drivers/clocksource/timer-u300.c

   1 /*
   2  * Copyright (C) 2007-2009 ST-Ericsson AB
   3  * License terms: GNU General Public License (GPL) version 2
   4  * Timer COH 901 328, runs the OS timer interrupt.
   5  * Author: Linus Walleij <linus.walleij@stericsson.com>
   6  */
   7 #include <linux/interrupt.h>
   8 #include <linux/time.h>
   9 #include <linux/timex.h>
  10 #include <linux/clockchips.h>
  11 #include <linux/clocksource.h>
  12 #include <linux/types.h>
  13 #include <linux/io.h>
  14 #include <linux/clk.h>
  15 #include <linux/err.h>
  16 #include <linux/irq.h>
  17 #include <linux/delay.h>
  18 #include <linux/of_address.h>
  19 #include <linux/of_irq.h>
  20 #include <linux/sched_clock.h>
  21
  22 /* Generic stuff */
  23 #include <asm/mach/map.h>
  24 #include <asm/mach/time.h>
  25
  26 /*
  27  * APP side special timer registers
  28  * This timer contains four timers which can fire an interrupt each.
  29  * OS (operating system) timer @ 32768 Hz
  30  * DD (device driver) timer @ 1 kHz
  31  * GP1 (general purpose 1) timer @ 1MHz
  32  * GP2 (general purpose 2) timer @ 1MHz
  33  */
  34
  35 /* Reset OS Timer 32bit (-/W) */
  36 #define U300_TIMER_APP_ROST                                     (0x0000)
  37 #define U300_TIMER_APP_ROST_TIMER_RESET                         (0x00000000)
  38 /* Enable OS Timer 32bit (-/W) */
  39 #define U300_TIMER_APP_EOST                                     (0x0004)
  40 #define U300_TIMER_APP_EOST_TIMER_ENABLE                        (0x00000000)
  41 /* Disable OS Timer 32bit (-/W) */
  42 #define U300_TIMER_APP_DOST                                     (0x0008)
  43 #define U300_TIMER_APP_DOST_TIMER_DISABLE                       (0x00000000)
  44 /* OS Timer Mode Register 32bit (-/W) */
  45 #define U300_TIMER_APP_SOSTM                                    (0x000c)
  46 #define U300_TIMER_APP_SOSTM_MODE_CONTINUOUS                    (0x00000000)
  47 #define U300_TIMER_APP_SOSTM_MODE_ONE_SHOT                      (0x00000001)
  48 /* OS Timer Status Register 32bit (R/-) */
  49 #define U300_TIMER_APP_OSTS                                     (0x0010)
  50 #define U300_TIMER_APP_OSTS_TIMER_STATE_MASK                    (0x0000000F)
  51 #define U300_TIMER_APP_OSTS_TIMER_STATE_IDLE                    (0x00000001)
  52 #define U300_TIMER_APP_OSTS_TIMER_STATE_ACTIVE                  (0x00000002)
  53 #define U300_TIMER_APP_OSTS_ENABLE_IND                          (0x00000010)
  54 #define U300_TIMER_APP_OSTS_MODE_MASK                           (0x00000020)
  55 #define U300_TIMER_APP_OSTS_MODE_CONTINUOUS                     (0x00000000)
  56 #define U300_TIMER_APP_OSTS_MODE_ONE_SHOT                       (0x00000020)
  57 #define U300_TIMER_APP_OSTS_IRQ_ENABLED_IND                     (0x00000040)
  58 #define U300_TIMER_APP_OSTS_IRQ_PENDING_IND                     (0x00000080)
  59 /* OS Timer Current Count Register 32bit (R/-) */
  60 #define U300_TIMER_APP_OSTCC                                    (0x0014)
  61 /* OS Timer Terminal Count Register 32bit (R/W) */
  62 #define U300_TIMER_APP_OSTTC                                    (0x0018)
  63 /* OS Timer Interrupt Enable Register 32bit (-/W) */
  64 #define U300_TIMER_APP_OSTIE                                    (0x001c)
