arch/x86/kernel/mfgpt_32.c

   1 /*
   2  * Driver/API for AMD Geode Multi-Function General Purpose Timers (MFGPT)
   3  *
   4  * Copyright (C) 2006, Advanced Micro Devices, Inc.
   5  * Copyright (C) 2007, Andres Salomon <dilinger@debian.org>
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of version 2 of the GNU General Public License
   9  * as published by the Free Software Foundation.
  10  *
  11  * The MFGPTs are documented in AMD Geode CS5536 Companion Device Data Book.
  12  */
  13
  14 /*
  15  * We are using the 32.768kHz input clock - it's the only one that has the
  16  * ranges we find desirable.  The following table lists the suitable
  17  * divisors and the associated Hz, minimum interval and the maximum interval:
  18  *
  19  *  Divisor   Hz      Min Delta (s)  Max Delta (s)
  20  *   1        32768   .00048828125      2.000
  21  *   2        16384   .0009765625       4.000
  22  *   4         8192   .001953125        8.000
  23  *   8         4096   .00390625        16.000
  24  *   16        2048   .0078125         32.000
  25  *   32        1024   .015625          64.000
  26  *   64         512   .03125          128.000
  27  *  128         256   .0625           256.000
  28  *  256         128   .125            512.000
  29  */
  30
  31 #include <linux/kernel.h>
  32 #include <linux/interrupt.h>
  33 #include <linux/module.h>
  34 #include <asm/geode.h>
  35
  36 #define MFGPT_DEFAULT_IRQ       7
  37
  38 static struct mfgpt_timer_t {
  39         unsigned int avail:1;
  40 } mfgpt_timers[MFGPT_MAX_TIMERS];
  41
  42 /* Selected from the table above */
  43
  44 #define MFGPT_DIVISOR 16
  45 #define MFGPT_SCALE  4     /* divisor = 2^(scale) */
  46 #define MFGPT_HZ  (32768 / MFGPT_DIVISOR)
  47 #define MFGPT_PERIODIC (MFGPT_HZ / HZ)
  48
  49 /* Allow for disabling of MFGPTs */
  50 static int disable;
  51 static int __init mfgpt_disable(char *s)
  52 {
  53         disable = 1;
  54         return 1;
  55 }
  56 __setup("nomfgpt", mfgpt_disable);
  57
  58 /* Reset the MFGPT timers. This is required by some broken BIOSes which already
  59  * do the same and leave the system in an unstable state. TinyBIOS 0.98 is
  60  * affected at least (0.99 is OK with MFGPT workaround left to off).
  61  */
  62 static int __init mfgpt_fix(char *s)
  63 {
  64         u32 val, dummy;
  65
  66         /* The following udocumented bit resets the MFGPT timers */
  67         val = 0xFF; dummy = 0;
  68         wrmsr(MSR_MFGPT_SETUP, val, dummy);
  69         return 1;
  70 }
  71 __setup("mfgptfix", mfgpt_fix);
  72
  73 /*
  74  * Check whether any MFGPTs are available for the kernel to use.  In most
  75  * cases, firmware that uses AMD's VSA code will claim all timers during
  76  * bootup; we certainly don't want to take them if they're already in use.
  77  * In other cases (such as with VSAless OpenFirmware), the system firmware
  78  * leaves timers available for us to use.
  79  */
  80
  81
  82 static int timers = -1;
  83
  84 static void geode_mfgpt_detect(void)
  85 {
  86         int i;
  87         u16 val;
  88
  89         timers = 0;
  90
  91         if (disable) {
  92                 printk(KERN_INFO "geode-mfgpt:  MFGPT support is disabled\n");
  93                 goto done;
  94         }
  95
  96         if (!geode_get_dev_base(GEODE_DEV_MFGPT)) {
  97                 printk(KERN_INFO "geode-mfgpt:  MFGPT LBAR is not set up\n");
  98                 goto done;
  99         }
 100
 101         for (i = 0; i < MFGPT_MAX_TIMERS; i++) {
 102                 val = geode_mfgpt_read(i, MFGPT_REG_SETUP);
 103                 if (!(val & MFGPT_SETUP_SETUP)) {
 104                         mfgpt_timers[i].avail = 1;
 105                         timers++;
 106                 }
 107         }
 108
 109 done:
 110         printk(KERN_INFO "geode-mfgpt:  %d MFGPT timers available.\n", timers);
 111 }
 112
 113 int geode_mfgpt_toggle_event(int timer, int cmp, int event, int enable)
 114 {
 115         u32 msr, mask, value, dummy;
 116         int shift = (cmp == MFGPT_CMP1) ? 0 : 8;
 117
 118         if (timer < 0 || timer >= MFGPT_MAX_TIMERS)
 119                 return -EIO;
 120
 121         /*
 122          * The register maps for these are described in sections 6.17.1.x of
 123          * the AMD Geode CS5536 Companion Device Data Book.
