linux/drivers/cpufreq/maple-cpufreq.c
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   1/*
   2 *  Copyright (C) 2011 Dmitry Eremin-Solenikov
   3 *  Copyright (C) 2002 - 2005 Benjamin Herrenschmidt <benh@kernel.crashing.org>
   4 *  and                       Markus Demleitner <msdemlei@cl.uni-heidelberg.de>
   5 *
   6 * This program is free software; you can redistribute it and/or modify
   7 * it under the terms of the GNU General Public License version 2 as
   8 * published by the Free Software Foundation.
   9 *
  10 * This driver adds basic cpufreq support for SMU & 970FX based G5 Macs,
  11 * that is iMac G5 and latest single CPU desktop.
  12 */
  13
  14#undef DEBUG
  15
  16#include <linux/module.h>
  17#include <linux/types.h>
  18#include <linux/errno.h>
  19#include <linux/kernel.h>
  20#include <linux/delay.h>
  21#include <linux/sched.h>
  22#include <linux/cpufreq.h>
  23#include <linux/init.h>
  24#include <linux/completion.h>
  25#include <linux/mutex.h>
  26#include <linux/time.h>
  27#include <linux/of_device.h>
  28
  29#define DBG(fmt...) pr_debug(fmt)
  30
  31/* see 970FX user manual */
  32
  33#define SCOM_PCR 0x0aa001                       /* PCR scom addr */
  34
  35#define PCR_HILO_SELECT         0x80000000U     /* 1 = PCR, 0 = PCRH */
  36#define PCR_SPEED_FULL          0x00000000U     /* 1:1 speed value */
  37#define PCR_SPEED_HALF          0x00020000U     /* 1:2 speed value */
  38#define PCR_SPEED_QUARTER       0x00040000U     /* 1:4 speed value */
  39#define PCR_SPEED_MASK          0x000e0000U     /* speed mask */
  40#define PCR_SPEED_SHIFT         17
  41#define PCR_FREQ_REQ_VALID      0x00010000U     /* freq request valid */
  42#define PCR_VOLT_REQ_VALID      0x00008000U     /* volt request valid */
  43#define PCR_TARGET_TIME_MASK    0x00006000U     /* target time */
  44#define PCR_STATLAT_MASK        0x00001f00U     /* STATLAT value */
  45#define PCR_SNOOPLAT_MASK       0x000000f0U     /* SNOOPLAT value */
  46#define PCR_SNOOPACC_MASK       0x0000000fU     /* SNOOPACC value */
  47
  48#define SCOM_PSR 0x408001                       /* PSR scom addr */
  49/* warning: PSR is a 64 bits register */
  50#define PSR_CMD_RECEIVED        0x2000000000000000U   /* command received */
  51#define PSR_CMD_COMPLETED       0x1000000000000000U   /* command completed */
  52#define PSR_CUR_SPEED_MASK      0x0300000000000000U   /* current speed */
  53#define PSR_CUR_SPEED_SHIFT     (56)
  54
  55/*
  56 * The G5 only supports two frequencies (Quarter speed is not supported)
  57 */
  58#define CPUFREQ_HIGH                  0
  59#define CPUFREQ_LOW                   1
  60
  61static struct cpufreq_frequency_table maple_cpu_freqs[] = {
  62        {CPUFREQ_HIGH,          0},
  63        {CPUFREQ_LOW,           0},
  64        {0,                     CPUFREQ_TABLE_END},
  65};
  66
  67static struct freq_attr *maple_cpu_freqs_attr[] = {
  68        &cpufreq_freq_attr_scaling_available_freqs,
  69        NULL,
  70};
  71
  72/* Power mode data is an array of the 32 bits PCR values to use for
  73 * the various frequencies, retrieved from the device-tree
  74 */
  75static int maple_pmode_cur;
  76
  77static DEFINE_MUTEX(maple_switch_mutex);
  78
  79static const u32 *maple_pmode_data;
  80static int maple_pmode_max;
  81
  82/*
  83 * SCOM based frequency switching for 970FX rev3
  84 */
  85static int maple_scom_switch_freq(int speed_mode)
  86{
  87        unsigned long flags;
  88        int to;
  89
  90        local_irq_save(flags);
  91
  92        /* Clear PCR high */
  93        scom970_write(SCOM_PCR, 0);
  94        /* Clear PCR low */
  95        scom970_write(SCOM_PCR, PCR_HILO_SELECT | 0);
  96        /* Set PCR low */
  97        scom970_write(SCOM_PCR, PCR_HILO_SELECT |
  98                      maple_pmode_data[speed_mode]);
  99
 100        /* Wait for completion */
