/*
 * CPPC (Collaborative Processor Performance Control) driver for
 * interfacing with the CPUfreq layer and governors. See
 * cppc_acpi.c for CPPC specific methods.
 *
 * (C) Copyright 2014, 2015 Linaro Ltd.
 * Author: Ashwin Chaugule <ashwin.chaugule@linaro.org>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; version 2
 * of the License.
 */

#define pr_fmt(fmt)     "CPPC Cpufreq:" fmt

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/delay.h>
#include <linux/cpu.h>
#include <linux/cpufreq.h>
#include <linux/dmi.h>
#include <linux/vmalloc.h>

#include <asm/unaligned.h>

#include <acpi/cppc_acpi.h>

/* Minimum struct length needed for the DMI processor entry we want */
#define DMI_ENTRY_PROCESSOR_MIN_LENGTH  48

/* Offest in the DMI processor structure for the max frequency */
#define DMI_PROCESSOR_MAX_SPEED  0x14

/*
 * These structs contain information parsed from per CPU
 * ACPI _CPC structures.
 * e.g. For each CPU the highest, lowest supported
 * performance capabilities, desired performance level
 * requested etc.
 */
static struct cppc_cpudata **all_cpu_data;

/* Capture the max KHz from DMI */
static u64 cppc_dmi_max_khz;

/* Callback function used to retrieve the max frequency from DMI */
static void cppc_find_dmi_mhz(const struct dmi_header *dm, void *private)
{
        const u8 *dmi_data = (const u8 *)dm;
        u16 *mhz = (u16 *)private;

        if (dm->type == DMI_ENTRY_PROCESSOR &&
            dm->length >= DMI_ENTRY_PROCESSOR_MIN_LENGTH) {
                u16 val = (u16)get_unaligned((const u16 *)
                                (dmi_data + DMI_PROCESSOR_MAX_SPEED));
                *mhz = val > *mhz ? val : *mhz;
        }
}

/* Look up the max frequency in DMI */
static u64 cppc_get_dmi_max_khz(void)
{
        u16 mhz = 0;

        dmi_walk(cppc_find_dmi_mhz, &mhz);

        /*
         * Real stupid fallback value, just in case there is no
         * actual value set.
         */
        mhz = mhz ? mhz : 1;

        return (1000 * mhz);
}

static int cppc_cpufreq_set_target(struct cpufreq_policy *policy,
                unsigned int target_freq,
                unsigned int relation)
{
        struct cppc_cpudata *cpu;
        struct cpufreq_freqs freqs;
        u32 desired_perf;
        int ret = 0;

        cpu = all_cpu_data[policy->cpu];

        desired_perf = (u64)target_freq * cpu->perf_caps.highest_perf / cppc_dmi_max_khz;
        /* Return if it is exactly the same perf */
        if (desired_perf == cpu->perf_ctrls.desired_perf)
                return ret;

        cpu->perf_ctrls.desired_perf = desired_perf;
        freqs.old = policy->cur;
        freqs.new = target_freq;

        cpufreq_freq_transition_begin(policy, &freqs);
        ret = cppc_set_perf(cpu->cpu, &cpu->perf_ctrls);
        cpufreq_freq_transition_end(policy, &freqs, ret != 0);

        if (ret)
                pr_debug("Failed to set target on CPU:%d. ret:%d\n",
                                cpu->cpu, ret);

        return ret;
}

static int cppc_verify_policy(struct cpufreq_policy *policy)
{
        cpufreq_verify_within_cpu_limits(policy);
        return 0;
}

static void cppc_cpufreq_stop_cpu(struct cpufreq_policy *policy)
{
        int cpu_num = policy->cpu;
        struct cppc_cpudata *cpu = all_cpu_data[cpu_num];
        int ret;

        cpu->perf_ctrls.desired_perf = cpu->perf_caps.lowest_perf;

        ret = cppc_set_perf(cpu_num, &cpu->perf_ctrls);
        if (ret)
                pr_debug("Err setting perf value:%d on CPU:%d. ret:%d\n",
                                cpu->perf_caps.lowest_perf, cpu_num, ret);
}

static int cppc_cpufreq_cpu_init(struct cpufreq_policy *policy)
{
        struct cppc_cpudata *cpu;
        unsigned int cpu_num = policy->cpu;
        int ret = 0;

        cpu = all_cpu_data[policy->cpu];

        cpu->cpu = cpu_num;
        ret = cppc_get_perf_caps(policy->cpu, &cpu->perf_caps);

        if (ret) {
                pr_debug("Err reading CPU%d perf capabilities. ret:%d\n",
                                cpu_num, ret);
                return ret;
        }

        cppc_dmi_max_khz = cppc_get_dmi_max_khz();

