arch/arc/kernel/time.c

   1 /*
   2  * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  *
   8  * vineetg: Jan 1011
   9  *  -sched_clock( ) no longer jiffies based. Uses the same clocksource
  10  *   as gtod
  11  *
  12  * Rajeshwarr/Vineetg: Mar 2008
  13  *  -Implemented CONFIG_GENERIC_TIME (rather deleted arch specific code)
  14  *   for arch independent gettimeofday()
  15  *  -Implemented CONFIG_GENERIC_CLOCKEVENTS as base for hrtimers
  16  *
  17  * Vineetg: Mar 2008: Forked off from time.c which now is time-jiff.c
  18  */
  19
  20 /* ARC700 has two 32bit independent prog Timers: TIMER0 and TIMER1
  21  * Each can programmed to go from @count to @limit and optionally
  22  * interrupt when that happens.
  23  * A write to Control Register clears the Interrupt
  24  *
  25  * We've designated TIMER0 for events (clockevents)
  26  * while TIMER1 for free running (clocksource)
  27  *
  28  * Newer ARC700 cores have 64bit clk fetching RTSC insn, preferred over TIMER1
  29  */
  30
  31 #include <linux/spinlock.h>
  32 #include <linux/interrupt.h>
  33 #include <linux/module.h>
  34 #include <linux/sched.h>
  35 #include <linux/kernel.h>
  36 #include <linux/time.h>
  37 #include <linux/init.h>
  38 #include <linux/timex.h>
  39 #include <linux/profile.h>
  40 #include <linux/clocksource.h>
  41 #include <linux/clockchips.h>
  42 #include <asm/irq.h>
  43 #include <asm/arcregs.h>
  44 #include <asm/clk.h>
  45 #include <asm/mach_desc.h>
  46
  47 /* Timer related Aux registers */
  48 #define ARC_REG_TIMER0_LIMIT    0x23    /* timer 0 limit */
  49 #define ARC_REG_TIMER0_CTRL     0x22    /* timer 0 control */
  50 #define ARC_REG_TIMER0_CNT      0x21    /* timer 0 count */
  51 #define ARC_REG_TIMER1_LIMIT    0x102   /* timer 1 limit */
  52 #define ARC_REG_TIMER1_CTRL     0x101   /* timer 1 control */
  53 #define ARC_REG_TIMER1_CNT      0x100   /* timer 1 count */
  54
  55 #define TIMER_CTRL_IE           (1 << 0) /* Interupt when Count reachs limit */
  56 #define TIMER_CTRL_NH           (1 << 1) /* Count only when CPU NOT halted */
  57
  58 #define ARC_TIMER_MAX   0xFFFFFFFF
  59
  60 /********** Clock Source Device *********/
  61
  62 #ifdef CONFIG_ARC_HAS_RTSC
  63
  64 int arc_counter_setup(void)
  65 {
  66         /* RTSC insn taps into cpu clk, needs no setup */
  67
  68         /* For SMP, only allowed if cross-core-sync, hence usable as cs */
  69         return 1;
  70 }
  71
  72 static cycle_t arc_counter_read(struct clocksource *cs)
  73 {
  74         unsigned long flags;
  75         union {
  76 #ifdef CONFIG_CPU_BIG_ENDIAN
  77                 struct { u32 high, low; };
  78 #else
  79                 struct { u32 low, high; };
  80 #endif
  81                 cycle_t  full;
  82         } stamp;
  83
  84         flags = arch_local_irq_save();
  85
  86         __asm__ __volatile(
  87         "       .extCoreRegister tsch, 58,  r, cannot_shortcut  \n"
  88         "       rtsc %0, 0      \n"
  89         "       mov  %1, 0      \n"
  90         : "=r" (stamp.low), "=r" (stamp.high));
  91
  92         arch_local_irq_restore(flags);
  93
  94         return stamp.full;
  95 }
  96
  97 static struct clocksource arc_counter = {
  98         .name   = "ARC RTSC",
  99         .rating = 300,
 100         .read   = arc_counter_read,
 101         .mask   = CLOCKSOURCE_MASK(32),
 102         .flags  = CLOCK_SOURCE_IS_CONTINUOUS,
 103 };
 104
 105 #else /* !CONFIG_ARC_HAS_RTSC */
 106
 107 static bool is_usable_as_clocksource(void)
 108 {
 109 #ifdef CONFIG_SMP
 110         return 0;
 111 #else
 112         return 1;
 113 #endif
 114 }
 115
 116 /*
 117  * set 32bit TIMER1 to keep counting monotonically and wraparound
 118  */
 119 int arc_counter_setup(void)
 120 {
 121         write_aux_reg(ARC_REG_TIMER1_LIMIT, ARC_TIMER_MAX);
 122         write_aux_reg(ARC_REG_TIMER1_CNT, 0);
 123         write_aux_reg(ARC_REG_TIMER1_CTRL, TIMER_CTRL_NH);
 124
 125         return is_usable_as_clocksource();
 126 }
 127
 128 static cycle_t arc_counter_read(struct clocksource *cs)
 129 {
 130         return (cycle_t) read_aux_reg(ARC_REG_TIMER1_CNT);
 131 }
 132
 133 static struct clocksource arc_counter = {
 134         .name   = "ARC Timer1",
 135         .rating = 300,
 136         .read   = arc_counter_read,
 137         .mask   = CLOCKSOURCE_MASK(32),
 138         .flags  = CLOCK_SOURCE_IS_CONTINUOUS,
 139 };
 140
 141 #endif
 142
 143 /********** Clock Event Device *********/
 144
 145 /*
 146  * Arm the timer to interrupt after @limit cycles
 147  * The distinction for oneshot/periodic is done in arc_event_timer_ack() below
 148  */
 149 static void arc_timer_event_setup(unsigned int limit)