  65 #define U300_TIMER_APP_OSTIE_IRQ_DISABLE                        (0x00000000)
  66 #define U300_TIMER_APP_OSTIE_IRQ_ENABLE                         (0x00000001)
  67 /* OS Timer Interrupt Acknowledge Register 32bit (-/W) */
  68 #define U300_TIMER_APP_OSTIA                                    (0x0020)
  69 #define U300_TIMER_APP_OSTIA_IRQ_ACK                            (0x00000080)
  70
  71 /* Reset DD Timer 32bit (-/W) */
  72 #define U300_TIMER_APP_RDDT                                     (0x0040)
  73 #define U300_TIMER_APP_RDDT_TIMER_RESET                         (0x00000000)
  74 /* Enable DD Timer 32bit (-/W) */
  75 #define U300_TIMER_APP_EDDT                                     (0x0044)
  76 #define U300_TIMER_APP_EDDT_TIMER_ENABLE                        (0x00000000)
  77 /* Disable DD Timer 32bit (-/W) */
  78 #define U300_TIMER_APP_DDDT                                     (0x0048)
  79 #define U300_TIMER_APP_DDDT_TIMER_DISABLE                       (0x00000000)
  80 /* DD Timer Mode Register 32bit (-/W) */
  81 #define U300_TIMER_APP_SDDTM                                    (0x004c)
  82 #define U300_TIMER_APP_SDDTM_MODE_CONTINUOUS                    (0x00000000)
  83 #define U300_TIMER_APP_SDDTM_MODE_ONE_SHOT                      (0x00000001)
  84 /* DD Timer Status Register 32bit (R/-) */
  85 #define U300_TIMER_APP_DDTS                                     (0x0050)
  86 #define U300_TIMER_APP_DDTS_TIMER_STATE_MASK                    (0x0000000F)
  87 #define U300_TIMER_APP_DDTS_TIMER_STATE_IDLE                    (0x00000001)
  88 #define U300_TIMER_APP_DDTS_TIMER_STATE_ACTIVE                  (0x00000002)
  89 #define U300_TIMER_APP_DDTS_ENABLE_IND                          (0x00000010)
  90 #define U300_TIMER_APP_DDTS_MODE_MASK                           (0x00000020)
  91 #define U300_TIMER_APP_DDTS_MODE_CONTINUOUS                     (0x00000000)
  92 #define U300_TIMER_APP_DDTS_MODE_ONE_SHOT                       (0x00000020)
  93 #define U300_TIMER_APP_DDTS_IRQ_ENABLED_IND                     (0x00000040)
  94 #define U300_TIMER_APP_DDTS_IRQ_PENDING_IND                     (0x00000080)
  95 /* DD Timer Current Count Register 32bit (R/-) */
  96 #define U300_TIMER_APP_DDTCC                                    (0x0054)
  97 /* DD Timer Terminal Count Register 32bit (R/W) */
  98 #define U300_TIMER_APP_DDTTC                                    (0x0058)
  99 /* DD Timer Interrupt Enable Register 32bit (-/W) */
 100 #define U300_TIMER_APP_DDTIE                                    (0x005c)
 101 #define U300_TIMER_APP_DDTIE_IRQ_DISABLE                        (0x00000000)
 102 #define U300_TIMER_APP_DDTIE_IRQ_ENABLE                         (0x00000001)
 103 /* DD Timer Interrupt Acknowledge Register 32bit (-/W) */
 104 #define U300_TIMER_APP_DDTIA                                    (0x0060)
 105 #define U300_TIMER_APP_DDTIA_IRQ_ACK                            (0x00000080)
 106
 107 /* Reset GP1 Timer 32bit (-/W) */
 108 #define U300_TIMER_APP_RGPT1                                    (0x0080)
 109 #define U300_TIMER_APP_RGPT1_TIMER_RESET                        (0x00000000)
 110 /* Enable GP1 Timer 32bit (-/W) */
 111 #define U300_TIMER_APP_EGPT1                                    (0x0084)
