drivers/clocksource/arm_generic.c

   1 /*
   2  * Generic timers support
   3  *
   4  * Copyright (C) 2012 ARM Ltd.
   5  * Author: Marc Zyngier <marc.zyngier@arm.com>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <linux/init.h>
  21 #include <linux/kernel.h>
  22 #include <linux/delay.h>
  23 #include <linux/device.h>
  24 #include <linux/smp.h>
  25 #include <linux/cpu.h>
  26 #include <linux/jiffies.h>
  27 #include <linux/interrupt.h>
  28 #include <linux/clockchips.h>
  29 #include <linux/of_irq.h>
  30 #include <linux/io.h>
  31
  32 #include <clocksource/arm_generic.h>
  33
  34 #include <asm/arm_generic.h>
  35
  36 static u32 arch_timer_rate;
  37 static u64 sched_clock_mult __read_mostly;
  38 static DEFINE_PER_CPU(struct clock_event_device, arch_timer_evt);
  39 static int arch_timer_ppi;
  40
  41 static irqreturn_t arch_timer_handle_irq(int irq, void *dev_id)
  42 {
  43         struct clock_event_device *evt = dev_id;
  44         unsigned long ctrl;
  45
  46         ctrl = arch_timer_reg_read(ARCH_TIMER_REG_CTRL);
  47         if (ctrl & ARCH_TIMER_CTRL_ISTATUS) {
  48                 ctrl |= ARCH_TIMER_CTRL_IMASK;
  49                 arch_timer_reg_write(ARCH_TIMER_REG_CTRL, ctrl);
  50                 evt->event_handler(evt);
  51                 return IRQ_HANDLED;
  52         }
  53
  54         return IRQ_NONE;
  55 }
  56
  57 static void arch_timer_stop(void)
  58 {
  59         unsigned long ctrl;
  60
  61         ctrl = arch_timer_reg_read(ARCH_TIMER_REG_CTRL);
  62         ctrl &= ~ARCH_TIMER_CTRL_ENABLE;
  63         arch_timer_reg_write(ARCH_TIMER_REG_CTRL, ctrl);
  64 }
  65
  66 static void arch_timer_set_mode(enum clock_event_mode mode,
  67                                 struct clock_event_device *clk)
  68 {
  69         switch (mode) {
  70         case CLOCK_EVT_MODE_UNUSED:
  71         case CLOCK_EVT_MODE_SHUTDOWN:
  72                 arch_timer_stop();
  73                 break;
  74         default:
  75                 break;
  76         }
  77 }
  78
  79 static int arch_timer_set_next_event(unsigned long evt,
  80                                      struct clock_event_device *unused)
  81 {
  82         unsigned long ctrl;
  83
  84         ctrl = arch_timer_reg_read(ARCH_TIMER_REG_CTRL);
  85         ctrl |= ARCH_TIMER_CTRL_ENABLE;
  86         ctrl &= ~ARCH_TIMER_CTRL_IMASK;
  87
  88         arch_timer_reg_write(ARCH_TIMER_REG_TVAL, evt);
  89         arch_timer_reg_write(ARCH_TIMER_REG_CTRL, ctrl);
  90
  91         return 0;
  92 }
  93
  94 static void __cpuinit arch_timer_setup(struct clock_event_device *clk)
  95 {
  96         /* Let's make sure the timer is off before doing anything else */
  97         arch_timer_stop();
  98
  99         clk->features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_C3STOP;
 100         clk->name = "arch_sys_timer";
 101         clk->rating = 400;
 102         clk->set_mode = arch_timer_set_mode;
 103         clk->set_next_event = arch_timer_set_next_event;
 104         clk->irq = arch_timer_ppi;
 105         clk->cpumask = cpumask_of(smp_processor_id());
 106
 107         clockevents_config_and_register(clk, arch_timer_rate,
 108                                         0xf, 0x7fffffff);
 109
 110         enable_percpu_irq(clk->irq, 0);
 111
 112         /* Ensure the virtual counter is visible to userspace for the vDSO. */
 113         arch_counter_enable_user_access();
 114 }
 115
 116 static void __init arch_timer_calibrate(void)
 117 {
 118         if (arch_timer_rate == 0) {
 119                 arch_timer_reg_write(ARCH_TIMER_REG_CTRL, 0);
 120                 arch_timer_rate = arch_timer_reg_read(ARCH_TIMER_REG_FREQ);
 121
 122                 /* Check the timer frequency. */
 123                 if (arch_timer_rate == 0)
 124                         panic("Architected timer frequency is set to zero.\n"
