/*
 *  pcc-cpufreq.c - Processor Clocking Control firmware cpufreq interface
 *
 *  Copyright (C) 2009 Red Hat, Matthew Garrett <mjg@redhat.com>
 *  Copyright (C) 2009 Hewlett-Packard Development Company, L.P.
 *      Nagananda Chumbalkar <nagananda.chumbalkar@hp.com>
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 *
 *  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.
 *
 *  This program is distributed in the hope that it will be useful, but
 *  WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or NON
 *  INFRINGEMENT. See the GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/smp.h>
#include <linux/sched.h>
#include <linux/cpufreq.h>
#include <linux/compiler.h>
#include <linux/slab.h>
#include <linux/platform_device.h>

#include <linux/acpi.h>
#include <linux/io.h>
#include <linux/spinlock.h>
#include <linux/uaccess.h>

#include <acpi/processor.h>

#define PCC_VERSION     "1.10.00"
#define POLL_LOOPS      300

#define CMD_COMPLETE    0x1
#define CMD_GET_FREQ    0x0
#define CMD_SET_FREQ    0x1

#define BUF_SZ          4

struct pcc_register_resource {
        u8 descriptor;
        u16 length;
        u8 space_id;
        u8 bit_width;
        u8 bit_offset;
        u8 access_size;
        u64 address;
} __attribute__ ((packed));

struct pcc_memory_resource {
        u8 descriptor;
        u16 length;
        u8 space_id;
        u8 resource_usage;
        u8 type_specific;
        u64 granularity;
        u64 minimum;
        u64 maximum;
        u64 translation_offset;
        u64 address_length;
} __attribute__ ((packed));

static struct cpufreq_driver pcc_cpufreq_driver;

struct pcc_header {
        u32 signature;
        u16 length;
        u8 major;
        u8 minor;
        u32 features;
        u16 command;
        u16 status;
        u32 latency;
        u32 minimum_time;
        u32 maximum_time;
        u32 nominal;
        u32 throttled_frequency;
        u32 minimum_frequency;
};

static void __iomem *pcch_virt_addr;
static struct pcc_header __iomem *pcch_hdr;

static DEFINE_SPINLOCK(pcc_lock);

static struct acpi_generic_address doorbell;

static u64 doorbell_preserve;
static u64 doorbell_write;

static u8 OSC_UUID[16] = {0x9F, 0x2C, 0x9B, 0x63, 0x91, 0x70, 0x1f, 0x49,
                          0xBB, 0x4F, 0xA5, 0x98, 0x2F, 0xA1, 0xB5, 0x46};

struct pcc_cpu {
        u32 input_offset;
        u32 output_offset;
};

static struct pcc_cpu __percpu *pcc_cpu_info;

static int pcc_cpufreq_verify(struct cpufreq_policy_data *policy)
{
        cpufreq_verify_within_cpu_limits(policy);
        return 0;
}

static inline void pcc_cmd(void)
{
        u64 doorbell_value;
        int i;

        acpi_read(&doorbell_value, &doorbell);
        acpi_write((doorbell_value & doorbell_preserve) | doorbell_write,
                   &doorbell);

        for (i = 0; i < POLL_LOOPS; i++) {
                if (ioread16(&pcch_hdr->status) & CMD_COMPLETE)
                        break;
        }
}

static inline void pcc_clear_mapping(void)
{
        if (pcch_virt_addr)
                iounmap(pcch_virt_addr);
        pcch_virt_addr = NULL;
}

static unsigned int pcc_get_freq(unsigned int cpu)
{
        struct pcc_cpu *pcc_cpu_data;
        unsigned int curr_freq;
        unsigned int freq_limit;
        u16 status;
        u32 input_buffer;
        u32 output_buffer;

        spin_lock(&pcc_lock);

        pr_debug("get: get_freq for CPU %d\n", cpu);
        pcc_cpu_data = per_cpu_ptr(pcc_cpu_info, cpu);

        input_buffer = 0x1;
        iowrite32(input_buffer,
                        (pcch_virt_addr + pcc_cpu_data->input_offset));
        iowrite16(CMD_GET_FREQ, &pcch_hdr->command);

        pcc_cmd();

        output_buffer =
                ioread32(pcch_virt_addr + pcc_cpu_data->output_offset);

