arch/arm/mach-u300/timer.c

   1 /*
   2  *
   3  * arch/arm/mach-u300/timer.c
   4  *
   5  *
   6  * Copyright (C) 2007-2009 ST-Ericsson AB
   7  * License terms: GNU General Public License (GPL) version 2
   8  * Timer COH 901 328, runs the OS timer interrupt.
   9  * Author: Linus Walleij <linus.walleij@stericsson.com>
  10  */
  11 #include <linux/interrupt.h>
  12 #include <linux/time.h>
  13 #include <linux/timex.h>
  14 #include <linux/clockchips.h>
  15 #include <linux/clocksource.h>
  16 #include <linux/types.h>
  17 #include <linux/io.h>
  18 #include <linux/clk.h>
  19 #include <linux/err.h>
  20 #include <linux/irq.h>
  21
  22 #include <mach/hardware.h>
  23 #include <mach/irqs.h>
  24
  25 /* Generic stuff */
  26 #include <asm/sched_clock.h>
  27 #include <asm/mach/map.h>
  28 #include <asm/mach/time.h>
  29
  30 #include "timer.h"
  31
  32 /*
  33  * APP side special timer registers
  34  * This timer contains four timers which can fire an interrupt each.
  35  * OS (operating system) timer @ 32768 Hz
  36  * DD (device driver) timer @ 1 kHz
  37  * GP1 (general purpose 1) timer @ 1MHz
  38  * GP2 (general purpose 2) timer @ 1MHz
  39  */
  40
  41 /* Reset OS Timer 32bit (-/W) */
  42 #define U300_TIMER_APP_ROST                                     (0x0000)
  43 #define U300_TIMER_APP_ROST_TIMER_RESET                         (0x00000000)
  44 /* Enable OS Timer 32bit (-/W) */
  45 #define U300_TIMER_APP_EOST                                     (0x0004)
  46 #define U300_TIMER_APP_EOST_TIMER_ENABLE                        (0x00000000)
  47 /* Disable OS Timer 32bit (-/W) */
  48 #define U300_TIMER_APP_DOST                                     (0x0008)
  49 #define U300_TIMER_APP_DOST_TIMER_DISABLE                       (0x00000000)
  50 /* OS Timer Mode Register 32bit (-/W) */
  51 #define U300_TIMER_APP_SOSTM                                    (0x000c)
  52 #define U300_TIMER_APP_SOSTM_MODE_CONTINUOUS                    (0x00000000)
  53 #define U300_TIMER_APP_SOSTM_MODE_ONE_SHOT                      (0x00000001)
  54 /* OS Timer Status Register 32bit (R/-) */
  55 #define U300_TIMER_APP_OSTS                                     (0x0010)
  56 #define U300_TIMER_APP_OSTS_TIMER_STATE_MASK                    (0x0000000F)
  57 #define U300_TIMER_APP_OSTS_TIMER_STATE_IDLE                    (0x00000001)
  58 #define U300_TIMER_APP_OSTS_TIMER_STATE_ACTIVE                  (0x00000002)
  59 #define U300_TIMER_APP_OSTS_ENABLE_IND                          (0x00000010)
  60 #define U300_TIMER_APP_OSTS_MODE_MASK                           (0x00000020)
  61 #define U300_TIMER_APP_OSTS_MODE_CONTINUOUS                     (0x00000000)
  62 #define U300_TIMER_APP_OSTS_MODE_ONE_SHOT                       (0x00000020)
  63 #define U300_TIMER_APP_OSTS_IRQ_ENABLED_IND                     (0x00000040)
  64 #define U300_TIMER_APP_OSTS_IRQ_PENDING_IND                     (0x00000080)
  65 /* OS Timer Current Count Register 32bit (R/-) */
  66 #define U300_TIMER_APP_OSTCC                                    (0x0014)
  67 /* OS Timer Terminal Count Register 32bit (R/W) */
  68 #define U300_TIMER_APP_OSTTC                                    (0x0018)
  69 /* OS Timer Interrupt Enable Register 32bit (-/W) */
  70 #define U300_TIMER_APP_OSTIE                                    (0x001c)
  71 #define U300_TIMER_APP_OSTIE_IRQ_DISABLE                        (0x00000000)
  72 #define U300_TIMER_APP_OSTIE_IRQ_ENABLE                         (0x00000001)
  73 /* OS Timer Interrupt Acknowledge Register 32bit (-/W) */
  74 #define U300_TIMER_APP_OSTIA                                    (0x0020)
