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gx-suspmod.c

/*
 *    Cyrix MediaGX and NatSemi Geode Suspend Modulation
 *    (C) 2002 Zwane Mwaikambo <zwane@commfireservices.com>
 *    (C) 2002 Hiroshi Miura   <miura@da-cha.org>
 *    All Rights Reserved
 *
 *    This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      version 2 as published by the Free Software Foundation
 *
 *      The author(s) of this software shall not be held liable for damages
 *      of any nature resulting due to the use of this software. This
 *      software is provided AS-IS with no warranties.
 *
 * Theoretical note:
 *
 *    (see Geode(tm) CS5530 manual (rev.4.1) page.56)
 *
 *    CPU frequency control on NatSemi Geode GX1/GXLV processor and CS55x0
 *    are based on Suspend Modulation.
 *
 *    Suspend Modulation works by asserting and de-asserting the SUSP# pin
 *    to CPU(GX1/GXLV) for configurable durations. When asserting SUSP#
 *    the CPU enters an idle state. GX1 stops its core clock when SUSP# is
 *    asserted then power consumption is reduced.
 *
 *    Suspend Modulation's OFF/ON duration are configurable
 *    with 'Suspend Modulation OFF Count Register'
 *    and 'Suspend Modulation ON Count Register'.
 *    These registers are 8bit counters that represent the number of
 *    32us intervals which the SUSP# pin is asserted(ON)/de-asserted(OFF)
 *    to the processor.
 *
 *    These counters define a ratio which is the effective frequency
 *    of operation of the system.
 *
 *                       OFF Count
 *    F_eff = Fgx * ----------------------
 *                    OFF Count + ON Count
 *
 *    0 <= On Count, Off Count <= 255
 *
 *    From these limits, we can get register values
 *
 *    off_duration + on_duration <= MAX_DURATION
 *    on_duration = off_duration * (stock_freq - freq) / freq
 *
 *      off_duration  =  (freq * DURATION) / stock_freq
 *      on_duration = DURATION - off_duration
 *
 *
 *---------------------------------------------------------------------------
 *
 * ChangeLog:
 *    Dec. 12, 2003     Hiroshi Miura <miura@da-cha.org>
 *          - fix on/off register mistake
 *          - fix cpu_khz calc when it stops cpu modulation.
 *
 *    Dec. 11, 2002     Hiroshi Miura <miura@da-cha.org>
 *          - rewrite for Cyrix MediaGX Cx5510/5520 and
 *            NatSemi Geode Cs5530(A).
 *
 *    Jul. ??, 2002  Zwane Mwaikambo <zwane@commfireservices.com>
 *          - cs5530_mod patch for 2.4.19-rc1.
 *
 *---------------------------------------------------------------------------
 *
 * Todo
 *    Test on machines with 5510, 5530, 5530A
 */

/************************************************************************
 *                Suspend Modulation - Definitions          *
 ************************************************************************/

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/smp.h>
#include <linux/cpufreq.h>
#include <linux/pci.h>
#include <asm/processor-cyrix.h>
#include <asm/errno.h>

/* PCI config registers, all at F0 */
#define PCI_PMER1 0x80  /* power management enable register 1 */
#define PCI_PMER2 0x81  /* power management enable register 2 */
#define PCI_PMER3 0x82  /* power management enable register 3 */
#define PCI_IRQTC 0x8c  /* irq speedup timer counter register:typical 2 to 4ms */
#define PCI_VIDTC 0x8d  /* video speedup timer counter register: typical 50 to 100ms */
#define PCI_MODOFF      0x94  /* suspend modulation OFF counter register, 1 = 32us */
#define PCI_MODON 0x95  /* suspend modulation ON counter register */
#define PCI_SUSCFG      0x96  /* suspend configuration register */

/* PMER1 bits */
#define GPM       (1<<0)      /* global power management */
#define GIT       (1<<1)      /* globally enable PM device idle timers */
#define GTR       (1<<2)      /* globally enable IO traps */
#define IRQ_SPDUP (1<<3)      /* disable clock throttle during interrupt handling */
#define VID_SPDUP (1<<4)      /* disable clock throttle during vga video handling */

/* SUSCFG bits */
#define SUSMOD          (1<<0)      /* enable/disable suspend modulation */
/* the below is supported only with cs5530 (after rev.1.2)/cs5530A */
#define SMISPDUP  (1<<1)      /* select how SMI re-enable suspend modulation: */
                        /* IRQTC timer or read SMI speedup disable reg.(F1BAR[08-09h]) */
#define SUSCFG          (1<<2)      /* enable powering down a GXLV processor. "Special 3Volt Suspend" mode */
/* the below is supported only with cs5530A */
#define PWRSVE_ISA      (1<<3)      /* stop ISA clock  */
#define PWRSVE          (1<<4)      /* active idle */

struct gxfreq_params {
      u8 on_duration;
      u8 off_duration;
      u8 pci_suscfg;
      u8 pci_pmer1;
      u8 pci_pmer2;
      struct pci_dev *cs55x0;
};

static struct gxfreq_params *gx_params;
static int stock_freq;