        /* Clear the input buffer - we are done with the current command */
        memset_io((pcch_virt_addr + pcc_cpu_data->input_offset), 0, BUF_SZ);

        status = ioread16(&pcch_hdr->status);
        if (status != CMD_COMPLETE) {
                pr_debug("get: FAILED: for CPU %d, status is %d\n",
                        cpu, status);
                goto cmd_incomplete;
        }
        iowrite16(0, &pcch_hdr->status);
        curr_freq = (((ioread32(&pcch_hdr->nominal) * (output_buffer & 0xff))
                        / 100) * 1000);

        pr_debug("get: SUCCESS: (virtual) output_offset for cpu %d is "
                "0x%p, contains a value of: 0x%x. Speed is: %d MHz\n",
                cpu, (pcch_virt_addr + pcc_cpu_data->output_offset),
                output_buffer, curr_freq);

        freq_limit = (output_buffer >> 8) & 0xff;
        if (freq_limit != 0xff) {
                pr_debug("get: frequency for cpu %d is being temporarily"
                        " capped at %d\n", cpu, curr_freq);
        }

        spin_unlock(&pcc_lock);
        return curr_freq;

cmd_incomplete:
        iowrite16(0, &pcch_hdr->status);
        spin_unlock(&pcc_lock);
        return 0;
}

static int pcc_cpufreq_target(struct cpufreq_policy *policy,
                              unsigned int target_freq,
                              unsigned int relation)
{
        struct pcc_cpu *pcc_cpu_data;
        struct cpufreq_freqs freqs;
        u16 status;
        u32 input_buffer;
        int cpu;

        cpu = policy->cpu;
        pcc_cpu_data = per_cpu_ptr(pcc_cpu_info, cpu);

        pr_debug("target: CPU %d should go to target freq: %d "
                "(virtual) input_offset is 0x%p\n",
                cpu, target_freq,
                (pcch_virt_addr + pcc_cpu_data->input_offset));

        freqs.old = policy->cur;
        freqs.new = target_freq;
        cpufreq_freq_transition_begin(policy, &freqs);
        spin_lock(&pcc_lock);

        input_buffer = 0x1 | (((target_freq * 100)
                               / (ioread32(&pcch_hdr->nominal) * 1000)) << 8);
        iowrite32(input_buffer,
                        (pcch_virt_addr + pcc_cpu_data->input_offset));
        iowrite16(CMD_SET_FREQ, &pcch_hdr->command);

        pcc_cmd();

        /* Clear the input buffer - we are done with the current command */
        memset_io((pcch_virt_addr + pcc_cpu_data->input_offset), 0, BUF_SZ);

        status = ioread16(&pcch_hdr->status);
        iowrite16(0, &pcch_hdr->status);

        spin_unlock(&pcc_lock);
        cpufreq_freq_transition_end(policy, &freqs, status != CMD_COMPLETE);

        if (status != CMD_COMPLETE) {
                pr_debug("target: FAILED for cpu %d, with status: 0x%x\n",
                        cpu, status);
                return -EINVAL;
        }

        pr_debug("target: was SUCCESSFUL for cpu %d\n", cpu);

        return 0;
}

static int pcc_get_offset(int cpu)
{
        acpi_status status;
        struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL};
        union acpi_object *pccp, *offset;
        struct pcc_cpu *pcc_cpu_data;
        struct acpi_processor *pr;
        int ret = 0;

        pr = per_cpu(processors, cpu);
        pcc_cpu_data = per_cpu_ptr(pcc_cpu_info, cpu);

        if (!pr)
                return -ENODEV;

        status = acpi_evaluate_object(pr->handle, "PCCP", NULL, &buffer);
        if (ACPI_FAILURE(status))
                return -ENODEV;

        pccp = buffer.pointer;
        if (!pccp || pccp->type != ACPI_TYPE_PACKAGE) {
                ret = -ENODEV;
                goto out_free;
        }

        offset = &(pccp->package.elements[0]);
        if (!offset || offset->type != ACPI_TYPE_INTEGER) {
                ret = -ENODEV;
                goto out_free;
        }

        pcc_cpu_data->input_offset = offset->integer.value;