 112 #define U300_TIMER_APP_EGPT1_TIMER_ENABLE                       (0x00000000)
 113 /* Disable GP1 Timer 32bit (-/W) */
 114 #define U300_TIMER_APP_DGPT1                                    (0x0088)
 115 #define U300_TIMER_APP_DGPT1_TIMER_DISABLE                      (0x00000000)
 116 /* GP1 Timer Mode Register 32bit (-/W) */
 117 #define U300_TIMER_APP_SGPT1M                                   (0x008c)
 118 #define U300_TIMER_APP_SGPT1M_MODE_CONTINUOUS                   (0x00000000)
 119 #define U300_TIMER_APP_SGPT1M_MODE_ONE_SHOT                     (0x00000001)
 120 /* GP1 Timer Status Register 32bit (R/-) */
 121 #define U300_TIMER_APP_GPT1S                                    (0x0090)
 122 #define U300_TIMER_APP_GPT1S_TIMER_STATE_MASK                   (0x0000000F)
 123 #define U300_TIMER_APP_GPT1S_TIMER_STATE_IDLE                   (0x00000001)
 124 #define U300_TIMER_APP_GPT1S_TIMER_STATE_ACTIVE                 (0x00000002)
 125 #define U300_TIMER_APP_GPT1S_ENABLE_IND                         (0x00000010)
 126 #define U300_TIMER_APP_GPT1S_MODE_MASK                          (0x00000020)
 127 #define U300_TIMER_APP_GPT1S_MODE_CONTINUOUS                    (0x00000000)
 128 #define U300_TIMER_APP_GPT1S_MODE_ONE_SHOT                      (0x00000020)
 129 #define U300_TIMER_APP_GPT1S_IRQ_ENABLED_IND                    (0x00000040)
 130 #define U300_TIMER_APP_GPT1S_IRQ_PENDING_IND                    (0x00000080)
 131 /* GP1 Timer Current Count Register 32bit (R/-) */
 132 #define U300_TIMER_APP_GPT1CC                                   (0x0094)
 133 /* GP1 Timer Terminal Count Register 32bit (R/W) */
 134 #define U300_TIMER_APP_GPT1TC                                   (0x0098)
 135 /* GP1 Timer Interrupt Enable Register 32bit (-/W) */
 136 #define U300_TIMER_APP_GPT1IE                                   (0x009c)
 137 #define U300_TIMER_APP_GPT1IE_IRQ_DISABLE                       (0x00000000)
 138 #define U300_TIMER_APP_GPT1IE_IRQ_ENABLE                        (0x00000001)
 139 /* GP1 Timer Interrupt Acknowledge Register 32bit (-/W) */
 140 #define U300_TIMER_APP_GPT1IA                                   (0x00a0)
 141 #define U300_TIMER_APP_GPT1IA_IRQ_ACK                           (0x00000080)
 142
 143 /* Reset GP2 Timer 32bit (-/W) */
 144 #define U300_TIMER_APP_RGPT2                                    (0x00c0)
 145 #define U300_TIMER_APP_RGPT2_TIMER_RESET                        (0x00000000)
 146 /* Enable GP2 Timer 32bit (-/W) */
 147 #define U300_TIMER_APP_EGPT2                                    (0x00c4)
 148 #define U300_TIMER_APP_EGPT2_TIMER_ENABLE                       (0x00000000)
 149 /* Disable GP2 Timer 32bit (-/W) */
 150 #define U300_TIMER_APP_DGPT2                                    (0x00c8)
 151 #define U300_TIMER_APP_DGPT2_TIMER_DISABLE                      (0x00000000)
 152 /* GP2 Timer Mode Register 32bit (-/W) */
 153 #define U300_TIMER_APP_SGPT2M                                   (0x00cc)
 154 #define U300_TIMER_APP_SGPT2M_MODE_CONTINUOUS                   (0x00000000)
 155 #define U300_TIMER_APP_SGPT2M_MODE_ONE_SHOT                     (0x00000001)
 156 /* GP2 Timer Status Register 32bit (R/-) */
 157 #define U300_TIMER_APP_GPT2S                                    (0x00d0)