/* PCI bus clock - defaults to 30.000 if cpu_khz is not available */
static int pci_busclk = 0;
module_param (pci_busclk, int, 0444);

/* maximum duration for which the cpu may be suspended
 * (32us * MAX_DURATION). If no parameter is given, this defaults
 * to 255.
 * Note that this leads to a maximum of 8 ms(!) where the CPU clock
 * is suspended -- processing power is just 0.39% of what it used to be,
 * though. 781.25 kHz(!) for a 200 MHz processor -- wow. */
static int max_duration = 255;
module_param (max_duration, int, 0444);

/* For the default policy, we want at least some processing power
 * - let's say 5%. (min = maxfreq / POLICY_MIN_DIV)
 */
#define POLICY_MIN_DIV 20


#define dprintk(msg...) cpufreq_debug_printk(CPUFREQ_DEBUG_DRIVER, "gx-suspmod", msg)

/**
 * we can detect a core multipiler from dir0_lsb
 * from GX1 datasheet p.56,
 *    MULT[3:0]:
 *    0000 = SYSCLK multiplied by 4 (test only)
 *    0001 = SYSCLK multiplied by 10
 *    0010 = SYSCLK multiplied by 4
 *    0011 = SYSCLK multiplied by 6
 *    0100 = SYSCLK multiplied by 9
 *    0101 = SYSCLK multiplied by 5
 *    0110 = SYSCLK multiplied by 7
 *    0111 = SYSCLK multiplied by 8
 *              of 33.3MHz
 **/
static int gx_freq_mult[16] = {
            4, 10, 4, 6, 9, 5, 7, 8,
            0, 0, 0, 0, 0, 0, 0, 0
};


/****************************************************************
 *    Low Level chipset interface                     *
 ****************************************************************/
static struct pci_device_id gx_chipset_tbl[] __initdata = {
      { PCI_VENDOR_ID_CYRIX, PCI_DEVICE_ID_CYRIX_5530_LEGACY, PCI_ANY_ID, PCI_ANY_ID },
      { PCI_VENDOR_ID_CYRIX, PCI_DEVICE_ID_CYRIX_5520, PCI_ANY_ID, PCI_ANY_ID },
      { PCI_VENDOR_ID_CYRIX, PCI_DEVICE_ID_CYRIX_5510, PCI_ANY_ID, PCI_ANY_ID },
      { 0, },
};

/**
 * gx_detect_chipset:
 *
 **/
static __init struct pci_dev *gx_detect_chipset(void)
{
      struct pci_dev *gx_pci = NULL;

      /* check if CPU is a MediaGX or a Geode. */
      if ((current_cpu_data.x86_vendor != X86_VENDOR_NSC) &&
          (current_cpu_data.x86_vendor != X86_VENDOR_CYRIX)) {
            dprintk("error: no MediaGX/Geode processor found!\n");
            return NULL;
      }

      /* detect which companion chip is used */
      while ((gx_pci = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, gx_pci)) != NULL) {
            if ((pci_match_id(gx_chipset_tbl, gx_pci)) != NULL)
                  return gx_pci;
      }

      dprintk("error: no supported chipset found!\n");
      return NULL;
}

/**
 * gx_get_cpuspeed:
 *
 * Finds out at which efficient frequency the Cyrix MediaGX/NatSemi Geode CPU runs.
 */
static unsigned int gx_get_cpuspeed(unsigned int cpu)
{
      if ((gx_params->pci_suscfg & SUSMOD) == 0)
            return stock_freq;

      return (stock_freq * gx_params->off_duration)
            / (gx_params->on_duration + gx_params->off_duration);
}

/**
 *      gx_validate_speed:
 *      determine current cpu speed
 *
 **/

static unsigned int gx_validate_speed(unsigned int khz, u8 *on_duration, u8 *off_duration)
{
      unsigned int i;
      u8 tmp_on, tmp_off;
      int old_tmp_freq = stock_freq;
      int tmp_freq;

