/*
 * (C) 2001  Dave Jones, Arjan van de ven.
 * (C) 2002 - 2003  Dominik Brodowski <linux@brodo.de>
 *
 *  Licensed under the terms of the GNU GPL License version 2.
 *  Based upon reverse engineered information, and on Intel documentation
 *  for chipsets ICH2-M and ICH3-M.
 *
 *  Many thanks to Ducrot Bruno for finding and fixing the last
 *  "missing link" for ICH2-M/ICH3-M support, and to Thomas Winkler
 *  for extensive testing.
 *
 *  BIG FAT DISCLAIMER: Work in progress code. Possibly *dangerous*
 */


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

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/cpufreq.h>
#include <linux/pci.h>
#include <linux/sched.h>

#include <asm/cpu_device_id.h>

#include "speedstep-lib.h"


/* speedstep_chipset:
 *   It is necessary to know which chipset is used. As accesses to
 * this device occur at various places in this module, we need a
 * static struct pci_dev * pointing to that device.
 */
static struct pci_dev *speedstep_chipset_dev;


/* speedstep_processor
 */
static enum speedstep_processor speedstep_processor;

static u32 pmbase;

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


/**
 * speedstep_find_register - read the PMBASE address
 *
 * Returns: -ENODEV if no register could be found
 */
static int speedstep_find_register(void)
{
        if (!speedstep_chipset_dev)
                return -ENODEV;

        /* get PMBASE */
        pci_read_config_dword(speedstep_chipset_dev, 0x40, &pmbase);
        if (!(pmbase & 0x01)) {
                pr_err("could not find speedstep register\n");
                return -ENODEV;
        }

        pmbase &= 0xFFFFFFFE;
        if (!pmbase) {
                pr_err("could not find speedstep register\n");
                return -ENODEV;
        }

        pr_debug("pmbase is 0x%x\n", pmbase);
        return 0;
}

/**
 * speedstep_set_state - set the SpeedStep state
 * @state: new processor frequency state (SPEEDSTEP_LOW or SPEEDSTEP_HIGH)
 *
 *   Tries to change the SpeedStep state.  Can be called from
 *   smp_call_function_single.
 */
static void speedstep_set_state(unsigned int state)
{
        u8 pm2_blk;
        u8 value;
        unsigned long flags;

        if (state > 0x1)
                return;

        /* Disable IRQs */
        local_irq_save(flags);

        /* read state */
        value = inb(pmbase + 0x50);

        pr_debug("read at pmbase 0x%x + 0x50 returned 0x%x\n", pmbase, value);

        /* write new state */
        value &= 0xFE;
        value |= state;

        pr_debug("writing 0x%x to pmbase 0x%x + 0x50\n", value, pmbase);

        /* Disable bus master arbitration */
        pm2_blk = inb(pmbase + 0x20);
        pm2_blk |= 0x01;
        outb(pm2_blk, (pmbase + 0x20));

        /* Actual transition */
        outb(value, (pmbase + 0x50));

        /* Restore bus master arbitration */
        pm2_blk &= 0xfe;
        outb(pm2_blk, (pmbase + 0x20));

        /* check if transition was successful */
        value = inb(pmbase + 0x50);

        /* Enable IRQs */
        local_irq_restore(flags);

        pr_debug("read at pmbase 0x%x + 0x50 returned 0x%x\n", pmbase, value);

        if (state == (value & 0x1))
                pr_debug("change to %u MHz succeeded\n",
                        speedstep_get_frequency(speedstep_processor) / 1000);
        else
                pr_err("change failed - I/O error\n");

        return;
}

/* Wrapper for smp_call_function_single. */
static void _speedstep_set_state(void *_state)
{
        speedstep_set_state(*(unsigned int *)_state);
}

/**
 * speedstep_activate - activate SpeedStep control in the chipset
 *
 *   Tries to activate the SpeedStep status and control registers.
 * Returns -EINVAL on an unsupported chipset, and zero on success.
 */
static int speedstep_activate(void)
{
        u16 value = 0;

        if (!speedstep_chipset_dev)
                return -EINVAL;

        pci_read_config_word(speedstep_chipset_dev, 0x00A0, &value);
        if (!(value & 0x08)) {
                value |= 0x08;
                pr_debug("activating SpeedStep (TM) registers\n");
                pci_write_config_word(speedstep_chipset_dev, 0x00A0, value);
        }

        return 0;
}


/**
 * speedstep_detect_chipset - detect the Southbridge which contains SpeedStep logic
 *
 *   Detects ICH2-M, ICH3-M and ICH4-M so far. The pci_dev points to
 * the LPC bridge / PM module which contains all power-management
 * functions. Returns the SPEEDSTEP_CHIPSET_-number for the detected
 * chipset, or zero on failure.
 */
static unsigned int speedstep_detect_chipset(void)
{
        speedstep_chipset_dev = pci_get_subsys(PCI_VENDOR_ID_INTEL,
                              PCI_DEVICE_ID_INTEL_82801DB_12,
                              PCI_ANY_ID, PCI_ANY_ID,
                              NULL);
        if (speedstep_chipset_dev)
                return 4; /* 4-M */

        speedstep_chipset_dev = pci_get_subsys(PCI_VENDOR_ID_INTEL,
                              PCI_DEVICE_ID_INTEL_82801CA_12,
                              PCI_ANY_ID, PCI_ANY_ID,
                              NULL);
        if (speedstep_chipset_dev)
                return 3; /* 3-M */


