gx-suspmod.c

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/*
 *  Cyrix MediaGX and NatSemi Geode Suspend Modulation
 *  (C) 2002 Zwane Mwaikambo <[email protected]>
 *  (C) 2002 Hiroshi Miura   <[email protected]>
 *  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 <[email protected]>
 *      - fix on/off register mistake
 *      - fix cpu_khz calc when it stops cpu modulation.
 *
 *  Dec. 11, 2002   Hiroshi Miura <[email protected]>
 *      - rewrite for Cyrix MediaGX Cx5510/5520 and
 *        NatSemi Geode Cs5530(A).
 *
 *  Jul. ??, 2002  Zwane Mwaikambo <[email protected]>
 *      - 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 <linux/errno.h>
#include <linux/slab.h>

#include <asm/cpu_device_id.h>
#include <asm/processor-cyrix.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;
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


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_VDEVICE(CYRIX, PCI_DEVICE_ID_CYRIX_5530_LEGACY), },
    { PCI_VDEVICE(CYRIX, PCI_DEVICE_ID_CYRIX_5520), },
    { PCI_VDEVICE(CYRIX, PCI_DEVICE_ID_CYRIX_5510), },
    { 0, },
};
MODULE_DEVICE_TABLE(pci, gx_chipset_tbl);

static void gx_write_byte(int reg, int value)
{
    pci_write_config_byte(gx_params->cs55x0, reg, value);
}

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

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

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

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);
}

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;
}


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 */
            /* typical 2 to 4ms */
            gx_write_byte(PCI_IRQTC, 4);
            /* typical 50 to 100ms */
            gx_write_byte(PCI_VIDTC, 100);
            gx_write_byte(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);
            pr_debug("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;
        pr_debug("suspend modulation disabled: cpu runs 100%% speed.\n");
    }

    gx_write_byte(PCI_MODOFF, gx_params->off_duration);
    gx_write_byte(PCI_MODON, gx_params->on_duration);

    gx_write_byte(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);

    pr_debug("suspend modulation w/ duration of ON:%d us, OFF:%d us\n",
        gx_params->on_duration * 32, gx_params->off_duration * 32);
    pr_debug("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);

    pr_debug("cpu max frequency is %d.\n", maxfreq);
    pr_debug("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 */
    gx_pci = gx_detect_chipset();
    if (gx_pci == NULL)
        return -ENODEV;

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

    pr_debug("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));

    ret = cpufreq_register_driver(&gx_suspmod_driver);
    if (ret) {
        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 <[email protected]>");
MODULE_DESCRIPTION("Cpufreq driver for Cyrix MediaGX and NatSemi Geode");
MODULE_LICENSE("GPL");

module_init(cpufreq_gx_init);
module_exit(cpufreq_gx_exit);