drivers/clocksource/mips-gic-timer.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 // Copyright (C) 2012 MIPS Technologies, Inc.  All rights reserved.
   3
   4 #define pr_fmt(fmt) "mips-gic-timer: " fmt
   5
   6 #include <linux/clk.h>
   7 #include <linux/clockchips.h>
   8 #include <linux/cpu.h>
   9 #include <linux/init.h>
  10 #include <linux/interrupt.h>
  11 #include <linux/notifier.h>
  12 #include <linux/of_irq.h>
  13 #include <linux/percpu.h>
  14 #include <linux/sched_clock.h>
  15 #include <linux/smp.h>
  16 #include <linux/time.h>
  17 #include <asm/mips-cps.h>
  18
  19 static DEFINE_PER_CPU(struct clock_event_device, gic_clockevent_device);
  20 static int gic_timer_irq;
  21 static unsigned int gic_frequency;
  22 static unsigned int gic_count_width;
  23 static bool __read_mostly gic_clock_unstable;
  24
  25 static void gic_clocksource_unstable(char *reason);
  26
  27 static u64 notrace gic_read_count_2x32(void)
  28 {
  29         unsigned int hi, hi2, lo;
  30
  31         do {
  32                 hi = read_gic_counter_32h();
  33                 lo = read_gic_counter_32l();
  34                 hi2 = read_gic_counter_32h();
  35         } while (hi2 != hi);
  36
  37         return (((u64) hi) << 32) + lo;
  38 }
  39
  40 static u64 notrace gic_read_count_64(void)
  41 {
  42         return read_gic_counter();
  43 }
  44
  45 static u64 notrace gic_read_count(void)
  46 {
  47         if (mips_cm_is64)
  48                 return gic_read_count_64();
  49
  50         return gic_read_count_2x32();
  51 }
  52
  53 static int gic_next_event(unsigned long delta, struct clock_event_device *evt)
  54 {
  55         int cpu = cpumask_first(evt->cpumask);
  56         u64 cnt;
  57         int res;
  58
  59         cnt = gic_read_count();
  60         cnt += (u64)delta;
  61         if (cpu == raw_smp_processor_id()) {
  62                 write_gic_vl_compare(cnt);
  63         } else {
  64                 write_gic_vl_other(mips_cm_vp_id(cpu));
  65                 write_gic_vo_compare(cnt);
  66         }
  67         res = ((int)(gic_read_count() - cnt) >= 0) ? -ETIME : 0;
  68         return res;
  69 }
  70
  71 static irqreturn_t gic_compare_interrupt(int irq, void *dev_id)
  72 {
  73         struct clock_event_device *cd = dev_id;
  74
  75         write_gic_vl_compare(read_gic_vl_compare());
  76         cd->event_handler(cd);
  77         return IRQ_HANDLED;
  78 }
  79
  80 static struct irqaction gic_compare_irqaction = {
  81         .handler = gic_compare_interrupt,
  82         .percpu_dev_id = &gic_clockevent_device,
  83         .flags = IRQF_PERCPU | IRQF_TIMER,
  84         .name = "timer",
  85 };
  86
  87 static void gic_clockevent_cpu_init(unsigned int cpu,
  88                                     struct clock_event_device *cd)
  89 {
  90         cd->name                = "MIPS GIC";
  91         cd->features            = CLOCK_EVT_FEAT_ONESHOT |
  92                                   CLOCK_EVT_FEAT_C3STOP;
  93
  94         cd->rating              = 350;
  95         cd->irq                 = gic_timer_irq;
  96         cd->cpumask             = cpumask_of(cpu);
  97         cd->set_next_event      = gic_next_event;
  98
  99         clockevents_config_and_register(cd, gic_frequency, 0x300, 0x7fffffff);
 100
 101         enable_percpu_irq(gic_timer_irq, IRQ_TYPE_NONE);
 102 }
 103
 104 static void gic_clockevent_cpu_exit(struct clock_event_device *cd)
 105 {
 106         disable_percpu_irq(gic_timer_irq);
 107 }
 108
 109 static void gic_update_frequency(void *data)
 110 {
 111         unsigned long rate = (unsigned long)data;
 112
 113         clockevents_update_freq(this_cpu_ptr(&gic_clockevent_device), rate);
 114 }
 115
 116 static int gic_starting_cpu(unsigned int cpu)
 117 {
 118         gic_clockevent_cpu_init(cpu, this_cpu_ptr(&gic_clockevent_device));
 119         return 0;
 120 }
 121
 122 static int gic_clk_notifier(struct notifier_block *nb, unsigned long action,
 123                             void *data)
 124 {
 125         struct clk_notifier_data *cnd = data;
 126
 127         if (action == POST_RATE_CHANGE) {
 128                 gic_clocksource_unstable("ref clock rate change");
 129                 on_each_cpu(gic_update_frequency, (void *)cnd->new_rate, 1);
 130         }
 131
 132         return NOTIFY_OK;
 133 }
 134
 135 static int gic_dying_cpu(unsigned int cpu)
 136 {
 137         gic_clockevent_cpu_exit(this_cpu_ptr(&gic_clockevent_device));
 138         return 0;
 139 }
 140
 141 static struct notifier_block gic_clk_nb = {
 142         .notifier_call = gic_clk_notifier,
 143 };
 144
 145 static int gic_clockevent_init(void)
 146 {
 147         int ret;
 148
