drivers/clocksource/timer-stm32.c

   1 /*
   2  * Copyright (C) Maxime Coquelin 2015
   3  * Author:  Maxime Coquelin <mcoquelin.stm32@gmail.com>
   4  * License terms:  GNU General Public License (GPL), version 2
   5  *
   6  * Inspired by time-efm32.c from Uwe Kleine-Koenig
   7  */
   8
   9 #include <linux/kernel.h>
  10 #include <linux/clocksource.h>
  11 #include <linux/clockchips.h>
  12 #include <linux/irq.h>
  13 #include <linux/interrupt.h>
  14 #include <linux/of.h>
  15 #include <linux/of_address.h>
  16 #include <linux/of_irq.h>
  17 #include <linux/clk.h>
  18 #include <linux/reset.h>
  19
  20 #define TIM_CR1         0x00
  21 #define TIM_DIER        0x0c
  22 #define TIM_SR          0x10
  23 #define TIM_EGR         0x14
  24 #define TIM_PSC         0x28
  25 #define TIM_ARR         0x2c
  26
  27 #define TIM_CR1_CEN     BIT(0)
  28 #define TIM_CR1_OPM     BIT(3)
  29 #define TIM_CR1_ARPE    BIT(7)
  30
  31 #define TIM_DIER_UIE    BIT(0)
  32
  33 #define TIM_SR_UIF      BIT(0)
  34
  35 #define TIM_EGR_UG      BIT(0)
  36
  37 struct stm32_clock_event_ddata {
  38         struct clock_event_device evtdev;
  39         unsigned periodic_top;
  40         void __iomem *base;
  41 };
  42
  43 static void stm32_clock_event_set_mode(enum clock_event_mode mode,
  44                                        struct clock_event_device *evtdev)
  45 {
  46         struct stm32_clock_event_ddata *data =
  47                 container_of(evtdev, struct stm32_clock_event_ddata, evtdev);
  48         void *base = data->base;
  49
  50         switch (mode) {
  51         case CLOCK_EVT_MODE_PERIODIC:
  52                 writel_relaxed(data->periodic_top, base + TIM_ARR);
  53                 writel_relaxed(TIM_CR1_ARPE | TIM_CR1_CEN, base + TIM_CR1);
  54                 break;
  55
  56         case CLOCK_EVT_MODE_ONESHOT:
  57         default:
  58                 writel_relaxed(0, base + TIM_CR1);
  59                 break;
  60         }
  61 }
  62
  63 static int stm32_clock_event_set_next_event(unsigned long evt,
  64                                             struct clock_event_device *evtdev)
  65 {
  66         struct stm32_clock_event_ddata *data =
  67                 container_of(evtdev, struct stm32_clock_event_ddata, evtdev);
  68
  69         writel_relaxed(evt, data->base + TIM_ARR);
  70         writel_relaxed(TIM_CR1_ARPE | TIM_CR1_OPM | TIM_CR1_CEN,
  71                        data->base + TIM_CR1);
  72
  73         return 0;
  74 }
  75
  76 static irqreturn_t stm32_clock_event_handler(int irq, void *dev_id)
  77 {
  78         struct stm32_clock_event_ddata *data = dev_id;
  79
  80         writel_relaxed(0, data->base + TIM_SR);
  81
  82         data->evtdev.event_handler(&data->evtdev);
  83
  84         return IRQ_HANDLED;
  85 }
  86
  87 static struct stm32_clock_event_ddata clock_event_ddata = {
  88         .evtdev = {
  89                 .name = "stm32 clockevent",
  90                 .features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_PERIODIC,
  91                 .set_mode = stm32_clock_event_set_mode,
  92                 .set_next_event = stm32_clock_event_set_next_event,
  93                 .rating = 200,
  94         },
  95 };
  96
  97 static void __init stm32_clockevent_init(struct device_node *np)
  98 {
  99         struct stm32_clock_event_ddata *data = &clock_event_ddata;
 100         struct clk *clk;
 101         struct reset_control *rstc;
 102         unsigned long rate, max_delta;
 103         int irq, ret, bits, prescaler = 1;
 104
 105         clk = of_clk_get(np, 0);
 106         if (IS_ERR(clk)) {
 107                 ret = PTR_ERR(clk);
 108                 pr_err("failed to get clock for clockevent (%d)\n", ret);
 109                 goto err_clk_get;
 110         }
 111
 112         ret = clk_prepare_enable(clk);
 113         if (ret) {
 114                 pr_err("failed to enable timer clock for clockevent (%d)\n",
 115                        ret);
 116                 goto err_clk_enable;
 117         }
 118
 119         rate = clk_get_rate(clk);
 120
 121         rstc = of_reset_control_get(np, NULL);
 122         if (!IS_ERR(rstc)) {
 123                 reset_control_assert(rstc);
 124                 reset_control_deassert(rstc);
 125         }
 126
 127         data->base = of_iomap(np, 0);
 128         if (!data->base) {
 129                 pr_err("failed to map registers for clockevent\n");
 130                 goto err_iomap;
 131         }
 132
 133         irq = irq_of_parse_and_map(np, 0);
 134         if (!irq) {
 135                 pr_err("%s: failed to get irq.\n", np->full_name);
 136                 goto err_get_irq;
 137         }
 138
 139         /* Detect whether the timer is 16 or 32 bits */
 140         writel_relaxed(~0U, data->base + TIM_ARR);
 141         max_delta = readl_relaxed(data->base + TIM_ARR);
 142         if (max_delta == ~0U) {
 143                 prescaler = 1;
 144                 bits = 32;
 145         } else {
 146                 prescaler = 1024;
 147                 bits = 16;
 148         }
 149         writel_relaxed(0, data->base + TIM_ARR);
 150
 151         writel_relaxed(prescaler - 1, data->base + TIM_PSC);
 152         writel_relaxed(TIM_EGR_UG, data->base + TIM_EGR);
 153         writel_relaxed(TIM_DIER_UIE, data->base + TIM_DIER);
 154         writel_relaxed(0, data->base + TIM_SR);
 155
 156         data->periodic_top = DIV_ROUND_CLOSEST(rate, prescaler * HZ);
 157
 158         clockevents_config_and_register(&data->evtdev,
 159                                         DIV_ROUND_CLOSEST(rate, prescaler),
 160                                         0x1, max_delta);
 161
 162         ret = request_irq(irq, stm32_clock_event_handler, IRQF_TIMER,
 163                         "stm32 clockevent", data);
 164         if (ret) {
 165                 pr_err("%s: failed to request irq.\n", np->full_name);
 166                 goto err_get_irq;
 167         }
 168
 169         pr_info("%s: STM32 clockevent driver initialized (%d bits)\n",
 170                         np->full_name, bits);
 171
 172         return;
 173
 174 err_get_irq:
 175         iounmap(data->base);
 176 err_iomap:
 177         clk_disable_unprepare(clk);
 178 err_clk_enable:
 179         clk_put(clk);
 180 err_clk_get:
 181         return;
 182 }
 183
 184 CLOCKSOURCE_OF_DECLARE(stm32, "st,stm32-timer", stm32_clockevent_init);