      *off_duration=1;
      *on_duration=0;

      for (i=max_duration; i>0; i--) {
            tmp_off = ((khz * i) / stock_freq) & 0xff;
            tmp_on = i - tmp_off;
            tmp_freq = (stock_freq * tmp_off) / i;
            /* if this relation is closer to khz, use this. If it's equal,
             * prefer it, too - lower latency */
            if (abs(tmp_freq - khz) <= abs(old_tmp_freq - khz)) {
                  *on_duration = tmp_on;
                  *off_duration = tmp_off;
                  old_tmp_freq = tmp_freq;
            }
      }

      return old_tmp_freq;
}


/**
 * gx_set_cpuspeed:
 * set cpu speed in khz.
 **/

static void gx_set_cpuspeed(unsigned int khz)
{
      u8 suscfg, pmer1;
      unsigned int new_khz;
      unsigned long flags;
      struct cpufreq_freqs freqs;

      freqs.cpu = 0;
      freqs.old = gx_get_cpuspeed(0);

      new_khz = gx_validate_speed(khz, &gx_params->on_duration, &gx_params->off_duration);

      freqs.new = new_khz;

      cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
      local_irq_save(flags);

      if (new_khz != stock_freq) {  /* if new khz == 100% of CPU speed, it is special case */
            switch (gx_params->cs55x0->device) {
            case PCI_DEVICE_ID_CYRIX_5530_LEGACY:
                  pmer1 = gx_params->pci_pmer1 | IRQ_SPDUP | VID_SPDUP;
                  /* FIXME: need to test other values -- Zwane,Miura */
                  pci_write_config_byte(gx_params->cs55x0, PCI_IRQTC, 4); /* typical 2 to 4ms */
                  pci_write_config_byte(gx_params->cs55x0, PCI_VIDTC, 100);/* typical 50 to 100ms */
                  pci_write_config_byte(gx_params->cs55x0, PCI_PMER1, pmer1);

                  if (gx_params->cs55x0->revision < 0x10) {   /* CS5530(rev 1.2, 1.3) */
                        suscfg = gx_params->pci_suscfg | SUSMOD;
                  } else {                           /* CS5530A,B.. */
                        suscfg = gx_params->pci_suscfg | SUSMOD | PWRSVE;
                  }
                  break;
            case PCI_DEVICE_ID_CYRIX_5520:
            case PCI_DEVICE_ID_CYRIX_5510:
                  suscfg = gx_params->pci_suscfg | SUSMOD;
                  break;
            default:
                  local_irq_restore(flags);
                  dprintk("fatal: try to set unknown chipset.\n");
                  return;
            }
      } else {
            suscfg = gx_params->pci_suscfg & ~(SUSMOD);
            gx_params->off_duration = 0;
            gx_params->on_duration = 0;
            dprintk("suspend modulation disabled: cpu runs 100 percent speed.\n");
      }

      pci_write_config_byte(gx_params->cs55x0, PCI_MODOFF, gx_params->off_duration);
      pci_write_config_byte(gx_params->cs55x0, PCI_MODON, gx_params->on_duration);

      pci_write_config_byte(gx_params->cs55x0, PCI_SUSCFG, suscfg);
      pci_read_config_byte(gx_params->cs55x0, PCI_SUSCFG, &suscfg);

      local_irq_restore(flags);

      gx_params->pci_suscfg = suscfg;

      cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);

      dprintk("suspend modulation w/ duration of ON:%d us, OFF:%d us\n",
            gx_params->on_duration * 32, gx_params->off_duration * 32);
      dprintk("suspend modulation w/ clock speed: %d kHz.\n", freqs.new);
}

/****************************************************************
 *             High level functions                             *
 ****************************************************************/

/*
 *    cpufreq_gx_verify: test if frequency range is valid
 *
 *    This function checks if a given frequency range in kHz is valid
 *      for the hardware supported by the driver.
 */

static int cpufreq_gx_verify(struct cpufreq_policy *policy)
{
      unsigned int tmp_freq = 0;
      u8 tmp1, tmp2;

      if (!stock_freq || !policy)
            return -EINVAL;

      policy->cpu = 0;
      cpufreq_verify_within_limits(policy, (stock_freq / max_duration), stock_freq);

      /* it needs to be assured that at least one supported frequency is
       * within policy->min and policy->max. If it is not, policy->max
       * needs to be increased until one freuqency is supported.
       * policy->min may not be decreased, though. This way we guarantee a
       * specific processing capacity.
       */
      tmp_freq = gx_validate_speed(policy->min, &tmp1, &tmp2);
      if (tmp_freq < policy->min)
            tmp_freq += stock_freq / max_duration;
      policy->min = tmp_freq;
      if (policy->min > policy->max)
            policy->max = tmp_freq;
      tmp_freq = gx_validate_speed(policy->max, &tmp1, &tmp2);
      if (tmp_freq > policy->max)
            tmp_freq -= stock_freq / max_duration;
      policy->max = tmp_freq;
      if (policy->max < policy->min)
            policy->max = policy->min;
      cpufreq_verify_within_limits(policy, (stock_freq / max_duration), stock_freq);

