drivers/clocksource/jcore-pit.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * J-Core SoC PIT/clocksource driver
   4  *
   5  * Copyright (C) 2015-2016 Smart Energy Instruments, Inc.
   6  */
   7
   8 #include <linux/kernel.h>
   9 #include <linux/slab.h>
  10 #include <linux/interrupt.h>
  11 #include <linux/clockchips.h>
  12 #include <linux/clocksource.h>
  13 #include <linux/sched_clock.h>
  14 #include <linux/cpu.h>
  15 #include <linux/cpuhotplug.h>
  16 #include <linux/of_address.h>
  17 #include <linux/of_irq.h>
  18
  19 #define PIT_IRQ_SHIFT           12
  20 #define PIT_PRIO_SHIFT          20
  21 #define PIT_ENABLE_SHIFT        26
  22 #define PIT_PRIO_MASK           0xf
  23
  24 #define REG_PITEN               0x00
  25 #define REG_THROT               0x10
  26 #define REG_COUNT               0x14
  27 #define REG_BUSPD               0x18
  28 #define REG_SECHI               0x20
  29 #define REG_SECLO               0x24
  30 #define REG_NSEC                0x28
  31
  32 struct jcore_pit {
  33         struct clock_event_device       ced;
  34         void __iomem                    *base;
  35         unsigned long                   periodic_delta;
  36         u32                             enable_val;
  37 };
  38
  39 static void __iomem *jcore_pit_base;
  40 static struct jcore_pit __percpu *jcore_pit_percpu;
  41
  42 static notrace u64 jcore_sched_clock_read(void)
  43 {
  44         u32 seclo, nsec, seclo0;
  45         __iomem void *base = jcore_pit_base;
  46
  47         seclo = readl(base + REG_SECLO);
  48         do {
  49                 seclo0 = seclo;
  50                 nsec  = readl(base + REG_NSEC);
  51                 seclo = readl(base + REG_SECLO);
  52         } while (seclo0 != seclo);
  53
  54         return seclo * NSEC_PER_SEC + nsec;
  55 }
  56
  57 static u64 jcore_clocksource_read(struct clocksource *cs)
  58 {
  59         return jcore_sched_clock_read();
  60 }
  61
  62 static int jcore_pit_disable(struct jcore_pit *pit)
  63 {
  64         writel(0, pit->base + REG_PITEN);
  65         return 0;
  66 }
  67
  68 static int jcore_pit_set(unsigned long delta, struct jcore_pit *pit)
  69 {
  70         jcore_pit_disable(pit);
  71         writel(delta, pit->base + REG_THROT);
  72         writel(pit->enable_val, pit->base + REG_PITEN);
  73         return 0;
  74 }
  75
  76 static int jcore_pit_set_state_shutdown(struct clock_event_device *ced)
  77 {
  78         struct jcore_pit *pit = container_of(ced, struct jcore_pit, ced);
  79
  80         return jcore_pit_disable(pit);
  81 }
  82
  83 static int jcore_pit_set_state_oneshot(struct clock_event_device *ced)
  84 {
  85         struct jcore_pit *pit = container_of(ced, struct jcore_pit, ced);
  86
  87         return jcore_pit_disable(pit);
  88 }
  89
  90 static int jcore_pit_set_state_periodic(struct clock_event_device *ced)
  91 {
  92         struct jcore_pit *pit = container_of(ced, struct jcore_pit, ced);
  93
  94         return jcore_pit_set(pit->periodic_delta, pit);
  95 }
  96
  97 static int jcore_pit_set_next_event(unsigned long delta,
  98                                     struct clock_event_device *ced)
  99 {
 100         struct jcore_pit *pit = container_of(ced, struct jcore_pit, ced);
 101
 102         return jcore_pit_set(delta, pit);
 103 }
 104
 105 static int jcore_pit_local_init(unsigned cpu)
 106 {
 107         struct jcore_pit *pit = this_cpu_ptr(jcore_pit_percpu);
 108         unsigned buspd, freq;
 109
 110         pr_info("Local J-Core PIT init on cpu %u\n", cpu);
 111
 112         buspd = readl(pit->base + REG_BUSPD);
 113         freq = DIV_ROUND_CLOSEST(NSEC_PER_SEC, buspd);
 114         pit->periodic_delta = DIV_ROUND_CLOSEST(NSEC_PER_SEC, HZ * buspd);
 115
 116         clockevents_config_and_register(&pit->ced, freq, 1, ULONG_MAX);
 117
 118         return 0;
 119 }
 120
 121 static irqreturn_t jcore_timer_interrupt(int irq, void *dev_id)
 122 {
 123         struct jcore_pit *pit = dev_id;
 124
 125         if (clockevent_state_oneshot(&pit->ced))
 126                 jcore_pit_disable(pit);
 127
 128         pit->ced.event_handler(&pit->ced);
 129
 130         return IRQ_HANDLED;
 131 }
 132
 133 static int __init jcore_pit_init(struct device_node *node)
 134 {
 135         int err;
 136         unsigned pit_irq, cpu;
 137         unsigned long hwirq;
 138         u32 irqprio, enable_val;
 139
 140         jcore_pit_base = of_iomap(node, 0);
 141         if (!jcore_pit_base) {
 142                 pr_err("Error: Cannot map base address for J-Core PIT\n");
 143                 return -ENXIO;
 144         }
