linux/drivers/clocksource/moxart_timer.c
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   1/*
   2 * MOXA ART SoCs timer handling.
   3 *
   4 * Copyright (C) 2013 Jonas Jensen
   5 *
   6 * Jonas Jensen <jonas.jensen@gmail.com>
   7 *
   8 * This file is licensed under the terms of the GNU General Public
   9 * License version 2.  This program is licensed "as is" without any
  10 * warranty of any kind, whether express or implied.
  11 */
  12
  13#include <linux/clk.h>
  14#include <linux/clockchips.h>
  15#include <linux/interrupt.h>
  16#include <linux/irq.h>
  17#include <linux/irqreturn.h>
  18#include <linux/of.h>
  19#include <linux/of_address.h>
  20#include <linux/of_irq.h>
  21#include <linux/io.h>
  22#include <linux/clocksource.h>
  23#include <linux/bitops.h>
  24
  25#define TIMER1_BASE             0x00
  26#define TIMER2_BASE             0x10
  27#define TIMER3_BASE             0x20
  28
  29#define REG_COUNT               0x0 /* writable */
  30#define REG_LOAD                0x4
  31#define REG_MATCH1              0x8
  32#define REG_MATCH2              0xC
  33
  34#define TIMER_CR                0x30
  35#define TIMER_INTR_STATE        0x34
  36#define TIMER_INTR_MASK         0x38
  37
  38/*
  39 * TIMER_CR flags:
  40 *
  41 * TIMEREG_CR_*_CLOCK   0: PCLK, 1: EXT1CLK
  42 * TIMEREG_CR_*_INT     overflow interrupt enable bit
  43 */
  44#define TIMEREG_CR_1_ENABLE     BIT(0)
  45#define TIMEREG_CR_1_CLOCK      BIT(1)
  46#define TIMEREG_CR_1_INT        BIT(2)
  47#define TIMEREG_CR_2_ENABLE     BIT(3)
  48#define TIMEREG_CR_2_CLOCK      BIT(4)
  49#define TIMEREG_CR_2_INT        BIT(5)
  50#define TIMEREG_CR_3_ENABLE     BIT(6)
  51#define TIMEREG_CR_3_CLOCK      BIT(7)
  52#define TIMEREG_CR_3_INT        BIT(8)
  53#define TIMEREG_CR_COUNT_UP     BIT(9)
  54
  55#define TIMER1_ENABLE           (TIMEREG_CR_2_ENABLE | TIMEREG_CR_1_ENABLE)
  56#define TIMER1_DISABLE          (TIMEREG_CR_2_ENABLE)
  57
  58static void __iomem *base;
  59static unsigned int clock_count_per_tick;
  60
  61static void moxart_clkevt_mode(enum clock_event_mode mode,
  62                               struct clock_event_device *clk)
  63{
  64        switch (mode) {
  65        case CLOCK_EVT_MODE_RESUME:
  66        case CLOCK_EVT_MODE_ONESHOT:
  67                writel(TIMER1_DISABLE, base + TIMER_CR);
  68                writel(~0, base + TIMER1_BASE + REG_LOAD);
  69                break;
  70        case CLOCK_EVT_MODE_PERIODIC:
  71                writel(clock_count_per_tick, base + TIMER1_BASE + REG_LOAD);
  72                writel(TIMER1_ENABLE, base + TIMER_CR);
  73                break;
  74        case CLOCK_EVT_MODE_UNUSED:
  75        case CLOCK_EVT_MODE_SHUTDOWN:
  76        default:
  77                writel(TIMER1_DISABLE, base + TIMER_CR);
  78                break;
  79        }
  80}
  81
  82static int moxart_clkevt_next_event(unsigned long cycles,
  83                                    struct clock_event_device *unused)
  84{
  85        u32 u;
  86
  87        writel(TIMER1_DISABLE, base + TIMER_CR);
  88
  89        u = readl(base + TIMER1_BASE + REG_COUNT) - cycles;
  90        writel(u, base + TIMER1_BASE + REG_MATCH1);
  91
  92        writel(TIMER1_ENABLE, base + TIMER_CR);
  93
  94        return 0;
  95}
  96
  97static struct clock_event_device moxart_clockevent = {
  98        .name           = "moxart_timer",
  99        .rating         = 200,
 100        .features       = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
 101        .set_mode       = moxart_clkevt_mode,
 102        .set_next_event = moxart_clkevt_next_event,
 103};
 104
 105static irqreturn_t moxart_timer_interrupt(int irq, void *dev_id)
 106{
 107        struct clock_event_device *evt = dev_id;
 108        evt->event_handler(evt);
 109        return IRQ_HANDLED;
 110}
 111
 112static struct irqaction moxart_timer_irq = {
 113        .name           = "moxart-timer",
 114        .flags          = IRQF_TIMER,
 115        .handler        = moxart_timer_interrupt,
 116        .dev_id         = &moxart_clockevent,
 117};
 118
 119static void __init moxart_timer_init(struct device_node *node)
 120{
 121        int ret, irq;
 122        unsigned long pclk;
 123        struct clk *clk;
 124
 125        base = of_iomap(node, 0);
 126        if (!base)
 127                panic("%s: of_iomap failed\n", node->full_name);
 128
 129        irq = irq_of_parse_and_map(node, 0);
 130        if (irq <= 0)
 131                panic("%s: irq_of_parse_and_map failed\n", node->full_name);
 132
 133        ret = setup_irq(irq, &moxart_timer_irq);
 134        if (ret)
 135                panic("%s: setup_irq failed\n", node->full_name);
 136
 137        clk = of_clk_get(node, 0);
 138        if (IS_ERR(clk))
 139                panic("%s: of_clk_get failed\n", node->full_name);
 140
 141        pclk = clk_get_rate(clk);
 142
 143        if (clocksource_mmio_init(base + TIMER2_BASE + REG_COUNT,
 144                                  "moxart_timer", pclk, 200, 32,
 145                                  clocksource_mmio_readl_down))
 146                panic("%s: clocksource_mmio_init failed\n", node->full_name);
 147
 148        clock_count_per_tick = DIV_ROUND_CLOSEST(pclk, HZ);
 149
 150        writel(~0, base + TIMER2_BASE + REG_LOAD);
 151        writel(TIMEREG_CR_2_ENABLE, base + TIMER_CR);
 152
 153        moxart_clockevent.cpumask = cpumask_of(0);
 154        moxart_clockevent.irq = irq;
 155
 156        /*
 157         * documentation is not publicly available:
 158         * min_delta / max_delta obtained by trial-and-error,
 159         * max_delta 0xfffffffe should be ok because count
 160         * register size is u32
 161         */
 162        clockevents_config_and_register(&moxart_clockevent, pclk,
 163                                        0x4, 0xfffffffe);
 164}
 165CLOCKSOURCE_OF_DECLARE(moxart, "moxa,moxart-timer", moxart_timer_init);
 166
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