longrun.c

Go to the documentation of this file.

/*
 * (C) 2002 - 2003  Dominik Brodowski <[email protected]>
 *
 *  Licensed under the terms of the GNU GPL License version 2.
 *
 *  BIG FAT DISCLAIMER: Work in progress code. Possibly *dangerous*
 */

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

#include <asm/msr.h>
#include <asm/processor.h>
#include <asm/cpu_device_id.h>

static struct cpufreq_driver    longrun_driver;

static unsigned int longrun_low_freq, longrun_high_freq;


static void __cpuinit longrun_get_policy(struct cpufreq_policy *policy)
{
    u32 msr_lo, msr_hi;

    rdmsr(MSR_TMTA_LONGRUN_FLAGS, msr_lo, msr_hi);
    pr_debug("longrun flags are %x - %x\n", msr_lo, msr_hi);
    if (msr_lo & 0x01)
        policy->policy = CPUFREQ_POLICY_PERFORMANCE;
    else
        policy->policy = CPUFREQ_POLICY_POWERSAVE;

    rdmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
    pr_debug("longrun ctrl is %x - %x\n", msr_lo, msr_hi);
    msr_lo &= 0x0000007F;
    msr_hi &= 0x0000007F;

    if (longrun_high_freq <= longrun_low_freq) {
        /* Assume degenerate Longrun table */
        policy->min = policy->max = longrun_high_freq;
    } else {
        policy->min = longrun_low_freq + msr_lo *
            ((longrun_high_freq - longrun_low_freq) / 100);
        policy->max = longrun_low_freq + msr_hi *
            ((longrun_high_freq - longrun_low_freq) / 100);
    }
    policy->cpu = 0;
}


static int longrun_set_policy(struct cpufreq_policy *policy)
{
    u32 msr_lo, msr_hi;
    u32 pctg_lo, pctg_hi;

    if (!policy)
        return -EINVAL;

    if (longrun_high_freq <= longrun_low_freq) {
        /* Assume degenerate Longrun table */
        pctg_lo = pctg_hi = 100;
    } else {
        pctg_lo = (policy->min - longrun_low_freq) /
            ((longrun_high_freq - longrun_low_freq) / 100);
        pctg_hi = (policy->max - longrun_low_freq) /
            ((longrun_high_freq - longrun_low_freq) / 100);
    }

    if (pctg_hi > 100)
        pctg_hi = 100;
    if (pctg_lo > pctg_hi)
        pctg_lo = pctg_hi;

    /* performance or economy mode */
    rdmsr(MSR_TMTA_LONGRUN_FLAGS, msr_lo, msr_hi);
    msr_lo &= 0xFFFFFFFE;
    switch (policy->policy) {
    case CPUFREQ_POLICY_PERFORMANCE:
        msr_lo |= 0x00000001;
        break;
    case CPUFREQ_POLICY_POWERSAVE:
        break;
    }
    wrmsr(MSR_TMTA_LONGRUN_FLAGS, msr_lo, msr_hi);

    /* lower and upper boundary */
    rdmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
    msr_lo &= 0xFFFFFF80;
    msr_hi &= 0xFFFFFF80;
    msr_lo |= pctg_lo;
    msr_hi |= pctg_hi;
    wrmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);

    return 0;
}


static int longrun_verify_policy(struct cpufreq_policy *policy)
{
    if (!policy)
        return -EINVAL;

    policy->cpu = 0;
    cpufreq_verify_within_limits(policy,
        policy->cpuinfo.min_freq,
        policy->cpuinfo.max_freq);

    if ((policy->policy != CPUFREQ_POLICY_POWERSAVE) &&
        (policy->policy != CPUFREQ_POLICY_PERFORMANCE))
        return -EINVAL;

    return 0;
}

static unsigned int longrun_get(unsigned int cpu)
{
    u32 eax, ebx, ecx, edx;

    if (cpu)
        return 0;

    cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
    pr_debug("cpuid eax is %u\n", eax);

    return eax * 1000;
}

static int __cpuinit longrun_determine_freqs(unsigned int *low_freq,
                              unsigned int *high_freq)
{
    u32 msr_lo, msr_hi;
    u32 save_lo, save_hi;
    u32 eax, ebx, ecx, edx;
    u32 try_hi;
    struct cpuinfo_x86 *c = &cpu_data(0);

    if (!low_freq || !high_freq)
        return -EINVAL;

    if (cpu_has(c, X86_FEATURE_LRTI)) {
        /* if the LongRun Table Interface is present, the
         * detection is a bit easier:
         * For minimum frequency, read out the maximum
         * level (msr_hi), write that into "currently
         * selected level", and read out the frequency.
         * For maximum frequency, read out level zero.
         */
        /* minimum */
        rdmsr(MSR_TMTA_LRTI_READOUT, msr_lo, msr_hi);
        wrmsr(MSR_TMTA_LRTI_READOUT, msr_hi, msr_hi);
        rdmsr(MSR_TMTA_LRTI_VOLT_MHZ, msr_lo, msr_hi);
        *low_freq = msr_lo * 1000; /* to kHz */