        offset = &(pccp->package.elements[1]);
        if (!offset || offset->type != ACPI_TYPE_INTEGER) {
                ret = -ENODEV;
                goto out_free;
        }

        pcc_cpu_data->output_offset = offset->integer.value;

        memset_io((pcch_virt_addr + pcc_cpu_data->input_offset), 0, BUF_SZ);
        memset_io((pcch_virt_addr + pcc_cpu_data->output_offset), 0, BUF_SZ);

        pr_debug("pcc_get_offset: for CPU %d: pcc_cpu_data "
                "input_offset: 0x%x, pcc_cpu_data output_offset: 0x%x\n",
                cpu, pcc_cpu_data->input_offset, pcc_cpu_data->output_offset);
out_free:
        kfree(buffer.pointer);
        return ret;
}

static int __init pcc_cpufreq_do_osc(acpi_handle *handle)
{
        acpi_status status;
        struct acpi_object_list input;
        struct acpi_buffer output = {ACPI_ALLOCATE_BUFFER, NULL};
        union acpi_object in_params[4];
        union acpi_object *out_obj;
        u32 capabilities[2];
        u32 errors;
        u32 supported;
        int ret = 0;

        input.count = 4;
        input.pointer = in_params;
        in_params[0].type               = ACPI_TYPE_BUFFER;
        in_params[0].buffer.length      = 16;
        in_params[0].buffer.pointer     = OSC_UUID;
        in_params[1].type               = ACPI_TYPE_INTEGER;
        in_params[1].integer.value      = 1;
        in_params[2].type               = ACPI_TYPE_INTEGER;
        in_params[2].integer.value      = 2;
        in_params[3].type               = ACPI_TYPE_BUFFER;
        in_params[3].buffer.length      = 8;
        in_params[3].buffer.pointer     = (u8 *)&capabilities;

        capabilities[0] = OSC_QUERY_ENABLE;
        capabilities[1] = 0x1;

        status = acpi_evaluate_object(*handle, "_OSC", &input, &output);
        if (ACPI_FAILURE(status))
                return -ENODEV;

        if (!output.length)
                return -ENODEV;

        out_obj = output.pointer;
        if (out_obj->type != ACPI_TYPE_BUFFER) {
                ret = -ENODEV;
                goto out_free;
        }

        errors = *((u32 *)out_obj->buffer.pointer) & ~(1 << 0);
        if (errors) {
                ret = -ENODEV;
                goto out_free;
        }

        supported = *((u32 *)(out_obj->buffer.pointer + 4));
        if (!(supported & 0x1)) {
                ret = -ENODEV;
                goto out_free;
        }

        kfree(output.pointer);
        output.pointer = NULL;
        output.length = ACPI_ALLOCATE_BUFFER;
        capabilities[0] = 0x0;
        capabilities[1] = 0x1;

        status = acpi_evaluate_object(*handle, "_OSC", &input, &output);
        if (ACPI_FAILURE(status))
                return -ENODEV;

        if (!output.length)
                return -ENODEV;

        out_obj = output.pointer;
        if (out_obj->type != ACPI_TYPE_BUFFER) {
                ret = -ENODEV;
                goto out_free;
        }

        errors = *((u32 *)out_obj->buffer.pointer) & ~(1 << 0);
        if (errors) {
                ret = -ENODEV;
                goto out_free;
        }

        supported = *((u32 *)(out_obj->buffer.pointer + 4));
        if (!(supported & 0x1)) {
                ret = -ENODEV;
                goto out_free;
        }

out_free:
        kfree(output.pointer);
        return ret;
}

static int __init pcc_cpufreq_evaluate(void)
{
        acpi_status status;
        struct acpi_buffer output = {ACPI_ALLOCATE_BUFFER, NULL};
        struct pcc_memory_resource *mem_resource;
        struct pcc_register_resource *reg_resource;
        union acpi_object *out_obj, *member;
        acpi_handle handle, osc_handle;
        int ret = 0;

        status = acpi_get_handle(NULL, "\\_SB", &handle);
        if (ACPI_FAILURE(status))
                return -ENODEV;

        if (!acpi_has_method(handle, "PCCH"))
                return -ENODEV;