        speedstep_chipset_dev = pci_get_subsys(PCI_VENDOR_ID_INTEL,
                              PCI_DEVICE_ID_INTEL_82801BA_10,
                              PCI_ANY_ID, PCI_ANY_ID,
                              NULL);
        if (speedstep_chipset_dev) {
                /* speedstep.c causes lockups on Dell Inspirons 8000 and
                 * 8100 which use a pretty old revision of the 82815
                 * host bridge. Abort on these systems.
                 */
                static struct pci_dev *hostbridge;

                hostbridge  = pci_get_subsys(PCI_VENDOR_ID_INTEL,
                              PCI_DEVICE_ID_INTEL_82815_MC,
                              PCI_ANY_ID, PCI_ANY_ID,
                              NULL);

                if (!hostbridge)
                        return 2; /* 2-M */

                if (hostbridge->revision < 5) {
                        pr_debug("hostbridge does not support speedstep\n");
                        speedstep_chipset_dev = NULL;
                        pci_dev_put(hostbridge);
                        return 0;
                }

                pci_dev_put(hostbridge);
                return 2; /* 2-M */
        }

        return 0;
}

static void get_freq_data(void *_speed)
{
        unsigned int *speed = _speed;

        *speed = speedstep_get_frequency(speedstep_processor);
}

static unsigned int speedstep_get(unsigned int cpu)
{
        unsigned int speed;

        /* You're supposed to ensure CPU is online. */
        if (smp_call_function_single(cpu, get_freq_data, &speed, 1) != 0)
                BUG();

        pr_debug("detected %u kHz as current frequency\n", speed);
        return speed;
}

/**
 * speedstep_target - set a new CPUFreq policy
 * @policy: new policy
 * @index: index of target frequency
 *
 * Sets a new CPUFreq policy.
 */
static int speedstep_target(struct cpufreq_policy *policy, unsigned int index)
{
        unsigned int policy_cpu;

        policy_cpu = cpumask_any_and(policy->cpus, cpu_online_mask);

        smp_call_function_single(policy_cpu, _speedstep_set_state, &index,
                                 true);

        return 0;
}


struct get_freqs {
        struct cpufreq_policy *policy;
        int ret;
};

static void get_freqs_on_cpu(void *_get_freqs)
{
        struct get_freqs *get_freqs = _get_freqs;

        get_freqs->ret =
                speedstep_get_freqs(speedstep_processor,
                            &speedstep_freqs[SPEEDSTEP_LOW].frequency,
                            &speedstep_freqs[SPEEDSTEP_HIGH].frequency,
                            &get_freqs->policy->cpuinfo.transition_latency,
                            &speedstep_set_state);
}

static int speedstep_cpu_init(struct cpufreq_policy *policy)
{
        unsigned int policy_cpu;
        struct get_freqs gf;

        /* only run on CPU to be set, or on its sibling */
#ifdef CONFIG_SMP
        cpumask_copy(policy->cpus, topology_sibling_cpumask(policy->cpu));
#endif
        policy_cpu = cpumask_any_and(policy->cpus, cpu_online_mask);

        /* detect low and high frequency and transition latency */
        gf.policy = policy;
        smp_call_function_single(policy_cpu, get_freqs_on_cpu, &gf, 1);
        if (gf.ret)
                return gf.ret;

        return cpufreq_table_validate_and_show(policy, speedstep_freqs);
}


static struct cpufreq_driver speedstep_driver = {
        .name   = "speedstep-ich",
        .verify = cpufreq_generic_frequency_table_verify,
        .target_index = speedstep_target,
        .init   = speedstep_cpu_init,
        .get    = speedstep_get,
        .attr   = cpufreq_generic_attr,
};

static const struct x86_cpu_id ss_smi_ids[] = {
        { X86_VENDOR_INTEL, 6, 0xb, },
        { X86_VENDOR_INTEL, 6, 0x8, },
        { X86_VENDOR_INTEL, 15, 2 },
        {}
};
#if 0
/* Autoload or not? Do not for now. */
MODULE_DEVICE_TABLE(x86cpu, ss_smi_ids);
#endif

/**
 * speedstep_init - initializes the SpeedStep CPUFreq driver
 *
 *   Initializes the SpeedStep support. Returns -ENODEV on unsupported
 * devices, -EINVAL on problems during initiatization, and zero on
 * success.
 */
static int __init speedstep_init(void)
{
        if (!x86_match_cpu(ss_smi_ids))
                return -ENODEV;

        /* detect processor */
        speedstep_processor = speedstep_detect_processor();
        if (!speedstep_processor) {
                pr_debug("Intel(R) SpeedStep(TM) capable processor "
                                "not found\n");
                return -ENODEV;
        }

        /* detect chipset */
        if (!speedstep_detect_chipset()) {
                pr_debug("Intel(R) SpeedStep(TM) for this chipset not "
                                "(yet) available.\n");
                return -ENODEV;
        }

        /* activate speedstep support */
        if (speedstep_activate()) {
                pci_dev_put(speedstep_chipset_dev);
                return -EINVAL;
        }

        if (speedstep_find_register())
                return -ENODEV;

        return cpufreq_register_driver(&speedstep_driver);
}


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


MODULE_AUTHOR("Dave Jones, Dominik Brodowski <linux@brodo.de>");
MODULE_DESCRIPTION("Speedstep driver for Intel mobile processors on chipsets "
                "with ICH-M southbridges.");
MODULE_LICENSE("GPL");

module_init(speedstep_init);
module_exit(speedstep_exit);