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speedstep-smi.c

/*
 * Intel SpeedStep SMI driver.
 *
 * (C) 2003  Hiroshi Miura <miura@da-cha.org>
 *
 *  Licensed under the terms of the GNU GPL License version 2.
 *
 */


/*********************************************************************
 *                        SPEEDSTEP - DEFINITIONS                    *
 *********************************************************************/

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>
#include <linux/cpufreq.h>
#include <linux/slab.h>
#include <linux/delay.h>
#include <asm/ist.h>
#include <asm/io.h>

#include "speedstep-lib.h"

/* speedstep system management interface port/command.
 *
 * These parameters are got from IST-SMI BIOS call.
 * If user gives it, these are used.
 *
 */
static int smi_port = 0;
static int smi_cmd = 0;
static unsigned int smi_sig = 0;

/* info about the processor */
static unsigned int speedstep_processor = 0;

/*
 * There are only two frequency states for each processor. Values
 * are in kHz for the time being.
 */
static struct cpufreq_frequency_table speedstep_freqs[] = {
      {SPEEDSTEP_HIGH,  0},
      {SPEEDSTEP_LOW,         0},
      {0,               CPUFREQ_TABLE_END},
};

#define GET_SPEEDSTEP_OWNER 0
#define GET_SPEEDSTEP_STATE 1
#define SET_SPEEDSTEP_STATE 2
#define GET_SPEEDSTEP_FREQS 4

/* how often shall the SMI call be tried if it failed, e.g. because
 * of DMA activity going on? */
#define SMI_TRIES 5

#define dprintk(msg...) cpufreq_debug_printk(CPUFREQ_DEBUG_DRIVER, "speedstep-smi", msg)

/**
 * speedstep_smi_ownership
 */
static int speedstep_smi_ownership (void)
{
      u32 command, result, magic;
      u32 function = GET_SPEEDSTEP_OWNER;
      unsigned char magic_data[] = "Copyright (c) 1999 Intel Corporation";

      command = (smi_sig & 0xffffff00) | (smi_cmd & 0xff);
      magic = virt_to_phys(magic_data);

      dprintk("trying to obtain ownership with command %x at port %x\n", command, smi_port);

      __asm__ __volatile__(
            "out %%al, (%%dx)\n"
            : "=D" (result)
            : "a" (command), "b" (function), "c" (0), "d" (smi_port),
                  "D" (0), "S" (magic)
            : "memory"
      );

      dprintk("result is %x\n", result);

      return result;
}

/**
 * speedstep_smi_get_freqs - get SpeedStep preferred & current freq.
 * @low: the low frequency value is placed here
 * @high: the high frequency value is placed here
 *
 * Only available on later SpeedStep-enabled systems, returns false results or
 * even hangs [cf. bugme.osdl.org # 1422] on earlier systems. Empirical testing
 * shows that the latter occurs if !(ist_info.event & 0xFFFF).
 */
static int speedstep_smi_get_freqs (unsigned int *low, unsigned int *high)
{
      u32 command, result = 0, edi, high_mhz, low_mhz;
      u32 state=0;
      u32 function = GET_SPEEDSTEP_FREQS;

      if (!(ist_info.event & 0xFFFF)) {
            dprintk("bug #1422 -- can't read freqs from BIOS\n");
            return -ENODEV;
      }

      command = (smi_sig & 0xffffff00) | (smi_cmd & 0xff);

      dprintk("trying to determine frequencies with command %x at port %x\n", command, smi_port);

      __asm__ __volatile__("movl $0, %%edi\n"
            "out %%al, (%%dx)\n"
            : "=a" (result), "=b" (high_mhz), "=c" (low_mhz), "=d" (state), "=D" (edi)
            : "a" (command), "b" (function), "c" (state), "d" (smi_port), "S" (0)
      );

      dprintk("result %x, low_freq %u, high_freq %u\n", result, low_mhz, high_mhz);

      /* abort if results are obviously incorrect... */
      if ((high_mhz + low_mhz) < 600)
            return -EINVAL;

      *high = high_mhz * 1000;
      *low  = low_mhz  * 1000;

      return result;
}

/**
 * speedstep_get_state - set the SpeedStep state
 * @state: processor frequency state (SPEEDSTEP_LOW or SPEEDSTEP_HIGH)
 *
 */
static int speedstep_get_state (void)
{
      u32 function=GET_SPEEDSTEP_STATE;
      u32 result, state, edi, command;

      command = (smi_sig & 0xffffff00) | (smi_cmd & 0xff);

      dprintk("trying to determine current setting with command %x at port %x\n", command, smi_port);

