drivers/clocksource/renesas-ostm.c

   1 /*
   2  * Renesas Timer Support - OSTM
   3  *
   4  * Copyright (C) 2017 Renesas Electronics America, Inc.
   5  * Copyright (C) 2017 Chris Brandt
   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 as published by
   9  * the Free Software Foundation; either version 2 of the License
  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  */
  17
  18 #include <linux/of_address.h>
  19 #include <linux/of_irq.h>
  20 #include <linux/clk.h>
  21 #include <linux/clockchips.h>
  22 #include <linux/interrupt.h>
  23 #include <linux/sched_clock.h>
  24 #include <linux/slab.h>
  25
  26 /*
  27  * The OSTM contains independent channels.
  28  * The first OSTM channel probed will be set up as a free running
  29  * clocksource. Additionally we will use this clocksource for the system
  30  * schedule timer sched_clock().
  31  *
  32  * The second (or more) channel probed will be set up as an interrupt
  33  * driven clock event.
  34  */
  35
  36 struct ostm_device {
  37         void __iomem *base;
  38         unsigned long ticks_per_jiffy;
  39         struct clock_event_device ced;
  40 };
  41
  42 static void __iomem *system_clock;      /* For sched_clock() */
  43
  44 /* OSTM REGISTERS */
  45 #define OSTM_CMP                0x000   /* RW,32 */
  46 #define OSTM_CNT                0x004   /* R,32 */
  47 #define OSTM_TE                 0x010   /* R,8 */
  48 #define OSTM_TS                 0x014   /* W,8 */
  49 #define OSTM_TT                 0x018   /* W,8 */
  50 #define OSTM_CTL                0x020   /* RW,8 */
  51
  52 #define TE                      0x01
  53 #define TS                      0x01
  54 #define TT                      0x01
  55 #define CTL_PERIODIC            0x00
  56 #define CTL_ONESHOT             0x02
  57 #define CTL_FREERUN             0x02
  58
  59 static struct ostm_device *ced_to_ostm(struct clock_event_device *ced)
  60 {
  61         return container_of(ced, struct ostm_device, ced);
  62 }
  63
  64 static void ostm_timer_stop(struct ostm_device *ostm)
  65 {
  66         if (readb(ostm->base + OSTM_TE) & TE) {
  67                 writeb(TT, ostm->base + OSTM_TT);
  68
  69                 /*
  70                  * Read back the register simply to confirm the write operation
  71                  * has completed since I/O writes can sometimes get queued by
  72                  * the bus architecture.
  73                  */
  74                 while (readb(ostm->base + OSTM_TE) & TE)
  75                         ;
  76         }
  77 }
  78
  79 static int __init ostm_init_clksrc(struct ostm_device *ostm, unsigned long rate)
  80 {
  81         /*
  82          * irq not used (clock sources don't use interrupts)
  83          */
  84
  85         ostm_timer_stop(ostm);
  86
  87         writel(0, ostm->base + OSTM_CMP);
  88         writeb(CTL_FREERUN, ostm->base + OSTM_CTL);
  89         writeb(TS, ostm->base + OSTM_TS);
  90
  91         return clocksource_mmio_init(ostm->base + OSTM_CNT,
  92                         "ostm", rate,
  93                         300, 32, clocksource_mmio_readl_up);
  94 }
  95
  96 static u64 notrace ostm_read_sched_clock(void)
  97 {
  98         return readl(system_clock);
  99 }
 100
 101 static void __init ostm_init_sched_clock(struct ostm_device *ostm,
 102                         unsigned long rate)
 103 {
 104         system_clock = ostm->base + OSTM_CNT;
 105         sched_clock_register(ostm_read_sched_clock, 32, rate);
 106 }
 107
 108 static int ostm_clock_event_next(unsigned long delta,
 109                                      struct clock_event_device *ced)
 110 {
 111         struct ostm_device *ostm = ced_to_ostm(ced);
 112
 113         ostm_timer_stop(ostm);
 114
 115         writel(delta, ostm->base + OSTM_CMP);
 116         writeb(CTL_ONESHOT, ostm->base + OSTM_CTL);
 117         writeb(TS, ostm->base + OSTM_TS);
 118
 119         return 0;
 120 }
 121
 122 static int ostm_shutdown(struct clock_event_device *ced)
 123 {
 124         struct ostm_device *ostm = ced_to_ostm(ced);
 125
 126         ostm_timer_stop(ostm);
 127
 128         return 0;
 129 }
 130 static int ostm_set_periodic(struct clock_event_device *ced)
 131 {
 132         struct ostm_device *ostm = ced_to_ostm(ced);
 133