        /*
         * Set min to lowest nonlinear perf to avoid any efficiency penalty (see
         * Section 8.4.7.1.1.5 of ACPI 6.1 spec)
         */
        policy->min = cpu->perf_caps.lowest_nonlinear_perf * cppc_dmi_max_khz /
                cpu->perf_caps.highest_perf;
        policy->max = cppc_dmi_max_khz;

        /*
         * Set cpuinfo.min_freq to Lowest to make the full range of performance
         * available if userspace wants to use any perf between lowest & lowest
         * nonlinear perf
         */
        policy->cpuinfo.min_freq = cpu->perf_caps.lowest_perf * cppc_dmi_max_khz /
                cpu->perf_caps.highest_perf;
        policy->cpuinfo.max_freq = cppc_dmi_max_khz;

        policy->cpuinfo.transition_latency = cppc_get_transition_latency(cpu_num);
        policy->shared_type = cpu->shared_type;

        if (policy->shared_type == CPUFREQ_SHARED_TYPE_ANY)
                cpumask_copy(policy->cpus, cpu->shared_cpu_map);
        else if (policy->shared_type == CPUFREQ_SHARED_TYPE_ALL) {
                /* Support only SW_ANY for now. */
                pr_debug("Unsupported CPU co-ord type\n");
                return -EFAULT;
        }

        cpumask_set_cpu(policy->cpu, policy->cpus);
        cpu->cur_policy = policy;

        /* Set policy->cur to max now. The governors will adjust later. */
        policy->cur = cppc_dmi_max_khz;
        cpu->perf_ctrls.desired_perf = cpu->perf_caps.highest_perf;

        ret = cppc_set_perf(cpu_num, &cpu->perf_ctrls);
        if (ret)
                pr_debug("Err setting perf value:%d on CPU:%d. ret:%d\n",
                                cpu->perf_caps.highest_perf, cpu_num, ret);

        return ret;
}

static struct cpufreq_driver cppc_cpufreq_driver = {
        .flags = CPUFREQ_CONST_LOOPS,
        .verify = cppc_verify_policy,
        .target = cppc_cpufreq_set_target,
        .init = cppc_cpufreq_cpu_init,
        .stop_cpu = cppc_cpufreq_stop_cpu,
        .name = "cppc_cpufreq",
};

static int __init cppc_cpufreq_init(void)
{
        int i, ret = 0;
        struct cppc_cpudata *cpu;

        if (acpi_disabled)
                return -ENODEV;

        all_cpu_data = kzalloc(sizeof(void *) * num_possible_cpus(), GFP_KERNEL);
        if (!all_cpu_data)
                return -ENOMEM;

        for_each_possible_cpu(i) {
                all_cpu_data[i] = kzalloc(sizeof(struct cppc_cpudata), GFP_KERNEL);
                if (!all_cpu_data[i])
                        goto out;

                cpu = all_cpu_data[i];
                if (!zalloc_cpumask_var(&cpu->shared_cpu_map, GFP_KERNEL))
                        goto out;
        }

        ret = acpi_get_psd_map(all_cpu_data);
        if (ret) {
                pr_debug("Error parsing PSD data. Aborting cpufreq registration.\n");
                goto out;
        }

        ret = cpufreq_register_driver(&cppc_cpufreq_driver);
        if (ret)
                goto out;

        return ret;

out:
        for_each_possible_cpu(i)
                kfree(all_cpu_data[i]);

        kfree(all_cpu_data);
        return -ENODEV;
}

static void __exit cppc_cpufreq_exit(void)
{
        struct cppc_cpudata *cpu;
        int i;

        cpufreq_unregister_driver(&cppc_cpufreq_driver);

        for_each_possible_cpu(i) {
                cpu = all_cpu_data[i];
                free_cpumask_var(cpu->shared_cpu_map);
                kfree(cpu);
        }

        kfree(all_cpu_data);
}

module_exit(cppc_cpufreq_exit);
MODULE_AUTHOR("Ashwin Chaugule");
MODULE_DESCRIPTION("CPUFreq driver based on the ACPI CPPC v5.0+ spec");
MODULE_LICENSE("GPL");

late_initcall(cppc_cpufreq_init);

static const struct acpi_device_id cppc_acpi_ids[] = {
        {ACPI_PROCESSOR_DEVICE_HID, },
        {}
};

MODULE_DEVICE_TABLE(acpi, cppc_acpi_ids);