drivers/cpufreq/highbank-cpufreq.c

   1 /*
   2  * Copyright (C) 2012 Calxeda, Inc.
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  *
   8  * This driver provides the clk notifier callbacks that are used when
   9  * the cpufreq-cpu0 driver changes to frequency to alert the highbank
  10  * EnergyCore Management Engine (ECME) about the need to change
  11  * voltage. The ECME interfaces with the actual voltage regulators.
  12  */
  13
  14 #define pr_fmt(fmt)     KBUILD_MODNAME ": " fmt
  15
  16 #include <linux/kernel.h>
  17 #include <linux/module.h>
  18 #include <linux/clk.h>
  19 #include <linux/cpu.h>
  20 #include <linux/err.h>
  21 #include <linux/of.h>
  22 #include <linux/pl320-ipc.h>
  23 #include <linux/platform_device.h>
  24
  25 #define HB_CPUFREQ_CHANGE_NOTE  0x80000001
  26 #define HB_CPUFREQ_IPC_LEN      7
  27 #define HB_CPUFREQ_VOLT_RETRIES 15
  28
  29 static int hb_voltage_change(unsigned int freq)
  30 {
  31         u32 msg[HB_CPUFREQ_IPC_LEN] = {HB_CPUFREQ_CHANGE_NOTE, freq / 1000000};
  32
  33         return pl320_ipc_transmit(msg);
  34 }
  35
  36 static int hb_cpufreq_clk_notify(struct notifier_block *nb,
  37                                 unsigned long action, void *hclk)
  38 {
  39         struct clk_notifier_data *clk_data = hclk;
  40         int i = 0;
  41
  42         if (action == PRE_RATE_CHANGE) {
  43                 if (clk_data->new_rate > clk_data->old_rate)
  44                         while (hb_voltage_change(clk_data->new_rate))
  45                                 if (i++ > HB_CPUFREQ_VOLT_RETRIES)
  46                                         return NOTIFY_BAD;
  47         } else if (action == POST_RATE_CHANGE) {
  48                 if (clk_data->new_rate < clk_data->old_rate)
  49                         while (hb_voltage_change(clk_data->new_rate))
  50                                 if (i++ > HB_CPUFREQ_VOLT_RETRIES)
  51                                         return NOTIFY_BAD;
  52         }
  53
  54         return NOTIFY_DONE;
  55 }
  56
  57 static struct notifier_block hb_cpufreq_clk_nb = {
  58         .notifier_call = hb_cpufreq_clk_notify,
  59 };
  60
  61 static int hb_cpufreq_driver_init(void)
  62 {
  63         struct platform_device_info devinfo = { .name = "cpufreq-cpu0", };
  64         struct device *cpu_dev;
  65         struct clk *cpu_clk;
  66         struct device_node *np;
  67         int ret;
  68
  69         if ((!of_machine_is_compatible("calxeda,highbank")) &&
  70                 (!of_machine_is_compatible("calxeda,ecx-2000")))
  71                 return -ENODEV;
  72
  73         for_each_child_of_node(of_find_node_by_path("/cpus"), np)
  74                 if (of_get_property(np, "operating-points", NULL))
  75                         break;
  76
  77         if (!np) {
  78                 pr_err("failed to find highbank cpufreq node\n");
  79                 return -ENOENT;
  80         }
  81
  82         cpu_dev = get_cpu_device(0);
  83         if (!cpu_dev) {
  84                 pr_err("failed to get highbank cpufreq device\n");
  85                 ret = -ENODEV;
  86                 goto out_put_node;
  87         }
  88
  89         cpu_dev->of_node = np;
  90
  91         cpu_clk = clk_get(cpu_dev, NULL);
  92         if (IS_ERR(cpu_clk)) {
  93                 ret = PTR_ERR(cpu_clk);
  94                 pr_err("failed to get cpu0 clock: %d\n", ret);
  95                 goto out_put_node;
  96         }
  97
  98         ret = clk_notifier_register(cpu_clk, &hb_cpufreq_clk_nb);
  99         if (ret) {
 100                 pr_err("failed to register clk notifier: %d\n", ret);
 101                 goto out_put_node;
 102         }
 103
 104         /* Instantiate cpufreq-cpu0 */
 105         platform_device_register_full(&devinfo);
 106
 107 out_put_node:
 108         of_node_put(np);
 109         return ret;
 110 }
 111 module_init(hb_cpufreq_driver_init);
 112
 113 MODULE_AUTHOR("Mark Langsdorf <mark.langsdorf@calxeda.com>");
 114 MODULE_DESCRIPTION("Calxeda Highbank cpufreq driver");
 115 MODULE_LICENSE("GPL");