linux/drivers/cpufreq/kirkwood-cpufreq.c
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   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(unsigned int index)
  59{
  60        struct cpufreq_freqs freqs;
  61        unsigned int state = kirkwood_freq_table[index].index;
  62        unsigned long reg;
  63
  64        freqs.old = kirkwood_cpufreq_get_cpu_frequency(0);
  65        freqs.new = kirkwood_freq_table[index].frequency;
  66        freqs.cpu = 0; /* Kirkwood is UP */
  67
  68        cpufreq_notify_transition(&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(&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(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        if (!res) {
 175                dev_err(&pdev->dev, "Cannot get memory resource\n");
 176                return -ENODEV;
 177        }
 178        priv.base = devm_request_and_ioremap(&pdev->dev, res);
 179        if (!priv.base) {
 180                dev_err(&pdev->dev, "Cannot ioremap\n");
 181                return -EADDRNOTAVAIL;
 182        }
 183
 184        np = of_find_node_by_path("/cpus/cpu@0");
 185        if (!np)
 186                return -ENODEV;
 187
 188        priv.cpu_clk = of_clk_get_by_name(np, "cpu_clk");
 189        if (IS_ERR(priv.cpu_clk)) {
 190                dev_err(priv.dev, "Unable to get cpuclk");
 191                return PTR_ERR(priv.cpu_clk);
 192        }
 193
 194        clk_prepare_enable(priv.cpu_clk);
 195        kirkwood_freq_table[0].frequency = clk_get_rate(priv.cpu_clk) / 1000;
 196
 197        priv.ddr_clk = of_clk_get_by_name(np, "ddrclk");
 198        if (IS_ERR(priv.ddr_clk)) {
 199                dev_err(priv.dev, "Unable to get ddrclk");
 200                err = PTR_ERR(priv.ddr_clk);
 201                goto out_cpu;
 202        }
 203
 204        clk_prepare_enable(priv.ddr_clk);
 205        kirkwood_freq_table[1].frequency = clk_get_rate(priv.ddr_clk) / 1000;
 206
 207        priv.powersave_clk = of_clk_get_by_name(np, "powersave");
 208        if (IS_ERR(priv.powersave_clk)) {
 209                dev_err(priv.dev, "Unable to get powersave");
 210                err = PTR_ERR(priv.powersave_clk);
 211                goto out_ddr;
 212        }
 213        clk_prepare(priv.powersave_clk);
 214
 215        of_node_put(np);
 216        np = NULL;
 217
 218        err = cpufreq_register_driver(&kirkwood_cpufreq_driver);
 219        if (!err)
 220                return 0;
 221
 222        dev_err(priv.dev, "Failed to register cpufreq driver");
 223
 224        clk_disable_unprepare(priv.powersave_clk);
 225out_ddr:
 226        clk_disable_unprepare(priv.ddr_clk);
 227out_cpu:
 228        clk_disable_unprepare(priv.cpu_clk);
 229        of_node_put(np);
 230
 231        return err;
 232}
 233
 234static int kirkwood_cpufreq_remove(struct platform_device *pdev)
 235{
 236        cpufreq_unregister_driver(&kirkwood_cpufreq_driver);
 237
 238        clk_disable_unprepare(priv.powersave_clk);
 239        clk_disable_unprepare(priv.ddr_clk);
 240        clk_disable_unprepare(priv.cpu_clk);
 241
 242        return 0;
 243}
 244
 245static struct platform_driver kirkwood_cpufreq_platform_driver = {
 246        .probe = kirkwood_cpufreq_probe,
 247        .remove = kirkwood_cpufreq_remove,
 248        .driver = {
 249                .name = "kirkwood-cpufreq",
 250                .owner = THIS_MODULE,
 251        },
 252};
 253
 254module_platform_driver(kirkwood_cpufreq_platform_driver);
 255
 256MODULE_LICENSE("GPL v2");
 257MODULE_AUTHOR("Andrew Lunn <andrew@lunn.ch");
 258MODULE_DESCRIPTION("cpufreq driver for Marvell's kirkwood CPU");
 259MODULE_ALIAS("platform:kirkwood-cpufreq");
 260
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