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/mailbox.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         int i;
  32         u32 msg[HB_CPUFREQ_IPC_LEN];
  33
  34         msg[0] = HB_CPUFREQ_CHANGE_NOTE;
  35         msg[1] = freq / 1000000;
  36         for (i = 2; i < HB_CPUFREQ_IPC_LEN; i++)
  37                 msg[i] = 0;
  38
  39         return pl320_ipc_transmit(msg);
  40 }
  41
  42 static int hb_cpufreq_clk_notify(struct notifier_block *nb,
  43                                 unsigned long action, void *hclk)
  44 {
  45         struct clk_notifier_data *clk_data = hclk;
  46         int i = 0;
  47
  48         if (action == PRE_RATE_CHANGE) {
  49                 if (clk_data->new_rate > clk_data->old_rate)
  50                         while (hb_voltage_change(clk_data->new_rate))
  51                                 if (i++ > HB_CPUFREQ_VOLT_RETRIES)
  52                                         return NOTIFY_BAD;
  53         } else if (action == POST_RATE_CHANGE) {
  54                 if (clk_data->new_rate < clk_data->old_rate)
  55                         while (hb_voltage_change(clk_data->new_rate))
  56                                 if (i++ > HB_CPUFREQ_VOLT_RETRIES)
  57                                         return NOTIFY_BAD;
  58         }
  59
  60         return NOTIFY_DONE;
  61 }
  62
  63 static struct notifier_block hb_cpufreq_clk_nb = {
  64         .notifier_call = hb_cpufreq_clk_notify,
  65 };
  66
  67 static int hb_cpufreq_driver_init(void)
  68 {
  69         struct platform_device_info devinfo = { .name = "cpufreq-cpu0", };
  70         struct device *cpu_dev;
  71         struct clk *cpu_clk;
  72         struct device_node *np;
  73         int ret;
  74
  75         if (!of_machine_is_compatible("calxeda,highbank"))
  76                 return -ENODEV;
  77
  78         for_each_child_of_node(of_find_node_by_path("/cpus"), np)
  79                 if (of_get_property(np, "operating-points", NULL))
  80                         break;
  81
  82         if (!np) {
  83                 pr_err("failed to find highbank cpufreq node\n");
  84                 return -ENOENT;
  85         }
  86
  87         cpu_dev = get_cpu_device(0);
  88         if (!cpu_dev) {
  89                 pr_err("failed to get highbank cpufreq device\n");
  90                 ret = -ENODEV;
  91                 goto out_put_node;
  92         }
  93
  94         cpu_dev->of_node = np;
  95
  96         cpu_clk = clk_get(cpu_dev, NULL);
  97         if (IS_ERR(cpu_clk)) {
  98                 ret = PTR_ERR(cpu_clk);
  99                 pr_err("failed to get cpu0 clock: %d\n", ret);
 100                 goto out_put_node;
 101         }
 102
 103         ret = clk_notifier_register(cpu_clk, &hb_cpufreq_clk_nb);
 104         if (ret) {
 105                 pr_err("failed to register clk notifier: %d\n", ret);
 106                 goto out_put_node;
 107         }
 108
 109         /* Instantiate cpufreq-cpu0 */
 110         platform_device_register_full(&devinfo);
 111
 112 out_put_node:
 113         of_node_put(np);
 114         return ret;
 115 }
 116 module_init(hb_cpufreq_driver_init);
 117
 118 MODULE_AUTHOR("Mark Langsdorf <mark.langsdorf@calxeda.com>");
 119 MODULE_DESCRIPTION("Calxeda Highbank cpufreq driver");
 120 MODULE_LICENSE("GPL");