 125                               "You must set this in your .dts file\n");
 126         }
 127
 128         /* Cache the sched_clock multiplier to save a divide in the hot path. */
 129
 130         sched_clock_mult = DIV_ROUND_CLOSEST(NSEC_PER_SEC, arch_timer_rate);
 131
 132         pr_info("Architected local timer running at %u.%02uMHz.\n",
 133                  arch_timer_rate / 1000000, (arch_timer_rate / 10000) % 100);
 134 }
 135
 136 static cycle_t arch_counter_read(struct clocksource *cs)
 137 {
 138         return arch_counter_get_cntpct();
 139 }
 140
 141 static struct clocksource clocksource_counter = {
 142         .name   = "arch_sys_counter",
 143         .rating = 400,
 144         .read   = arch_counter_read,
 145         .mask   = CLOCKSOURCE_MASK(56),
 146         .flags  = (CLOCK_SOURCE_IS_CONTINUOUS | CLOCK_SOURCE_VALID_FOR_HRES),
 147 };
 148
 149 int read_current_timer(unsigned long *timer_value)
 150 {
 151         *timer_value = arch_counter_get_cntpct();
 152         return 0;
 153 }
 154
 155 unsigned long long notrace sched_clock(void)
 156 {
 157         return arch_counter_get_cntvct() * sched_clock_mult;
 158 }
 159
 160 static int __cpuinit arch_timer_cpu_notify(struct notifier_block *self,
 161                                            unsigned long action, void *hcpu)
 162 {
 163         int cpu = (long)hcpu;
 164         struct clock_event_device *clk = per_cpu_ptr(&arch_timer_evt, cpu);
 165
 166         switch(action) {
 167         case CPU_STARTING:
 168         case CPU_STARTING_FROZEN:
 169                 arch_timer_setup(clk);
 170                 break;
 171
 172         case CPU_DYING:
 173         case CPU_DYING_FROZEN:
 174                 pr_debug("arch_timer_teardown disable IRQ%d cpu #%d\n",
 175                          clk->irq, cpu);
 176                 disable_percpu_irq(clk->irq);
 177                 arch_timer_set_mode(CLOCK_EVT_MODE_UNUSED, clk);
 178                 break;
 179         }
 180
 181         return NOTIFY_OK;
 182 }
 183
 184 static struct notifier_block __cpuinitdata arch_timer_cpu_nb = {
 185         .notifier_call = arch_timer_cpu_notify,
 186 };
 187
 188 static const struct of_device_id arch_timer_of_match[] __initconst = {
 189         { .compatible = "arm,armv8-timer" },
 190         {},
 191 };
 192
 193 int __init arm_generic_timer_init(void)
 194 {
 195         struct device_node *np;
 196         int err;
 197         u32 freq;
 198
 199         np = of_find_matching_node(NULL, arch_timer_of_match);
 200         if (!np) {
 201                 pr_err("arch_timer: can't find DT node\n");
 202                 return -ENODEV;
 203         }
 204
 205         /* Try to determine the frequency from the device tree or CNTFRQ */
 206         if (!of_property_read_u32(np, "clock-frequency", &freq))
 207                 arch_timer_rate = freq;
 208         arch_timer_calibrate();
 209
 210         arch_timer_ppi = irq_of_parse_and_map(np, 0);
 211         pr_info("arch_timer: found %s irq %d\n", np->name, arch_timer_ppi);
 212
 213         err = request_percpu_irq(arch_timer_ppi, arch_timer_handle_irq,
 214                                  np->name, &arch_timer_evt);
 215         if (err) {
 216                 pr_err("arch_timer: can't register interrupt %d (%d)\n",
 217                        arch_timer_ppi, err);
 218                 return err;
 219         }
 220
 221         clocksource_register_hz(&clocksource_counter, arch_timer_rate);
 222
 223         /* Calibrate the delay loop directly */
 224         lpj_fine = DIV_ROUND_CLOSEST(arch_timer_rate, HZ);
 225
 226         /* Immediately configure the timer on the boot CPU */
 227         arch_timer_setup(this_cpu_ptr(&arch_timer_evt));
 228
 229         register_cpu_notifier(&arch_timer_cpu_nb);
 230
 231         return 0;
 232 }