drivers/cpufreq/speedstep-smi.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Intel SpeedStep SMI driver.
   4  *
   5  * (C) 2003  Hiroshi Miura <miura@da-cha.org>
   6  */
   7
   8
   9 /*********************************************************************
  10  *                        SPEEDSTEP - DEFINITIONS                    *
  11  *********************************************************************/
  12
  13 #define pr_fmt(fmt) "cpufreq: " fmt
  14
  15 #include <linux/kernel.h>
  16 #include <linux/module.h>
  17 #include <linux/moduleparam.h>
  18 #include <linux/init.h>
  19 #include <linux/cpufreq.h>
  20 #include <linux/delay.h>
  21 #include <linux/io.h>
  22 #include <asm/ist.h>
  23 #include <asm/cpu_device_id.h>
  24
  25 #include "speedstep-lib.h"
  26
  27 /* speedstep system management interface port/command.
  28  *
  29  * These parameters are got from IST-SMI BIOS call.
  30  * If user gives it, these are used.
  31  *
  32  */
  33 static int smi_port;
  34 static int smi_cmd;
  35 static unsigned int smi_sig;
  36
  37 /* info about the processor */
  38 static enum speedstep_processor speedstep_processor;
  39
  40 /*
  41  * There are only two frequency states for each processor. Values
  42  * are in kHz for the time being.
  43  */
  44 static struct cpufreq_frequency_table speedstep_freqs[] = {
  45         {0, SPEEDSTEP_HIGH,     0},
  46         {0, SPEEDSTEP_LOW,      0},
  47         {0, 0,                  CPUFREQ_TABLE_END},
  48 };
  49
  50 #define GET_SPEEDSTEP_OWNER 0
  51 #define GET_SPEEDSTEP_STATE 1
  52 #define SET_SPEEDSTEP_STATE 2
  53 #define GET_SPEEDSTEP_FREQS 4
  54
  55 /* how often shall the SMI call be tried if it failed, e.g. because
  56  * of DMA activity going on? */
  57 #define SMI_TRIES 5
  58
  59 /**
  60  * speedstep_smi_ownership
  61  */
  62 static int speedstep_smi_ownership(void)
  63 {
  64         u32 command, result, magic, dummy;
  65         u32 function = GET_SPEEDSTEP_OWNER;
  66         unsigned char magic_data[] = "Copyright (c) 1999 Intel Corporation";
  67
  68         command = (smi_sig & 0xffffff00) | (smi_cmd & 0xff);
  69         magic = virt_to_phys(magic_data);
  70
  71         pr_debug("trying to obtain ownership with command %x at port %x\n",
  72                         command, smi_port);
  73
  74         __asm__ __volatile__(
  75                 "push %%ebp\n"
  76                 "out %%al, (%%dx)\n"
  77                 "pop %%ebp\n"
  78                 : "=D" (result),
  79                   "=a" (dummy), "=b" (dummy), "=c" (dummy), "=d" (dummy),
  80                   "=S" (dummy)
  81                 : "a" (command), "b" (function), "c" (0), "d" (smi_port),
  82                   "D" (0), "S" (magic)
  83                 : "memory"
  84         );
  85
  86         pr_debug("result is %x\n", result);
  87
  88         return result;
  89 }
  90
  91 /**
  92  * speedstep_smi_get_freqs - get SpeedStep preferred & current freq.
  93  * @low: the low frequency value is placed here
  94  * @high: the high frequency value is placed here
  95  *
  96  * Only available on later SpeedStep-enabled systems, returns false results or
  97  * even hangs [cf. bugme.osdl.org # 1422] on earlier systems. Empirical testing
  98  * shows that the latter occurs if !(ist_info.event & 0xFFFF).