  75 #define U300_TIMER_APP_OSTIA_IRQ_ACK                            (0x00000080)
  76
  77 /* Reset DD Timer 32bit (-/W) */
  78 #define U300_TIMER_APP_RDDT                                     (0x0040)
  79 #define U300_TIMER_APP_RDDT_TIMER_RESET                         (0x00000000)
  80 /* Enable DD Timer 32bit (-/W) */
  81 #define U300_TIMER_APP_EDDT                                     (0x0044)
  82 #define U300_TIMER_APP_EDDT_TIMER_ENABLE                        (0x00000000)
  83 /* Disable DD Timer 32bit (-/W) */
  84 #define U300_TIMER_APP_DDDT                                     (0x0048)
  85 #define U300_TIMER_APP_DDDT_TIMER_DISABLE                       (0x00000000)
  86 /* DD Timer Mode Register 32bit (-/W) */
  87 #define U300_TIMER_APP_SDDTM                                    (0x004c)
  88 #define U300_TIMER_APP_SDDTM_MODE_CONTINUOUS                    (0x00000000)
  89 #define U300_TIMER_APP_SDDTM_MODE_ONE_SHOT                      (0x00000001)
  90 /* DD Timer Status Register 32bit (R/-) */
  91 #define U300_TIMER_APP_DDTS                                     (0x0050)
  92 #define U300_TIMER_APP_DDTS_TIMER_STATE_MASK                    (0x0000000F)
  93 #define U300_TIMER_APP_DDTS_TIMER_STATE_IDLE                    (0x00000001)
  94 #define U300_TIMER_APP_DDTS_TIMER_STATE_ACTIVE                  (0x00000002)
  95 #define U300_TIMER_APP_DDTS_ENABLE_IND                          (0x00000010)
  96 #define U300_TIMER_APP_DDTS_MODE_MASK                           (0x00000020)
  97 #define U300_TIMER_APP_DDTS_MODE_CONTINUOUS                     (0x00000000)
  98 #define U300_TIMER_APP_DDTS_MODE_ONE_SHOT                       (0x00000020)
  99 #define U300_TIMER_APP_DDTS_IRQ_ENABLED_IND                     (0x00000040)
 100 #define U300_TIMER_APP_DDTS_IRQ_PENDING_IND                     (0x00000080)
 101 /* DD Timer Current Count Register 32bit (R/-) */
 102 #define U300_TIMER_APP_DDTCC                                    (0x0054)
 103 /* DD Timer Terminal Count Register 32bit (R/W) */
 104 #define U300_TIMER_APP_DDTTC                                    (0x0058)
 105 /* DD Timer Interrupt Enable Register 32bit (-/W) */
 106 #define U300_TIMER_APP_DDTIE                                    (0x005c)
 107 #define U300_TIMER_APP_DDTIE_IRQ_DISABLE                        (0x00000000)
 108 #define U300_TIMER_APP_DDTIE_IRQ_ENABLE                         (0x00000001)
 109 /* DD Timer Interrupt Acknowledge Register 32bit (-/W) */
 110 #define U300_TIMER_APP_DDTIA                                    (0x0060)
 111 #define U300_TIMER_APP_DDTIA_IRQ_ACK                            (0x00000080)
 112
 113 /* Reset GP1 Timer 32bit (-/W) */
 114 #define U300_TIMER_APP_RGPT1                                    (0x0080)
 115 #define U300_TIMER_APP_RGPT1_TIMER_RESET                        (0x00000000)
 116 /* Enable GP1 Timer 32bit (-/W) */
 117 #define U300_TIMER_APP_EGPT1                                    (0x0084)
 118 #define U300_TIMER_APP_EGPT1_TIMER_ENABLE                       (0x00000000)
 119 /* Disable GP1 Timer 32bit (-/W) */
 120 #define U300_TIMER_APP_DGPT1                                    (0x0088)
 121 #define U300_TIMER_APP_DGPT1_TIMER_DISABLE                      (0x00000000)
 122 /* GP1 Timer Mode Register 32bit (-/W) */
 123 #define U300_TIMER_APP_SGPT1M                                   (0x008c)
 124 #define U300_TIMER_APP_SGPT1M_MODE_CONTINUOUS                   (0x00000000)
 125 #define U300_TIMER_APP_SGPT1M_MODE_ONE_SHOT                     (0x00000001)
 126 /* GP1 Timer Status Register 32bit (R/-) */