 158 #define U300_TIMER_APP_GPT2S_TIMER_STATE_MASK                   (0x0000000F)
 159 #define U300_TIMER_APP_GPT2S_TIMER_STATE_IDLE                   (0x00000001)
 160 #define U300_TIMER_APP_GPT2S_TIMER_STATE_ACTIVE                 (0x00000002)
 161 #define U300_TIMER_APP_GPT2S_ENABLE_IND                         (0x00000010)
 162 #define U300_TIMER_APP_GPT2S_MODE_MASK                          (0x00000020)
 163 #define U300_TIMER_APP_GPT2S_MODE_CONTINUOUS                    (0x00000000)
 164 #define U300_TIMER_APP_GPT2S_MODE_ONE_SHOT                      (0x00000020)
 165 #define U300_TIMER_APP_GPT2S_IRQ_ENABLED_IND                    (0x00000040)
 166 #define U300_TIMER_APP_GPT2S_IRQ_PENDING_IND                    (0x00000080)
 167 /* GP2 Timer Current Count Register 32bit (R/-) */
 168 #define U300_TIMER_APP_GPT2CC                                   (0x00d4)
 169 /* GP2 Timer Terminal Count Register 32bit (R/W) */
 170 #define U300_TIMER_APP_GPT2TC                                   (0x00d8)
 171 /* GP2 Timer Interrupt Enable Register 32bit (-/W) */
 172 #define U300_TIMER_APP_GPT2IE                                   (0x00dc)
 173 #define U300_TIMER_APP_GPT2IE_IRQ_DISABLE                       (0x00000000)
 174 #define U300_TIMER_APP_GPT2IE_IRQ_ENABLE                        (0x00000001)
 175 /* GP2 Timer Interrupt Acknowledge Register 32bit (-/W) */
 176 #define U300_TIMER_APP_GPT2IA                                   (0x00e0)
 177 #define U300_TIMER_APP_GPT2IA_IRQ_ACK                           (0x00000080)
 178
 179 /* Clock request control register - all four timers */
 180 #define U300_TIMER_APP_CRC                                      (0x100)
 181 #define U300_TIMER_APP_CRC_CLOCK_REQUEST_ENABLE                 (0x00000001)
 182
 183 static void __iomem *u300_timer_base;
 184
 185 struct u300_clockevent_data {
 186         struct clock_event_device cevd;
 187         unsigned ticks_per_jiffy;
 188 };
 189
 190 static int u300_shutdown(struct clock_event_device *evt)
 191 {
 192         /* Disable interrupts on GP1 */
 193         writel(U300_TIMER_APP_GPT1IE_IRQ_DISABLE,
 194                u300_timer_base + U300_TIMER_APP_GPT1IE);
 195         /* Disable GP1 */
 196         writel(U300_TIMER_APP_DGPT1_TIMER_DISABLE,
 197                u300_timer_base + U300_TIMER_APP_DGPT1);
 198         return 0;
 199 }
 200
 201 /*
 202  * If we have oneshot timer active, the oneshot scheduling function
 203  * u300_set_next_event() is called immediately after.
 204  */
 205 static int u300_set_oneshot(struct clock_event_device *evt)
 206 {
 207         /* Just return; here? */
 208         /*
 209          * The actual event will be programmed by the next event hook,
 210          * so we just set a dummy value somewhere at the end of the
 211          * universe here.
 212          */
 213         /* Disable interrupts on GPT1 */
 214         writel(U300_TIMER_APP_GPT1IE_IRQ_DISABLE,
 215                u300_timer_base + U300_TIMER_APP_GPT1IE);
 216         /* Disable GP1 while we're reprogramming it. */
 217         writel(U300_TIMER_APP_DGPT1_TIMER_DISABLE,
 218                u300_timer_base + U300_TIMER_APP_DGPT1);
 219         /*
 220          * Expire far in the future, u300_set_next_event() will be
 221          * called soon...