  99  */
 100 static int speedstep_smi_get_freqs(unsigned int *low, unsigned int *high)
 101 {
 102         u32 command, result = 0, edi, high_mhz, low_mhz, dummy;
 103         u32 state = 0;
 104         u32 function = GET_SPEEDSTEP_FREQS;
 105
 106         if (!(ist_info.event & 0xFFFF)) {
 107                 pr_debug("bug #1422 -- can't read freqs from BIOS\n");
 108                 return -ENODEV;
 109         }
 110
 111         command = (smi_sig & 0xffffff00) | (smi_cmd & 0xff);
 112
 113         pr_debug("trying to determine frequencies with command %x at port %x\n",
 114                         command, smi_port);
 115
 116         __asm__ __volatile__(
 117                 "push %%ebp\n"
 118                 "out %%al, (%%dx)\n"
 119                 "pop %%ebp"
 120                 : "=a" (result),
 121                   "=b" (high_mhz),
 122                   "=c" (low_mhz),
 123                   "=d" (state), "=D" (edi), "=S" (dummy)
 124                 : "a" (command),
 125                   "b" (function),
 126                   "c" (state),
 127                   "d" (smi_port), "S" (0), "D" (0)
 128         );
 129
 130         pr_debug("result %x, low_freq %u, high_freq %u\n",
 131                         result, low_mhz, high_mhz);
 132
 133         /* abort if results are obviously incorrect... */
 134         if ((high_mhz + low_mhz) < 600)
 135                 return -EINVAL;
 136
 137         *high = high_mhz * 1000;
 138         *low  = low_mhz  * 1000;
 139
 140         return result;
 141 }
 142
 143 /**
 144  * speedstep_set_state - set the SpeedStep state
 145  * @state: new processor frequency state (SPEEDSTEP_LOW or SPEEDSTEP_HIGH)
 146  *
 147  */
 148 static void speedstep_set_state(unsigned int state)
 149 {
 150         unsigned int result = 0, command, new_state, dummy;
 151         unsigned long flags;
 152         unsigned int function = SET_SPEEDSTEP_STATE;
 153         unsigned int retry = 0;
 154
 155         if (state > 0x1)
 156                 return;
 157
 158         /* Disable IRQs */
 159         preempt_disable();
 160         local_irq_save(flags);
 161
 162         command = (smi_sig & 0xffffff00) | (smi_cmd & 0xff);
 163
 164         pr_debug("trying to set frequency to state %u "
 165                 "with command %x at port %x\n",
 166                 state, command, smi_port);
 167
 168         do {
 169                 if (retry) {
 170                         /*
 171                          * We need to enable interrupts, otherwise the blockage
 172                          * won't resolve.
 173                          *
 174                          * We disable preemption so that other processes don't
 175                          * run. If other processes were running, they could
 176                          * submit more DMA requests, making the blockage worse.
 177                          */
 178                         pr_debug("retry %u, previous result %u, waiting...\n",
 179                                         retry, result);
 180                         local_irq_enable();
 181                         mdelay(retry * 50);
 182                         local_irq_disable();
 183                 }
 184                 retry++;
 185                 __asm__ __volatile__(
 186                         "push %%ebp\n"
 187                         "out %%al, (%%dx)\n"
 188                         "pop %%ebp"
 189                         : "=b" (new_state), "=D" (result),
 190                           "=c" (dummy), "=a" (dummy),
 191                           "=d" (dummy), "=S" (dummy)
 192                         : "a" (command), "b" (function), "c" (state),
 193                           "d" (smi_port), "S" (0), "D" (0)
 194                         );
 195         } while ((new_state != state) && (retry <= SMI_TRIES));
 196
 197         /* enable IRQs */
 198         local_irq_restore(flags);
 199         preempt_enable();
 200
 201         if (new_state == state)
 202                 pr_debug("change to %u MHz succeeded after %u tries "
 203                         "with result %u\n",
 204                         (speedstep_freqs[new_state].frequency / 1000),
 205                         retry, result);
 206         else
 207                 pr_err("change to state %u failed with new_state %u and result %u\n",
 208                        state, new_state, result);
 209
 210         return;
 211 }
 212
 213
 214 /**
 215  * speedstep_target - set a new CPUFreq policy
 216  * @policy: new policy
 217  * @index: index of new freq
 218  *
 219  * Sets a new CPUFreq policy/freq.
 220  */
 221 static int speedstep_target(struct cpufreq_policy *policy, unsigned int index)
 222 {
 223         speedstep_set_state(index);
 224
 225         return 0;
 226 }
 227
 228
 229 static int speedstep_cpu_init(struct cpufreq_policy *policy)
 230 {
 231         int result;
 232         unsigned int *low, *high;
 233
 234         /* capability check */
 235         if (policy->cpu != 0)
 236                 return -ENODEV;
 237
 238         result = speedstep_smi_ownership();
 239         if (result) {
 240                 pr_debug("fails in acquiring ownership of a SMI interface.\n");
 241                 return -EINVAL;
 242         }
 243
 244         /* detect low and high frequency */
 245         low = &speedstep_freqs[SPEEDSTEP_LOW].frequency;
 246         high = &speedstep_freqs[SPEEDSTEP_HIGH].frequency;