      __asm__ __volatile__("movl $0, %%edi\n"
            "out %%al, (%%dx)\n"
            : "=a" (result), "=b" (state), "=D" (edi)
            : "a" (command), "b" (function), "c" (0), "d" (smi_port), "S" (0)
      );

      dprintk("state is %x, result is %x\n", state, result);

      return (state & 1);
}


/**
 * speedstep_set_state - set the SpeedStep state
 * @state: new processor frequency state (SPEEDSTEP_LOW or SPEEDSTEP_HIGH)
 *
 */
static void speedstep_set_state (unsigned int state)
{
      unsigned int result = 0, command, new_state;
      unsigned long flags;
      unsigned int function=SET_SPEEDSTEP_STATE;
      unsigned int retry = 0;

      if (state > 0x1)
            return;

      /* Disable IRQs */
      local_irq_save(flags);

      command = (smi_sig & 0xffffff00) | (smi_cmd & 0xff);

      dprintk("trying to set frequency to state %u with command %x at port %x\n", state, command, smi_port);

      do {
            if (retry) {
                  dprintk("retry %u, previous result %u, waiting...\n", retry, result);
                  mdelay(retry * 50);
            }
            retry++;
            __asm__ __volatile__(
                  "movl $0, %%edi\n"
                  "out %%al, (%%dx)\n"
                  : "=b" (new_state), "=D" (result)
                  : "a" (command), "b" (function), "c" (state), "d" (smi_port), "S" (0)
                  );
      } while ((new_state != state) && (retry <= SMI_TRIES));

      /* enable IRQs */
      local_irq_restore(flags);

      if (new_state == state) {
            dprintk("change to %u MHz succeeded after %u tries with result %u\n", (speedstep_freqs[new_state].frequency / 1000), retry, result);
      } else {
            printk(KERN_ERR "cpufreq: change failed with new_state %u and result %u\n", new_state, result);
      }

      return;
}


/**
 * speedstep_target - set a new CPUFreq policy
 * @policy: new policy
 * @target_freq: new freq
 * @relation:
 *
 * Sets a new CPUFreq policy/freq.
 */
static int speedstep_target (struct cpufreq_policy *policy,
                  unsigned int target_freq, unsigned int relation)
{
      unsigned int newstate = 0;
      struct cpufreq_freqs freqs;

      if (cpufreq_frequency_table_target(policy, &speedstep_freqs[0], target_freq, relation, &newstate))
            return -EINVAL;

      freqs.old = speedstep_freqs[speedstep_get_state()].frequency;
      freqs.new = speedstep_freqs[newstate].frequency;
      freqs.cpu = 0; /* speedstep.c is UP only driver */

      if (freqs.old == freqs.new)
            return 0;

      cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
      speedstep_set_state(newstate);
      cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);

      return 0;
}


/**
 * speedstep_verify - verifies a new CPUFreq policy
 * @policy: new policy
 *
 * Limit must be within speedstep_low_freq and speedstep_high_freq, with
 * at least one border included.
 */
static int speedstep_verify (struct cpufreq_policy *policy)
{
      return cpufreq_frequency_table_verify(policy, &speedstep_freqs[0]);
}


static int speedstep_cpu_init(struct cpufreq_policy *policy)
{
      int result;
      unsigned int speed,state;

      /* capability check */
      if (policy->cpu != 0)
            return -ENODEV;

      result = speedstep_smi_ownership();
      if (result) {
            dprintk("fails in aquiring ownership of a SMI interface.\n");
            return -EINVAL;
      }

      /* detect low and high frequency */
      result = speedstep_smi_get_freqs(&speedstep_freqs[SPEEDSTEP_LOW].frequency,
                        &speedstep_freqs[SPEEDSTEP_HIGH].frequency);
      if (result) {
            /* fall back to speedstep_lib.c dection mechanism: try both states out */
            dprintk("could not detect low and high frequencies by SMI call.\n");
            result = speedstep_get_freqs(speedstep_processor,
                        &speedstep_freqs[SPEEDSTEP_LOW].frequency,
                        &speedstep_freqs[SPEEDSTEP_HIGH].frequency,
                        NULL,
                        &speedstep_set_state);

            if (result) {
                  dprintk("could not detect two different speeds -- aborting.\n");
                  return result;
            } else
                  dprintk("workaround worked.\n");
      }

