drivers/clocksource/timer-keystone.c

   1 /*
   2  * Keystone broadcast clock-event
   3  *
   4  * Copyright 2013 Texas Instruments, Inc.
   5  *
   6  * Author: Ivan Khoronzhuk <ivan.khoronzhuk@ti.com>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  *
  12  */
  13
  14 #include <linux/clk.h>
  15 #include <linux/clockchips.h>
  16 #include <linux/clocksource.h>
  17 #include <linux/interrupt.h>
  18 #include <linux/of_address.h>
  19 #include <linux/of_irq.h>
  20
  21 #define TIMER_NAME                      "timer-keystone"
  22
  23 /* Timer register offsets */
  24 #define TIM12                           0x10
  25 #define TIM34                           0x14
  26 #define PRD12                           0x18
  27 #define PRD34                           0x1c
  28 #define TCR                             0x20
  29 #define TGCR                            0x24
  30 #define INTCTLSTAT                      0x44
  31
  32 /* Timer register bitfields */
  33 #define TCR_ENAMODE_MASK                0xC0
  34 #define TCR_ENAMODE_ONESHOT_MASK        0x40
  35 #define TCR_ENAMODE_PERIODIC_MASK       0x80
  36
  37 #define TGCR_TIM_UNRESET_MASK           0x03
  38 #define INTCTLSTAT_ENINT_MASK           0x01
  39
  40 /**
  41  * struct keystone_timer: holds timer's data
  42  * @base: timer memory base address
  43  * @hz_period: cycles per HZ period
  44  * @event_dev: event device based on timer
  45  */
  46 static struct keystone_timer {
  47         void __iomem *base;
  48         unsigned long hz_period;
  49         struct clock_event_device event_dev;
  50 } timer;
  51
  52 static inline u32 keystone_timer_readl(unsigned long rg)
  53 {
  54         return readl_relaxed(timer.base + rg);
  55 }
  56
  57 static inline void keystone_timer_writel(u32 val, unsigned long rg)
  58 {
  59         writel_relaxed(val, timer.base + rg);
  60 }
  61
  62 /**
  63  * keystone_timer_barrier: write memory barrier
  64  * use explicit barrier to avoid using readl/writel non relaxed function
  65  * variants, because in our case non relaxed variants hide the true places
  66  * where barrier is needed.
  67  */
  68 static inline void keystone_timer_barrier(void)
  69 {
  70         __iowmb();
  71 }
  72
  73 /**
  74  * keystone_timer_config: configures timer to work in oneshot/periodic modes.
  75  * @ mask: mask of the mode to configure
  76  * @ period: cycles number to configure for
  77  */
  78 static int keystone_timer_config(u64 period, int mask)
  79 {
  80         u32 tcr;
  81         u32 off;
  82
  83         tcr = keystone_timer_readl(TCR);
  84         off = tcr & ~(TCR_ENAMODE_MASK);
  85
  86         /* set enable mode */
  87         tcr |= mask;
  88
  89         /* disable timer */
  90         keystone_timer_writel(off, TCR);
  91         /* here we have to be sure the timer has been disabled */
  92         keystone_timer_barrier();
  93
  94         /* reset counter to zero, set new period */
  95         keystone_timer_writel(0, TIM12);
  96         keystone_timer_writel(0, TIM34);
  97         keystone_timer_writel(period & 0xffffffff, PRD12);
  98         keystone_timer_writel(period >> 32, PRD34);
  99
 100         /*
 101          * enable timer
 102          * here we have to be sure that CNTLO, CNTHI, PRDLO, PRDHI registers
 103          * have been written.