 247
 248         result = speedstep_smi_get_freqs(low, high);
 249         if (result) {
 250                 /* fall back to speedstep_lib.c dection mechanism:
 251                  * try both states out */
 252                 pr_debug("could not detect low and high frequencies "
 253                                 "by SMI call.\n");
 254                 result = speedstep_get_freqs(speedstep_processor,
 255                                 low, high,
 256                                 NULL,
 257                                 &speedstep_set_state);
 258
 259                 if (result) {
 260                         pr_debug("could not detect two different speeds"
 261                                         " -- aborting.\n");
 262                         return result;
 263                 } else
 264                         pr_debug("workaround worked.\n");
 265         }
 266
 267         policy->freq_table = speedstep_freqs;
 268
 269         return 0;
 270 }
 271
 272 static unsigned int speedstep_get(unsigned int cpu)
 273 {
 274         if (cpu)
 275                 return -ENODEV;
 276         return speedstep_get_frequency(speedstep_processor);
 277 }
 278
 279
 280 static int speedstep_resume(struct cpufreq_policy *policy)
 281 {
 282         int result = speedstep_smi_ownership();
 283
 284         if (result)
 285                 pr_debug("fails in re-acquiring ownership of a SMI interface.\n");
 286
 287         return result;
 288 }
 289
 290 static struct cpufreq_driver speedstep_driver = {
 291         .name           = "speedstep-smi",
 292         .flags          = CPUFREQ_NO_AUTO_DYNAMIC_SWITCHING,
 293         .verify         = cpufreq_generic_frequency_table_verify,
 294         .target_index   = speedstep_target,
 295         .init           = speedstep_cpu_init,
 296         .get            = speedstep_get,
 297         .resume         = speedstep_resume,
 298         .attr           = cpufreq_generic_attr,
 299 };
 300
 301 static const struct x86_cpu_id ss_smi_ids[] = {
 302         { X86_VENDOR_INTEL, 6, 0xb, },
 303         { X86_VENDOR_INTEL, 6, 0x8, },
 304         { X86_VENDOR_INTEL, 15, 2 },
 305         {}
 306 };
 307 #if 0
 308 /* Not auto loaded currently */
 309 MODULE_DEVICE_TABLE(x86cpu, ss_smi_ids);
 310 #endif
 311
 312 /**
 313  * speedstep_init - initializes the SpeedStep CPUFreq driver
 314  *
 315  *   Initializes the SpeedStep support. Returns -ENODEV on unsupported
 316  * BIOS, -EINVAL on problems during initiatization, and zero on
 317  * success.
 318  */
 319 static int __init speedstep_init(void)
 320 {
 321         if (!x86_match_cpu(ss_smi_ids))
 322                 return -ENODEV;
 323
 324         speedstep_processor = speedstep_detect_processor();
 325
 326         switch (speedstep_processor) {
 327         case SPEEDSTEP_CPU_PIII_T:
 328         case SPEEDSTEP_CPU_PIII_C:
 329         case SPEEDSTEP_CPU_PIII_C_EARLY:
 330                 break;
 331         default:
 332                 speedstep_processor = 0;
 333         }
 334
 335         if (!speedstep_processor) {
 336                 pr_debug("No supported Intel CPU detected.\n");
 337                 return -ENODEV;
 338         }
 339
 340         pr_debug("signature:0x%.8x, command:0x%.8x, "
 341                 "event:0x%.8x, perf_level:0x%.8x.\n",
 342                 ist_info.signature, ist_info.command,
 343                 ist_info.event, ist_info.perf_level);
 344
 345         /* Error if no IST-SMI BIOS or no PARM
 346                  sig= 'ISGE' aka 'Intel Speedstep Gate E' */
 347         if ((ist_info.signature !=  0x47534943) && (
 348             (smi_port == 0) || (smi_cmd == 0)))
 349                 return -ENODEV;
 350
 351         if (smi_sig == 1)
 352                 smi_sig = 0x47534943;
 353         else
 354                 smi_sig = ist_info.signature;
 355
 356         /* setup smi_port from MODLULE_PARM or BIOS */
 357         if ((smi_port > 0xff) || (smi_port < 0))
 358                 return -EINVAL;
 359         else if (smi_port == 0)
 360                 smi_port = ist_info.command & 0xff;
 361
 362         if ((smi_cmd > 0xff) || (smi_cmd < 0))
 363                 return -EINVAL;
 364         else if (smi_cmd == 0)
 365                 smi_cmd = (ist_info.command >> 16) & 0xff;
 366
 367         return cpufreq_register_driver(&speedstep_driver);
 368 }
 369
 370
 371 /**
 372  * speedstep_exit - unregisters SpeedStep support
 373  *
 374  *   Unregisters SpeedStep support.
 375  */
 376 static void __exit speedstep_exit(void)
 377 {
 378         cpufreq_unregister_driver(&speedstep_driver);
 379 }
 380
 381 module_param_hw(smi_port, int, ioport, 0444);
 382 module_param(smi_cmd,  int, 0444);
 383 module_param(smi_sig, uint, 0444);
 384
 385 MODULE_PARM_DESC(smi_port, "Override the BIOS-given IST port with this value "
 386                 "-- Intel's default setting is 0xb2");
 387 MODULE_PARM_DESC(smi_cmd, "Override the BIOS-given IST command with this value "
 388                 "-- Intel's default setting is 0x82");
 389 MODULE_PARM_DESC(smi_sig, "Set to 1 to fake the IST signature when using the "
 390                 "SMI interface.");
 391
 392 MODULE_AUTHOR("Hiroshi Miura");
 393 MODULE_DESCRIPTION("Speedstep driver for IST applet SMI interface.");
 394 MODULE_LICENSE("GPL");
 395
 396 module_init(speedstep_init);
 397 module_exit(speedstep_exit);