 134         if (clockevent_state_oneshot(ced) || clockevent_state_periodic(ced))
 135                 ostm_timer_stop(ostm);
 136
 137         writel(ostm->ticks_per_jiffy - 1, ostm->base + OSTM_CMP);
 138         writeb(CTL_PERIODIC, ostm->base + OSTM_CTL);
 139         writeb(TS, ostm->base + OSTM_TS);
 140
 141         return 0;
 142 }
 143
 144 static int ostm_set_oneshot(struct clock_event_device *ced)
 145 {
 146         struct ostm_device *ostm = ced_to_ostm(ced);
 147
 148         ostm_timer_stop(ostm);
 149
 150         return 0;
 151 }
 152
 153 static irqreturn_t ostm_timer_interrupt(int irq, void *dev_id)
 154 {
 155         struct ostm_device *ostm = dev_id;
 156
 157         if (clockevent_state_oneshot(&ostm->ced))
 158                 ostm_timer_stop(ostm);
 159
 160         /* notify clockevent layer */
 161         if (ostm->ced.event_handler)
 162                 ostm->ced.event_handler(&ostm->ced);
 163
 164         return IRQ_HANDLED;
 165 }
 166
 167 static int __init ostm_init_clkevt(struct ostm_device *ostm, int irq,
 168                         unsigned long rate)
 169 {
 170         struct clock_event_device *ced = &ostm->ced;
 171         int ret = -ENXIO;
 172
 173         ret = request_irq(irq, ostm_timer_interrupt,
 174                           IRQF_TIMER | IRQF_IRQPOLL,
 175                           "ostm", ostm);
 176         if (ret) {
 177                 pr_err("ostm: failed to request irq\n");
 178                 return ret;
 179         }
 180
 181         ced->name = "ostm";
 182         ced->features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_PERIODIC;
 183         ced->set_state_shutdown = ostm_shutdown;
 184         ced->set_state_periodic = ostm_set_periodic;
 185         ced->set_state_oneshot = ostm_set_oneshot;
 186         ced->set_next_event = ostm_clock_event_next;
 187         ced->shift = 32;
 188         ced->rating = 300;
 189         ced->cpumask = cpumask_of(0);
 190         clockevents_config_and_register(ced, rate, 0xf, 0xffffffff);
 191
 192         return 0;
 193 }
 194
 195 static int __init ostm_init(struct device_node *np)
 196 {
 197         struct ostm_device *ostm;
 198         int ret = -EFAULT;
 199         struct clk *ostm_clk = NULL;
 200         int irq;
 201         unsigned long rate;
 202
 203         ostm = kzalloc(sizeof(*ostm), GFP_KERNEL);
 204         if (!ostm)
 205                 return -ENOMEM;
 206
 207         ostm->base = of_iomap(np, 0);
 208         if (!ostm->base) {
 209                 pr_err("ostm: failed to remap I/O memory\n");
 210                 goto err;
 211         }
 212
 213         irq = irq_of_parse_and_map(np, 0);
 214         if (irq < 0) {
 215                 pr_err("ostm: Failed to get irq\n");
 216                 goto err;
 217         }
 218
 219         ostm_clk = of_clk_get(np, 0);
 220         if (IS_ERR(ostm_clk)) {
 221                 pr_err("ostm: Failed to get clock\n");
 222                 ostm_clk = NULL;
 223                 goto err;
 224         }
 225
 226         ret = clk_prepare_enable(ostm_clk);
 227         if (ret) {
 228                 pr_err("ostm: Failed to enable clock\n");
 229                 goto err;
 230         }
 231
 232         rate = clk_get_rate(ostm_clk);
 233         ostm->ticks_per_jiffy = (rate + HZ / 2) / HZ;
 234
 235         /*
 236          * First probed device will be used as system clocksource. Any
 237          * additional devices will be used as clock events.
 238          */
 239         if (!system_clock) {
 240                 ret = ostm_init_clksrc(ostm, rate);
 241
 242                 if (!ret) {
 243                         ostm_init_sched_clock(ostm, rate);
 244                         pr_info("ostm: used for clocksource\n");
 245                 }
 246
 247         } else {
 248                 ret = ostm_init_clkevt(ostm, irq, rate);
 249
 250                 if (!ret)
 251                         pr_info("ostm: used for clock events\n");
 252         }
 253
 254 err:
 255         if (ret) {
 256                 clk_disable_unprepare(ostm_clk);
 257                 iounmap(ostm->base);
 258                 kfree(ostm);
 259                 return ret;
 260         }
 261
 262         return 0;
 263 }
 264
 265 CLOCKSOURCE_OF_DECLARE(ostm, "renesas,ostm", ostm_init);