arch/arm/plat-nomadik/timer.c

   1 /*
   2  *  linux/arch/arm/plat-nomadik/timer.c
   3  *
   4  * Copyright (C) 2008 STMicroelectronics
   5  * Copyright (C) 2010 Alessandro Rubini
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2, as
   9  * published by the Free Software Foundation.
  10  */
  11 #include <linux/init.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/irq.h>
  14 #include <linux/io.h>
  15 #include <linux/clockchips.h>
  16 #include <linux/clk.h>
  17 #include <linux/jiffies.h>
  18 #include <linux/err.h>
  19 #include <asm/mach/time.h>
  20
  21 #include <plat/mtu.h>
  22
  23 void __iomem *mtu_base; /* ssigned by machine code */
  24
  25 /*
  26  * Kernel assumes that sched_clock can be called early
  27  * but the MTU may not yet be initialized.
  28  */
  29 static cycle_t nmdk_read_timer_dummy(struct clocksource *cs)
  30 {
  31         return 0;
  32 }
  33
  34 /* clocksource: MTU decrements, so we negate the value being read. */
  35 static cycle_t nmdk_read_timer(struct clocksource *cs)
  36 {
  37         return -readl(mtu_base + MTU_VAL(0));
  38 }
  39
  40 static struct clocksource nmdk_clksrc = {
  41         .name           = "mtu_0",
  42         .rating         = 200,
  43         .read           = nmdk_read_timer_dummy,
  44         .mask           = CLOCKSOURCE_MASK(32),
  45         .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
  46 };
  47
  48 /*
  49  * Override the global weak sched_clock symbol with this
  50  * local implementation which uses the clocksource to get some
  51  * better resolution when scheduling the kernel. We accept that
  52  * this wraps around for now, since it is just a relative time
  53  * stamp. (Inspired by OMAP implementation.)
  54  */
  55 unsigned long long notrace sched_clock(void)
  56 {
  57         return clocksource_cyc2ns(nmdk_clksrc.read(
  58                                   &nmdk_clksrc),
  59                                   nmdk_clksrc.mult,
  60                                   nmdk_clksrc.shift);
  61 }
  62
  63 /* Clockevent device: use one-shot mode */
  64 static void nmdk_clkevt_mode(enum clock_event_mode mode,
  65                              struct clock_event_device *dev)
  66 {
  67         u32 cr;
  68
  69         switch (mode) {
  70         case CLOCK_EVT_MODE_PERIODIC:
  71                 pr_err("%s: periodic mode not supported\n", __func__);
  72                 break;
  73         case CLOCK_EVT_MODE_ONESHOT:
  74                 /* Load highest value, enable device, enable interrupts */
  75                 cr = readl(mtu_base + MTU_CR(1));
  76                 writel(0, mtu_base + MTU_LR(1));
  77                 writel(cr | MTU_CRn_ENA, mtu_base + MTU_CR(1));
  78                 writel(1 << 1, mtu_base + MTU_IMSC);
  79                 break;
  80         case CLOCK_EVT_MODE_SHUTDOWN:
  81         case CLOCK_EVT_MODE_UNUSED:
  82                 /* disable irq */
  83                 writel(0, mtu_base + MTU_IMSC);
  84                 /* disable timer */
  85                 cr = readl(mtu_base + MTU_CR(1));
  86                 cr &= ~MTU_CRn_ENA;
  87                 writel(cr, mtu_base + MTU_CR(1));
  88                 /* load some high default value */
  89                 writel(0xffffffff, mtu_base + MTU_LR(1));
  90                 break;
  91         case CLOCK_EVT_MODE_RESUME:
  92                 break;
  93         }
  94 }
  95
  96 static int nmdk_clkevt_next(unsigned long evt, struct clock_event_device *ev)
  97 {
  98         /* writing the value has immediate effect */
  99         writel(evt, mtu_base + MTU_LR(1));
 100         return 0;
 101 }
 102
 103 static struct clock_event_device nmdk_clkevt = {
 104         .name           = "mtu_1",
 105         .features       = CLOCK_EVT_FEAT_ONESHOT,
 106         .rating         = 200,
 107         .set_mode       = nmdk_clkevt_mode,
 108         .set_next_event = nmdk_clkevt_next,
 109 };
 110
 111 /*
 112  * IRQ Handler for timer 1 of the MTU block.