 222          */
 223         writel(0xFFFFFFFF, u300_timer_base + U300_TIMER_APP_GPT1TC);
 224         /* We run one shot per tick here! */
 225         writel(U300_TIMER_APP_SGPT1M_MODE_ONE_SHOT,
 226                u300_timer_base + U300_TIMER_APP_SGPT1M);
 227         /* Enable interrupts for this timer */
 228         writel(U300_TIMER_APP_GPT1IE_IRQ_ENABLE,
 229                u300_timer_base + U300_TIMER_APP_GPT1IE);
 230         /* Enable timer */
 231         writel(U300_TIMER_APP_EGPT1_TIMER_ENABLE,
 232                u300_timer_base + U300_TIMER_APP_EGPT1);
 233         return 0;
 234 }
 235
 236 static int u300_set_periodic(struct clock_event_device *evt)
 237 {
 238         struct u300_clockevent_data *cevdata =
 239                 container_of(evt, struct u300_clockevent_data, cevd);
 240
 241         /* Disable interrupts on GPT1 */
 242         writel(U300_TIMER_APP_GPT1IE_IRQ_DISABLE,
 243                u300_timer_base + U300_TIMER_APP_GPT1IE);
 244         /* Disable GP1 while we're reprogramming it. */
 245         writel(U300_TIMER_APP_DGPT1_TIMER_DISABLE,
 246                u300_timer_base + U300_TIMER_APP_DGPT1);
 247         /*
 248          * Set the periodic mode to a certain number of ticks per
 249          * jiffy.
 250          */
 251         writel(cevdata->ticks_per_jiffy,
 252                u300_timer_base + U300_TIMER_APP_GPT1TC);
 253         /*
 254          * Set continuous mode, so the timer keeps triggering
 255          * interrupts.
 256          */
 257         writel(U300_TIMER_APP_SGPT1M_MODE_CONTINUOUS,
 258                u300_timer_base + U300_TIMER_APP_SGPT1M);
 259         /* Enable timer interrupts */
 260         writel(U300_TIMER_APP_GPT1IE_IRQ_ENABLE,
 261                u300_timer_base + U300_TIMER_APP_GPT1IE);
 262         /* Then enable the OS timer again */
 263         writel(U300_TIMER_APP_EGPT1_TIMER_ENABLE,
 264                u300_timer_base + U300_TIMER_APP_EGPT1);
 265         return 0;
 266 }
 267
 268 /*
 269  * The app timer in one shot mode obviously has to be reprogrammed
 270  * in EXACTLY this sequence to work properly. Do NOT try to e.g. replace
 271  * the interrupt disable + timer disable commands with a reset command,
 272  * it will fail miserably. Apparently (and I found this the hard way)
 273  * the timer is very sensitive to the instruction order, though you don't
 274  * get that impression from the data sheet.
 275  */
 276 static int u300_set_next_event(unsigned long cycles,
 277                                struct clock_event_device *evt)
 278
 279 {
 280         /* Disable interrupts on GPT1 */
 281         writel(U300_TIMER_APP_GPT1IE_IRQ_DISABLE,
 282                u300_timer_base + U300_TIMER_APP_GPT1IE);
 283         /* Disable GP1 while we're reprogramming it. */
 284         writel(U300_TIMER_APP_DGPT1_TIMER_DISABLE,
 285                u300_timer_base + U300_TIMER_APP_DGPT1);
 286         /* Reset the General Purpose timer 1. */
 287         writel(U300_TIMER_APP_RGPT1_TIMER_RESET,
 288                u300_timer_base + U300_TIMER_APP_RGPT1);
 289         /* IRQ in n * cycles */
 290         writel(cycles, u300_timer_base + U300_TIMER_APP_GPT1TC);
 291         /*
 292          * We run one shot per tick here! (This is necessary to reconfigure,
 293          * the timer will tilt if you don't!)