 149         if (!gic_frequency)
 150                 return -ENXIO;
 151
 152         ret = setup_percpu_irq(gic_timer_irq, &gic_compare_irqaction);
 153         if (ret < 0) {
 154                 pr_err("IRQ %d setup failed (%d)\n", gic_timer_irq, ret);
 155                 return ret;
 156         }
 157
 158         cpuhp_setup_state(CPUHP_AP_MIPS_GIC_TIMER_STARTING,
 159                           "clockevents/mips/gic/timer:starting",
 160                           gic_starting_cpu, gic_dying_cpu);
 161         return 0;
 162 }
 163
 164 static u64 gic_hpt_read(struct clocksource *cs)
 165 {
 166         return gic_read_count();
 167 }
 168
 169 static struct clocksource gic_clocksource = {
 170         .name                   = "GIC",
 171         .read                   = gic_hpt_read,
 172         .flags                  = CLOCK_SOURCE_IS_CONTINUOUS,
 173         .vdso_clock_mode        = VDSO_CLOCKMODE_GIC,
 174 };
 175
 176 static void gic_clocksource_unstable(char *reason)
 177 {
 178         if (gic_clock_unstable)
 179                 return;
 180
 181         gic_clock_unstable = true;
 182
 183         pr_info("GIC timer is unstable due to %s\n", reason);
 184
 185         clocksource_mark_unstable(&gic_clocksource);
 186 }
 187
 188 static int __init __gic_clocksource_init(void)
 189 {
 190         int ret;
 191
 192         /* Set clocksource mask. */
 193         gic_count_width = read_gic_config() & GIC_CONFIG_COUNTBITS;
 194         gic_count_width >>= __ffs(GIC_CONFIG_COUNTBITS);
 195         gic_count_width *= 4;
 196         gic_count_width += 32;
 197         gic_clocksource.mask = CLOCKSOURCE_MASK(gic_count_width);
 198
 199         /* Calculate a somewhat reasonable rating value. */
 200         if (mips_cm_revision() >= CM_REV_CM3 || !IS_ENABLED(CONFIG_CPU_FREQ))
 201                 gic_clocksource.rating = 300; /* Good when frequecy is stable */
 202         else
 203                 gic_clocksource.rating = 200;
 204         gic_clocksource.rating += clamp(gic_frequency / 10000000, 0, 99);
 205
 206         ret = clocksource_register_hz(&gic_clocksource, gic_frequency);
 207         if (ret < 0)
 208                 pr_warn("Unable to register clocksource\n");
 209
 210         return ret;
 211 }
 212
 213 static int __init gic_clocksource_of_init(struct device_node *node)
 214 {
 215         struct clk *clk;
 216         int ret;
 217
 218         if (!mips_gic_present() || !node->parent ||
 219             !of_device_is_compatible(node->parent, "mti,gic")) {
 220                 pr_warn("No DT definition\n");
 221                 return -ENXIO;
 222         }
 223
 224         clk = of_clk_get(node, 0);
 225         if (!IS_ERR(clk)) {
 226                 ret = clk_prepare_enable(clk);
 227                 if (ret < 0) {
 228                         pr_err("Failed to enable clock\n");
 229                         clk_put(clk);
 230                         return ret;
 231                 }
 232
 233                 gic_frequency = clk_get_rate(clk);
 234         } else if (of_property_read_u32(node, "clock-frequency",
 235                                         &gic_frequency)) {
 236                 pr_err("Frequency not specified\n");
 237                 return -EINVAL;
 238         }
 239         gic_timer_irq = irq_of_parse_and_map(node, 0);
 240         if (!gic_timer_irq) {
 241                 pr_err("IRQ not specified\n");
 242                 return -EINVAL;
 243         }
 244
 245         ret = __gic_clocksource_init();
 246         if (ret)
 247                 return ret;
 248
 249         ret = gic_clockevent_init();
 250         if (!ret && !IS_ERR(clk)) {
 251                 if (clk_notifier_register(clk, &gic_clk_nb) < 0)
 252                         pr_warn("Unable to register clock notifier\n");
 253         }
 254
 255         /* And finally start the counter */
 256         clear_gic_config(GIC_CONFIG_COUNTSTOP);
 257
 258         /*
 259          * It's safe to use the MIPS GIC timer as a sched clock source only if
 260          * its ticks are stable, which is true on either the platforms with
 261          * stable CPU frequency or on the platforms with CM3 and CPU frequency
 262          * change performed by the CPC core clocks divider.
 263          */
 264         if (mips_cm_revision() >= CM_REV_CM3 || !IS_ENABLED(CONFIG_CPU_FREQ)) {
 265                 sched_clock_register(mips_cm_is64 ?
 266                                      gic_read_count_64 : gic_read_count_2x32,
 267                                      gic_count_width, gic_frequency);
 268         }
 269
 270         return 0;
 271 }
 272 TIMER_OF_DECLARE(mips_gic_timer, "mti,gic-timer",
 273                        gic_clocksource_of_init);