 113  */
 114 static irqreturn_t nmdk_timer_interrupt(int irq, void *dev_id)
 115 {
 116         struct clock_event_device *evdev = dev_id;
 117
 118         writel(1 << 1, mtu_base + MTU_ICR); /* Interrupt clear reg */
 119         evdev->event_handler(evdev);
 120         return IRQ_HANDLED;
 121 }
 122
 123 static struct irqaction nmdk_timer_irq = {
 124         .name           = "Nomadik Timer Tick",
 125         .flags          = IRQF_DISABLED | IRQF_TIMER,
 126         .handler        = nmdk_timer_interrupt,
 127         .dev_id         = &nmdk_clkevt,
 128 };
 129
 130 void __init nmdk_timer_init(void)
 131 {
 132         unsigned long rate;
 133         struct clk *clk0;
 134         u32 cr = MTU_CRn_32BITS;
 135
 136         clk0 = clk_get_sys("mtu0", NULL);
 137         BUG_ON(IS_ERR(clk0));
 138
 139         clk_enable(clk0);
 140
 141         /*
 142          * Tick rate is 2.4MHz for Nomadik and 2.4Mhz, 100MHz or 133 MHz
 143          * for ux500.
 144          * Use a divide-by-16 counter if the tick rate is more than 32MHz.
 145          * At 32 MHz, the timer (with 32 bit counter) can be programmed
 146          * to wake-up at a max 127s a head in time. Dividing a 2.4 MHz timer
 147          * with 16 gives too low timer resolution.
 148          */
 149         rate = clk_get_rate(clk0);
 150         if (rate > 32000000) {
 151                 rate /= 16;
 152                 cr |= MTU_CRn_PRESCALE_16;
 153         } else {
 154                 cr |= MTU_CRn_PRESCALE_1;
 155         }
 156         clocksource_calc_mult_shift(&nmdk_clksrc, rate, MTU_MIN_RANGE);
 157
 158         /* Timer 0 is the free running clocksource */
 159         writel(cr, mtu_base + MTU_CR(0));
 160         writel(0, mtu_base + MTU_LR(0));
 161         writel(0, mtu_base + MTU_BGLR(0));
 162         writel(cr | MTU_CRn_ENA, mtu_base + MTU_CR(0));
 163
 164         /* Now the scheduling clock is ready */
 165         nmdk_clksrc.read = nmdk_read_timer;
 166
 167         if (clocksource_register(&nmdk_clksrc))
 168                 pr_err("timer: failed to initialize clock source %s\n",
 169                        nmdk_clksrc.name);
 170
 171         /* Timer 1 is used for events */
 172
 173         clockevents_calc_mult_shift(&nmdk_clkevt, rate, MTU_MIN_RANGE);
 174
 175         writel(cr | MTU_CRn_ONESHOT, mtu_base + MTU_CR(1)); /* off, currently */
 176
 177         nmdk_clkevt.max_delta_ns =
 178                 clockevent_delta2ns(0xffffffff, &nmdk_clkevt);
 179         nmdk_clkevt.min_delta_ns =
 180                 clockevent_delta2ns(0x00000002, &nmdk_clkevt);
 181         nmdk_clkevt.cpumask     = cpumask_of(0);
 182
 183         /* Register irq and clockevents */
 184         setup_irq(IRQ_MTU0, &nmdk_timer_irq);
 185         clockevents_register_device(&nmdk_clkevt);
 186 }