        /* maximum */
        wrmsr(MSR_TMTA_LRTI_READOUT, 0, msr_hi);
        rdmsr(MSR_TMTA_LRTI_VOLT_MHZ, msr_lo, msr_hi);
        *high_freq = msr_lo * 1000; /* to kHz */

        pr_debug("longrun table interface told %u - %u kHz\n",
                *low_freq, *high_freq);

        if (*low_freq > *high_freq)
            *low_freq = *high_freq;
        return 0;
    }

    /* set the upper border to the value determined during TSC init */
    *high_freq = (cpu_khz / 1000);
    *high_freq = *high_freq * 1000;
    pr_debug("high frequency is %u kHz\n", *high_freq);

    /* get current borders */
    rdmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);
    save_lo = msr_lo & 0x0000007F;
    save_hi = msr_hi & 0x0000007F;

    /* if current perf_pctg is larger than 90%, we need to decrease the
     * upper limit to make the calculation more accurate.
     */
    cpuid(0x80860007, &eax, &ebx, &ecx, &edx);
    /* try decreasing in 10% steps, some processors react only
     * on some barrier values */
    for (try_hi = 80; try_hi > 0 && ecx > 90; try_hi -= 10) {
        /* set to 0 to try_hi perf_pctg */
        msr_lo &= 0xFFFFFF80;
        msr_hi &= 0xFFFFFF80;
        msr_hi |= try_hi;
        wrmsr(MSR_TMTA_LONGRUN_CTRL, msr_lo, msr_hi);

        /* read out current core MHz and current perf_pctg */
        cpuid(0x80860007, &eax, &ebx, &ecx, &edx);

        /* restore values */
        wrmsr(MSR_TMTA_LONGRUN_CTRL, save_lo, save_hi);
    }
    pr_debug("percentage is %u %%, freq is %u MHz\n", ecx, eax);

    /* performance_pctg = (current_freq - low_freq)/(high_freq - low_freq)
     * eqals
     * low_freq * (1 - perf_pctg) = (cur_freq - high_freq * perf_pctg)
     *
     * high_freq * perf_pctg is stored tempoarily into "ebx".
     */
    ebx = (((cpu_khz / 1000) * ecx) / 100); /* to MHz */

    if ((ecx > 95) || (ecx == 0) || (eax < ebx))
        return -EIO;

    edx = ((eax - ebx) * 100) / (100 - ecx);
    *low_freq = edx * 1000; /* back to kHz */

    pr_debug("low frequency is %u kHz\n", *low_freq);

    if (*low_freq > *high_freq)
        *low_freq = *high_freq;

    return 0;
}


static int __cpuinit longrun_cpu_init(struct cpufreq_policy *policy)
{
    int result = 0;

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

    /* detect low and high frequency */
    result = longrun_determine_freqs(&longrun_low_freq, &longrun_high_freq);
    if (result)
        return result;

    /* cpuinfo and default policy values */
    policy->cpuinfo.min_freq = longrun_low_freq;
    policy->cpuinfo.max_freq = longrun_high_freq;
    policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
    longrun_get_policy(policy);

    return 0;
}


static struct cpufreq_driver longrun_driver = {
    .flags      = CPUFREQ_CONST_LOOPS,
    .verify     = longrun_verify_policy,
    .setpolicy  = longrun_set_policy,
    .get        = longrun_get,
    .init       = longrun_cpu_init,
    .name       = "longrun",
    .owner      = THIS_MODULE,
};

static const struct x86_cpu_id longrun_ids[] = {
    { X86_VENDOR_TRANSMETA, X86_FAMILY_ANY, X86_MODEL_ANY,
      X86_FEATURE_LONGRUN },
    {}
};
MODULE_DEVICE_TABLE(x86cpu, longrun_ids);

static int __init longrun_init(void)
{
    if (!x86_match_cpu(longrun_ids))
        return -ENODEV;
    return cpufreq_register_driver(&longrun_driver);
}


static void __exit longrun_exit(void)
{
    cpufreq_unregister_driver(&longrun_driver);
}


MODULE_AUTHOR("Dominik Brodowski <[email protected]>");
MODULE_DESCRIPTION("LongRun driver for Transmeta Crusoe and "
        "Efficeon processors.");
MODULE_LICENSE("GPL");

module_init(longrun_init);
module_exit(longrun_exit);