/*
 *      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 <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


/**
 * 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_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);
}

/**
 * gx_detect_chipset:
 *
 **/
static struct pci_dev * __init 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;
}

/**
 * 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(struct cpufreq_policy *policy, unsigned int khz)
{
        u8 suscfg, pmer1;
        unsigned int new_khz;
        unsigned long flags;
        struct cpufreq_freqs freqs;

        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_freq_transition_begin(policy, &freqs);
        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_freq_transition_end(policy, &freqs, 0);

        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(policy, tmp_freq);

        return 0;
}

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

        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;

        pr_debug("cpu max frequency is %d.\n", maxfreq);

        /* 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->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",
};

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(*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 <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);