 294          */
 295         writel(U300_TIMER_APP_SGPT1M_MODE_ONE_SHOT,
 296                u300_timer_base + U300_TIMER_APP_SGPT1M);
 297         /* Enable timer interrupts */
 298         writel(U300_TIMER_APP_GPT1IE_IRQ_ENABLE,
 299                u300_timer_base + U300_TIMER_APP_GPT1IE);
 300         /* Then enable the OS timer again */
 301         writel(U300_TIMER_APP_EGPT1_TIMER_ENABLE,
 302                u300_timer_base + U300_TIMER_APP_EGPT1);
 303         return 0;
 304 }
 305
 306 static struct u300_clockevent_data u300_clockevent_data = {
 307         /* Use general purpose timer 1 as clock event */
 308         .cevd = {
 309                 .name                   = "GPT1",
 310                 /* Reasonably fast and accurate clock event */
 311                 .rating                 = 300,
 312                 .features               = CLOCK_EVT_FEAT_PERIODIC |
 313                                           CLOCK_EVT_FEAT_ONESHOT,
 314                 .set_next_event         = u300_set_next_event,
 315                 .set_state_shutdown     = u300_shutdown,
 316                 .set_state_periodic     = u300_set_periodic,
 317                 .set_state_oneshot      = u300_set_oneshot,
 318         },
 319 };
 320
 321 /* Clock event timer interrupt handler */
 322 static irqreturn_t u300_timer_interrupt(int irq, void *dev_id)
 323 {
 324         struct clock_event_device *evt = &u300_clockevent_data.cevd;
 325         /* ACK/Clear timer IRQ for the APP GPT1 Timer */
 326
 327         writel(U300_TIMER_APP_GPT1IA_IRQ_ACK,
 328                 u300_timer_base + U300_TIMER_APP_GPT1IA);
 329         evt->event_handler(evt);
 330         return IRQ_HANDLED;
 331 }
 332
 333 static struct irqaction u300_timer_irq = {
 334         .name           = "U300 Timer Tick",
 335         .flags          = IRQF_TIMER | IRQF_IRQPOLL,
 336         .handler        = u300_timer_interrupt,
 337 };
 338
 339 /*
 340  * Override the global weak sched_clock symbol with this
 341  * local implementation which uses the clocksource to get some
 342  * better resolution when scheduling the kernel. We accept that
 343  * this wraps around for now, since it is just a relative time
 344  * stamp. (Inspired by OMAP implementation.)
 345  */
 346
 347 static u64 notrace u300_read_sched_clock(void)
 348 {
 349         return readl(u300_timer_base + U300_TIMER_APP_GPT2CC);
 350 }
 351
 352 static unsigned long u300_read_current_timer(void)
 353 {
 354         return readl(u300_timer_base + U300_TIMER_APP_GPT2CC);
 355 }
 356
 357 static struct delay_timer u300_delay_timer;
 358
 359 /*
 360  * This sets up the system timers, clock source and clock event.
 361  */
 362 static int __init u300_timer_init_of(struct device_node *np)
 363 {
 364         unsigned int irq;
 365         struct clk *clk;
 366         unsigned long rate;
 367         int ret;
 368
 369         u300_timer_base = of_iomap(np, 0);
 370         if (!u300_timer_base) {
 371                 pr_err("could not ioremap system timer\n");
 372                 return -ENXIO;
 373         }
 374
 375         /* Get the IRQ for the GP1 timer */
 376         irq = irq_of_parse_and_map(np, 2);
 377         if (!irq) {
 378                 pr_err("no IRQ for system timer\n");
 379                 return -EINVAL;
 380         }
 381
 382         pr_info("U300 GP1 timer @ base: %p, IRQ: %u\n", u300_timer_base, irq);
 383
 384         /* Clock the interrupt controller */
 385         clk = of_clk_get(np, 0);
 386         if (IS_ERR(clk))
 387                 return PTR_ERR(clk);
 388
 389         ret = clk_prepare_enable(clk);
 390         if (ret)
 391                 return ret;
 392
 393         rate = clk_get_rate(clk);
 394
 395         u300_clockevent_data.ticks_per_jiffy = DIV_ROUND_CLOSEST(rate, HZ);
 396
 397         sched_clock_register(u300_read_sched_clock, 32, rate);
 398
 399         u300_delay_timer.read_current_timer = &u300_read_current_timer;
 400         u300_delay_timer.freq = rate;
 401         register_current_timer_delay(&u300_delay_timer);
 402
 403         /*
 404          * Disable the "OS" and "DD" timers - these are designed for Symbian!
