drivers/cpufreq/arm_big_little_dt.c

   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 */
  35 static 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
  61 static 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
  77 static 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
  93 static 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
  99 static 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
 111 static int generic_bL_remove(struct platform_device *pdev)
 112 {
 113         bL_cpufreq_unregister(&dt_bL_ops);
 114         return 0;
 115 }
 116
 117 static 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 };
 125 module_platform_driver(generic_bL_platdrv);
 126
 127 MODULE_AUTHOR("Viresh Kumar <viresh.kumar@linaro.org>");
 128 MODULE_DESCRIPTION("Generic ARM big LITTLE cpufreq driver via DT");
 129 MODULE_LICENSE("GPL");