/* us3_cpufreq.c: UltraSPARC-III cpu frequency support
 *
 * Copyright (C) 2003 David S. Miller (davem@redhat.com)
 *
 * Many thanks to Dominik Brodowski for fixing up the cpufreq
 * infrastructure in order to make this driver easier to implement.
 */

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

#include <asm/head.h>
#include <asm/timer.h>

static struct cpufreq_driver *cpufreq_us3_driver;

struct us3_freq_percpu_info {
	struct cpufreq_frequency_table table[4];
};

/* Indexed by cpu number. */
static struct us3_freq_percpu_info *us3_freq_table;

/* UltraSPARC-III has three dividers: 1, 2, and 32.  These are controlled
 * in the Safari config register.
 */
#define SAFARI_CFG_DIV_1	0x0000000000000000UL
#define SAFARI_CFG_DIV_2	0x0000000040000000UL
#define SAFARI_CFG_DIV_32	0x0000000080000000UL
#define SAFARI_CFG_DIV_MASK	0x00000000C0000000UL

static void read_safari_cfg(void *arg)
{
	unsigned long ret, *val = arg;

	__asm__ __volatile__("ldxa	[%%g0] %1, %0"
			     : "=&r" (ret)
			     : "i" (ASI_SAFARI_CONFIG));
	*val = ret;
}

static void update_safari_cfg(void *arg)
{
	unsigned long reg, *new_bits = arg;

	read_safari_cfg(&reg);
	reg &= ~SAFARI_CFG_DIV_MASK;
	reg |= *new_bits;

	__asm__ __volatile__("stxa	%0, [%%g0] %1\n\t"
			     "membar	#Sync"
			     : /* no outputs */
			     : "r" (reg), "i" (ASI_SAFARI_CONFIG)
			     : "memory");
}

static unsigned long get_current_freq(unsigned int cpu, unsigned long safari_cfg)
{
	unsigned long clock_tick = sparc64_get_clock_tick(cpu) / 1000;
	unsigned long ret;

	switch (safari_cfg & SAFARI_CFG_DIV_MASK) {
	case SAFARI_CFG_DIV_1:
		ret = clock_tick / 1;
		break;
	case SAFARI_CFG_DIV_2:
		ret = clock_tick / 2;
		break;
	case SAFARI_CFG_DIV_32:
		ret = clock_tick / 32;
		break;
	default:
		BUG();
	}

	return ret;
}

static unsigned int us3_freq_get(unsigned int cpu)
{
	unsigned long reg;

	if (smp_call_function_single(cpu, read_safari_cfg, &reg, 1))
		return 0;
	return get_current_freq(cpu, reg);
}

static int us3_freq_target(struct cpufreq_policy *policy, unsigned int index)
{
	unsigned int cpu = policy->cpu;
	unsigned long new_bits, new_freq;

	new_freq = sparc64_get_clock_tick(cpu) / 1000;
	switch (index) {
	case 0:
		new_bits = SAFARI_CFG_DIV_1;
		new_freq /= 1;
		break;
	case 1:
		new_bits = SAFARI_CFG_DIV_2;
		new_freq /= 2;
		break;
	case 2:
		new_bits = SAFARI_CFG_DIV_32;
		new_freq /= 32;
		break;

	default:
		BUG();
	}

	return smp_call_function_single(cpu, update_safari_cfg, &new_bits, 1);
}

static int __init us3_freq_cpu_init(struct cpufreq_policy *policy)
{
	unsigned int cpu = policy->cpu;
	unsigned long clock_tick = sparc64_get_clock_tick(cpu) / 1000;
	struct cpufreq_frequency_table *table =
		&us3_freq_table[cpu].table[0];

	table[0].driver_data = 0;
	table[0].frequency = clock_tick / 1;
	table[1].driver_data = 1;
	table[1].frequency = clock_tick / 2;
	table[2].driver_data = 2;
	table[2].frequency = clock_tick / 32;
	table[3].driver_data = 0;
	table[3].frequency = CPUFREQ_TABLE_END;

	policy->cpuinfo.transition_latency = 0;
	policy->cur = clock_tick;
	policy->freq_table = table;

	return 0;
}

static int us3_freq_cpu_exit(struct cpufreq_policy *policy)
{
	if (cpufreq_us3_driver)
		us3_freq_target(policy, 0);

	return 0;
}

static int __init us3_freq_init(void)
{
	unsigned long manuf, impl, ver;
	int ret;

	if (tlb_type != cheetah && tlb_type != cheetah_plus)
		return -ENODEV;

	__asm__("rdpr %%ver, %0" : "=r" (ver));
	manuf = ((ver >> 48) & 0xffff);
	impl  = ((ver >> 32) & 0xffff);

	if (manuf == CHEETAH_MANUF &&
	    (impl == CHEETAH_IMPL ||
	     impl == CHEETAH_PLUS_IMPL ||
	     impl == JAGUAR_IMPL ||
	     impl == PANTHER_IMPL)) {
		struct cpufreq_driver *driver;

		ret = -ENOMEM;
		driver = kzalloc(sizeof(*driver), GFP_KERNEL);
		if (!driver)
			goto err_out;

		us3_freq_table = kzalloc((NR_CPUS * sizeof(*us3_freq_table)),
			GFP_KERNEL);
		if (!us3_freq_table)
			goto err_out;

		driver->init = us3_freq_cpu_init;
		driver->verify = cpufreq_generic_frequency_table_verify;
		driver->target_index = us3_freq_target;
		driver->get = us3_freq_get;
		driver->exit = us3_freq_cpu_exit;
		strcpy(driver->name, "UltraSPARC-III");

		cpufreq_us3_driver = driver;
		ret = cpufreq_register_driver(driver);
		if (ret)
			goto err_out;

		return 0;

err_out:
		if (driver) {
			kfree(driver);
			cpufreq_us3_driver = NULL;
		}
		kfree(us3_freq_table);
		us3_freq_table = NULL;
		return ret;
	}

	return -ENODEV;
}

static void __exit us3_freq_exit(void)
{
	if (cpufreq_us3_driver) {
		cpufreq_unregister_driver(cpufreq_us3_driver);
		kfree(cpufreq_us3_driver);
		cpufreq_us3_driver = NULL;
		kfree(us3_freq_table);
		us3_freq_table = NULL;
	}
}

MODULE_AUTHOR("David S. Miller <davem@redhat.com>");
MODULE_DESCRIPTION("cpufreq driver for UltraSPARC-III");
MODULE_LICENSE("GPL");

module_init(us3_freq_init);
module_exit(us3_freq_exit);