 124          */
 125         switch (event) {
 126         case MFGPT_EVENT_RESET:
 127                 /*
 128                  * XXX: According to the docs, we cannot reset timers above
 129                  * 6; that is, resets for 7 and 8 will be ignored.  Is this
 130                  * a problem?   -dilinger
 131                  */
 132                 msr = MSR_MFGPT_NR;
 133                 mask = 1 << (timer + 24);
 134                 break;
 135
 136         case MFGPT_EVENT_NMI:
 137                 msr = MSR_MFGPT_NR;
 138                 mask = 1 << (timer + shift);
 139                 break;
 140
 141         case MFGPT_EVENT_IRQ:
 142                 msr = MSR_MFGPT_IRQ;
 143                 mask = 1 << (timer + shift);
 144                 break;
 145
 146         default:
 147                 return -EIO;
 148         }
 149
 150         rdmsr(msr, value, dummy);
 151
 152         if (enable)
 153                 value |= mask;
 154         else
 155                 value &= ~mask;
 156
 157         wrmsr(msr, value, dummy);
 158         return 0;
 159 }
 160 EXPORT_SYMBOL_GPL(geode_mfgpt_toggle_event);
 161
 162 int geode_mfgpt_set_irq(int timer, int cmp, int *irq, int enable)
 163 {
 164         u32 zsel, lpc, dummy;
 165         int shift;
 166
 167         if (timer < 0 || timer >= MFGPT_MAX_TIMERS)
 168                 return -EIO;
 169
 170         /*
 171          * Unfortunately, MFGPTs come in pairs sharing their IRQ lines. If VSA
 172          * is using the same CMP of the timer's Siamese twin, the IRQ is set to
 173          * 2, and we mustn't use nor change it.
 174          * XXX: Likewise, 2 Linux drivers might clash if the 2nd overwrites the
 175          * IRQ of the 1st. This can only happen if forcing an IRQ, calling this
 176          * with *irq==0 is safe. Currently there _are_ no 2 drivers.
 177          */
 178         rdmsr(MSR_PIC_ZSEL_LOW, zsel, dummy);
 179         shift = ((cmp == MFGPT_CMP1 ? 0 : 4) + timer % 4) * 4;
 180         if (((zsel >> shift) & 0xF) == 2)
 181                 return -EIO;
 182
 183         /* Choose IRQ: if none supplied, keep IRQ already set or use default */
 184         if (!*irq)
 185                 *irq = (zsel >> shift) & 0xF;
 186         if (!*irq)
 187                 *irq = MFGPT_DEFAULT_IRQ;
 188
 189         /* Can't use IRQ if it's 0 (=disabled), 2, or routed to LPC */
 190         if (*irq < 1 || *irq == 2 || *irq > 15)
 191                 return -EIO;
 192         rdmsr(MSR_PIC_IRQM_LPC, lpc, dummy);
 193         if (lpc & (1 << *irq))
 194                 return -EIO;
 195
 196         /* All chosen and checked - go for it */
 197         if (geode_mfgpt_toggle_event(timer, cmp, MFGPT_EVENT_IRQ, enable))
 198                 return -EIO;
 199         if (enable) {
 200                 zsel = (zsel & ~(0xF << shift)) | (*irq << shift);
 201                 wrmsr(MSR_PIC_ZSEL_LOW, zsel, dummy);
 202         }
 203
 204         return 0;
 205 }
 206
 207 static int mfgpt_get(int timer)
 208 {
 209         mfgpt_timers[timer].avail = 0;
 210         printk(KERN_INFO "geode-mfgpt:  Registered timer %d\n", timer);
 211         return timer;
 212 }
 213
 214 int geode_mfgpt_alloc_timer(int timer, int domain)
 215 {
 216         int i;
 217
 218         if (timers == -1) {
 219                 /* timers haven't been detected yet */
 220                 geode_mfgpt_detect();
