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   1 /*
   2  *  linux/arch/ppc64/kernel/pmc.c
   3  *
   4  *  Copyright (C) 2004 David Gibson, IBM Corporation.
   5  *
   6  *  This program is free software; you can redistribute it and/or
   7  *  modify it under the terms of the GNU General Public License
   8  *  as published by the Free Software Foundation; either version
   9  *  2 of the License, or (at your option) any later version.
  10  */
  11
  12 #include <linux/config.h>
  13 #include <linux/errno.h>
  14 #include <linux/spinlock.h>
  15 #include <linux/module.h>
  16
  17 #include <asm/processor.h>
  18 #include <asm/pmc.h>
  19
  20 /* Ensure exceptions are disabled */
  21 static void dummy_perf(struct pt_regs *regs)
  22 {
  23         unsigned int mmcr0 = mfspr(SPRN_MMCR0);
  24
  25         mmcr0 &= ~(MMCR0_PMXE|MMCR0_PMAO);
  26         mtspr(SPRN_MMCR0, mmcr0);
  27 }
  28
  29 static spinlock_t pmc_owner_lock = SPIN_LOCK_UNLOCKED;
  30 static void *pmc_owner_caller; /* mostly for debugging */
  31 perf_irq_t perf_irq = dummy_perf;
  32
  33 int reserve_pmc_hardware(perf_irq_t new_perf_irq)
  34 {
  35         int err = 0;
  36
  37         spin_lock(&pmc_owner_lock);
  38
  39         if (pmc_owner_caller) {
  40                 printk(KERN_WARNING "reserve_pmc_hardware: "
  41                        "PMC hardware busy (reserved by caller %p)\n",
  42                        pmc_owner_caller);
  43                 err = -EBUSY;
  44                 goto out;
  45         }
  46
  47         pmc_owner_caller = __builtin_return_address(0);
  48         perf_irq = new_perf_irq ? : dummy_perf;
  49
  50  out:
  51         spin_unlock(&pmc_owner_lock);
  52         return err;
  53 }
  54 EXPORT_SYMBOL_GPL(reserve_pmc_hardware);
  55
  56 void release_pmc_hardware(void)
  57 {
  58         spin_lock(&pmc_owner_lock);
  59
  60         WARN_ON(! pmc_owner_caller);
  61
  62         pmc_owner_caller = NULL;
  63         perf_irq = dummy_perf;
  64
  65         spin_unlock(&pmc_owner_lock);
  66 }
  67 EXPORT_SYMBOL_GPL(release_pmc_hardware);