 101        for (to = 0; to < 10; to++) {
 102                unsigned long psr = scom970_read(SCOM_PSR);
 103
 104                if ((psr & PSR_CMD_RECEIVED) == 0 &&
 105                    (((psr >> PSR_CUR_SPEED_SHIFT) ^
 106                      (maple_pmode_data[speed_mode] >> PCR_SPEED_SHIFT)) & 0x3)
 107                    == 0)
 108                        break;
 109                if (psr & PSR_CMD_COMPLETED)
 110                        break;
 111                udelay(100);
 112        }
 113
 114        local_irq_restore(flags);
 115
 116        maple_pmode_cur = speed_mode;
 117        ppc_proc_freq = maple_cpu_freqs[speed_mode].frequency * 1000ul;
 118
 119        return 0;
 120}
 121
 122static int maple_scom_query_freq(void)
 123{
 124        unsigned long psr = scom970_read(SCOM_PSR);
 125        int i;
 126
 127        for (i = 0; i <= maple_pmode_max; i++)
 128                if ((((psr >> PSR_CUR_SPEED_SHIFT) ^
 129                      (maple_pmode_data[i] >> PCR_SPEED_SHIFT)) & 0x3) == 0)
 130                        break;
 131        return i;
 132}
 133
 134/*
 135 * Common interface to the cpufreq core
 136 */
 137
 138static int maple_cpufreq_verify(struct cpufreq_policy *policy)
 139{
 140        return cpufreq_frequency_table_verify(policy, maple_cpu_freqs);
 141}
 142
 143static int maple_cpufreq_target(struct cpufreq_policy *policy,
 144        unsigned int target_freq, unsigned int relation)
 145{
 146        unsigned int newstate = 0;
 147        struct cpufreq_freqs freqs;
 148        int rc;
 149
 150        if (cpufreq_frequency_table_target(policy, maple_cpu_freqs,
 151                        target_freq, relation, &newstate))
 152                return -EINVAL;
 153
 154        if (maple_pmode_cur == newstate)
 155                return 0;
 156
 157        mutex_lock(&maple_switch_mutex);
 158
 159        freqs.old = maple_cpu_freqs[maple_pmode_cur].frequency;
 160        freqs.new = maple_cpu_freqs[newstate].frequency;
 161
 162        cpufreq_notify_transition(policy, &freqs, CPUFREQ_PRECHANGE);
 163        rc = maple_scom_switch_freq(newstate);
 164        cpufreq_notify_transition(policy, &freqs, CPUFREQ_POSTCHANGE);
 165
 166        mutex_unlock(&maple_switch_mutex);
 167
 168        return rc;
 169}
 170
 171static unsigned int maple_cpufreq_get_speed(unsigned int cpu)
 172{
 173        return maple_cpu_freqs[maple_pmode_cur].frequency;
 174}
 175
 176static int maple_cpufreq_cpu_init(struct cpufreq_policy *policy)
 177{
 178        policy->cpuinfo.transition_latency = 12000;
 179        policy->cur = maple_cpu_freqs[maple_scom_query_freq()].frequency;
 180        /* secondary CPUs are tied to the primary one by the
 181         * cpufreq core if in the secondary policy we tell it that
 182         * it actually must be one policy together with all others. */
 183        cpumask_setall(policy->cpus);
 184        cpufreq_frequency_table_get_attr(maple_cpu_freqs, policy->cpu);
 185
 186        return cpufreq_frequency_table_cpuinfo(policy,
 187                maple_cpu_freqs);
 188}
 189
 190
 191static struct cpufreq_driver maple_cpufreq_driver = {
 192        .name           = "maple",
 193        .flags          = CPUFREQ_CONST_LOOPS,
 194        .init           = maple_cpufreq_cpu_init,
 195        .verify         = maple_cpufreq_verify,
 196        .target         = maple_cpufreq_target,
 197        .get            = maple_cpufreq_get_speed,
 198        .attr           = maple_cpu_freqs_attr,
 199};
 200
 201static int __init maple_cpufreq_init(void)
 202{
 203        struct device_node *cpunode;
 204        unsigned int psize;
 205        unsigned long max_freq;
 206        const u32 *valp;
 207        u32 pvr_hi;
 208        int rc = -ENODEV;
 209
 210        /*
 211         * Behave here like powermac driver which checks machine compatibility
 212         * to ease merging of two drivers in future.
