linux/drivers/cpufreq/kirkwood-cpufreq.c
<<
>>
Prefs
   1/*
   2 *      kirkwood_freq.c: cpufreq driver for the Marvell kirkwood
   3 *
   4 *      Copyright (C) 2013 Andrew Lunn <andrew@lunn.ch>
   5 *
   6 *      This program is free software; you can redistribute it and/or
   7 *      modify it under the terms of the GNU General Public License
   8 *      as published by the Free Software Foundation; either version
   9 *      2 of the License, or (at your option) any later version.
  10 */
  11
  12#include <linux/kernel.h>
  13#include <linux/module.h>
  14#include <linux/clk.h>
  15#include <linux/clk-provider.h>
  16#include <linux/cpufreq.h>
  17#include <linux/of.h>
  18#include <linux/platform_device.h>
  19#include <linux/io.h>
  20#include <asm/proc-fns.h>
  21
  22#define CPU_SW_INT_BLK BIT(28)
  23
  24static struct priv
  25{
  26        struct clk *cpu_clk;
  27        struct clk *ddr_clk;
  28        struct clk *powersave_clk;
  29        struct device *dev;
  30        void __iomem *base;
  31} priv;
  32
  33#define STATE_CPU_FREQ 0x01
  34#define STATE_DDR_FREQ 0x02
  35
  36/*
  37 * Kirkwood can swap the clock to the CPU between two clocks:
  38 *
  39 * - cpu clk
  40 * - ddr clk
  41 *
  42 * The frequencies are set at runtime before registering this *
  43 * table.
  44 */
  45static struct cpufreq_frequency_table kirkwood_freq_table[] = {
  46        {STATE_CPU_FREQ,        0}, /* CPU uses cpuclk */
  47        {STATE_DDR_FREQ,        0}, /* CPU uses ddrclk */
  48        {0,                     CPUFREQ_TABLE_END},
  49};
  50
  51static unsigned int kirkwood_cpufreq_get_cpu_frequency(unsigned int cpu)
  52{
  53        if (__clk_is_enabled(priv.powersave_clk))
  54                return kirkwood_freq_table[1].frequency;
  55        return kirkwood_freq_table[0].frequency;
  56}
  57
  58static void kirkwood_cpufreq_set_cpu_state(struct cpufreq_policy *policy,
  59                unsigned int index)
  60{
  61        struct cpufreq_freqs freqs;
  62        unsigned int state = kirkwood_freq_table[index].index;
  63        unsigned long reg;
  64
  65        freqs.old = kirkwood_cpufreq_get_cpu_frequency(0);
  66        freqs.new = kirkwood_freq_table[index].frequency;
  67
  68        cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE);
  69
  70        dev_dbg(priv.dev, "Attempting to set frequency to %i KHz\n",
  71                kirkwood_freq_table[index].frequency);
  72        dev_dbg(priv.dev, "old frequency was %i KHz\n",
  73                kirkwood_cpufreq_get_cpu_frequency(0));
  74
  75        if (freqs.old != freqs.new) {
  76                local_irq_disable();
  77
  78                /* Disable interrupts to the CPU */
  79                reg = readl_relaxed(priv.base);
  80                reg |= CPU_SW_INT_BLK;
  81                writel_relaxed(reg, priv.base);
  82
  83                switch (state) {
  84                case STATE_CPU_FREQ:
  85                        clk_disable(priv.powersave_clk);
  86                        break;
  87                case STATE_DDR_FREQ:
  88                        clk_enable(priv.powersave_clk);
  89                        break;
  90                }
  91
  92                /* Wait-for-Interrupt, while the hardware changes frequency */
  93                cpu_do_idle();
  94
  95                /* Enable interrupts to the CPU */
  96                reg = readl_relaxed(priv.base);
  97                reg &= ~CPU_SW_INT_BLK;
  98                writel_relaxed(reg, priv.base);
  99
 100                local_irq_enable();
 101        }
 102        cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE);
 103};
 104
 105static int kirkwood_cpufreq_verify(struct cpufreq_policy *policy)
 106{
 107        return cpufreq_frequency_table_verify(policy, kirkwood_freq_table);
 108}
 109
 110static int kirkwood_cpufreq_target(struct cpufreq_policy *policy,
 111                            unsigned int target_freq,
 112                            unsigned int relation)
 113{
 114        unsigned int index = 0;
 115
 116        if (cpufreq_frequency_table_target(policy, kirkwood_freq_table,
 117                                target_freq, relation, &index))
 118                return -EINVAL;
 119
 120        kirkwood_cpufreq_set_cpu_state(policy, index);
 121
 122        return 0;
 123}
 124
 125/* Module init and exit code */
