drivers/clocksource/nomadik-mtu.c

   1 /*
   2  * Copyright (C) 2008 STMicroelectronics
   3  * Copyright (C) 2010 Alessandro Rubini
   4  * Copyright (C) 2010 Linus Walleij for ST-Ericsson
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2, as
   8  * published by the Free Software Foundation.
   9  */
  10 #include <linux/init.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/irq.h>
  13 #include <linux/io.h>
  14 #include <linux/clockchips.h>
  15 #include <linux/clocksource.h>
  16 #include <linux/clk.h>
  17 #include <linux/jiffies.h>
  18 #include <linux/err.h>
  19 #include <linux/platform_data/clocksource-nomadik-mtu.h>
  20 #include <asm/mach/time.h>
  21 #include <asm/sched_clock.h>
  22
  23 /*
  24  * The MTU device hosts four different counters, with 4 set of
  25  * registers. These are register names.
  26  */
  27
  28 #define MTU_IMSC        0x00    /* Interrupt mask set/clear */
  29 #define MTU_RIS         0x04    /* Raw interrupt status */
  30 #define MTU_MIS         0x08    /* Masked interrupt status */
  31 #define MTU_ICR         0x0C    /* Interrupt clear register */
  32
  33 /* per-timer registers take 0..3 as argument */
  34 #define MTU_LR(x)       (0x10 + 0x10 * (x) + 0x00)      /* Load value */
  35 #define MTU_VAL(x)      (0x10 + 0x10 * (x) + 0x04)      /* Current value */
  36 #define MTU_CR(x)       (0x10 + 0x10 * (x) + 0x08)      /* Control reg */
  37 #define MTU_BGLR(x)     (0x10 + 0x10 * (x) + 0x0c)      /* At next overflow */
  38
  39 /* bits for the control register */
  40 #define MTU_CRn_ENA             0x80
  41 #define MTU_CRn_PERIODIC        0x40    /* if 0 = free-running */
  42 #define MTU_CRn_PRESCALE_MASK   0x0c
  43 #define MTU_CRn_PRESCALE_1              0x00
  44 #define MTU_CRn_PRESCALE_16             0x04
  45 #define MTU_CRn_PRESCALE_256            0x08
  46 #define MTU_CRn_32BITS          0x02
  47 #define MTU_CRn_ONESHOT         0x01    /* if 0 = wraps reloading from BGLR*/
  48
  49 /* Other registers are usual amba/primecell registers, currently not used */
  50 #define MTU_ITCR        0xff0
  51 #define MTU_ITOP        0xff4
  52
  53 #define MTU_PERIPH_ID0  0xfe0
  54 #define MTU_PERIPH_ID1  0xfe4
  55 #define MTU_PERIPH_ID2  0xfe8
  56 #define MTU_PERIPH_ID3  0xfeC
  57
  58 #define MTU_PCELL0      0xff0
  59 #define MTU_PCELL1      0xff4
  60 #define MTU_PCELL2      0xff8
  61 #define MTU_PCELL3      0xffC
  62
  63 static void __iomem *mtu_base;
  64 static bool clkevt_periodic;
  65 static u32 clk_prescale;
  66 static u32 nmdk_cycle;          /* write-once */
  67
  68 #ifdef CONFIG_NOMADIK_MTU_SCHED_CLOCK
  69 /*
  70  * Override the global weak sched_clock symbol with this
  71  * local implementation which uses the clocksource to get some
  72  * better resolution when scheduling the kernel.
  73  */
  74 static u32 notrace nomadik_read_sched_clock(void)
  75 {
  76         if (unlikely(!mtu_base))
  77                 return 0;
  78
  79         return -readl(mtu_base + MTU_VAL(0));
  80 }
  81 #endif
  82
  83 /* Clockevent device: use one-shot mode */
  84 static int nmdk_clkevt_next(unsigned long evt, struct clock_event_device *ev)
  85 {
  86         writel(1 << 1, mtu_base + MTU_IMSC);
  87         writel(evt, mtu_base + MTU_LR(1));
  88         /* Load highest value, enable device, enable interrupts */
  89         writel(MTU_CRn_ONESHOT | clk_prescale |
  90                MTU_CRn_32BITS | MTU_CRn_ENA,
  91                mtu_base + MTU_CR(1));
  92
  93         return 0;
  94 }
  95
  96 void nmdk_clkevt_reset(void)
  97 {
  98         if (clkevt_periodic) {
  99                 /* Timer: configure load and background-load, and fire it up */
 100                 writel(nmdk_cycle, mtu_base + MTU_LR(1));
 101                 writel(nmdk_cycle, mtu_base + MTU_BGLR(1));
 102
 103                 writel(MTU_CRn_PERIODIC | clk_prescale |
 104                        MTU_CRn_32BITS | MTU_CRn_ENA,
 105                        mtu_base + MTU_CR(1));
 106                 writel(1 << 1, mtu_base + MTU_IMSC);
 107         } else {
 108                 /* Generate an interrupt to start the clockevent again */
 109                 (void) nmdk_clkevt_next(nmdk_cycle, NULL);
 110         }
 111 }
 112
 113 static void nmdk_clkevt_mode(enum clock_event_mode mode,
 114                              struct clock_event_device *dev)
 115 {
 116         switch (mode) {
 117         case CLOCK_EVT_MODE_PERIODIC:
 118                 clkevt_periodic = true;
 119                 nmdk_clkevt_reset();
 120                 break;
 121         case CLOCK_EVT_MODE_ONESHOT:
 122                 clkevt_periodic = false;
 123                 break;
 124         case CLOCK_EVT_MODE_SHUTDOWN:
 125         case CLOCK_EVT_MODE_UNUSED:
 126                 writel(0, mtu_base + MTU_IMSC);
 127                 /* disable timer */
 128                 writel(0, mtu_base + MTU_CR(1));
 129                 /* load some high default value */
 130                 writel(0xffffffff, mtu_base + MTU_LR(1));
 131                 break;
 132         case CLOCK_EVT_MODE_RESUME:
 133                 break;
 134         }
 135 }
 136
 137 static struct clock_event_device nmdk_clkevt = {
 138         .name           = "mtu_1",
 139         .features       = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_PERIODIC,
 140         .rating         = 200,
 141         .set_mode       = nmdk_clkevt_mode,
 142         .set_next_event = nmdk_clkevt_next,
 143 };
 144
 145 /*
 146  * IRQ Handler for timer 1 of the MTU block.