 213         */
 214        if (!of_machine_is_compatible("Momentum,Maple") &&
 215            !of_machine_is_compatible("Momentum,Apache"))
 216                return 0;
 217
 218        /* Get first CPU node */
 219        cpunode = of_cpu_device_node_get(0);
 220        if (cpunode == NULL) {
 221                printk(KERN_ERR "cpufreq: Can't find any CPU 0 node\n");
 222                goto bail_noprops;
 223        }
 224
 225        /* Check 970FX for now */
 226        /* we actually don't care on which CPU to access PVR */
 227        pvr_hi = PVR_VER(mfspr(SPRN_PVR));
 228        if (pvr_hi != 0x3c && pvr_hi != 0x44) {
 229                printk(KERN_ERR "cpufreq: Unsupported CPU version (%x)\n",
 230                                pvr_hi);
 231                goto bail_noprops;
 232        }
 233
 234        /* Look for the powertune data in the device-tree */
 235        /*
 236         * On Maple this property is provided by PIBS in dual-processor config,
 237         * not provided by PIBS in CPU0 config and also not provided by SLOF,
 238         * so YMMV
 239         */
 240        maple_pmode_data = of_get_property(cpunode, "power-mode-data", &psize);
 241        if (!maple_pmode_data) {
 242                DBG("No power-mode-data !\n");
 243                goto bail_noprops;
 244        }
 245        maple_pmode_max = psize / sizeof(u32) - 1;
 246
 247        /*
 248         * From what I see, clock-frequency is always the maximal frequency.
 249         * The current driver can not slew sysclk yet, so we really only deal
 250         * with powertune steps for now. We also only implement full freq and
 251         * half freq in this version. So far, I haven't yet seen a machine
 252         * supporting anything else.
 253         */
 254        valp = of_get_property(cpunode, "clock-frequency", NULL);
 255        if (!valp)
 256                return -ENODEV;
 257        max_freq = (*valp)/1000;
 258        maple_cpu_freqs[0].frequency = max_freq;
 259        maple_cpu_freqs[1].frequency = max_freq/2;
 260
 261        /* Force apply current frequency to make sure everything is in
 262         * sync (voltage is right for example). Firmware may leave us with
 263         * a strange setting ...
 264         */
 265        msleep(10);
 266        maple_pmode_cur = -1;
 267        maple_scom_switch_freq(maple_scom_query_freq());
 268
 269        printk(KERN_INFO "Registering Maple CPU frequency driver\n");
 270        printk(KERN_INFO "Low: %d Mhz, High: %d Mhz, Cur: %d MHz\n",
 271                maple_cpu_freqs[1].frequency/1000,
 272                maple_cpu_freqs[0].frequency/1000,
 273                maple_cpu_freqs[maple_pmode_cur].frequency/1000);
 274
 275        rc = cpufreq_register_driver(&maple_cpufreq_driver);
 276
 277        of_node_put(cpunode);
 278
 279        return rc;
 280
 281bail_noprops:
 282        of_node_put(cpunode);
 283
 284        return rc;
 285}
 286
 287module_init(maple_cpufreq_init);
 288
 289
 290MODULE_LICENSE("GPL");
 291
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