 221         }
 222
 223         if (!timers)
 224                 return -1;
 225
 226         if (timer >= MFGPT_MAX_TIMERS)
 227                 return -1;
 228
 229         if (timer < 0) {
 230                 /* Try to find an available timer */
 231                 for (i = 0; i < MFGPT_MAX_TIMERS; i++) {
 232                         if (mfgpt_timers[i].avail)
 233                                 return mfgpt_get(i);
 234
 235                         if (i == 5 && domain == MFGPT_DOMAIN_WORKING)
 236                                 break;
 237                 }
 238         } else {
 239                 /* If they requested a specific timer, try to honor that */
 240                 if (mfgpt_timers[timer].avail)
 241                         return mfgpt_get(timer);
 242         }
 243
 244         /* No timers available - too bad */
 245         return -1;
 246 }
 247 EXPORT_SYMBOL_GPL(geode_mfgpt_alloc_timer);
 248
 249
 250 #ifdef CONFIG_GEODE_MFGPT_TIMER
 251
 252 /*
 253  * The MFPGT timers on the CS5536 provide us with suitable timers to use
 254  * as clock event sources - not as good as a HPET or APIC, but certainly
 255  * better than the PIT.  This isn't a general purpose MFGPT driver, but
 256  * a simplified one designed specifically to act as a clock event source.
 257  * For full details about the MFGPT, please consult the CS5536 data sheet.
 258  */
 259
 260 #include <linux/clocksource.h>
 261 #include <linux/clockchips.h>
 262
 263 static unsigned int mfgpt_tick_mode = CLOCK_EVT_MODE_SHUTDOWN;
 264 static u16 mfgpt_event_clock;
 265
 266 static int irq;
 267 static int __init mfgpt_setup(char *str)
 268 {
 269         get_option(&str, &irq);
 270         return 1;
 271 }
 272 __setup("mfgpt_irq=", mfgpt_setup);
 273
 274 static void mfgpt_disable_timer(u16 clock)
 275 {
 276         /* avoid races by clearing CMP1 and CMP2 unconditionally */
 277         geode_mfgpt_write(clock, MFGPT_REG_SETUP, (u16) ~MFGPT_SETUP_CNTEN |
 278                         MFGPT_SETUP_CMP1 | MFGPT_SETUP_CMP2);
 279 }
 280
 281 static int mfgpt_next_event(unsigned long, struct clock_event_device *);
 282 static void mfgpt_set_mode(enum clock_event_mode, struct clock_event_device *);
 283
 284 static struct clock_event_device mfgpt_clockevent = {
 285         .name = "mfgpt-timer",
 286         .features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
 287         .set_mode = mfgpt_set_mode,
 288         .set_next_event = mfgpt_next_event,
 289         .rating = 250,
 290         .cpumask = cpu_all_mask,
 291         .shift = 32
 292 };
 293
 294 static void mfgpt_start_timer(u16 delta)
 295 {
 296         geode_mfgpt_write(mfgpt_event_clock, MFGPT_REG_CMP2, (u16) delta);
 297         geode_mfgpt_write(mfgpt_event_clock, MFGPT_REG_COUNTER, 0);
 298
 299         geode_mfgpt_write(mfgpt_event_clock, MFGPT_REG_SETUP,
 300                           MFGPT_SETUP_CNTEN | MFGPT_SETUP_CMP2);
 301 }
 302
 303 static void mfgpt_set_mode(enum clock_event_mode mode,
 304                            struct clock_event_device *evt)
 305 {
 306         mfgpt_disable_timer(mfgpt_event_clock);
 307
 308         if (mode == CLOCK_EVT_MODE_PERIODIC)
 309                 mfgpt_start_timer(MFGPT_PERIODIC);
 310
 311         mfgpt_tick_mode = mode;
 312 }
 313
 314 static int mfgpt_next_event(unsigned long delta, struct clock_event_device *evt)
 315 {
 316         mfgpt_start_timer(delta);
