arch/mips/kernel/cevt-r4k.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) 2007 MIPS Technologies, Inc.
   7  * Copyright (C) 2007 Ralf Baechle <ralf@linux-mips.org>
   8  */
   9 #include <linux/clockchips.h>
  10 #include <linux/interrupt.h>
  11 #include <linux/percpu.h>
  12 #include <linux/smp.h>
  13
  14 #include <asm/smtc_ipi.h>
  15 #include <asm/time.h>
  16 #include <asm/cevt-r4k.h>
  17
  18 /*
  19  * The SMTC Kernel for the 34K, 1004K, et. al. replaces several
  20  * of these routines with SMTC-specific variants.
  21  */
  22
  23 #ifndef CONFIG_MIPS_MT_SMTC
  24
  25 static int mips_next_event(unsigned long delta,
  26                            struct clock_event_device *evt)
  27 {
  28         unsigned int cnt;
  29         int res;
  30
  31         cnt = read_c0_count();
  32         cnt += delta;
  33         write_c0_compare(cnt);
  34         res = ((int)(read_c0_count() - cnt) > 0) ? -ETIME : 0;
  35         return res;
  36 }
  37
  38 #endif /* CONFIG_MIPS_MT_SMTC */
  39
  40 void mips_set_clock_mode(enum clock_event_mode mode,
  41                                 struct clock_event_device *evt)
  42 {
  43         /* Nothing to do ...  */
  44 }
  45
  46 DEFINE_PER_CPU(struct clock_event_device, mips_clockevent_device);
  47 int cp0_timer_irq_installed;
  48
  49 #ifndef CONFIG_MIPS_MT_SMTC
  50
  51 irqreturn_t c0_compare_interrupt(int irq, void *dev_id)
  52 {
  53         const int r2 = cpu_has_mips_r2;
  54         struct clock_event_device *cd;
  55         int cpu = smp_processor_id();
  56
  57         /*
  58          * Suckage alert:
  59          * Before R2 of the architecture there was no way to see if a
  60          * performance counter interrupt was pending, so we have to run
  61          * the performance counter interrupt handler anyway.
  62          */
  63         if (handle_perf_irq(r2))
  64                 goto out;
  65
  66         /*
  67          * The same applies to performance counter interrupts.  But with the
  68          * above we now know that the reason we got here must be a timer
  69          * interrupt.  Being the paranoiacs we are we check anyway.
  70          */
  71         if (!r2 || (read_c0_cause() & (1 << 30))) {
  72                 /* Clear Count/Compare Interrupt */
  73                 write_c0_compare(read_c0_compare());
  74                 cd = &per_cpu(mips_clockevent_device, cpu);
  75                 cd->event_handler(cd);
  76         }
  77
  78 out:
  79         return IRQ_HANDLED;
  80 }
  81
  82 #endif /* Not CONFIG_MIPS_MT_SMTC */
  83
  84 struct irqaction c0_compare_irqaction = {
  85         .handler = c0_compare_interrupt,
  86         .flags = IRQF_DISABLED | IRQF_PERCPU,
  87         .name = "timer",
  88 };
  89
  90
  91 void mips_event_handler(struct clock_event_device *dev)
  92 {
  93 }
  94
  95 /*
  96  * FIXME: This doesn't hold for the relocated E9000 compare interrupt.
  97  */
  98 static int c0_compare_int_pending(void)
  99 {
 100         return (read_c0_cause() >> cp0_compare_irq) & 0x100;
 101 }
 102
 103 /*
 104  * Compare interrupt can be routed and latched outside the core,
 105  * so a single execution hazard barrier may not be enough to give
 106  * it time to clear as seen in the Cause register.  4 time the
 107  * pipeline depth seems reasonably conservative, and empirically
 108  * works better in configurations with high CPU/bus clock ratios.
 109  */
 110
 111 #define compare_change_hazard() \
 112         do { \
 113                 irq_disable_hazard(); \
 114                 irq_disable_hazard(); \
 115                 irq_disable_hazard(); \
 116                 irq_disable_hazard(); \
 117         } while (0)
 118
 119 int c0_compare_int_usable(void)
 120 {
 121         unsigned int delta;
 122         unsigned int cnt;
 123
 124         /*
 125          * IP7 already pending?  Try to clear it by acking the timer.
 126          */
 127         if (c0_compare_int_pending()) {
 128                 write_c0_compare(read_c0_count());
 129                 compare_change_hazard();
 130                 if (c0_compare_int_pending())
 131                         return 0;
 132         }
 133
 134         for (delta = 0x10; delta <= 0x400000; delta <<= 1) {
 135                 cnt = read_c0_count();
 136                 cnt += delta;
 137                 write_c0_compare(cnt);
 138                 compare_change_hazard();
 139                 if ((int)(read_c0_count() - cnt) < 0)
 140                     break;
 141                 /* increase delta if the timer was already expired */
 142         }
 143
 144         while ((int)(read_c0_count() - cnt) <= 0)
 145                 ;       /* Wait for expiry  */
 146
 147         compare_change_hazard();
 148         if (!c0_compare_int_pending())
 149                 return 0;
 150
 151         write_c0_compare(read_c0_count());
 152         compare_change_hazard();
 153         if (c0_compare_int_pending())
 154                 return 0;
 155
 156         /*
 157          * Feels like a real count / compare timer.
 158          */
 159         return 1;
 160 }
 161
 162 #ifndef CONFIG_MIPS_MT_SMTC
 163
 164 int __cpuinit r4k_clockevent_init(void)
 165 {
 166         uint64_t mips_freq = mips_hpt_frequency;
 167         unsigned int cpu = smp_processor_id();
 168         struct clock_event_device *cd;
 169         unsigned int irq;
 170
 171         if (!cpu_has_counter || !mips_hpt_frequency)
 172                 return -ENXIO;
 173
 174         if (!c0_compare_int_usable())
 175                 return -ENXIO;
 176
 177         /*
 178          * With vectored interrupts things are getting platform specific.
 179          * get_c0_compare_int is a hook to allow a platform to return the
 180          * interrupt number of it's liking.
 181          */
 182         irq = MIPS_CPU_IRQ_BASE + cp0_compare_irq;
 183         if (get_c0_compare_int)
 184                 irq = get_c0_compare_int();
 185
 186         cd = &per_cpu(mips_clockevent_device, cpu);
 187
 188         cd->name                = "MIPS";
 189         cd->features            = CLOCK_EVT_FEAT_ONESHOT;
 190
 191         /* Calculate the min / max delta */
 192         cd->mult        = div_sc((unsigned long) mips_freq, NSEC_PER_SEC, 32);
 193         cd->shift               = 32;
 194         cd->max_delta_ns        = clockevent_delta2ns(0x7fffffff, cd);
 195         cd->min_delta_ns        = clockevent_delta2ns(0x300, cd);
 196
 197         cd->rating              = 300;
 198         cd->irq                 = irq;
 199         cd->cpumask             = cpumask_of(cpu);
 200         cd->set_next_event      = mips_next_event;
 201         cd->set_mode            = mips_set_clock_mode;
 202         cd->event_handler       = mips_event_handler;
 203
 204         clockevents_register_device(cd);
 205
 206         if (cp0_timer_irq_installed)
 207                 return 0;
 208
 209         cp0_timer_irq_installed = 1;
 210
 211         setup_irq(irq, &c0_compare_irqaction);
 212
 213         return 0;
 214 }
 215
 216 #endif /* Not CONFIG_MIPS_MT_SMTC */