 147  */
 148 static irqreturn_t nmdk_timer_interrupt(int irq, void *dev_id)
 149 {
 150         struct clock_event_device *evdev = dev_id;
 151
 152         writel(1 << 1, mtu_base + MTU_ICR); /* Interrupt clear reg */
 153         evdev->event_handler(evdev);
 154         return IRQ_HANDLED;
 155 }
 156
 157 static struct irqaction nmdk_timer_irq = {
 158         .name           = "Nomadik Timer Tick",
 159         .flags          = IRQF_DISABLED | IRQF_TIMER,
 160         .handler        = nmdk_timer_interrupt,
 161         .dev_id         = &nmdk_clkevt,
 162 };
 163
 164 void nmdk_clksrc_reset(void)
 165 {
 166         /* Disable */
 167         writel(0, mtu_base + MTU_CR(0));
 168
 169         /* ClockSource: configure load and background-load, and fire it up */
 170         writel(nmdk_cycle, mtu_base + MTU_LR(0));
 171         writel(nmdk_cycle, mtu_base + MTU_BGLR(0));
 172
 173         writel(clk_prescale | MTU_CRn_32BITS | MTU_CRn_ENA,
 174                mtu_base + MTU_CR(0));
 175 }
 176
 177 void __init nmdk_timer_init(void __iomem *base, int irq)
 178 {
 179         unsigned long rate;
 180         struct clk *clk0, *pclk0;
 181
 182         mtu_base = base;
 183
 184         pclk0 = clk_get_sys("mtu0", "apb_pclk");
 185         BUG_ON(IS_ERR(pclk0));
 186         BUG_ON(clk_prepare(pclk0) < 0);
 187         BUG_ON(clk_enable(pclk0) < 0);
 188
 189         clk0 = clk_get_sys("mtu0", NULL);
 190         BUG_ON(IS_ERR(clk0));
 191         BUG_ON(clk_prepare(clk0) < 0);
 192         BUG_ON(clk_enable(clk0) < 0);
 193
 194         /*
 195          * Tick rate is 2.4MHz for Nomadik and 2.4Mhz, 100MHz or 133 MHz
 196          * for ux500.
 197          * Use a divide-by-16 counter if the tick rate is more than 32MHz.
 198          * At 32 MHz, the timer (with 32 bit counter) can be programmed
 199          * to wake-up at a max 127s a head in time. Dividing a 2.4 MHz timer
 200          * with 16 gives too low timer resolution.
 201          */
 202         rate = clk_get_rate(clk0);
 203         if (rate > 32000000) {
 204                 rate /= 16;
 205                 clk_prescale = MTU_CRn_PRESCALE_16;
 206         } else {
 207                 clk_prescale = MTU_CRn_PRESCALE_1;
 208         }
 209
 210         /* Cycles for periodic mode */
 211         nmdk_cycle = DIV_ROUND_CLOSEST(rate, HZ);
 212
 213
 214         /* Timer 0 is the free running clocksource */
 215         nmdk_clksrc_reset();
 216
 217         if (clocksource_mmio_init(mtu_base + MTU_VAL(0), "mtu_0",
 218                         rate, 200, 32, clocksource_mmio_readl_down))
 219                 pr_err("timer: failed to initialize clock source %s\n",
 220                        "mtu_0");
 221
 222 #ifdef CONFIG_NOMADIK_MTU_SCHED_CLOCK
 223         setup_sched_clock(nomadik_read_sched_clock, 32, rate);
 224 #endif
 225
 226         /* Timer 1 is used for events, register irq and clockevents */
 227         setup_irq(irq, &nmdk_timer_irq);
 228         nmdk_clkevt.cpumask = cpumask_of(0);
 229         clockevents_config_and_register(&nmdk_clkevt, rate, 2, 0xffffffffU);
 230 }