        status = acpi_get_handle(handle, "_OSC", &osc_handle);
        if (ACPI_SUCCESS(status)) {
                ret = pcc_cpufreq_do_osc(&osc_handle);
                if (ret)
                        pr_debug("probe: _OSC evaluation did not succeed\n");
                /* Firmware's use of _OSC is optional */
                ret = 0;
        }

        status = acpi_evaluate_object(handle, "PCCH", NULL, &output);
        if (ACPI_FAILURE(status))
                return -ENODEV;

        out_obj = output.pointer;
        if (out_obj->type != ACPI_TYPE_PACKAGE) {
                ret = -ENODEV;
                goto out_free;
        }

        member = &out_obj->package.elements[0];
        if (member->type != ACPI_TYPE_BUFFER) {
                ret = -ENODEV;
                goto out_free;
        }

        mem_resource = (struct pcc_memory_resource *)member->buffer.pointer;

        pr_debug("probe: mem_resource descriptor: 0x%x,"
                " length: %d, space_id: %d, resource_usage: %d,"
                " type_specific: %d, granularity: 0x%llx,"
                " minimum: 0x%llx, maximum: 0x%llx,"
                " translation_offset: 0x%llx, address_length: 0x%llx\n",
                mem_resource->descriptor, mem_resource->length,
                mem_resource->space_id, mem_resource->resource_usage,
                mem_resource->type_specific, mem_resource->granularity,
                mem_resource->minimum, mem_resource->maximum,
                mem_resource->translation_offset,
                mem_resource->address_length);

        if (mem_resource->space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY) {
                ret = -ENODEV;
                goto out_free;
        }

        pcch_virt_addr = ioremap(mem_resource->minimum,
                                        mem_resource->address_length);
        if (pcch_virt_addr == NULL) {
                pr_debug("probe: could not map shared mem region\n");
                ret = -ENOMEM;
                goto out_free;
        }
        pcch_hdr = pcch_virt_addr;

        pr_debug("probe: PCCH header (virtual) addr: 0x%p\n", pcch_hdr);
        pr_debug("probe: PCCH header is at physical address: 0x%llx,"
                " signature: 0x%x, length: %d bytes, major: %d, minor: %d,"
                " supported features: 0x%x, command field: 0x%x,"
                " status field: 0x%x, nominal latency: %d us\n",
                mem_resource->minimum, ioread32(&pcch_hdr->signature),
                ioread16(&pcch_hdr->length), ioread8(&pcch_hdr->major),
                ioread8(&pcch_hdr->minor), ioread32(&pcch_hdr->features),
                ioread16(&pcch_hdr->command), ioread16(&pcch_hdr->status),
                ioread32(&pcch_hdr->latency));

        pr_debug("probe: min time between commands: %d us,"
                " max time between commands: %d us,"
                " nominal CPU frequency: %d MHz,"
                " minimum CPU frequency: %d MHz,"
                " minimum CPU frequency without throttling: %d MHz\n",
                ioread32(&pcch_hdr->minimum_time),
                ioread32(&pcch_hdr->maximum_time),
                ioread32(&pcch_hdr->nominal),
                ioread32(&pcch_hdr->throttled_frequency),
                ioread32(&pcch_hdr->minimum_frequency));

        member = &out_obj->package.elements[1];
        if (member->type != ACPI_TYPE_BUFFER) {
                ret = -ENODEV;
                goto pcch_free;
        }

        reg_resource = (struct pcc_register_resource *)member->buffer.pointer;

        doorbell.space_id = reg_resource->space_id;
        doorbell.bit_width = reg_resource->bit_width;
        doorbell.bit_offset = reg_resource->bit_offset;
        doorbell.access_width = 4;
        doorbell.address = reg_resource->address;

        pr_debug("probe: doorbell: space_id is %d, bit_width is %d, "
                "bit_offset is %d, access_width is %d, address is 0x%llx\n",
                doorbell.space_id, doorbell.bit_width, doorbell.bit_offset,
                doorbell.access_width, reg_resource->address);

        member = &out_obj->package.elements[2];
        if (member->type != ACPI_TYPE_INTEGER) {
                ret = -ENODEV;
                goto pcch_free;
        }

        doorbell_preserve = member->integer.value;

