/*
 *  Copyright (C) 2011 Dmitry Eremin-Solenikov
 *  Copyright (C) 2002 - 2005 Benjamin Herrenschmidt <benh@kernel.crashing.org>
 *  and                       Markus Demleitner <msdemlei@cl.uni-heidelberg.de>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * This driver adds basic cpufreq support for SMU & 970FX based G5 Macs,
 * that is iMac G5 and latest single CPU desktop.
 */

#undef DEBUG

#include <linux/module.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/sched.h>
#include <linux/cpufreq.h>
#include <linux/init.h>
#include <linux/completion.h>
#include <linux/mutex.h>
#include <linux/time.h>
#include <linux/of.h>

#define DBG(fmt...) pr_debug(fmt)

/* see 970FX user manual */

#define SCOM_PCR 0x0aa001                       /* PCR scom addr */

#define PCR_HILO_SELECT         0x80000000U     /* 1 = PCR, 0 = PCRH */
#define PCR_SPEED_FULL          0x00000000U     /* 1:1 speed value */
#define PCR_SPEED_HALF          0x00020000U     /* 1:2 speed value */
#define PCR_SPEED_QUARTER       0x00040000U     /* 1:4 speed value */
#define PCR_SPEED_MASK          0x000e0000U     /* speed mask */
#define PCR_SPEED_SHIFT         17
#define PCR_FREQ_REQ_VALID      0x00010000U     /* freq request valid */
#define PCR_VOLT_REQ_VALID      0x00008000U     /* volt request valid */
#define PCR_TARGET_TIME_MASK    0x00006000U     /* target time */
#define PCR_STATLAT_MASK        0x00001f00U     /* STATLAT value */
#define PCR_SNOOPLAT_MASK       0x000000f0U     /* SNOOPLAT value */
#define PCR_SNOOPACC_MASK       0x0000000fU     /* SNOOPACC value */

#define SCOM_PSR 0x408001                       /* PSR scom addr */
/* warning: PSR is a 64 bits register */
#define PSR_CMD_RECEIVED        0x2000000000000000U   /* command received */
#define PSR_CMD_COMPLETED       0x1000000000000000U   /* command completed */
#define PSR_CUR_SPEED_MASK      0x0300000000000000U   /* current speed */
#define PSR_CUR_SPEED_SHIFT     (56)

/*
 * The G5 only supports two frequencies (Quarter speed is not supported)
 */
#define CPUFREQ_HIGH                  0
#define CPUFREQ_LOW                   1

static struct cpufreq_frequency_table maple_cpu_freqs[] = {
        {CPUFREQ_HIGH,          0},
        {CPUFREQ_LOW,           0},
        {0,                     CPUFREQ_TABLE_END},
};

static struct freq_attr *maple_cpu_freqs_attr[] = {
        &cpufreq_freq_attr_scaling_available_freqs,
        NULL,
};

/* Power mode data is an array of the 32 bits PCR values to use for
 * the various frequencies, retrieved from the device-tree
 */
static int maple_pmode_cur;

static DEFINE_MUTEX(maple_switch_mutex);

static const u32 *maple_pmode_data;
static int maple_pmode_max;

/*
 * SCOM based frequency switching for 970FX rev3
 */
static int maple_scom_switch_freq(int speed_mode)
{
        unsigned long flags;
        int to;

        local_irq_save(flags);

        /* Clear PCR high */
        scom970_write(SCOM_PCR, 0);
        /* Clear PCR low */
        scom970_write(SCOM_PCR, PCR_HILO_SELECT | 0);
        /* Set PCR low */
        scom970_write(SCOM_PCR, PCR_HILO_SELECT |
                      maple_pmode_data[speed_mode]);

        /* Wait for completion */
        for (to = 0; to < 10; to++) {
                unsigned long psr = scom970_read(SCOM_PSR);

                if ((psr & PSR_CMD_RECEIVED) == 0 &&
                    (((psr >> PSR_CUR_SPEED_SHIFT) ^
                      (maple_pmode_data[speed_mode] >> PCR_SPEED_SHIFT)) & 0x3)
                    == 0)
                        break;
                if (psr & PSR_CMD_COMPLETED)
                        break;
                udelay(100);
        }

        local_irq_restore(flags);

        maple_pmode_cur = speed_mode;
        ppc_proc_freq = maple_cpu_freqs[speed_mode].frequency * 1000ul;

        return 0;
}

static int maple_scom_query_freq(void)
{
        unsigned long psr = scom970_read(SCOM_PSR);
        int i;

        for (i = 0; i <= maple_pmode_max; i++)
                if ((((psr >> PSR_CUR_SPEED_SHIFT) ^
                      (maple_pmode_data[i] >> PCR_SPEED_SHIFT)) & 0x3) == 0)
                        break;
        return i;
}