      /* get current speed setting */
      state = speedstep_get_state();
      speed = speedstep_freqs[state].frequency;

      dprintk("currently at %s speed setting - %i MHz\n",
            (speed == speedstep_freqs[SPEEDSTEP_LOW].frequency) ? "low" : "high",
            (speed / 1000));

      /* cpuinfo and default policy values */
      policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
      policy->cur = speed;

      result = cpufreq_frequency_table_cpuinfo(policy, speedstep_freqs);
      if (result)
            return (result);

      cpufreq_frequency_table_get_attr(speedstep_freqs, policy->cpu);

      return 0;
}

static int speedstep_cpu_exit(struct cpufreq_policy *policy)
{
      cpufreq_frequency_table_put_attr(policy->cpu);
      return 0;
}

static unsigned int speedstep_get(unsigned int cpu)
{
      if (cpu)
            return -ENODEV;
      return speedstep_get_processor_frequency(speedstep_processor);
}


static int speedstep_resume(struct cpufreq_policy *policy)
{
      int result = speedstep_smi_ownership();

      if (result)
            dprintk("fails in re-aquiring ownership of a SMI interface.\n");

      return result;
}

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

static struct cpufreq_driver speedstep_driver = {
      .name       = "speedstep-smi",
      .verify           = speedstep_verify,
      .target           = speedstep_target,
      .init       = speedstep_cpu_init,
      .exit       = speedstep_cpu_exit,
      .get        = speedstep_get,
      .resume           = speedstep_resume,
      .owner            = THIS_MODULE,
      .attr       = speedstep_attr,
};

/**
 * speedstep_init - initializes the SpeedStep CPUFreq driver
 *
 *   Initializes the SpeedStep support. Returns -ENODEV on unsupported
 * BIOS, -EINVAL on problems during initiatization, and zero on
 * success.
 */
static int __init speedstep_init(void)
{
      speedstep_processor = speedstep_detect_processor();

      switch (speedstep_processor) {
      case SPEEDSTEP_PROCESSOR_PIII_T:
      case SPEEDSTEP_PROCESSOR_PIII_C:
      case SPEEDSTEP_PROCESSOR_PIII_C_EARLY:
            break;
      default:
            speedstep_processor = 0;
      }

      if (!speedstep_processor) {
            dprintk ("No supported Intel CPU detected.\n");
            return -ENODEV;
      }

      dprintk("signature:0x%.8lx, command:0x%.8lx, event:0x%.8lx, perf_level:0x%.8lx.\n",
            ist_info.signature, ist_info.command, ist_info.event, ist_info.perf_level);

      /* Error if no IST-SMI BIOS or no PARM
             sig= 'ISGE' aka 'Intel Speedstep Gate E' */
      if ((ist_info.signature !=  0x47534943) && (
          (smi_port == 0) || (smi_cmd == 0)))
            return -ENODEV;

      if (smi_sig == 1)
            smi_sig = 0x47534943;
      else
            smi_sig = ist_info.signature;

      /* setup smi_port from MODLULE_PARM or BIOS */
      if ((smi_port > 0xff) || (smi_port < 0))
            return -EINVAL;
      else if (smi_port == 0)
            smi_port = ist_info.command & 0xff;

      if ((smi_cmd > 0xff) || (smi_cmd < 0))
            return -EINVAL;
      else if (smi_cmd == 0)
            smi_cmd = (ist_info.command >> 16) & 0xff;

      return cpufreq_register_driver(&speedstep_driver);
}


/**
 * speedstep_exit - unregisters SpeedStep support
 *
 *   Unregisters SpeedStep support.
 */
static void __exit speedstep_exit(void)
{
      cpufreq_unregister_driver(&speedstep_driver);
}

module_param(smi_port,  int, 0444);
module_param(smi_cmd,   int, 0444);
module_param(smi_sig,  uint, 0444);

MODULE_PARM_DESC(smi_port, "Override the BIOS-given IST port with this value -- Intel's default setting is 0xb2");
MODULE_PARM_DESC(smi_cmd, "Override the BIOS-given IST command with this value -- Intel's default setting is 0x82");
MODULE_PARM_DESC(smi_sig, "Set to 1 to fake the IST signature when using the SMI interface.");

MODULE_AUTHOR ("Hiroshi Miura");
MODULE_DESCRIPTION ("Speedstep driver for IST applet SMI interface.");
MODULE_LICENSE ("GPL");

module_init(speedstep_init);
module_exit(speedstep_exit);

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