 150 {
 151         write_aux_reg(ARC_REG_TIMER0_LIMIT, limit);
 152         write_aux_reg(ARC_REG_TIMER0_CNT, 0);   /* start from 0 */
 153
 154         write_aux_reg(ARC_REG_TIMER0_CTRL, TIMER_CTRL_IE | TIMER_CTRL_NH);
 155 }
 156
 157 /*
 158  * Acknowledge the interrupt (oneshot) and optionally re-arm it (periodic)
 159  * -Any write to CTRL Reg will ack the intr (NH bit: Count when not halted)
 160  * -Rearming is done by setting the IE bit
 161  *
 162  * Small optimisation: Normal code would have been
 163  *   if (irq_reenable)
 164  *     CTRL_REG = (IE | NH);
 165  *   else
 166  *     CTRL_REG = NH;
 167  * However since IE is BIT0 we can fold the branch
 168  */
 169 static void arc_timer_event_ack(unsigned int irq_reenable)
 170 {
 171         write_aux_reg(ARC_REG_TIMER0_CTRL, irq_reenable | TIMER_CTRL_NH);
 172 }
 173
 174 static int arc_clkevent_set_next_event(unsigned long delta,
 175                                        struct clock_event_device *dev)
 176 {
 177         arc_timer_event_setup(delta);
 178         return 0;
 179 }
 180
 181 static void arc_clkevent_set_mode(enum clock_event_mode mode,
 182                                   struct clock_event_device *dev)
 183 {
 184         switch (mode) {
 185         case CLOCK_EVT_MODE_PERIODIC:
 186                 arc_timer_event_setup(arc_get_core_freq() / HZ);
 187                 break;
 188         case CLOCK_EVT_MODE_ONESHOT:
 189                 break;
 190         default:
 191                 break;
 192         }
 193
 194         return;
 195 }
 196
 197 static DEFINE_PER_CPU(struct clock_event_device, arc_clockevent_device) = {
 198         .name           = "ARC Timer0",
 199         .features       = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_PERIODIC,
 200         .mode           = CLOCK_EVT_MODE_UNUSED,
 201         .rating         = 300,
 202         .irq            = TIMER0_IRQ,   /* hardwired, no need for resources */
 203         .set_next_event = arc_clkevent_set_next_event,
 204         .set_mode       = arc_clkevent_set_mode,
 205 };
 206
 207 static irqreturn_t timer_irq_handler(int irq, void *dev_id)
 208 {
 209         struct clock_event_device *clk = &__get_cpu_var(arc_clockevent_device);
 210
 211         arc_timer_event_ack(clk->mode == CLOCK_EVT_MODE_PERIODIC);
 212         clk->event_handler(clk);
 213         return IRQ_HANDLED;
 214 }
 215
 216 static struct irqaction arc_timer_irq = {
 217         .name    = "Timer0 (clock-evt-dev)",
 218         .flags   = IRQF_TIMER | IRQF_PERCPU,
 219         .handler = timer_irq_handler,
 220 };
 221
 222 /*
 223  * Setup the local event timer for @cpu
 224  * N.B. weak so that some exotic ARC SoCs can completely override it
 225  */
 226 void __attribute__((weak)) arc_local_timer_setup(unsigned int cpu)
 227 {
 228         struct clock_event_device *clk = &per_cpu(arc_clockevent_device, cpu);
 229
 230         clk->cpumask = cpumask_of(cpu);
 231         clockevents_config_and_register(clk, arc_get_core_freq(),
 232                                         0, ARC_TIMER_MAX);
 233
 234         /*
 235          * setup the per-cpu timer IRQ handler - for all cpus
 236          * For non boot CPU explicitly unmask at intc
 237          * setup_irq() -> .. -> irq_startup() already does this on boot-cpu
 238          */
 239         if (!cpu)
 240                 setup_irq(TIMER0_IRQ, &arc_timer_irq);
 241         else
 242                 arch_unmask_irq(TIMER0_IRQ);
 243 }
 244
 245 /*
 246  * Called from start_kernel() - boot CPU only
 247  *
 248  * -Sets up h/w timers as applicable on boot cpu
 249  * -Also sets up any global state needed for timer subsystem:
 250  *    - for "counting" timer, registers a clocksource, usable across CPUs
 251  *      (provided that underlying counter h/w is synchronized across cores)
 252  *    - for "event" timer, sets up TIMER0 IRQ (as that is platform agnostic)
 253  */
 254 void __init time_init(void)
 255 {
 256         /*
 257          * sets up the timekeeping free-flowing counter which also returns
 258          * whether the counter is usable as clocksource
 259          */
 260         if (arc_counter_setup())
 261                 /*
 262                  * CLK upto 4.29 GHz can be safely represented in 32 bits
 263                  * because Max 32 bit number is 4,294,967,295
 264                  */
 265                 clocksource_register_hz(&arc_counter, arc_get_core_freq());
 266
 267         /* sets up the periodic event timer */
 268         arc_local_timer_setup(smp_processor_id());
 269
 270         if (machine_desc->init_time)
 271                 machine_desc->init_time();
 272 }