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/cpufreq.h>
  23 #include <linux/device.h>
  24 #include <linux/export.h>
  25 #include <linux/module.h>
  26 #include <linux/of.h>
  27 #include <linux/opp.h>
  28 #include <linux/slab.h>
  29 #include <linux/types.h>
  30 #include "arm_big_little.h"
  31
  32 static int dt_init_opp_table(struct device *cpu_dev)
  33 {
  34         struct device_node *np, *parent;
  35         int count = 0, ret;
  36
  37         parent = of_find_node_by_path("/cpus");
  38         if (!parent) {
  39                 pr_err("failed to find OF /cpus\n");
  40                 return -ENOENT;
  41         }
  42
  43         for_each_child_of_node(parent, np) {
  44                 if (count++ != cpu_dev->id)
  45                         continue;
  46                 if (!of_get_property(np, "operating-points", NULL)) {
  47                         ret = -ENODATA;
  48                 } else {
  49                         cpu_dev->of_node = np;
  50                         ret = of_init_opp_table(cpu_dev);
  51                 }
  52                 of_node_put(np);
  53                 of_node_put(parent);
  54
  55                 return ret;
  56         }
  57
  58         return -ENODEV;
  59 }
  60
  61 static int dt_get_transition_latency(struct device *cpu_dev)
  62 {
  63         struct device_node *np, *parent;
  64         u32 transition_latency = CPUFREQ_ETERNAL;
  65         int count = 0;
  66
  67         parent = of_find_node_by_path("/cpus");
  68         if (!parent) {
  69                 pr_err("failed to find OF /cpus\n");
  70                 return -ENOENT;
  71         }
  72
  73         for_each_child_of_node(parent, np) {
  74                 if (count++ != cpu_dev->id)
  75                         continue;
  76
  77                 of_property_read_u32(np, "clock-latency", &transition_latency);
  78                 of_node_put(np);
  79                 of_node_put(parent);
  80
  81                 return 0;
  82         }
  83
  84         return -ENODEV;
  85 }
  86
  87 static struct cpufreq_arm_bL_ops dt_bL_ops = {
  88         .name   = "dt-bl",
  89         .get_transition_latency = dt_get_transition_latency,
  90         .init_opp_table = dt_init_opp_table,
  91 };
  92
  93 static int generic_bL_init(void)
  94 {
  95         return bL_cpufreq_register(&dt_bL_ops);
  96 }
  97 module_init(generic_bL_init);
  98
  99 static void generic_bL_exit(void)
 100 {
 101         return bL_cpufreq_unregister(&dt_bL_ops);
 102 }
 103 module_exit(generic_bL_exit);
 104
 105 MODULE_AUTHOR("Viresh Kumar <viresh.kumar@linaro.org>");
 106 MODULE_DESCRIPTION("Generic ARM big LITTLE cpufreq driver via DT");
 107 MODULE_LICENSE("GPL");