LXR linux/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-dt 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
  29static 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
  36static 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
  57static struct notifier_block hb_cpufreq_clk_nb = {
  58        .notifier_call = hb_cpufreq_clk_notify,
  59};
  60
  61static int hb_cpufreq_driver_init(void)
  62{
  63        struct platform_device_info devinfo = { .name = "cpufreq-dt", };
  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        cpu_dev = get_cpu_device(0);
  74        if (!cpu_dev) {
  75                pr_err("failed to get highbank cpufreq device\n");
  76                return -ENODEV;
  77        }
  78
  79        np = of_node_get(cpu_dev->of_node);
  80        if (!np) {
  81                pr_err("failed to find highbank cpufreq node\n");
  82                return -ENOENT;
  83        }
  84
  85        cpu_clk = clk_get(cpu_dev, NULL);
  86        if (IS_ERR(cpu_clk)) {
  87                ret = PTR_ERR(cpu_clk);
  88                pr_err("failed to get cpu0 clock: %d\n", ret);
  89                goto out_put_node;
  90        }
  91
  92        ret = clk_notifier_register(cpu_clk, &hb_cpufreq_clk_nb);
  93        if (ret) {
  94                pr_err("failed to register clk notifier: %d\n", ret);
  95                goto out_put_node;
  96        }
  97
  98        /* Instantiate cpufreq-dt */
  99        platform_device_register_full(&devinfo);
 100
 101out_put_node:
 102        of_node_put(np);
 103        return ret;
 104}
 105module_init(hb_cpufreq_driver_init);
 106
 107MODULE_AUTHOR("Mark Langsdorf <mark.langsdorf@calxeda.com>");
 108MODULE_DESCRIPTION("Calxeda Highbank cpufreq driver");
 109MODULE_LICENSE("GPL");
 110