linux/drivers/cpufreq/arm_big_little_dt.c
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   1/*
   2 * Generic big.LITTLE CPUFreq Interface driver
   3 *
   4 * It provides necessary ops to arm_big_little cpufreq driver and gets
   5 * Frequency information from Device Tree. Freq table in DT must be in KHz.
   6 *
   7 * Copyright (C) 2013 Linaro.
   8 * Viresh Kumar <viresh.kumar@linaro.org>
   9 *
  10 * This program is free software; you can redistribute it and/or modify
  11 * it under the terms of the GNU General Public License version 2 as
  12 * published by the Free Software Foundation.
  13 *
  14 * This program is distributed "as is" WITHOUT ANY WARRANTY of any
  15 * kind, whether express or implied; without even the implied warranty
  16 * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  17 * GNU General Public License for more details.
  18 */
  19
  20#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  21
  22#include <linux/cpu.h>
  23#include <linux/cpufreq.h>
  24#include <linux/device.h>
  25#include <linux/export.h>
  26#include <linux/module.h>
  27#include <linux/of.h>
  28#include <linux/opp.h>
  29#include <linux/platform_device.h>
  30#include <linux/slab.h>
  31#include <linux/types.h>
  32#include "arm_big_little.h"
  33
  34/* get cpu node with valid operating-points */
  35static struct device_node *get_cpu_node_with_valid_op(int cpu)
  36{
  37        struct device_node *np = NULL, *parent;
  38        int count = 0;
  39
  40        parent = of_find_node_by_path("/cpus");
  41        if (!parent) {
  42                pr_err("failed to find OF /cpus\n");
  43                return NULL;
  44        }
  45
  46        for_each_child_of_node(parent, np) {
  47                if (count++ != cpu)
  48                        continue;
  49                if (!of_get_property(np, "operating-points", NULL)) {
  50                        of_node_put(np);
  51                        np = NULL;
  52                }
  53
  54                break;
  55        }
  56
  57        of_node_put(parent);
  58        return np;
  59}
  60
  61static int dt_init_opp_table(struct device *cpu_dev)
  62{
  63        struct device_node *np;
  64        int ret;
  65
  66        np = get_cpu_node_with_valid_op(cpu_dev->id);
  67        if (!np)
  68                return -ENODATA;
  69
  70        cpu_dev->of_node = np;
  71        ret = of_init_opp_table(cpu_dev);
  72        of_node_put(np);
  73
  74        return ret;
  75}
  76
  77static int dt_get_transition_latency(struct device *cpu_dev)
  78{
  79        struct device_node *np;
  80        u32 transition_latency = CPUFREQ_ETERNAL;
  81
  82        np = get_cpu_node_with_valid_op(cpu_dev->id);
  83        if (!np)
  84                return CPUFREQ_ETERNAL;
  85
  86        of_property_read_u32(np, "clock-latency", &transition_latency);
  87        of_node_put(np);
  88
  89        pr_debug("%s: clock-latency: %d\n", __func__, transition_latency);
  90        return transition_latency;
  91}
  92
  93static struct cpufreq_arm_bL_ops dt_bL_ops = {
  94        .name   = "dt-bl",
  95        .get_transition_latency = dt_get_transition_latency,
  96        .init_opp_table = dt_init_opp_table,
  97};
  98
  99static int generic_bL_probe(struct platform_device *pdev)
 100{
 101        struct device_node *np;
 102
 103        np = get_cpu_node_with_valid_op(0);
 104        if (!np)
 105                return -ENODEV;
 106
 107        of_node_put(np);
 108        return bL_cpufreq_register(&dt_bL_ops);
 109}
 110
 111static int generic_bL_remove(struct platform_device *pdev)
 112{
 113        bL_cpufreq_unregister(&dt_bL_ops);
 114        return 0;
 115}
 116
 117static struct platform_driver generic_bL_platdrv = {
 118        .driver = {
 119                .name   = "arm-bL-cpufreq-dt",
 120                .owner  = THIS_MODULE,
 121        },
 122        .probe          = generic_bL_probe,
 123        .remove         = generic_bL_remove,
 124};
 125module_platform_driver(generic_bL_platdrv);
 126
 127MODULE_AUTHOR("Viresh Kumar <viresh.kumar@linaro.org>");
 128MODULE_DESCRIPTION("Generic ARM big LITTLE cpufreq driver via DT");
 129MODULE_LICENSE("GPL");
 130
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