 104          */
 105         keystone_timer_barrier();
 106         keystone_timer_writel(tcr, TCR);
 107         return 0;
 108 }
 109
 110 static void keystone_timer_disable(void)
 111 {
 112         u32 tcr;
 113
 114         tcr = keystone_timer_readl(TCR);
 115
 116         /* disable timer */
 117         tcr &= ~(TCR_ENAMODE_MASK);
 118         keystone_timer_writel(tcr, TCR);
 119 }
 120
 121 static irqreturn_t keystone_timer_interrupt(int irq, void *dev_id)
 122 {
 123         struct clock_event_device *evt = dev_id;
 124
 125         evt->event_handler(evt);
 126         return IRQ_HANDLED;
 127 }
 128
 129 static int keystone_set_next_event(unsigned long cycles,
 130                                   struct clock_event_device *evt)
 131 {
 132         return keystone_timer_config(cycles, TCR_ENAMODE_ONESHOT_MASK);
 133 }
 134
 135 static int keystone_shutdown(struct clock_event_device *evt)
 136 {
 137         keystone_timer_disable();
 138         return 0;
 139 }
 140
 141 static int keystone_set_periodic(struct clock_event_device *evt)
 142 {
 143         keystone_timer_config(timer.hz_period, TCR_ENAMODE_PERIODIC_MASK);
 144         return 0;
 145 }
 146
 147 static int __init keystone_timer_init(struct device_node *np)
 148 {
 149         struct clock_event_device *event_dev = &timer.event_dev;
 150         unsigned long rate;
 151         struct clk *clk;
 152         int irq, error;
 153
 154         irq  = irq_of_parse_and_map(np, 0);
 155         if (!irq) {
 156                 pr_err("%s: failed to map interrupts\n", __func__);
 157                 return -EINVAL;
 158         }
 159
 160         timer.base = of_iomap(np, 0);
 161         if (!timer.base) {
 162                 pr_err("%s: failed to map registers\n", __func__);
 163                 return -ENXIO;
 164         }
 165
 166         clk = of_clk_get(np, 0);
 167         if (IS_ERR(clk)) {
 168                 pr_err("%s: failed to get clock\n", __func__);
 169                 iounmap(timer.base);
 170                 return PTR_ERR(clk);
 171         }
 172
 173         error = clk_prepare_enable(clk);
 174         if (error) {
 175                 pr_err("%s: failed to enable clock\n", __func__);
 176                 goto err;
 177         }
 178
 179         rate = clk_get_rate(clk);
 180
 181         /* disable, use internal clock source */
 182         keystone_timer_writel(0, TCR);
 183         /* here we have to be sure the timer has been disabled */
 184         keystone_timer_barrier();
 185
 186         /* reset timer as 64-bit, no pre-scaler, plus features are disabled */
 187         keystone_timer_writel(0, TGCR);
 188
 189         /* unreset timer */
 190         keystone_timer_writel(TGCR_TIM_UNRESET_MASK, TGCR);
 191
 192         /* init counter to zero */
 193         keystone_timer_writel(0, TIM12);
 194         keystone_timer_writel(0, TIM34);
 195
 196         timer.hz_period = DIV_ROUND_UP(rate, HZ);
 197
 198         /* enable timer interrupts */
 199         keystone_timer_writel(INTCTLSTAT_ENINT_MASK, INTCTLSTAT);
 200
 201         error = request_irq(irq, keystone_timer_interrupt, IRQF_TIMER,
 202                             TIMER_NAME, event_dev);
 203         if (error) {
 204                 pr_err("%s: failed to setup irq\n", __func__);
 205                 goto err;
 206         }
 207
 208         /* setup clockevent */
 209         event_dev->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
 210         event_dev->set_next_event = keystone_set_next_event;
 211         event_dev->set_state_shutdown = keystone_shutdown;
 212         event_dev->set_state_periodic = keystone_set_periodic;
 213         event_dev->set_state_oneshot = keystone_shutdown;
 214         event_dev->cpumask = cpu_all_mask;
 215         event_dev->owner = THIS_MODULE;
 216         event_dev->name = TIMER_NAME;
 217         event_dev->irq = irq;
 218
 219         clockevents_config_and_register(event_dev, rate, 1, ULONG_MAX);
 220
 221         pr_info("keystone timer clock @%lu Hz\n", rate);
 222         return 0;
 223 err:
 224         clk_put(clk);
 225         iounmap(timer.base);
 226         return error;
 227 }
 228
 229 TIMER_OF_DECLARE(keystone_timer, "ti,keystone-timer",
 230                            keystone_timer_init);