release/src-rt-6.x.4708/linux/linux-2.6.36/arch/mips/wrppmc/time.c

   1 /*
   2  * time.c: MIPS CPU Count/Compare timer hookup
   3  *
   4  * Author: Mark.Zhan, <rongkai.zhan@windriver.com>
   5  *
   6  * This file is subject to the terms and conditions of the GNU General Public
   7  * License.  See the file "COPYING" in the main directory of this archive
   8  * for more details.
   9  *
  10  * Copyright (C) 1996, 1997, 2004 by Ralf Baechle (ralf@linux-mips.org)
  11  * Copyright (C) 2006, Wind River System Inc.
  12  */
  13 #include <linux/init.h>
  14 #include <linux/interrupt.h>
  15 #include <linux/irq.h>
  16
  17 #include <asm/gt64120.h>
  18 #include <asm/time.h>
  19
  20 #define WRPPMC_CPU_CLK_FREQ 40000000 /* 40MHZ */
  21
  22 /*
  23  * Estimate CPU frequency.  Sets mips_hpt_frequency as a side-effect
  24  *
  25  * NOTE: We disable all GT64120 timers, and use MIPS processor internal
  26  * timer as the source of kernel clock tick.
  27  */
  28 void __init plat_time_init(void)
  29 {
  30         /* Disable GT64120 timers */
  31         GT_WRITE(GT_TC_CONTROL_OFS, 0x00);
  32         GT_WRITE(GT_TC0_OFS, 0x00);
  33         GT_WRITE(GT_TC1_OFS, 0x00);
  34         GT_WRITE(GT_TC2_OFS, 0x00);
  35         GT_WRITE(GT_TC3_OFS, 0x00);
  36
  37         /* Use MIPS compare/count internal timer */
  38         mips_hpt_frequency = WRPPMC_CPU_CLK_FREQ;
  39 }