drivers/clocksource/mips-gic-timer.c

   1 /*
   2  * This file is subject to the terms and conditions of the GNU General Public
   3  * License.  See the file "COPYING" in the main directory of this archive
   4  * for more details.
   5  *
   6  * Copyright (C) 2012 MIPS Technologies, Inc.  All rights reserved.
   7  */
   8
   9 #define pr_fmt(fmt) "mips-gic-timer: " fmt
  10
  11 #include <linux/clk.h>
  12 #include <linux/clockchips.h>
  13 #include <linux/cpu.h>
  14 #include <linux/init.h>
  15 #include <linux/interrupt.h>
  16 #include <linux/notifier.h>
  17 #include <linux/of_irq.h>
  18 #include <linux/percpu.h>
  19 #include <linux/sched_clock.h>
  20 #include <linux/smp.h>
  21 #include <linux/time.h>
  22 #include <asm/mips-cps.h>
  23
  24 static DEFINE_PER_CPU(struct clock_event_device, gic_clockevent_device);
  25 static int gic_timer_irq;
  26 static unsigned int gic_frequency;
  27 static bool __read_mostly gic_clock_unstable;
  28
  29 static void gic_clocksource_unstable(char *reason);
  30
  31 static u64 notrace gic_read_count_2x32(void)
  32 {
  33         unsigned int hi, hi2, lo;
  34
  35         do {
  36                 hi = read_gic_counter_32h();
  37                 lo = read_gic_counter_32l();
  38                 hi2 = read_gic_counter_32h();
  39         } while (hi2 != hi);
  40
  41         return (((u64) hi) << 32) + lo;
  42 }
  43
  44 static u64 notrace gic_read_count_64(void)
  45 {
  46         return read_gic_counter();
  47 }
  48
  49 static u64 notrace gic_read_count(void)
  50 {
  51         if (mips_cm_is64)
  52                 return gic_read_count_64();
  53
  54         return gic_read_count_2x32();
  55 }
  56
  57 static int gic_next_event(unsigned long delta, struct clock_event_device *evt)
  58 {
  59         int cpu = cpumask_first(evt->cpumask);
  60         u64 cnt;
  61         int res;
  62
  63         cnt = gic_read_count();
  64         cnt += (u64)delta;
  65         if (cpu == raw_smp_processor_id()) {
  66                 write_gic_vl_compare(cnt);
  67         } else {
  68                 write_gic_vl_other(mips_cm_vp_id(cpu));
  69                 write_gic_vo_compare(cnt);
  70         }
  71         res = ((int)(gic_read_count() - cnt) >= 0) ? -ETIME : 0;
  72         return res;
  73 }
  74
  75 static irqreturn_t gic_compare_interrupt(int irq, void *dev_id)
  76 {
  77         struct clock_event_device *cd = dev_id;
  78
  79         write_gic_vl_compare(read_gic_vl_compare());
  80         cd->event_handler(cd);
  81         return IRQ_HANDLED;
  82 }
  83
  84 static struct irqaction gic_compare_irqaction = {
  85         .handler = gic_compare_interrupt,
  86         .percpu_dev_id = &gic_clockevent_device,
  87         .flags = IRQF_PERCPU | IRQF_TIMER,
  88         .name = "timer",
  89 };
  90
  91 static void gic_clockevent_cpu_init(unsigned int cpu,
  92                                     struct clock_event_device *cd)
  93 {
  94         cd->name                = "MIPS GIC";
  95         cd->features            = CLOCK_EVT_FEAT_ONESHOT |
  96                                   CLOCK_EVT_FEAT_C3STOP;
  97
  98         cd->rating              = 350;
  99         cd->irq                 = gic_timer_irq;
 100         cd->cpumask             = cpumask_of(cpu);
 101         cd->set_next_event      = gic_next_event;
 102
 103         clockevents_config_and_register(cd, gic_frequency, 0x300, 0x7fffffff);
 104
 105         enable_percpu_irq(gic_timer_irq, IRQ_TYPE_NONE);
 106 }
 107
 108 static void gic_clockevent_cpu_exit(struct clock_event_device *cd)
 109 {
 110         disable_percpu_irq(gic_timer_irq);
 111 }
 112
 113 static void gic_update_frequency(void *data)
 114 {
 115         unsigned long rate = (unsigned long)data;
 116
 117         clockevents_update_freq(this_cpu_ptr(&gic_clockevent_device), rate);
 118 }
 119
 120 static int gic_starting_cpu(unsigned int cpu)
 121 {
 122         gic_clockevent_cpu_init(cpu, this_cpu_ptr(&gic_clockevent_device));
 123         return 0;
 124 }
 125
 126 static int gic_clk_notifier(struct notifier_block *nb, unsigned long action,
 127                             void *data)
 128 {
 129         struct clk_notifier_data *cnd = data;
 130
 131         if (action == POST_RATE_CHANGE) {
 132                 gic_clocksource_unstable("ref clock rate change");
 133                 on_each_cpu(gic_update_frequency, (void *)cnd->new_rate, 1);
 134         }
 135
 136         return NOTIFY_OK;
 137 }
 138
 139 static int gic_dying_cpu(unsigned int cpu)
 140 {
 141         gic_clockevent_cpu_exit(this_cpu_ptr(&gic_clockevent_device));
 142         return 0;
 143 }
 144