        member = &out_obj->package.elements[3];
        if (member->type != ACPI_TYPE_INTEGER) {
                ret = -ENODEV;
                goto pcch_free;
        }

        doorbell_write = member->integer.value;

        pr_debug("probe: doorbell_preserve: 0x%llx,"
                " doorbell_write: 0x%llx\n",
                doorbell_preserve, doorbell_write);

        pcc_cpu_info = alloc_percpu(struct pcc_cpu);
        if (!pcc_cpu_info) {
                ret = -ENOMEM;
                goto pcch_free;
        }

        printk(KERN_DEBUG "pcc-cpufreq: (v%s) driver loaded with frequency"
               " limits: %d MHz, %d MHz\n", PCC_VERSION,
               ioread32(&pcch_hdr->minimum_frequency),
               ioread32(&pcch_hdr->nominal));
        kfree(output.pointer);
        return ret;
pcch_free:
        pcc_clear_mapping();
out_free:
        kfree(output.pointer);
        return ret;
}

static int pcc_cpufreq_cpu_init(struct cpufreq_policy *policy)
{
        unsigned int cpu = policy->cpu;
        unsigned int result = 0;

        if (!pcch_virt_addr) {
                result = -1;
                goto out;
        }

        result = pcc_get_offset(cpu);
        if (result) {
                pr_debug("init: PCCP evaluation failed\n");
                goto out;
        }

        policy->cpuinfo.max_freq = ioread32(&pcch_hdr->nominal) * 1000;
        policy->cpuinfo.min_freq = ioread32(&pcch_hdr->minimum_frequency) * 1000;

        pr_debug("init: max_freq is %d, min_freq is %d\n",
                 policy->cpuinfo.max_freq, policy->cpuinfo.min_freq);
out:
        return result;
}

static struct cpufreq_driver pcc_cpufreq_driver = {
        .flags = CPUFREQ_CONST_LOOPS,
        .get = pcc_get_freq,
        .verify = pcc_cpufreq_verify,
        .target = pcc_cpufreq_target,
        .init = pcc_cpufreq_cpu_init,
        .name = "pcc-cpufreq",
};

static int __init pcc_cpufreq_probe(struct platform_device *pdev)
{
        int ret;

        /* Skip initialization if another cpufreq driver is there. */
        if (cpufreq_get_current_driver())
                return -ENODEV;

        if (acpi_disabled)
                return -ENODEV;

        ret = pcc_cpufreq_evaluate();
        if (ret) {
                pr_debug("pcc_cpufreq_probe: PCCH evaluation failed\n");
                return ret;
        }

        if (num_present_cpus() > 4) {
                pcc_cpufreq_driver.flags |= CPUFREQ_NO_AUTO_DYNAMIC_SWITCHING;
                pr_err("%s: Too many CPUs, dynamic performance scaling disabled\n",
                       __func__);
                pr_err("%s: Try to enable another scaling driver through BIOS settings\n",
                       __func__);
                pr_err("%s: and complain to the system vendor\n", __func__);
        }

        ret = cpufreq_register_driver(&pcc_cpufreq_driver);

        return ret;
}

static void pcc_cpufreq_remove(struct platform_device *pdev)
{
        cpufreq_unregister_driver(&pcc_cpufreq_driver);

        pcc_clear_mapping();

        free_percpu(pcc_cpu_info);
}

static struct platform_driver pcc_cpufreq_platdrv = {
        .driver = {
                .name   = "pcc-cpufreq",
        },
        .remove         = pcc_cpufreq_remove,
};

static int __init pcc_cpufreq_init(void)
{
        return platform_driver_probe(&pcc_cpufreq_platdrv, pcc_cpufreq_probe);
}

static void __exit pcc_cpufreq_exit(void)
{
        platform_driver_unregister(&pcc_cpufreq_platdrv);
}

MODULE_ALIAS("platform:pcc-cpufreq");

MODULE_AUTHOR("Matthew Garrett, Naga Chumbalkar");
MODULE_VERSION(PCC_VERSION);
MODULE_DESCRIPTION("Processor Clocking Control interface driver");
MODULE_LICENSE("GPL");

late_initcall(pcc_cpufreq_init);
module_exit(pcc_cpufreq_exit);