target/linux/brcm63xx/files/arch/mips/bcm963xx/time.c

   1 /*
   2 <:copyright-gpl
   3  Copyright 2004 Broadcom Corp. All Rights Reserved.
   4
   5  This program is free software; you can distribute it and/or modify it
   6  under the terms of the GNU General Public License (Version 2) as
   7  published by the Free Software Foundation.
   8
   9  This program is distributed in the hope it will be useful, but WITHOUT
  10  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  for more details.
  13
  14  You should have received a copy of the GNU General Public License along
  15  with this program; if not, write to the Free Software Foundation, Inc.,
  16  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
  17 :>
  18 */
  19 /*
  20  * Setup time for Broadcom 963xx MIPS boards
  21  */
  22
  23 #include <linux/autoconf.h>
  24 #include <linux/init.h>
  25 #include <linux/kernel_stat.h>
  26 #include <linux/sched.h>
  27 #include <linux/spinlock.h>
  28 #include <linux/interrupt.h>
  29 #include <linux/module.h>
  30 #include <linux/time.h>
  31 #include <linux/timex.h>
  32
  33 #include <asm/mipsregs.h>
  34 #include <asm/ptrace.h>
  35 #include <asm/div64.h>
  36 #include <asm/time.h>
  37
  38 #include <6348_map_part.h>
  39 #include <6348_intr.h>
  40 #include <bcm_map_part.h>
  41 #include <bcm_intr.h>
  42
  43 static unsigned long r4k_offset;        /* Amount to increment compare reg each time */
  44 static unsigned long r4k_cur;           /* What counter should be at next timer irq */
  45
  46 /*  *********************************************************************
  47     *  calculateCpuSpeed()
  48     *      Calculate the BCM6348 CPU speed by reading the PLL strap register
  49     *      and applying the following formula:
  50     *      cpu_clk = (.25 * 64MHz freq) * (N1 + 1) * (N2 + 2) / (M1_CPU + 1)
  51     *  Input parameters:
  52     *      none
  53     *  Return value:
  54     *      none
  55     ********************************************************************* */
  56
  57 static inline unsigned long __init calculateCpuSpeed(void)
  58 {
  59     u32 pllStrap = PERF->PllStrap;
  60     int n1 = (pllStrap & PLL_N1_MASK) >> PLL_N1_SHFT;
  61     int n2 = (pllStrap & PLL_N2_MASK) >> PLL_N2_SHFT;
  62     int m1cpu = (pllStrap & PLL_M1_CPU_MASK) >> PLL_M1_CPU_SHFT;
  63
  64         return (16 * (n1 + 1) * (n2 + 2) / (m1cpu + 1)) * 1000000;
  65 }
  66
  67
  68 static inline unsigned long __init cal_r4koff(void)
  69 {
  70         mips_hpt_frequency = calculateCpuSpeed() / 2;
  71         return (mips_hpt_frequency / HZ);
  72 }
  73
  74
  75 /*
  76  * There are a lot of conceptually broken versions of the MIPS timer interrupt
  77  * handler floating around.  This one is rather different, but the algorithm
  78  * is provably more robust.
  79  */
  80 irqreturn_t brcm_timer_interrupt(struct pt_regs *regs)
  81 {
  82         int irq = MIPS_TIMER_INT;
  83
  84         irq_enter();
  85         kstat_this_cpu.irqs[irq]++;
  86
  87         timer_interrupt(irq, regs);
  88         irq_exit();
  89         return IRQ_HANDLED;
  90 }
  91
  92
  93 void __init brcm_time_init(void)
  94 {
  95         unsigned int est_freq, flags;
  96         local_irq_save(flags);
  97
  98         printk("calculating r4koff... ");
  99         r4k_offset = cal_r4koff();
 100         printk("%08lx(%d)\n", r4k_offset, (int)r4k_offset);
 101
 102         est_freq = 2 * r4k_offset * HZ;
 103         est_freq += 5000;   /* round */
 104         est_freq -= est_freq % 10000;
 105         printk("CPU frequency %d.%02d MHz\n", est_freq / 1000000,
 106                    (est_freq % 1000000) * 100 / 1000000);
 107         local_irq_restore(flags);
 108 }
 109
 110
 111 void __init plat_timer_setup(struct irqaction *irq)
 112 {
 113         r4k_cur = (read_c0_count() + r4k_offset);
 114         write_c0_compare(r4k_cur);
 115         set_c0_status(IE_IRQ5);
 116 }