 126static int kirkwood_cpufreq_cpu_init(struct cpufreq_policy *policy)
 127{
 128        int result;
 129
 130        /* cpuinfo and default policy values */
 131        policy->cpuinfo.transition_latency = 5000; /* 5uS */
 132        policy->cur = kirkwood_cpufreq_get_cpu_frequency(0);
 133
 134        result = cpufreq_frequency_table_cpuinfo(policy, kirkwood_freq_table);
 135        if (result)
 136                return result;
 137
 138        cpufreq_frequency_table_get_attr(kirkwood_freq_table, policy->cpu);
 139
 140        return 0;
 141}
 142
 143static int kirkwood_cpufreq_cpu_exit(struct cpufreq_policy *policy)
 144{
 145        cpufreq_frequency_table_put_attr(policy->cpu);
 146        return 0;
 147}
 148
 149static struct freq_attr *kirkwood_cpufreq_attr[] = {
 150        &cpufreq_freq_attr_scaling_available_freqs,
 151        NULL,
 152};
 153
 154static struct cpufreq_driver kirkwood_cpufreq_driver = {
 155        .get    = kirkwood_cpufreq_get_cpu_frequency,
 156        .verify = kirkwood_cpufreq_verify,
 157        .target = kirkwood_cpufreq_target,
 158        .init   = kirkwood_cpufreq_cpu_init,
 159        .exit   = kirkwood_cpufreq_cpu_exit,
 160        .name   = "kirkwood-cpufreq",
 161        .owner  = THIS_MODULE,
 162        .attr   = kirkwood_cpufreq_attr,
 163};
 164
 165static int kirkwood_cpufreq_probe(struct platform_device *pdev)
 166{
 167        struct device_node *np;
 168        struct resource *res;
 169        int err;
 170
 171        priv.dev = &pdev->dev;
 172
 173        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 174        priv.base = devm_ioremap_resource(&pdev->dev, res);
 175        if (IS_ERR(priv.base))
 176                return PTR_ERR(priv.base);
 177
 178        np = of_find_node_by_path("/cpus/cpu@0");
 179        if (!np)
 180                return -ENODEV;
 181
 182        priv.cpu_clk = of_clk_get_by_name(np, "cpu_clk");
 183        if (IS_ERR(priv.cpu_clk)) {
 184                dev_err(priv.dev, "Unable to get cpuclk");
 185                return PTR_ERR(priv.cpu_clk);
 186        }
 187
 188        clk_prepare_enable(priv.cpu_clk);
 189        kirkwood_freq_table[0].frequency = clk_get_rate(priv.cpu_clk) / 1000;
 190
 191        priv.ddr_clk = of_clk_get_by_name(np, "ddrclk");
 192        if (IS_ERR(priv.ddr_clk)) {
 193                dev_err(priv.dev, "Unable to get ddrclk");
 194                err = PTR_ERR(priv.ddr_clk);
 195                goto out_cpu;
 196        }
 197
 198        clk_prepare_enable(priv.ddr_clk);
 199        kirkwood_freq_table[1].frequency = clk_get_rate(priv.ddr_clk) / 1000;
 200
 201        priv.powersave_clk = of_clk_get_by_name(np, "powersave");
 202        if (IS_ERR(priv.powersave_clk)) {
 203                dev_err(priv.dev, "Unable to get powersave");
 204                err = PTR_ERR(priv.powersave_clk);
 205                goto out_ddr;
 206        }
 207        clk_prepare(priv.powersave_clk);
 208
 209        of_node_put(np);
 210        np = NULL;
 211
 212        err = cpufreq_register_driver(&kirkwood_cpufreq_driver);
 213        if (!err)
 214                return 0;
 215
 216        dev_err(priv.dev, "Failed to register cpufreq driver");
 217
 218        clk_disable_unprepare(priv.powersave_clk);
 219out_ddr:
 220        clk_disable_unprepare(priv.ddr_clk);
 221out_cpu:
 222        clk_disable_unprepare(priv.cpu_clk);
 223        of_node_put(np);
 224
 225        return err;
 226}
 227
 228static int kirkwood_cpufreq_remove(struct platform_device *pdev)
 229{
 230        cpufreq_unregister_driver(&kirkwood_cpufreq_driver);
 231
 232        clk_disable_unprepare(priv.powersave_clk);
 233        clk_disable_unprepare(priv.ddr_clk);
 234        clk_disable_unprepare(priv.cpu_clk);
 235
 236        return 0;
 237}
 238
 239static struct platform_driver kirkwood_cpufreq_platform_driver = {
 240        .probe = kirkwood_cpufreq_probe,
 241        .remove = kirkwood_cpufreq_remove,
 242        .driver = {
 243                .name = "kirkwood-cpufreq",
 244                .owner = THIS_MODULE,
 245        },
 246};
 247
 248module_platform_driver(kirkwood_cpufreq_platform_driver);
 249
 250MODULE_LICENSE("GPL v2");
 251MODULE_AUTHOR("Andrew Lunn <andrew@lunn.ch");
 252MODULE_DESCRIPTION("cpufreq driver for Marvell's kirkwood CPU");
 253MODULE_ALIAS("platform:kirkwood-cpufreq");
 254
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.