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