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/*
* Copyright 2011 Broadcom Corporation.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; version 2
* of the License.
*
* This driver dynamically manages the CPU Frequency of the ARM
* processor. Messages are sent to Videocore either setting or requesting the
* frequency of the ARM in order to match an appropiate frequency to the current
* usage of the processor. The policy which selects the frequency to use is
* defined in the kernel .config file, but can be changed during runtime.
*/
/* ---------- INCLUDES ---------- */
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/cpufreq.h>
#include <soc/bcm2835/raspberrypi-firmware.h>
/* ---------- DEFINES ---------- */
/*#define CPUFREQ_DEBUG_ENABLE*/ /* enable debugging */
#define MODULE_NAME "bcm2835-cpufreq"
#define VCMSG_ID_ARM_CLOCK 0x000000003 /* Clock/Voltage ID's */
/* debug printk macros */
#ifdef CPUFREQ_DEBUG_ENABLE
#define print_debug(fmt,...) pr_debug("%s:%s:%d: "fmt, MODULE_NAME, __func__, __LINE__, ##__VA_ARGS__)
#else
#define print_debug(fmt,...)
#endif
#define print_err(fmt,...) pr_err("%s:%s:%d: "fmt, MODULE_NAME, __func__,__LINE__, ##__VA_ARGS__)
#define print_info(fmt,...) pr_info("%s: "fmt, MODULE_NAME, ##__VA_ARGS__)
/* ---------- GLOBALS ---------- */
static struct cpufreq_driver bcm2835_cpufreq_driver; /* the cpufreq driver global */
static unsigned int min_frequency, max_frequency;
static struct cpufreq_frequency_table bcm2835_freq_table[3];
/*
===============================================
clk_rate either gets or sets the clock rates.
===============================================
*/
static int bcm2835_cpufreq_clock_property(u32 tag, u32 id, u32 *val)
{
struct rpi_firmware *fw = rpi_firmware_get(NULL);
struct {
u32 id;
u32 val;
} packet;
int ret;
packet.id = id;
packet.val = *val;
ret = rpi_firmware_property(fw, tag, &packet, sizeof(packet));
if (ret)
return ret;
*val = packet.val;
return 0;
}
static uint32_t bcm2835_cpufreq_set_clock(int cur_rate, int arm_rate)
{
u32 rate = arm_rate * 1000;
int ret;
ret = bcm2835_cpufreq_clock_property(RPI_FIRMWARE_SET_CLOCK_RATE, VCMSG_ID_ARM_CLOCK, &rate);
if (ret) {
print_err("Failed to set clock: %d (%d)\n", arm_rate, ret);
return 0;
}
rate /= 1000;
print_debug("Setting new frequency = %d -> %d (actual %d)\n", cur_rate, arm_rate, rate);
return rate;
}
static uint32_t bcm2835_cpufreq_get_clock(int tag)
{
u32 rate = 0;
int ret;
ret = bcm2835_cpufreq_clock_property(tag, VCMSG_ID_ARM_CLOCK, &rate);
if (ret) {
print_err("Failed to get clock (%d)\n", ret);
return 0;
}
rate /= 1000;
print_debug("%s frequency = %u\n",
tag == RPI_FIRMWARE_GET_CLOCK_RATE ? "Current":
tag == RPI_FIRMWARE_GET_MIN_CLOCK_RATE ? "Min":
tag == RPI_FIRMWARE_GET_MAX_CLOCK_RATE ? "Max":
"Unexpected", rate);
return rate;
}
/*
====================================================
Module Initialisation registers the cpufreq driver
====================================================
*/
static int __init bcm2835_cpufreq_module_init(void)
{
print_debug("IN\n");
return cpufreq_register_driver(&bcm2835_cpufreq_driver);
}
/*
=============
Module exit
=============
*/
static void __exit bcm2835_cpufreq_module_exit(void)
{
print_debug("IN\n");
cpufreq_unregister_driver(&bcm2835_cpufreq_driver);
return;
}
/*
==============================================================
Initialisation function sets up the CPU policy for first use
==============================================================
*/
static int bcm2835_cpufreq_driver_init(struct cpufreq_policy *policy)
{
/* measured value of how long it takes to change frequency */
const unsigned int transition_latency = 355000; /* ns */
if (!rpi_firmware_get(NULL)) {
print_err("Firmware is not available\n");
return -ENODEV;
}
/* now find out what the maximum and minimum frequencies are */
min_frequency = bcm2835_cpufreq_get_clock(RPI_FIRMWARE_GET_MIN_CLOCK_RATE);
max_frequency = bcm2835_cpufreq_get_clock(RPI_FIRMWARE_GET_MAX_CLOCK_RATE);
if (min_frequency == max_frequency) {
bcm2835_freq_table[0].frequency = min_frequency;
bcm2835_freq_table[1].frequency = CPUFREQ_TABLE_END;
} else {
bcm2835_freq_table[0].frequency = min_frequency;
bcm2835_freq_table[1].frequency = max_frequency;
bcm2835_freq_table[2].frequency = CPUFREQ_TABLE_END;
}
print_info("min=%d max=%d\n", min_frequency, max_frequency);
cpufreq_generic_init(policy, bcm2835_freq_table, transition_latency);
return 0;
}
/*
=====================================================================
Target index function chooses the requested frequency from the table
=====================================================================
*/
static int bcm2835_cpufreq_driver_target_index(struct cpufreq_policy *policy, unsigned int state)
{
unsigned int target_freq = state == 0 ? min_frequency : max_frequency;
unsigned int cur = bcm2835_cpufreq_set_clock(policy->cur, target_freq);
if (!cur)
{
print_err("Error occurred setting a new frequency (%d)\n", target_freq);
return -EINVAL;
}
print_debug("%s: %i: freq %d->%d\n", policy->governor->name, state, policy->cur, cur);
return 0;
}
/*
======================================================
Get function returns the current frequency from table
======================================================
*/
static unsigned int bcm2835_cpufreq_driver_get(unsigned int cpu)
{
unsigned int actual_rate = bcm2835_cpufreq_get_clock(RPI_FIRMWARE_GET_CLOCK_RATE);
print_debug("cpu%d: freq=%d\n", cpu, actual_rate);
return actual_rate <= min_frequency ? min_frequency : max_frequency;
}
/* the CPUFreq driver */
static struct cpufreq_driver bcm2835_cpufreq_driver = {
.name = "BCM2835 CPUFreq",
.init = bcm2835_cpufreq_driver_init,
.verify = cpufreq_generic_frequency_table_verify,
.target_index = bcm2835_cpufreq_driver_target_index,
.get = bcm2835_cpufreq_driver_get,
.attr = cpufreq_generic_attr,
};
MODULE_AUTHOR("Dorian Peake and Dom Cobley");
MODULE_DESCRIPTION("CPU frequency driver for BCM2835 chip");
MODULE_LICENSE("GPL");
module_init(bcm2835_cpufreq_module_init);
module_exit(bcm2835_cpufreq_module_exit);
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