freq_table;
  98
  99        cpu_dev = get_cpu_device(policy->cpu);
 100        if (!cpu_dev) {
 101                pr_err("failed to get cpu%d device\n", policy->cpu);
 102                return -ENODEV;
 103        }
 104
 105        ret = scpi_ops->add_opps_to_device(cpu_dev);
 106        if (ret) {
 107                dev_warn(cpu_dev, "failed to add opps to the device\n");
 108                return ret;
 109        }
 110
 111        ret = scpi_get_sharing_cpus(cpu_dev, policy->cpus);
 112        if (ret) {
 113                dev_warn(cpu_dev, "failed to get sharing cpumask\n");
 114                return ret;
 115        }
 116
 117        ret = dev_pm_opp_set_sharing_cpus(cpu_dev, policy->cpus);
 118        if (ret) {
 119                dev_err(cpu_dev, "%s: failed to mark OPPs as shared: %d\n",
 120                        __func__, ret);
 121                return ret;
 122        }
 123
 124        ret = dev_pm_opp_get_opp_count(cpu_dev);
 125        if (ret <= 0) {
 126                dev_dbg(cpu_dev, "OPP table is not ready, deferring probe\n");
 127                ret = -EPROBE_DEFER;
 128                goto out_free_opp;
 129        }
 130
 131        priv = kzalloc(sizeof(*priv), GFP_KERNEL);
 132        if (!priv) {
 133                ret = -ENOMEM;
 134                goto out_free_opp;
 135        }
 136
 137        ret = dev_pm_opp_init_cpufreq_table(cpu_dev, &freq_table);
 138        if (ret) {
 139                dev_err(cpu_dev, "failed to init cpufreq table: %d\n", ret);
 140                goto out_free_priv;
 141        }
 142
 143        priv->cpu_dev = cpu_dev;
 144        priv->clk = clk_get(cpu_dev, NULL);
 145        if (IS_ERR(priv->clk)) {
 146                dev_err(cpu_dev, "%s: Failed to get clk for cpu: %d\n",
 147                        __func__, cpu_dev->id);
 148                ret = PTR_ERR(priv->clk);
 149                goto out_free_cpufreq_table;
 150        }
 151
 152        policy->driver_data = priv;
 153        policy->freq_table = freq_table;
 154
 155        /* scpi allows DVFS request for any domain from any CPU */
 156        policy->dvfs_possible_from_any_cpu = true;
 157
 158        latency = scpi_ops->get_transition_latency(cpu_dev);
 159        if (!latency)
 160                latency = CPUFREQ_ETERNAL;
 161
 162        policy->cpuinfo.transition_latency = latency;
 163
 164        policy->fast_switch_possible = false;
 165
 166        dev_pm_opp_of_register_em(cpu_dev, policy->cpus);
 167
 168        return 0;
 169
 170out_free_cpufreq_table:
 171        dev_pm_opp_free_cpufreq_table(cpu_dev, &freq_table);
 172out_free_priv:
 173        kfree(priv);
 174out_free_opp:
 175        dev_pm_opp_remove_all_dynamic(cpu_dev);
 176
 177        return ret;
 178}
 179
 180static int scpi_cpufreq_exit(struct cpufreq_policy *policy)
 181{
 182        struct scpi_data *priv = policy->driver_data;
 183
 184        clk_put(priv->clk);
 185        dev_pm_opp_free_cpufreq_table(priv->cpu_dev, &policy->freq_table);
 186        dev_pm_opp_remove_all_dynamic(priv->cpu_dev);
 187        kfree(priv);
 188
 189        return 0;
 190}
 191
 192static struct cpufreq_driver scpi_cpufreq_driver = {
 193        .name   = "scpi-cpufreq",
 194        .flags  = CPUFREQ_HAVE_GOVERNOR_PER_POLICY |
 195                  CPUFREQ_NEED_INITIAL_FREQ_CHECK |
 196                  CPUFREQ_IS_COOLING_DEV,
 197        .verify = cpufreq_generic_frequency_table_verify,
 198        .attr   = cpufreq_generic_attr,
 199        .get    = scpi_cpufreq_get_rate,
 200        .init   = scpi_cpufreq_init,
 201        .exit   = scpi_cpufreq_exit,
 202        .target_index   = scpi_cpufreq_set_target,
 203};
 204
 205static int scpi_cpufreq_probe(struct platform_device *pdev)
 206{
 207        int ret;
 208
 209        scpi_ops = get_scpi_ops();
 210        if (!scpi_ops)
 211                return -EIO;
 212
 213        ret = cpufreq_register_driver(&scpi_cpufreq_driver);
 214        if (ret)
 215                dev_err(&pdev->dev, "%s: registering cpufreq failed, err: %d\n",
 216                        __func__, ret);
 217        return ret;
 218}
 219
 220static int scpi_cpufreq_remove(struct platform_device *pdev)
 221{
 222        cpufreq_unregister_driver(&scpi_cpufreq_driver);
 223        scpi_ops = NULL;
 224        return 0;
 225}
 226
 227static struct platform_driver scpi_cpufreq_platdrv = {
 228        .driver = {
 229                .name   = "scpi-cpufreq",
 230        },
 231        .probe          = scpi_cpufreq_probe,
 232        .remove         = scpi_cpufreq_remove,
 233};
 234module_platform_driver(scpi_cpufreq_platdrv);
 235
 236MODULE_ALIAS("platform:scpi-cpufreq");
 237MODULE_AUTHOR("Sudeep Holla <sudeep.holla@arm.com>");
 238MODULE_DESCRIPTION("ARM SCPI CPUFreq interface driver");
 239MODULE_LICENSE("GPL v2");
 240