drivers/clocksource/sun4i_timer.c

   1 /*
   2  * Allwinner A1X SoCs timer handling.
   3  *
   4  * Copyright (C) 2012 Maxime Ripard
   5  *
   6  * Maxime Ripard <maxime.ripard@free-electrons.com>
   7  *
   8  * Based on code from
   9  * Allwinner Technology Co., Ltd. <www.allwinnertech.com>
  10  * Benn Huang <benn@allwinnertech.com>
  11  *
  12  * This file is licensed under the terms of the GNU General Public
  13  * License version 2.  This program is licensed "as is" without any
  14  * warranty of any kind, whether express or implied.
  15  */
  16
  17 #include <linux/clk.h>
  18 #include <linux/clockchips.h>
  19 #include <linux/interrupt.h>
  20 #include <linux/irq.h>
  21 #include <linux/irqreturn.h>
  22 #include <linux/sched_clock.h>
  23 #include <linux/of.h>
  24 #include <linux/of_address.h>
  25 #include <linux/of_irq.h>
  26
  27 #define TIMER_IRQ_EN_REG        0x00
  28 #define TIMER_IRQ_EN(val)               BIT(val)
  29 #define TIMER_IRQ_ST_REG        0x04
  30 #define TIMER_CTL_REG(val)      (0x10 * val + 0x10)
  31 #define TIMER_CTL_ENABLE                BIT(0)
  32 #define TIMER_CTL_RELOAD                BIT(1)
  33 #define TIMER_CTL_CLK_SRC(val)          (((val) & 0x3) << 2)
  34 #define TIMER_CTL_CLK_SRC_OSC24M                (1)
  35 #define TIMER_CTL_CLK_PRES(val)         (((val) & 0x7) << 4)
  36 #define TIMER_CTL_ONESHOT               BIT(7)
  37 #define TIMER_INTVAL_REG(val)   (0x10 * (val) + 0x14)
  38 #define TIMER_CNTVAL_REG(val)   (0x10 * (val) + 0x18)
  39
  40 #define TIMER_SYNC_TICKS        3
  41
  42 static void __iomem *timer_base;
  43 static u32 ticks_per_jiffy;
  44
  45 /*
  46  * When we disable a timer, we need to wait at least for 2 cycles of
  47  * the timer source clock. We will use for that the clocksource timer
  48  * that is already setup and runs at the same frequency than the other
  49  * timers, and we never will be disabled.
  50  */
  51 static void sun4i_clkevt_sync(void)
  52 {
  53         u32 old = readl(timer_base + TIMER_CNTVAL_REG(1));
  54
  55         while ((old - readl(timer_base + TIMER_CNTVAL_REG(1))) < TIMER_SYNC_TICKS)
  56                 cpu_relax();
  57 }
  58
  59 static void sun4i_clkevt_time_stop(u8 timer)
  60 {
  61         u32 val = readl(timer_base + TIMER_CTL_REG(timer));
  62         writel(val & ~TIMER_CTL_ENABLE, timer_base + TIMER_CTL_REG(timer));
  63         sun4i_clkevt_sync();
  64 }
  65
  66 static void sun4i_clkevt_time_setup(u8 timer, unsigned long delay)
  67 {
  68         writel(delay, timer_base + TIMER_INTVAL_REG(timer));
  69 }
  70
  71 static void sun4i_clkevt_time_start(u8 timer, bool periodic)
  72 {
  73         u32 val = readl(timer_base + TIMER_CTL_REG(timer));
  74
  75         if (periodic)
  76                 val &= ~TIMER_CTL_ONESHOT;
  77         else
  78                 val |= TIMER_CTL_ONESHOT;
  79
  80         writel(val | TIMER_CTL_ENABLE | TIMER_CTL_RELOAD,
  81                timer_base + TIMER_CTL_REG(timer));
  82 }
  83
  84 static void sun4i_clkevt_mode(enum clock_event_mode mode,
  85                               struct clock_event_device *clk)
  86 {
  87         switch (mode) {
  88         case CLOCK_EVT_MODE_PERIODIC:
  89                 sun4i_clkevt_time_stop(0);
  90                 sun4i_clkevt_time_setup(0, ticks_per_jiffy);
  91                 sun4i_clkevt_time_start(0, true);
  92                 break;
  93         case CLOCK_EVT_MODE_ONESHOT:
  94                 sun4i_clkevt_time_stop(0);
  95                 sun4i_clkevt_time_start(0, false);
  96                 break;
