release/src-rt-6.x.4708/linux/linux-2.6.36/arch/mips/kernel/csrc-gic.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) 2011 MIPS Technologies, Inc.
   7  */
   8 #include <linux/clocksource.h>
   9 #include <linux/init.h>
  10
  11 #include <asm/time.h>
  12 #include <asm/gic.h>
  13
  14 static cycle_t gic_hpt_read(struct clocksource *cs)
  15 {
  16         unsigned int hi, hi2, lo;
  17
  18         do {
  19                 GICREAD(GIC_REG(SHARED, GIC_SH_COUNTER_63_32), hi);
  20                 GICREAD(GIC_REG(SHARED, GIC_SH_COUNTER_31_00), lo);
  21                 GICREAD(GIC_REG(SHARED, GIC_SH_COUNTER_63_32), hi2);
  22         } while (hi2 != hi);
  23
  24         return (((cycle_t) hi) << 32) + lo;
  25 }
  26
  27 static struct clocksource gic_clocksource = {
  28         .name   = "GIC",
  29         .read   = gic_hpt_read,
  30         .flags  = CLOCK_SOURCE_IS_CONTINUOUS,
  31 };
  32
  33 void __init gic_clocksource_init(void)
  34 {
  35         unsigned int config, bits;
  36
  37         if (!cpu_has_counter || !mips_hpt_frequency)
  38                 BUG();
  39
  40         /* Calculate the clocksource mask. */
  41         GICREAD(GIC_REG(SHARED, GIC_SH_CONFIG), config);
  42         bits = 32 + ((config & GIC_SH_CONFIG_COUNTBITS_MSK) >>
  43                 (GIC_SH_CONFIG_COUNTBITS_SHF - 2));
  44
  45         /* Set clocksource mask. */
  46         gic_clocksource.mask = CLOCKSOURCE_MASK(bits);
  47
  48         /* Calculate a somewhat reasonable rating value. */
  49         gic_clocksource.rating = 200 + (mips_hpt_frequency * 2) / 10000000;
  50
  51         clocksource_set_clock(&gic_clocksource, mips_hpt_frequency);
  52         clocksource_register(&gic_clocksource);
  53 }