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* elanfreq: cpufreq driver for the AMD ELAN family
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* (c) Copyright 2002 Robert Schwebel <r.schwebel@pengutronix.de>
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* Parts of this code are (c) Sven Geggus <sven@geggus.net>
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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* 2002-02-13: - initial revision for 2.4.18-pre9 by Robert Schwebel
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/delay.h>
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#include <linux/cpufreq.h>
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#include <linux/timex.h>
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#define REG_CSCIR 0x22 /* Chip Setup and Control Index Register */
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#define REG_CSCDR 0x23 /* Chip Setup and Control Data Register */
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/* Module parameter */
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struct s_elan_multiplier {
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int clock; /* frequency in kHz */
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int val40h; /* PMU Force Mode register */
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int val80h; /* CPU Clock Speed Register */
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* It is important that the frequencies
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* are listed in ascending order here!
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static struct s_elan_multiplier elan_multiplier[] = {
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static struct cpufreq_frequency_table elanfreq_table[] = {
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{0, CPUFREQ_TABLE_END},
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* elanfreq_get_cpu_frequency: determine current cpu speed
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* Finds out at which frequency the CPU of the Elan SOC runs
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* at the moment. Frequencies from 1 to 33 MHz are generated
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* the normal way, 66 and 99 MHz are called "Hyperspeed Mode"
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* and have the rest of the chip running with 33 MHz.
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static unsigned int elanfreq_get_cpu_frequency(unsigned int cpu)
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u8 clockspeed_reg; /* Clock Speed Register */
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outb_p(0x80, REG_CSCIR);
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clockspeed_reg = inb_p(REG_CSCDR);
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if ((clockspeed_reg & 0xE0) == 0xE0)
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/* Are we in CPU clock multiplied mode (66/99 MHz)? */
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if ((clockspeed_reg & 0xE0) == 0xC0) {
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if ((clockspeed_reg & 0x01) == 0)
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/* 33 MHz is not 32 MHz... */
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if ((clockspeed_reg & 0xE0) == 0xA0)
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return (1<<((clockspeed_reg & 0xE0) >> 5)) * 1000;
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* elanfreq_set_cpu_frequency: Change the CPU core frequency
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* @freq: frequency in kHz
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* This function takes a frequency value and changes the CPU frequency
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* according to this. Note that the frequency has to be checked by
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* elanfreq_validatespeed() for correctness!
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* There is no return value.
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static void elanfreq_set_cpu_state(unsigned int state)
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struct cpufreq_freqs freqs;
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freqs.old = elanfreq_get_cpu_frequency(0);
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freqs.new = elan_multiplier[state].clock;
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freqs.cpu = 0; /* elanfreq.c is UP only driver */
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cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
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printk(KERN_INFO "elanfreq: attempting to set frequency to %i kHz\n",
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elan_multiplier[state].clock);
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* Access to the Elan's internal registers is indexed via
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* 0x22: Chip Setup & Control Register Index Register (CSCI)
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* 0x23: Chip Setup & Control Register Data Register (CSCD)
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* 0x40 is the Power Management Unit's Force Mode Register.
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* Bit 6 enables Hyperspeed Mode (66/100 MHz core frequency)
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outb_p(0x40, REG_CSCIR); /* Disable hyperspeed mode */
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outb_p(0x00, REG_CSCDR);
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local_irq_enable(); /* wait till internal pipelines and */
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udelay(1000); /* buffers have cleaned up */
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/* now, set the CPU clock speed register (0x80) */
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outb_p(0x80, REG_CSCIR);
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outb_p(elan_multiplier[state].val80h, REG_CSCDR);
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/* now, the hyperspeed bit in PMU Force Mode Register (0x40) */
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outb_p(0x40, REG_CSCIR);
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outb_p(elan_multiplier[state].val40h, REG_CSCDR);
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cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
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* elanfreq_validatespeed: test if frequency range is valid
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* @policy: the policy to validate
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* This function checks if a given frequency range in kHz is valid
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* for the hardware supported by the driver.
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static int elanfreq_verify(struct cpufreq_policy *policy)
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return cpufreq_frequency_table_verify(policy, &elanfreq_table[0]);
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static int elanfreq_target(struct cpufreq_policy *policy,
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unsigned int target_freq,
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unsigned int relation)
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unsigned int newstate = 0;
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if (cpufreq_frequency_table_target(policy, &elanfreq_table[0],
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target_freq, relation, &newstate))
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elanfreq_set_cpu_state(newstate);
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* Module init and exit code
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static int elanfreq_cpu_init(struct cpufreq_policy *policy)
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struct cpuinfo_x86 *c = &cpu_data(0);
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/* capability check */
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if ((c->x86_vendor != X86_VENDOR_AMD) ||
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(c->x86 != 4) || (c->x86_model != 10))
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max_freq = elanfreq_get_cpu_frequency(0);
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for (i = 0; (elanfreq_table[i].frequency != CPUFREQ_TABLE_END); i++) {
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if (elanfreq_table[i].frequency > max_freq)
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elanfreq_table[i].frequency = CPUFREQ_ENTRY_INVALID;
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/* cpuinfo and default policy values */
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policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
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policy->cur = elanfreq_get_cpu_frequency(0);
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result = cpufreq_frequency_table_cpuinfo(policy, elanfreq_table);
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cpufreq_frequency_table_get_attr(elanfreq_table, policy->cpu);
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static int elanfreq_cpu_exit(struct cpufreq_policy *policy)
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cpufreq_frequency_table_put_attr(policy->cpu);
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* elanfreq_setup - elanfreq command line parameter parsing
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* elanfreq command line parameter. Use:
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* to set the maximum CPU frequency to 66 MHz. Note that in
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* case you do not give this boot parameter, the maximum
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* frequency will fall back to _current_ CPU frequency which
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* might be lower. If you build this as a module, use the
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* max_freq module parameter instead.
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static int __init elanfreq_setup(char *str)
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max_freq = simple_strtoul(str, &str, 0);
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printk(KERN_WARNING "You're using the deprecated elanfreq command line option. Use elanfreq.max_freq instead, please!\n");
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__setup("elanfreq=", elanfreq_setup);
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static struct freq_attr *elanfreq_attr[] = {
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&cpufreq_freq_attr_scaling_available_freqs,
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static struct cpufreq_driver elanfreq_driver = {
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.get = elanfreq_get_cpu_frequency,
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.verify = elanfreq_verify,
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.target = elanfreq_target,
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.init = elanfreq_cpu_init,
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.exit = elanfreq_cpu_exit,
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.owner = THIS_MODULE,
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.attr = elanfreq_attr,
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static int __init elanfreq_init(void)
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struct cpuinfo_x86 *c = &cpu_data(0);
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/* Test if we have the right hardware */
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if ((c->x86_vendor != X86_VENDOR_AMD) ||
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(c->x86 != 4) || (c->x86_model != 10)) {
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printk(KERN_INFO "elanfreq: error: no Elan processor found!\n");
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return cpufreq_register_driver(&elanfreq_driver);
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static void __exit elanfreq_exit(void)
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cpufreq_unregister_driver(&elanfreq_driver);
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module_param(max_freq, int, 0444);
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Robert Schwebel <r.schwebel@pengutronix.de>, "
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"Sven Geggus <sven@geggus.net>");
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MODULE_DESCRIPTION("cpufreq driver for AMD's Elan CPUs");
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module_init(elanfreq_init);
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module_exit(elanfreq_exit);