 317         return 0;
 318 }
 319
 320 static irqreturn_t mfgpt_tick(int irq, void *dev_id)
 321 {
 322         u16 val = geode_mfgpt_read(mfgpt_event_clock, MFGPT_REG_SETUP);
 323
 324         /* See if the interrupt was for us */
 325         if (!(val & (MFGPT_SETUP_SETUP  | MFGPT_SETUP_CMP2 | MFGPT_SETUP_CMP1)))
 326                 return IRQ_NONE;
 327
 328         /* Turn off the clock (and clear the event) */
 329         mfgpt_disable_timer(mfgpt_event_clock);
 330
 331         if (mfgpt_tick_mode == CLOCK_EVT_MODE_SHUTDOWN)
 332                 return IRQ_HANDLED;
 333
 334         /* Clear the counter */
 335         geode_mfgpt_write(mfgpt_event_clock, MFGPT_REG_COUNTER, 0);
 336
 337         /* Restart the clock in periodic mode */
 338
 339         if (mfgpt_tick_mode == CLOCK_EVT_MODE_PERIODIC) {
 340                 geode_mfgpt_write(mfgpt_event_clock, MFGPT_REG_SETUP,
 341                                   MFGPT_SETUP_CNTEN | MFGPT_SETUP_CMP2);
 342         }
 343
 344         mfgpt_clockevent.event_handler(&mfgpt_clockevent);
 345         return IRQ_HANDLED;
 346 }
 347
 348 static struct irqaction mfgptirq  = {
 349         .handler = mfgpt_tick,
 350         .flags = IRQF_DISABLED | IRQF_NOBALANCING | IRQF_TIMER,
 351         .name = "mfgpt-timer"
 352 };
 353
 354 int __init mfgpt_timer_setup(void)
 355 {
 356         int timer, ret;
 357         u16 val;
 358
 359         timer = geode_mfgpt_alloc_timer(MFGPT_TIMER_ANY, MFGPT_DOMAIN_WORKING);
 360         if (timer < 0) {
 361                 printk(KERN_ERR
 362                        "mfgpt-timer:  Could not allocate a MFPGT timer\n");
 363                 return -ENODEV;
 364         }
 365
 366         mfgpt_event_clock = timer;
 367
 368         /* Set up the IRQ on the MFGPT side */
 369         if (geode_mfgpt_setup_irq(mfgpt_event_clock, MFGPT_CMP2, &irq)) {
 370                 printk(KERN_ERR "mfgpt-timer:  Could not set up IRQ %d\n", irq);
 371                 return -EIO;
 372         }
 373
 374         /* And register it with the kernel */
 375         ret = setup_irq(irq, &mfgptirq);
 376
 377         if (ret) {
 378                 printk(KERN_ERR
 379                        "mfgpt-timer:  Unable to set up the interrupt.\n");
 380                 goto err;
 381         }
 382
 383         /* Set the clock scale and enable the event mode for CMP2 */
 384         val = MFGPT_SCALE | (3 << 8);
 385
 386         geode_mfgpt_write(mfgpt_event_clock, MFGPT_REG_SETUP, val);
 387
 388         /* Set up the clock event */
 389         mfgpt_clockevent.mult = div_sc(MFGPT_HZ, NSEC_PER_SEC,
 390                                        mfgpt_clockevent.shift);
 391         mfgpt_clockevent.min_delta_ns = clockevent_delta2ns(0xF,
 392                         &mfgpt_clockevent);
 393         mfgpt_clockevent.max_delta_ns = clockevent_delta2ns(0xFFFE,
 394                         &mfgpt_clockevent);
 395
 396         printk(KERN_INFO
 397                "mfgpt-timer:  Registering MFGPT timer %d as a clock event, using IRQ %d\n",
 398                timer, irq);
 399         clockevents_register_device(&mfgpt_clockevent);
 400
 401         return 0;
 402
 403 err:
 404         geode_mfgpt_release_irq(mfgpt_event_clock, MFGPT_CMP2, &irq);
 405         printk(KERN_ERR
 406                "mfgpt-timer:  Unable to set up the MFGPT clock source\n");
 407         return -EIO;
 408 }
 409
 410 #endif