LXR linux/drivers/clocksource/metag

   1/*
   2 * Copyright (C) 2005-2013 Imagination Technologies Ltd.
   3 *
   4 * This program is free software; you can redistribute it and/or modify
   5 * it under the terms of the GNU General Public License version 2 as
   6 * published by the Free Software Foundation.
   7 *
   8 * This program is distributed in the hope that it will be useful,
   9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11 * GNU General Public License for more details.
  12 *
  13 * You should have received a copy of the GNU General Public License
  14 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  15 *
  16 *
  17 * Support for Meta per-thread timers.
  18 *
  19 * Meta hardware threads have 2 timers. The background timer (TXTIMER) is used
  20 * as a free-running time base (hz clocksource), and the interrupt timer
  21 * (TXTIMERI) is used for the timer interrupt (clock event). Both counters
  22 * traditionally count at approximately 1MHz.
  23 */
  24
  25#include <clocksource/metag_generic.h>
  26#include <linux/cpu.h>
  27#include <linux/errno.h>
  28#include <linux/sched.h>
  29#include <linux/kernel.h>
  30#include <linux/param.h>
  31#include <linux/time.h>
  32#include <linux/init.h>
  33#include <linux/proc_fs.h>
  34#include <linux/clocksource.h>
  35#include <linux/clockchips.h>
  36#include <linux/interrupt.h>
  37
  38#include <asm/clock.h>
  39#include <asm/hwthread.h>
  40#include <asm/core_reg.h>
  41#include <asm/metag_mem.h>
  42#include <asm/tbx.h>
  43
  44#define HARDWARE_FREQ           1000000 /* 1MHz */
  45#define HARDWARE_DIV            1       /* divide by 1 = 1MHz clock */
  46#define HARDWARE_TO_NS_SHIFT    10      /* convert ticks to ns */
  47
  48static unsigned int hwtimer_freq = HARDWARE_FREQ;
  49static DEFINE_PER_CPU(struct clock_event_device, local_clockevent);
  50static DEFINE_PER_CPU(char [11], local_clockevent_name);
  51
  52static int metag_timer_set_next_event(unsigned long delta,
  53                                      struct clock_event_device *dev)
  54{
  55        __core_reg_set(TXTIMERI, -delta);
  56        return 0;
  57}
  58
  59static cycle_t metag_clocksource_read(struct clocksource *cs)
  60{
  61        return __core_reg_get(TXTIMER);
  62}
  63
  64static struct clocksource clocksource_metag = {
  65        .name = "META",
  66        .rating = 200,
  67        .mask = CLOCKSOURCE_MASK(32),
  68        .read = metag_clocksource_read,
  69        .flags = CLOCK_SOURCE_IS_CONTINUOUS,
  70};
  71
  72static irqreturn_t metag_timer_interrupt(int irq, void *dummy)
  73{
  74        struct clock_event_device *evt = this_cpu_ptr(&local_clockevent);
  75
  76        evt->event_handler(evt);
  77
  78        return IRQ_HANDLED;
  79}
  80
  81static struct irqaction metag_timer_irq = {
  82        .name = "META core timer",
  83        .handler = metag_timer_interrupt,
  84        .flags = IRQF_TIMER | IRQF_IRQPOLL | IRQF_PERCPU,
  85};
  86
  87unsigned long long sched_clock(void)
  88{
  89        unsigned long long ticks = __core_reg_get(TXTIMER);
  90        return ticks << HARDWARE_TO_NS_SHIFT;
  91}
  92
  93static void arch_timer_setup(unsigned int cpu)
  94{
  95        unsigned int txdivtime;
  96        struct clock_event_device *clk = &per_cpu(local_clockevent, cpu);
  97        char *name = per_cpu(local_clockevent_name, cpu);
  98
  99        txdivtime = __core_reg_get(TXDIVTIME);
 100
 101        txdivtime &= ~TXDIVTIME_DIV_BITS;
 102        txdivtime |= (HARDWARE_DIV & TXDIVTIME_DIV_BITS);
 103
 104        __core_reg_set(TXDIVTIME, txdivtime);
 105
 106        sprintf(name, "META %d", cpu);
 107        clk->name = name;
 108        clk->features = CLOCK_EVT_FEAT_ONESHOT,
 109
 110        clk->rating = 200,
 111        clk->shift = 12,
 112        clk->irq = tbisig_map(TBID_SIGNUM_TRT),
 113        clk->set_next_event = metag_timer_set_next_event,
 114
 115        clk->mult = div_sc(hwtimer_freq, NSEC_PER_SEC, clk->shift);
 116        clk->max_delta_ns = clockevent_delta2ns(0x7fffffff, clk);
 117        clk->min_delta_ns = clockevent_delta2ns(0xf, clk);
 118        clk->cpumask = cpumask_of(cpu);
 119
 120        clockevents_register_device(clk);
 121
 122        /*
 123         * For all non-boot CPUs we need to synchronize our free
 124         * running clock (TXTIMER) with the boot CPU's clock.
 125         *
 126         * While this won't be accurate, it should be close enough.
 127         */
 128        if (cpu) {
 129                unsigned int thread0 = cpu_2_hwthread_id[0];
 130                unsigned long val;
 131
 132                val = core_reg_read(TXUCT_ID, TXTIMER_REGNUM, thread0);
 133                __core_reg_set(TXTIMER, val);
 134        }
 135}
 136
 137static int arch_timer_cpu_notify(struct notifier_block *self,
 138                                           unsigned long action, void *hcpu)
 139{
 140        int cpu = (long)hcpu;
 141
 142        switch (action) {
 143        case CPU_STARTING:
 144        case CPU_STARTING_FROZEN:
 145                arch_timer_setup(cpu);
 146                break;
 147        }
 148
 149        return NOTIFY_OK;
 150}
 151
 152static struct notifier_block arch_timer_cpu_nb = {
 153        .notifier_call = arch_timer_cpu_notify,
 154};
 155
 156int __init metag_generic_timer_init(void)
 157{
 158        /*
 159         * On Meta 2 SoCs, the actual frequency of the timer is based on the
 160         * Meta core clock speed divided by an integer, so it is only
 161         * approximately 1MHz. Calculating the real frequency here drastically
 162         * reduces clock skew on these SoCs.
 163         */
 164#ifdef CONFIG_METAG_META21
 165        hwtimer_freq = get_coreclock() / (metag_in32(EXPAND_TIMER_DIV) + 1);
 166#endif
 167        pr_info("Timer frequency: %u Hz\n", hwtimer_freq);
 168
 169        clocksource_register_hz(&clocksource_metag, hwtimer_freq);
 170
 171        setup_irq(tbisig_map(TBID_SIGNUM_TRT), &metag_timer_irq);
 172
 173        /* Configure timer on boot CPU */
 174        arch_timer_setup(smp_processor_id());
 175
 176        /* Hook cpu boot to configure other CPU's timers */
 177        register_cpu_notifier(&arch_timer_cpu_nb);
 178
 179        return 0;
 180}
 181