 127 #define U300_TIMER_APP_GPT1S                                    (0x0090)
 128 #define U300_TIMER_APP_GPT1S_TIMER_STATE_MASK                   (0x0000000F)
 129 #define U300_TIMER_APP_GPT1S_TIMER_STATE_IDLE                   (0x00000001)
 130 #define U300_TIMER_APP_GPT1S_TIMER_STATE_ACTIVE                 (0x00000002)
 131 #define U300_TIMER_APP_GPT1S_ENABLE_IND                         (0x00000010)
 132 #define U300_TIMER_APP_GPT1S_MODE_MASK                          (0x00000020)
 133 #define U300_TIMER_APP_GPT1S_MODE_CONTINUOUS                    (0x00000000)
 134 #define U300_TIMER_APP_GPT1S_MODE_ONE_SHOT                      (0x00000020)
 135 #define U300_TIMER_APP_GPT1S_IRQ_ENABLED_IND                    (0x00000040)
 136 #define U300_TIMER_APP_GPT1S_IRQ_PENDING_IND                    (0x00000080)
 137 /* GP1 Timer Current Count Register 32bit (R/-) */
 138 #define U300_TIMER_APP_GPT1CC                                   (0x0094)
 139 /* GP1 Timer Terminal Count Register 32bit (R/W) */
 140 #define U300_TIMER_APP_GPT1TC                                   (0x0098)
 141 /* GP1 Timer Interrupt Enable Register 32bit (-/W) */
 142 #define U300_TIMER_APP_GPT1IE                                   (0x009c)
 143 #define U300_TIMER_APP_GPT1IE_IRQ_DISABLE                       (0x00000000)
 144 #define U300_TIMER_APP_GPT1IE_IRQ_ENABLE                        (0x00000001)
 145 /* GP1 Timer Interrupt Acknowledge Register 32bit (-/W) */
 146 #define U300_TIMER_APP_GPT1IA                                   (0x00a0)
 147 #define U300_TIMER_APP_GPT1IA_IRQ_ACK                           (0x00000080)
 148
 149 /* Reset GP2 Timer 32bit (-/W) */
 150 #define U300_TIMER_APP_RGPT2                                    (0x00c0)
 151 #define U300_TIMER_APP_RGPT2_TIMER_RESET                        (0x00000000)
 152 /* Enable GP2 Timer 32bit (-/W) */
 153 #define U300_TIMER_APP_EGPT2                                    (0x00c4)
 154 #define U300_TIMER_APP_EGPT2_TIMER_ENABLE                       (0x00000000)
 155 /* Disable GP2 Timer 32bit (-/W) */
 156 #define U300_TIMER_APP_DGPT2                                    (0x00c8)
 157 #define U300_TIMER_APP_DGPT2_TIMER_DISABLE                      (0x00000000)
 158 /* GP2 Timer Mode Register 32bit (-/W) */
 159 #define U300_TIMER_APP_SGPT2M                                   (0x00cc)
 160 #define U300_TIMER_APP_SGPT2M_MODE_CONTINUOUS                   (0x00000000)
 161 #define U300_TIMER_APP_SGPT2M_MODE_ONE_SHOT                     (0x00000001)
 162 /* GP2 Timer Status Register 32bit (R/-) */
 163 #define U300_TIMER_APP_GPT2S                                    (0x00d0)
 164 #define U300_TIMER_APP_GPT2S_TIMER_STATE_MASK                   (0x0000000F)
 165 #define U300_TIMER_APP_GPT2S_TIMER_STATE_IDLE                   (0x00000001)
 166 #define U300_TIMER_APP_GPT2S_TIMER_STATE_ACTIVE                 (0x00000002)
 167 #define U300_TIMER_APP_GPT2S_ENABLE_IND                         (0x00000010)
 168 #define U300_TIMER_APP_GPT2S_MODE_MASK                          (0x00000020)
 169 #define U300_TIMER_APP_GPT2S_MODE_CONTINUOUS                    (0x00000000)
 170 #define U300_TIMER_APP_GPT2S_MODE_ONE_SHOT                      (0x00000020)
 171 #define U300_TIMER_APP_GPT2S_IRQ_ENABLED_IND                    (0x00000040)
 172 #define U300_TIMER_APP_GPT2S_IRQ_PENDING_IND                    (0x00000080)
 173 /* GP2 Timer Current Count Register 32bit (R/-) */
 174 #define U300_TIMER_APP_GPT2CC                                   (0x00d4)
 175 /* GP2 Timer Terminal Count Register 32bit (R/W) */
 176 #define U300_TIMER_APP_GPT2TC                                   (0x00d8)