/*
 * Common interface to the cpufreq core
 */

static int maple_cpufreq_verify(struct cpufreq_policy *policy)
{
        return cpufreq_frequency_table_verify(policy, maple_cpu_freqs);
}

static int maple_cpufreq_target(struct cpufreq_policy *policy,
        unsigned int target_freq, unsigned int relation)
{
        unsigned int newstate = 0;
        struct cpufreq_freqs freqs;
        int rc;

        if (cpufreq_frequency_table_target(policy, maple_cpu_freqs,
                        target_freq, relation, &newstate))
                return -EINVAL;

        if (maple_pmode_cur == newstate)
                return 0;

        mutex_lock(&maple_switch_mutex);

        freqs.old = maple_cpu_freqs[maple_pmode_cur].frequency;
        freqs.new = maple_cpu_freqs[newstate].frequency;

        cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE);
        rc = maple_scom_switch_freq(newstate);
        cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE);

        mutex_unlock(&maple_switch_mutex);

        return rc;
}

static unsigned int maple_cpufreq_get_speed(unsigned int cpu)
{
        return maple_cpu_freqs[maple_pmode_cur].frequency;
}

static int maple_cpufreq_cpu_init(struct cpufreq_policy *policy)
{
        policy->cpuinfo.transition_latency = 12000;
        policy->cur = maple_cpu_freqs[maple_scom_query_freq()].frequency;
        /* secondary CPUs are tied to the primary one by the
         * cpufreq core if in the secondary policy we tell it that
         * it actually must be one policy together with all others. */
        cpumask_setall(policy->cpus);
        cpufreq_frequency_table_get_attr(maple_cpu_freqs, policy->cpu);

        return cpufreq_frequency_table_cpuinfo(policy,
                maple_cpu_freqs);
}


static struct cpufreq_driver maple_cpufreq_driver = {
        .name           = "maple",
        .owner          = THIS_MODULE,
        .flags          = CPUFREQ_CONST_LOOPS,
        .init           = maple_cpufreq_cpu_init,
        .verify         = maple_cpufreq_verify,
        .target         = maple_cpufreq_target,
        .get            = maple_cpufreq_get_speed,
        .attr           = maple_cpu_freqs_attr,
};

static int __init maple_cpufreq_init(void)
{
        struct device_node *cpus;
        struct device_node *cpunode;
        unsigned int psize;
        unsigned long max_freq;
        const u32 *valp;
        u32 pvr_hi;
        int rc = -ENODEV;

        /*
         * Behave here like powermac driver which checks machine compatibility
         * to ease merging of two drivers in future.
         */
        if (!of_machine_is_compatible("Momentum,Maple") &&
            !of_machine_is_compatible("Momentum,Apache"))
                return 0;

        cpus = of_find_node_by_path("/cpus");
        if (cpus == NULL) {
                DBG("No /cpus node !\n");
                return -ENODEV;
        }

        /* Get first CPU node */
        for (cpunode = NULL;
             (cpunode = of_get_next_child(cpus, cpunode)) != NULL;) {
                const u32 *reg = of_get_property(cpunode, "reg", NULL);
                if (reg == NULL || (*reg) != 0)
                        continue;
                if (!strcmp(cpunode->type, "cpu"))
                        break;
        }
        if (cpunode == NULL) {
                printk(KERN_ERR "cpufreq: Can't find any CPU 0 node\n");
                goto bail_cpus;
        }

        /* Check 970FX for now */
        /* we actually don't care on which CPU to access PVR */
        pvr_hi = PVR_VER(mfspr(SPRN_PVR));
        if (pvr_hi != 0x3c && pvr_hi != 0x44) {
                printk(KERN_ERR "cpufreq: Unsupported CPU version (%x)\n",
                                pvr_hi);
                goto bail_noprops;
        }

        /* Look for the powertune data in the device-tree */
        /*
         * On Maple this property is provided by PIBS in dual-processor config,
         * not provided by PIBS in CPU0 config and also not provided by SLOF,
         * so YMMV
         */
        maple_pmode_data = of_get_property(cpunode, "power-mode-data", &psize);
        if (!maple_pmode_data) {
                DBG("No power-mode-data !\n");
                goto bail_noprops;
        }
        maple_pmode_max = psize / sizeof(u32) - 1;

        /*
         * From what I see, clock-frequency is always the maximal frequency.
         * The current driver can not slew sysclk yet, so we really only deal
         * with powertune steps for now. We also only implement full freq and
         * half freq in this version. So far, I haven't yet seen a machine
         * supporting anything else.
         */
        valp = of_get_property(cpunode, "clock-frequency", NULL);
        if (!valp)
                return -ENODEV;
        max_freq = (*valp)/1000;
        maple_cpu_freqs[0].frequency = max_freq;
        maple_cpu_freqs[1].frequency = max_freq/2;

        /* Force apply current frequency to make sure everything is in
         * sync (voltage is right for example). Firmware may leave us with
         * a strange setting ...
         */
        msleep(10);
        maple_pmode_cur = -1;
        maple_scom_switch_freq(maple_scom_query_freq());

        printk(KERN_INFO "Registering Maple CPU frequency driver\n");
        printk(KERN_INFO "Low: %d Mhz, High: %d Mhz, Cur: %d MHz\n",
                maple_cpu_freqs[1].frequency/1000,
                maple_cpu_freqs[0].frequency/1000,
                maple_cpu_freqs[maple_pmode_cur].frequency/1000);

        rc = cpufreq_register_driver(&maple_cpufreq_driver);

        of_node_put(cpunode);
        of_node_put(cpus);

        return rc;

bail_noprops:
        of_node_put(cpunode);
bail_cpus:
        of_node_put(cpus);

        return rc;
}

module_init(maple_cpufreq_init);


MODULE_LICENSE("GPL");