 405          * Example usage in cnh1601578 cpu subsystem pd_timer_app.c
 406          */
 407         writel(U300_TIMER_APP_CRC_CLOCK_REQUEST_ENABLE,
 408                 u300_timer_base + U300_TIMER_APP_CRC);
 409         writel(U300_TIMER_APP_ROST_TIMER_RESET,
 410                 u300_timer_base + U300_TIMER_APP_ROST);
 411         writel(U300_TIMER_APP_DOST_TIMER_DISABLE,
 412                 u300_timer_base + U300_TIMER_APP_DOST);
 413         writel(U300_TIMER_APP_RDDT_TIMER_RESET,
 414                 u300_timer_base + U300_TIMER_APP_RDDT);
 415         writel(U300_TIMER_APP_DDDT_TIMER_DISABLE,
 416                 u300_timer_base + U300_TIMER_APP_DDDT);
 417
 418         /* Reset the General Purpose timer 1. */
 419         writel(U300_TIMER_APP_RGPT1_TIMER_RESET,
 420                 u300_timer_base + U300_TIMER_APP_RGPT1);
 421
 422         /* Set up the IRQ handler */
 423         ret = setup_irq(irq, &u300_timer_irq);
 424         if (ret)
 425                 return ret;
 426
 427         /* Reset the General Purpose timer 2 */
 428         writel(U300_TIMER_APP_RGPT2_TIMER_RESET,
 429                 u300_timer_base + U300_TIMER_APP_RGPT2);
 430         /* Set this timer to run around forever */
 431         writel(0xFFFFFFFFU, u300_timer_base + U300_TIMER_APP_GPT2TC);
 432         /* Set continuous mode so it wraps around */
 433         writel(U300_TIMER_APP_SGPT2M_MODE_CONTINUOUS,
 434                u300_timer_base + U300_TIMER_APP_SGPT2M);
 435         /* Disable timer interrupts */
 436         writel(U300_TIMER_APP_GPT2IE_IRQ_DISABLE,
 437                 u300_timer_base + U300_TIMER_APP_GPT2IE);
 438         /* Then enable the GP2 timer to use as a free running us counter */
 439         writel(U300_TIMER_APP_EGPT2_TIMER_ENABLE,
 440                 u300_timer_base + U300_TIMER_APP_EGPT2);
 441
 442         /* Use general purpose timer 2 as clock source */
 443         ret = clocksource_mmio_init(u300_timer_base + U300_TIMER_APP_GPT2CC,
 444                                     "GPT2", rate, 300, 32, clocksource_mmio_readl_up);
 445         if (ret) {
 446                 pr_err("timer: failed to initialize U300 clock source\n");
 447                 return ret;
 448         }
 449
 450         /* Configure and register the clockevent */
 451         clockevents_config_and_register(&u300_clockevent_data.cevd, rate,
 452                                         1, 0xffffffff);
 453
 454         /*
 455          * TODO: init and register the rest of the timers too, they can be
 456          * used by hrtimers!
 457          */
 458         return 0;
 459 }
 460
 461 CLOCKSOURCE_OF_DECLARE(u300_timer, "stericsson,u300-apptimer",
 462                        u300_timer_init_of);