 145
 146         pit_irq = irq_of_parse_and_map(node, 0);
 147         if (!pit_irq) {
 148                 pr_err("Error: J-Core PIT has no IRQ\n");
 149                 return -ENXIO;
 150         }
 151
 152         pr_info("Initializing J-Core PIT at %p IRQ %d\n",
 153                 jcore_pit_base, pit_irq);
 154
 155         err = clocksource_mmio_init(jcore_pit_base, "jcore_pit_cs",
 156                                     NSEC_PER_SEC, 400, 32,
 157                                     jcore_clocksource_read);
 158         if (err) {
 159                 pr_err("Error registering clocksource device: %d\n", err);
 160                 return err;
 161         }
 162
 163         sched_clock_register(jcore_sched_clock_read, 32, NSEC_PER_SEC);
 164
 165         jcore_pit_percpu = alloc_percpu(struct jcore_pit);
 166         if (!jcore_pit_percpu) {
 167                 pr_err("Failed to allocate memory for clock event device\n");
 168                 return -ENOMEM;
 169         }
 170
 171         err = request_percpu_irq(pit_irq, jcore_timer_interrupt,
 172                                  "jcore_pit", jcore_pit_percpu);
 173         if (err) {
 174                 pr_err("pit irq request failed: %d\n", err);
 175                 free_percpu(jcore_pit_percpu);
 176                 return err;
 177         }
 178
 179         /*
 180          * The J-Core PIT is not hard-wired to a particular IRQ, but
 181          * integrated with the interrupt controller such that the IRQ it
 182          * generates is programmable, as follows:
 183          *
 184          * The bit layout of the PIT enable register is:
 185          *
 186          *      .....e..ppppiiiiiiii............
 187          *
 188          * where the .'s indicate unrelated/unused bits, e is enable,
 189          * p is priority, and i is hard irq number.
 190          *
 191          * For the PIT included in AIC1 (obsolete but still in use),
 192          * any hard irq (trap number) can be programmed via the 8
 193          * iiiiiiii bits, and a priority (0-15) is programmable
 194          * separately in the pppp bits.
 195          *
 196          * For the PIT included in AIC2 (current), the programming
 197          * interface is equivalent modulo interrupt mapping. This is
 198          * why a different compatible tag was not used. However only
 199          * traps 64-127 (the ones actually intended to be used for
 200          * interrupts, rather than syscalls/exceptions/etc.) can be
 201          * programmed (the high 2 bits of i are ignored) and the
 202          * priority pppp is <<2'd and or'd onto the irq number. This
 203          * choice seems to have been made on the hardware engineering
 204          * side under an assumption that preserving old AIC1 priority
 205          * mappings was important. Future models will likely ignore
 206          * the pppp field.
 207          */
 208         hwirq = irq_get_irq_data(pit_irq)->hwirq;
 209         irqprio = (hwirq >> 2) & PIT_PRIO_MASK;
 210         enable_val = (1U << PIT_ENABLE_SHIFT)
 211                    | (hwirq << PIT_IRQ_SHIFT)
 212                    | (irqprio << PIT_PRIO_SHIFT);
 213
 214         for_each_present_cpu(cpu) {
 215                 struct jcore_pit *pit = per_cpu_ptr(jcore_pit_percpu, cpu);
 216
 217                 pit->base = of_iomap(node, cpu);
 218                 if (!pit->base) {
 219                         pr_err("Unable to map PIT for cpu %u\n", cpu);
 220                         continue;
 221                 }
 222
 223                 pit->ced.name = "jcore_pit";
 224                 pit->ced.features = CLOCK_EVT_FEAT_PERIODIC
 225                                   | CLOCK_EVT_FEAT_ONESHOT
 226                                   | CLOCK_EVT_FEAT_PERCPU;
 227                 pit->ced.cpumask = cpumask_of(cpu);
 228                 pit->ced.rating = 400;
 229                 pit->ced.irq = pit_irq;
 230                 pit->ced.set_state_shutdown = jcore_pit_set_state_shutdown;
 231                 pit->ced.set_state_periodic = jcore_pit_set_state_periodic;
 232                 pit->ced.set_state_oneshot = jcore_pit_set_state_oneshot;
 233                 pit->ced.set_next_event = jcore_pit_set_next_event;
 234
 235                 pit->enable_val = enable_val;
 236         }
 237
 238         cpuhp_setup_state(CPUHP_AP_JCORE_TIMER_STARTING,
 239                           "clockevents/jcore:starting",
 240                           jcore_pit_local_init, NULL);
 241
 242         return 0;
 243 }
 244
 245 TIMER_OF_DECLARE(jcore_pit, "jcore,pit", jcore_pit_init);