// SPDX-License-Identifier: GPL-2.0-only
/*
 * Intel SpeedStep SMI driver.
 *
 * (C) 2003  Hiroshi Miura <miura@da-cha.org>
 */


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

#define pr_fmt(fmt) "cpufreq: " fmt

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/init.h>
#include <linux/cpufreq.h>
#include <linux/delay.h>
#include <linux/io.h>
#include <asm/ist.h>
#include <asm/cpu_device_id.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;
static int smi_cmd;
static unsigned int smi_sig;

/* info about the processor */
static enum speedstep_processor speedstep_processor;

/*
 * 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},
};

#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

/**
 * speedstep_smi_ownership
 */
static int speedstep_smi_ownership(void)
{
        u32 command, result, magic, dummy;
        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);

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

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

        pr_debug("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, dummy;
        u32 state = 0;
        u32 function = GET_SPEEDSTEP_FREQS;

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

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

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

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

        pr_debug("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_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, dummy;
        unsigned long flags;
        unsigned int function = SET_SPEEDSTEP_STATE;
        unsigned int retry = 0;

        if (state > 0x1)
                return;

        /* Disable IRQs */
        preempt_disable();
        local_irq_save(flags);

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

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

        do {
                if (retry) {
                        /*
                         * We need to enable interrupts, otherwise the blockage
                         * won't resolve.
                         *
                         * We disable preemption so that other processes don't
                         * run. If other processes were running, they could
                         * submit more DMA requests, making the blockage worse.
                         */
                        pr_debug("retry %u, previous result %u, waiting...\n",
                                        retry, result);
                        local_irq_enable();
                        mdelay(retry * 50);
                        local_irq_disable();
                }
                retry++;
                __asm__ __volatile__(
                        "push %%ebp\n"
                        "out %%al, (%%dx)\n"
                        "pop %%ebp"
                        : "=b" (new_state), "=D" (result),
                          "=c" (dummy), "=a" (dummy),
                          "=d" (dummy), "=S" (dummy)
                        : "a" (command), "b" (function), "c" (state),
                          "d" (smi_port), "S" (0), "D" (0)
                        );
        } while ((new_state != state) && (retry <= SMI_TRIES));

        /* enable IRQs */
        local_irq_restore(flags);
        preempt_enable();

        if (new_state == state)
                pr_debug("change to %u MHz succeeded after %u tries "
                        "with result %u\n",
                        (speedstep_freqs[new_state].frequency / 1000),
                        retry, result);
        else
                pr_err("change to state %u failed with new_state %u and result %u\n",
                       state, new_state, result);

        return;
}


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

        return 0;
}


static int speedstep_cpu_init(struct cpufreq_policy *policy)
{
        int result;
        unsigned int *low, *high;

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

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

        /* detect low and high frequency */
        low = &speedstep_freqs[SPEEDSTEP_LOW].frequency;
        high = &speedstep_freqs[SPEEDSTEP_HIGH].frequency;

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

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

        policy->freq_table = speedstep_freqs;

        return 0;
}

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


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

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

        return result;
}

static struct cpufreq_driver speedstep_driver = {
        .name           = "speedstep-smi",
        .flags          = CPUFREQ_NO_AUTO_DYNAMIC_SWITCHING,
        .verify         = cpufreq_generic_frequency_table_verify,
        .target_index   = speedstep_target,
        .init           = speedstep_cpu_init,
        .get            = speedstep_get,
        .resume         = speedstep_resume,
        .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
/* Not auto loaded currently */
MODULE_DEVICE_TABLE(x86cpu, ss_smi_ids);
#endif

/**
 * 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)
{
        if (!x86_match_cpu(ss_smi_ids))
                return -ENODEV;

        speedstep_processor = speedstep_detect_processor();

        switch (speedstep_processor) {
        case SPEEDSTEP_CPU_PIII_T:
        case SPEEDSTEP_CPU_PIII_C:
        case SPEEDSTEP_CPU_PIII_C_EARLY:
                break;
        default:
                speedstep_processor = 0;
        }

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

        pr_debug("signature:0x%.8x, command:0x%.8x, "
                "event:0x%.8x, perf_level:0x%.8x.\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_hw(smi_port, int, ioport, 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);