/*
 *  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);

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

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

	pr_debug("init: policy->max is %d, policy->min is %d\n",
		policy->max, policy->min);
out:
	return result;
}

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

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,
	.exit = pcc_cpufreq_cpu_exit,
	.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 -EEXIST;

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

	pcc_clear_mapping();

	free_percpu(pcc_cpu_info);

	return 0;
}

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);