 177 /* GP2 Timer Interrupt Enable Register 32bit (-/W) */
 178 #define U300_TIMER_APP_GPT2IE                                   (0x00dc)
 179 #define U300_TIMER_APP_GPT2IE_IRQ_DISABLE                       (0x00000000)
 180 #define U300_TIMER_APP_GPT2IE_IRQ_ENABLE                        (0x00000001)
 181 /* GP2 Timer Interrupt Acknowledge Register 32bit (-/W) */
 182 #define U300_TIMER_APP_GPT2IA                                   (0x00e0)
 183 #define U300_TIMER_APP_GPT2IA_IRQ_ACK                           (0x00000080)
 184
 185 /* Clock request control register - all four timers */
 186 #define U300_TIMER_APP_CRC                                      (0x100)
 187 #define U300_TIMER_APP_CRC_CLOCK_REQUEST_ENABLE                 (0x00000001)
 188
 189 #define TICKS_PER_JIFFY ((CLOCK_TICK_RATE + (HZ/2)) / HZ)
 190 #define US_PER_TICK ((1000000 + (HZ/2)) / HZ)
 191
 192 /*
 193  * The u300_set_mode() function is always called first, if we
 194  * have oneshot timer active, the oneshot scheduling function
 195  * u300_set_next_event() is called immediately after.
 196  */
 197 static void u300_set_mode(enum clock_event_mode mode,
 198                           struct clock_event_device *evt)
 199 {
 200         switch (mode) {
 201         case CLOCK_EVT_MODE_PERIODIC:
 202                 /* Disable interrupts on GPT1 */
 203                 writel(U300_TIMER_APP_GPT1IE_IRQ_DISABLE,
 204                        U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT1IE);
 205                 /* Disable GP1 while we're reprogramming it. */
 206                 writel(U300_TIMER_APP_DGPT1_TIMER_DISABLE,
 207                        U300_TIMER_APP_VBASE + U300_TIMER_APP_DGPT1);
 208                 /*
 209                  * Set the periodic mode to a certain number of ticks per
 210                  * jiffy.
 211                  */
 212                 writel(TICKS_PER_JIFFY,
 213                        U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT1TC);
 214                 /*
 215                  * Set continuous mode, so the timer keeps triggering
 216                  * interrupts.
 217                  */
 218                 writel(U300_TIMER_APP_SGPT1M_MODE_CONTINUOUS,
 219                        U300_TIMER_APP_VBASE + U300_TIMER_APP_SGPT1M);
 220                 /* Enable timer interrupts */
 221                 writel(U300_TIMER_APP_GPT1IE_IRQ_ENABLE,
 222                        U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT1IE);
 223                 /* Then enable the OS timer again */
 224                 writel(U300_TIMER_APP_EGPT1_TIMER_ENABLE,
 225                        U300_TIMER_APP_VBASE + U300_TIMER_APP_EGPT1);
 226                 break;
 227         case CLOCK_EVT_MODE_ONESHOT:
 228                 /* Just break; here? */
 229                 /*
 230                  * The actual event will be programmed by the next event hook,
 231                  * so we just set a dummy value somewhere at the end of the
 232                  * universe here.
 233                  */
 234                 /* Disable interrupts on GPT1 */
 235                 writel(U300_TIMER_APP_GPT1IE_IRQ_DISABLE,
 236                        U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT1IE);
 237                 /* Disable GP1 while we're reprogramming it. */
 238                 writel(U300_TIMER_APP_DGPT1_TIMER_DISABLE,
 239                        U300_TIMER_APP_VBASE + U300_TIMER_APP_DGPT1);
 240                 /*
 241                  * Expire far in the future, u300_set_next_event() will be
 242                  * called soon...
