// SPDX-License-Identifier: GPL-2.0-only
/* 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>

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 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 void us3_freq_cpu_exit(struct cpufreq_policy *policy)
{
        us3_freq_target(policy, 0);
}

static struct cpufreq_driver cpufreq_us3_driver = {
        .name = "UltraSPARC-III",
        .init = us3_freq_cpu_init,
        .verify = cpufreq_generic_frequency_table_verify,
        .target_index = us3_freq_target,
        .get = us3_freq_get,
        .exit = us3_freq_cpu_exit,
};

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)) {
                us3_freq_table = kzalloc_objs(*us3_freq_table, NR_CPUS);
                if (!us3_freq_table)
                        return -ENOMEM;

                ret = cpufreq_register_driver(&cpufreq_us3_driver);
                if (ret)
                        kfree(us3_freq_table);

                return ret;
        }

        return -ENODEV;
}

static void __exit us3_freq_exit(void)
{
        cpufreq_unregister_driver(&cpufreq_us3_driver);
        kfree(us3_freq_table);
}

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);