  97         case CLOCK_EVT_MODE_UNUSED:
  98         case CLOCK_EVT_MODE_SHUTDOWN:
  99         default:
 100                 sun4i_clkevt_time_stop(0);
 101                 break;
 102         }
 103 }
 104
 105 static int sun4i_clkevt_next_event(unsigned long evt,
 106                                    struct clock_event_device *unused)
 107 {
 108         sun4i_clkevt_time_stop(0);
 109         sun4i_clkevt_time_setup(0, evt - TIMER_SYNC_TICKS);
 110         sun4i_clkevt_time_start(0, false);
 111
 112         return 0;
 113 }
 114
 115 static struct clock_event_device sun4i_clockevent = {
 116         .name = "sun4i_tick",
 117         .rating = 300,
 118         .features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
 119         .set_mode = sun4i_clkevt_mode,
 120         .set_next_event = sun4i_clkevt_next_event,
 121 };
 122
 123
 124 static irqreturn_t sun4i_timer_interrupt(int irq, void *dev_id)
 125 {
 126         struct clock_event_device *evt = (struct clock_event_device *)dev_id;
 127
 128         writel(0x1, timer_base + TIMER_IRQ_ST_REG);
 129         evt->event_handler(evt);
 130
 131         return IRQ_HANDLED;
 132 }
 133
 134 static struct irqaction sun4i_timer_irq = {
 135         .name = "sun4i_timer0",
 136         .flags = IRQF_TIMER | IRQF_IRQPOLL,
 137         .handler = sun4i_timer_interrupt,
 138         .dev_id = &sun4i_clockevent,
 139 };
 140
 141 static u32 sun4i_timer_sched_read(void)
 142 {
 143         return ~readl(timer_base + TIMER_CNTVAL_REG(1));
 144 }
 145
 146 static void __init sun4i_timer_init(struct device_node *node)
 147 {
 148         unsigned long rate = 0;
 149         struct clk *clk;
 150         int ret, irq;
 151         u32 val;
 152
 153         timer_base = of_iomap(node, 0);
 154         if (!timer_base)
 155                 panic("Can't map registers");
 156
 157         irq = irq_of_parse_and_map(node, 0);
 158         if (irq <= 0)
 159                 panic("Can't parse IRQ");
 160
 161         clk = of_clk_get(node, 0);
 162         if (IS_ERR(clk))
 163                 panic("Can't get timer clock");
 164         clk_prepare_enable(clk);
 165
 166         rate = clk_get_rate(clk);
 167
 168         writel(~0, timer_base + TIMER_INTVAL_REG(1));
 169         writel(TIMER_CTL_ENABLE | TIMER_CTL_RELOAD |
 170                TIMER_CTL_CLK_SRC(TIMER_CTL_CLK_SRC_OSC24M),
 171                timer_base + TIMER_CTL_REG(1));
 172
 173         setup_sched_clock(sun4i_timer_sched_read, 32, rate);
 174         clocksource_mmio_init(timer_base + TIMER_CNTVAL_REG(1), node->name,
 175                               rate, 300, 32, clocksource_mmio_readl_down);
 176
 177         ticks_per_jiffy = DIV_ROUND_UP(rate, HZ);
 178
 179         writel(TIMER_CTL_CLK_SRC(TIMER_CTL_CLK_SRC_OSC24M),
 180                timer_base + TIMER_CTL_REG(0));
 181
 182         /* Make sure timer is stopped before playing with interrupts */
 183         sun4i_clkevt_time_stop(0);
 184
 185         ret = setup_irq(irq, &sun4i_timer_irq);
 186         if (ret)
 187                 pr_warn("failed to setup irq %d\n", irq);
 188
 189         /* Enable timer0 interrupt */
 190         val = readl(timer_base + TIMER_IRQ_EN_REG);
 191         writel(val | TIMER_IRQ_EN(0), timer_base + TIMER_IRQ_EN_REG);
 192
 193         sun4i_clockevent.cpumask = cpumask_of(0);
 194
 195         clockevents_config_and_register(&sun4i_clockevent, rate,
 196                                         TIMER_SYNC_TICKS, 0xffffffff);
 197 }
 198 CLOCKSOURCE_OF_DECLARE(sun4i, "allwinner,sun4i-timer",
 199                        sun4i_timer_init);