 243                  */
 244                 writel(0xFFFFFFFF, U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT1TC);
 245                 /* We run one shot per tick here! */
 246                 writel(U300_TIMER_APP_SGPT1M_MODE_ONE_SHOT,
 247                        U300_TIMER_APP_VBASE + U300_TIMER_APP_SGPT1M);
 248                 /* Enable interrupts for this timer */
 249                 writel(U300_TIMER_APP_GPT1IE_IRQ_ENABLE,
 250                        U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT1IE);
 251                 /* Enable timer */
 252                 writel(U300_TIMER_APP_EGPT1_TIMER_ENABLE,
 253                        U300_TIMER_APP_VBASE + U300_TIMER_APP_EGPT1);
 254                 break;
 255         case CLOCK_EVT_MODE_UNUSED:
 256         case CLOCK_EVT_MODE_SHUTDOWN:
 257                 /* Disable interrupts on GP1 */
 258                 writel(U300_TIMER_APP_GPT1IE_IRQ_DISABLE,
 259                        U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT1IE);
 260                 /* Disable GP1 */
 261                 writel(U300_TIMER_APP_DGPT1_TIMER_DISABLE,
 262                        U300_TIMER_APP_VBASE + U300_TIMER_APP_DGPT1);
 263                 break;
 264         case CLOCK_EVT_MODE_RESUME:
 265                 /* Ignore this call */
 266                 break;
 267         }
 268 }
 269
 270 /*
 271  * The app timer in one shot mode obviously has to be reprogrammed
 272  * in EXACTLY this sequence to work properly. Do NOT try to e.g. replace
 273  * the interrupt disable + timer disable commands with a reset command,
 274  * it will fail miserably. Apparently (and I found this the hard way)
 275  * the timer is very sensitive to the instruction order, though you don't
 276  * get that impression from the data sheet.
 277  */
 278 static int u300_set_next_event(unsigned long cycles,
 279                                struct clock_event_device *evt)
 280
 281 {
 282         /* Disable interrupts on GPT1 */
 283         writel(U300_TIMER_APP_GPT1IE_IRQ_DISABLE,
 284                U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT1IE);
 285         /* Disable GP1 while we're reprogramming it. */
 286         writel(U300_TIMER_APP_DGPT1_TIMER_DISABLE,
 287                U300_TIMER_APP_VBASE + U300_TIMER_APP_DGPT1);
 288         /* Reset the General Purpose timer 1. */
 289         writel(U300_TIMER_APP_RGPT1_TIMER_RESET,
 290                U300_TIMER_APP_VBASE + U300_TIMER_APP_RGPT1);
 291         /* IRQ in n * cycles */
 292         writel(cycles, U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT1TC);
 293         /*
 294          * We run one shot per tick here! (This is necessary to reconfigure,
 295          * the timer will tilt if you don't!)
 296          */
 297         writel(U300_TIMER_APP_SGPT1M_MODE_ONE_SHOT,
 298                U300_TIMER_APP_VBASE + U300_TIMER_APP_SGPT1M);
 299         /* Enable timer interrupts */
 300         writel(U300_TIMER_APP_GPT1IE_IRQ_ENABLE,
 301                U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT1IE);
 302         /* Then enable the OS timer again */
 303         writel(U300_TIMER_APP_EGPT1_TIMER_ENABLE,
 304                U300_TIMER_APP_VBASE + U300_TIMER_APP_EGPT1);
 305         return 0;
 306 }
 307
 308
 309 /* Use general purpose timer 1 as clock event */
 310 static struct clock_event_device clockevent_u300_1mhz = {
 311         .name           = "GPT1",
 312         .rating         = 300, /* Reasonably fast and accurate clock event */
 313         .features       = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
 314         .set_next_event = u300_set_next_event,
 315         .set_mode       = u300_set_mode,
 316 };
 317
 318 /* Clock event timer interrupt handler */
 319 static irqreturn_t u300_timer_interrupt(int irq, void *dev_id)
 320 {
 321         struct clock_event_device *evt = &clockevent_u300_1mhz;
 322         /* ACK/Clear timer IRQ for the APP GPT1 Timer */
 323         writel(U300_TIMER_APP_GPT1IA_IRQ_ACK,
 324                 U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT1IA);
 325         evt->event_handler(evt);
 326         return IRQ_HANDLED;
 327 }
 328
 329 static struct irqaction u300_timer_irq = {
 330         .name           = "U300 Timer Tick",
 331         .flags          = IRQF_DISABLED | IRQF_TIMER | IRQF_IRQPOLL,
 332         .handler        = u300_timer_interrupt,
 333 };
 334
 335 /*
 336  * Override the global weak sched_clock symbol with this
 337  * local implementation which uses the clocksource to get some
 338  * better resolution when scheduling the kernel. We accept that
 339  * this wraps around for now, since it is just a relative time
 340  * stamp. (Inspired by OMAP implementation.)
