[Atrix 4G Q&A, Help & Troubleshooting] KeRmiT80:
i found this file around tegra cpu driver

cpu-tegra.c

/*
* arch/arm/mach-tegra/cpu-tegra.c
*
* Copyright (C) 2010 Google, Inc.
*
* Author:
*	Colin Cross <ccross@google.com>
*	Based on arch/arm/plat-omap/cpu-omap.c, (C) 2005 Nokia Corporation
*
* This software is licensed under the terms of the GNU General Public
* License version 2, as published by the Free Software Foundation, and
* may be copied, distributed, and modified under those terms.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
*/

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/sched.h>
#include <linux/cpufreq.h>
#include <linux/delay.h>
#include <linux/init.h>
#include <linux/err.h>
#include <linux/clk.h>
#include <linux/io.h>

#include <asm/system.h>

#include <mach/hardware.h>
#include <mach/clk.h>

/* Frequency table index must be sequential starting at 0 */
static struct cpufreq_frequency_table freq_table[] = {
{ 0, 312000 },
{ 1, 456000 },
{ 2, 608000 },
{ 3, 760000 },
{ 4, 816000 },
{ 5, 912000 },
{ 6, 1000000 },
{ 7, CPUFREQ_TABLE_END },
};

#define NUM_CPUS	2

static struct clk *cpu_clk;

static unsigned long target_cpu_speed[NUM_CPUS];

int tegra_verify_speed(struct cpufreq_policy *policy)
{
return cpufreq_frequency_table_verify(policy, freq_table);
}

unsigned int tegra_getspeed(unsigned int cpu)
{
unsigned long rate;

if (cpu >= NUM_CPUS)
return 0;

rate = clk_get_rate(cpu_clk) / 1000;
return rate;
}

static int tegra_update_cpu_speed(void)
{
int i;
unsigned long rate = 0;
int ret = 0;
struct cpufreq_freqs freqs;

for_each_online_cpu(i)
rate = max(rate, target_cpu_speed[i]);

freqs.old = tegra_getspeed(0);
freqs.new = rate;

if (freqs.old == freqs.new)
return ret;

for_each_online_cpu(freqs.cpu)
cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);

#ifdef CONFIG_CPU_FREQ_DEBUG
printk(KERN_DEBUG "cpufreq-tegra: transition: %u --> %u\n",
freqs.old, freqs.new);
#endif

ret = clk_set_rate_cansleep(cpu_clk, freqs.new * 1000);
if (ret) {
pr_err("cpu-tegra: Failed to set cpu frequency to %d kHz\n",
freqs.new);
return ret;
}

for_each_online_cpu(freqs.cpu)
cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);

return 0;
}

static int tegra_target(struct cpufreq_policy *policy,
unsigned int target_freq,
unsigned int relation)
{
int idx;
unsigned int freq;

cpufreq_frequency_table_target(policy, freq_table, target_freq,
relation, &idx);

freq = freq_table[idx].frequency;

target_cpu_speed[policy->cpu] = freq;

return tegra_update_cpu_speed();
}

static int tegra_cpu_init(struct cpufreq_policy *policy)
{
if (policy->cpu >= NUM_CPUS)
return -EINVAL;

cpu_clk = clk_get_sys(NULL, "cpu");
if (IS_ERR(cpu_clk))
return PTR_ERR(cpu_clk);

cpufreq_frequency_table_cpuinfo(policy, freq_table);
cpufreq_frequency_table_get_attr(freq_table, policy->cpu);
policy->cur = tegra_getspeed(policy->cpu);
target_cpu_speed[policy->cpu] = policy->cur;

/* FIXME: what's the actual transition time? */
policy->cpuinfo.transition_latency = 300 * 1000;

policy->shared_type = CPUFREQ_SHARED_TYPE_ALL;
cpumask_copy(policy->related_cpus, cpu_possible_mask);

return 0;
}

static int tegra_cpu_exit(struct cpufreq_policy *policy)
{
cpufreq_frequency_table_cpuinfo(policy, freq_table);
clk_put(cpu_clk);
return 0;
}

static struct freq_attr *tegra_cpufreq_attr[] = {
&cpufreq_freq_attr_scaling_available_freqs,
NULL,
};

static struct cpufreq_driver tegra_cpufreq_driver = {
.verify	= tegra_verify_speed,
.target	= tegra_target,
.get	= tegra_getspeed,
.init	= tegra_cpu_init,
.exit	= tegra_cpu_exit,
.name	= "tegra",
.attr	= tegra_cpufreq_attr,
};

static int __init tegra_cpufreq_init(void)
{
return cpufreq_register_driver(&tegra_cpufreq_driver);
}

static void __exit tegra_cpufreq_exit(void)
{
cpufreq_unregister_driver(&tegra_cpufreq_driver);
}

MODULE_AUTHOR("Colin Cross <ccross@android.com>");
MODULE_DESCRIPTION("cpufreq driver for Nvidia Tegra2");
MODULE_LICENSE("GPL");
module_init(tegra_cpufreq_init);
module_exit(tegra_cpufreq_exit);

it contains the drivers to set cpu frequencies and scaling...

i suppose that we should find somewhere a module based on this, where?

how to use?