 145 static struct notifier_block gic_clk_nb = {
 146         .notifier_call = gic_clk_notifier,
 147 };
 148
 149 static int gic_clockevent_init(void)
 150 {
 151         int ret;
 152
 153         if (!gic_frequency)
 154                 return -ENXIO;
 155
 156         ret = setup_percpu_irq(gic_timer_irq, &gic_compare_irqaction);
 157         if (ret < 0) {
 158                 pr_err("IRQ %d setup failed (%d)\n", gic_timer_irq, ret);
 159                 return ret;
 160         }
 161
 162         cpuhp_setup_state(CPUHP_AP_MIPS_GIC_TIMER_STARTING,
 163                           "clockevents/mips/gic/timer:starting",
 164                           gic_starting_cpu, gic_dying_cpu);
 165         return 0;
 166 }
 167
 168 static u64 gic_hpt_read(struct clocksource *cs)
 169 {
 170         return gic_read_count();
 171 }
 172
 173 static struct clocksource gic_clocksource = {
 174         .name                   = "GIC",
 175         .read                   = gic_hpt_read,
 176         .flags                  = CLOCK_SOURCE_IS_CONTINUOUS,
 177         .vdso_clock_mode        = VDSO_CLOCKMODE_GIC,
 178 };
 179
 180 static void gic_clocksource_unstable(char *reason)
 181 {
 182         if (gic_clock_unstable)
 183                 return;
 184
 185         gic_clock_unstable = true;
 186
 187         pr_info("GIC timer is unstable due to %s\n", reason);
 188
 189         clocksource_mark_unstable(&gic_clocksource);
 190 }
 191
 192 static int __init __gic_clocksource_init(void)
 193 {
 194         unsigned int count_width;
 195         int ret;
 196
 197         /* Set clocksource mask. */
 198         count_width = read_gic_config() & GIC_CONFIG_COUNTBITS;
 199         count_width >>= __ffs(GIC_CONFIG_COUNTBITS);
 200         count_width *= 4;
 201         count_width += 32;
 202         gic_clocksource.mask = CLOCKSOURCE_MASK(count_width);
 203
 204         /* Calculate a somewhat reasonable rating value. */
 205         gic_clocksource.rating = 200 + gic_frequency / 10000000;
 206
 207         ret = clocksource_register_hz(&gic_clocksource, gic_frequency);
 208         if (ret < 0)
 209                 pr_warn("Unable to register clocksource\n");
 210
 211         return ret;
 212 }
 213
 214 static int __init gic_clocksource_of_init(struct device_node *node)
 215 {
 216         struct clk *clk;
 217         int ret;
 218
 219         if (!mips_gic_present() || !node->parent ||
 220             !of_device_is_compatible(node->parent, "mti,gic")) {
 221                 pr_warn("No DT definition\n");
 222                 return -ENXIO;
 223         }
 224
 225         clk = of_clk_get(node, 0);
 226         if (!IS_ERR(clk)) {
 227                 ret = clk_prepare_enable(clk);
 228                 if (ret < 0) {
 229                         pr_err("Failed to enable clock\n");
 230                         clk_put(clk);
 231                         return ret;
 232                 }
 233
 234                 gic_frequency = clk_get_rate(clk);
 235         } else if (of_property_read_u32(node, "clock-frequency",
 236                                         &gic_frequency)) {
 237                 pr_err("Frequency not specified\n");
 238                 return -EINVAL;
 239         }
 240         gic_timer_irq = irq_of_parse_and_map(node, 0);
 241         if (!gic_timer_irq) {
 242                 pr_err("IRQ not specified\n");
 243                 return -EINVAL;
 244         }
 245
 246         ret = __gic_clocksource_init();
 247         if (ret)
 248                 return ret;
 249
 250         ret = gic_clockevent_init();
 251         if (!ret && !IS_ERR(clk)) {
 252                 if (clk_notifier_register(clk, &gic_clk_nb) < 0)
 253                         pr_warn("Unable to register clock notifier\n");
 254         }
 255
 256         /* And finally start the counter */
 257         clear_gic_config(GIC_CONFIG_COUNTSTOP);
 258
 259         /*
 260          * It's safe to use the MIPS GIC timer as a sched clock source only if
 261          * its ticks are stable, which is true on either the platforms with
 262          * stable CPU frequency or on the platforms with CM3 and CPU frequency
 263          * change performed by the CPC core clocks divider.
 264          */
 265         if (mips_cm_revision() >= CM_REV_CM3 || !IS_ENABLED(CONFIG_CPU_FREQ)) {
 266                 sched_clock_register(mips_cm_is64 ?
 267                                      gic_read_count_64 : gic_read_count_2x32,
 268                                      64, gic_frequency);
 269         }
 270
 271         return 0;
 272 }
 273 TIMER_OF_DECLARE(mips_gic_timer, "mti,gic-timer",
 274                        gic_clocksource_of_init);