 341  */
 342
 343 static u32 notrace u300_read_sched_clock(void)
 344 {
 345         return readl(U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT2CC);
 346 }
 347
 348
 349 /*
 350  * This sets up the system timers, clock source and clock event.
 351  */
 352 static void __init u300_timer_init(void)
 353 {
 354         struct clk *clk;
 355         unsigned long rate;
 356
 357         /* Clock the interrupt controller */
 358         clk = clk_get_sys("apptimer", NULL);
 359         BUG_ON(IS_ERR(clk));
 360         clk_prepare_enable(clk);
 361         rate = clk_get_rate(clk);
 362
 363         setup_sched_clock(u300_read_sched_clock, 32, rate);
 364
 365         /*
 366          * Disable the "OS" and "DD" timers - these are designed for Symbian!
 367          * Example usage in cnh1601578 cpu subsystem pd_timer_app.c
 368          */
 369         writel(U300_TIMER_APP_CRC_CLOCK_REQUEST_ENABLE,
 370                 U300_TIMER_APP_VBASE + U300_TIMER_APP_CRC);
 371         writel(U300_TIMER_APP_ROST_TIMER_RESET,
 372                 U300_TIMER_APP_VBASE + U300_TIMER_APP_ROST);
 373         writel(U300_TIMER_APP_DOST_TIMER_DISABLE,
 374                 U300_TIMER_APP_VBASE + U300_TIMER_APP_DOST);
 375         writel(U300_TIMER_APP_RDDT_TIMER_RESET,
 376                 U300_TIMER_APP_VBASE + U300_TIMER_APP_RDDT);
 377         writel(U300_TIMER_APP_DDDT_TIMER_DISABLE,
 378                 U300_TIMER_APP_VBASE + U300_TIMER_APP_DDDT);
 379
 380         /* Reset the General Purpose timer 1. */
 381         writel(U300_TIMER_APP_RGPT1_TIMER_RESET,
 382                 U300_TIMER_APP_VBASE + U300_TIMER_APP_RGPT1);
 383
 384         /* Set up the IRQ handler */
 385         setup_irq(IRQ_U300_TIMER_APP_GP1, &u300_timer_irq);
 386
 387         /* Reset the General Purpose timer 2 */
 388         writel(U300_TIMER_APP_RGPT2_TIMER_RESET,
 389                 U300_TIMER_APP_VBASE + U300_TIMER_APP_RGPT2);
 390         /* Set this timer to run around forever */
 391         writel(0xFFFFFFFFU, U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT2TC);
 392         /* Set continuous mode so it wraps around */
 393         writel(U300_TIMER_APP_SGPT2M_MODE_CONTINUOUS,
 394                U300_TIMER_APP_VBASE + U300_TIMER_APP_SGPT2M);
 395         /* Disable timer interrupts */
 396         writel(U300_TIMER_APP_GPT2IE_IRQ_DISABLE,
 397                 U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT2IE);
 398         /* Then enable the GP2 timer to use as a free running us counter */
 399         writel(U300_TIMER_APP_EGPT2_TIMER_ENABLE,
 400                 U300_TIMER_APP_VBASE + U300_TIMER_APP_EGPT2);
 401
 402         /* Use general purpose timer 2 as clock source */
 403         if (clocksource_mmio_init(U300_TIMER_APP_VBASE + U300_TIMER_APP_GPT2CC,
 404                         "GPT2", rate, 300, 32, clocksource_mmio_readl_up))
 405                 pr_err("timer: failed to initialize U300 clock source\n");
 406
 407         /* Configure and register the clockevent */
 408         clockevents_config_and_register(&clockevent_u300_1mhz, rate,
 409                                         1, 0xffffffff);
 410
 411         /*
 412          * TODO: init and register the rest of the timers too, they can be
 413          * used by hrtimers!
 414          */
 415 }
 416
 417 /*
 418  * Very simple system timer that only register the clock event and
 419  * clock source.
 420  */
 421 struct sys_timer u300_timer = {
 422         .init           = u300_timer_init,
 423 };