      return 0;
}

/*
 *      cpufreq_gx_target:
 *
 */
static int cpufreq_gx_target(struct cpufreq_policy *policy,
                       unsigned int target_freq,
                       unsigned int relation)
{
      u8 tmp1, tmp2;
      unsigned int tmp_freq;

      if (!stock_freq || !policy)
            return -EINVAL;

      policy->cpu = 0;

      tmp_freq = gx_validate_speed(target_freq, &tmp1, &tmp2);
      while (tmp_freq < policy->min) {
            tmp_freq += stock_freq / max_duration;
            tmp_freq = gx_validate_speed(tmp_freq, &tmp1, &tmp2);
      }
      while (tmp_freq > policy->max) {
            tmp_freq -= stock_freq / max_duration;
            tmp_freq = gx_validate_speed(tmp_freq, &tmp1, &tmp2);
      }

      gx_set_cpuspeed(tmp_freq);

      return 0;
}

static int cpufreq_gx_cpu_init(struct cpufreq_policy *policy)
{
      unsigned int maxfreq, curfreq;

      if (!policy || policy->cpu != 0)
            return -ENODEV;

      /* determine maximum frequency */
      if (pci_busclk) {
            maxfreq = pci_busclk * gx_freq_mult[getCx86(CX86_DIR1) & 0x0f];
      } else if (cpu_khz) {
            maxfreq = cpu_khz;
      } else {
            maxfreq = 30000 * gx_freq_mult[getCx86(CX86_DIR1) & 0x0f];
      }
      stock_freq = maxfreq;
      curfreq = gx_get_cpuspeed(0);

      dprintk("cpu max frequency is %d.\n", maxfreq);
      dprintk("cpu current frequency is %dkHz.\n",curfreq);

      /* setup basic struct for cpufreq API */
      policy->cpu = 0;

      if (max_duration < POLICY_MIN_DIV)
            policy->min = maxfreq / max_duration;
      else
            policy->min = maxfreq / POLICY_MIN_DIV;
      policy->max = maxfreq;
      policy->cur = curfreq;
      policy->cpuinfo.min_freq = maxfreq / max_duration;
      policy->cpuinfo.max_freq = maxfreq;
      policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;

      return 0;
}

/*
 * cpufreq_gx_init:
 *   MediaGX/Geode GX initialize cpufreq driver
 */
static struct cpufreq_driver gx_suspmod_driver = {
      .get        = gx_get_cpuspeed,
      .verify           = cpufreq_gx_verify,
      .target           = cpufreq_gx_target,
      .init       = cpufreq_gx_cpu_init,
      .name       = "gx-suspmod",
      .owner            = THIS_MODULE,
};

static int __init cpufreq_gx_init(void)
{
      int ret;
      struct gxfreq_params *params;
      struct pci_dev *gx_pci;

      /* Test if we have the right hardware */
      if ((gx_pci = gx_detect_chipset()) == NULL)
            return -ENODEV;

      /* check whether module parameters are sane */
      if (max_duration > 0xff)
            max_duration = 0xff;

      dprintk("geode suspend modulation available.\n");

      params = kzalloc(sizeof(struct gxfreq_params), GFP_KERNEL);
      if (params == NULL)
            return -ENOMEM;

      params->cs55x0 = gx_pci;
      gx_params = params;

      /* keep cs55x0 configurations */
      pci_read_config_byte(params->cs55x0, PCI_SUSCFG, &(params->pci_suscfg));
      pci_read_config_byte(params->cs55x0, PCI_PMER1, &(params->pci_pmer1));
      pci_read_config_byte(params->cs55x0, PCI_PMER2, &(params->pci_pmer2));
      pci_read_config_byte(params->cs55x0, PCI_MODON, &(params->on_duration));
      pci_read_config_byte(params->cs55x0, PCI_MODOFF, &(params->off_duration));

      if ((ret = cpufreq_register_driver(&gx_suspmod_driver))) {
            kfree(params);
            return ret;                   /* register error! */
      }

      return 0;
}

static void __exit cpufreq_gx_exit(void)
{
      cpufreq_unregister_driver(&gx_suspmod_driver);
      pci_dev_put(gx_params->cs55x0);
      kfree(gx_params);
}

MODULE_AUTHOR ("Hiroshi Miura <miura@da-cha.org>");
MODULE_DESCRIPTION ("Cpufreq driver for Cyrix MediaGX and NatSemi Geode");
MODULE_LICENSE ("GPL");

module_init(cpufreq_gx_init);
module_exit(cpufreq_gx_exit);


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