release/src-rt-6.x/linux/linux-2.6/include/asm-arm/arch-ns9xxx/clock.h

   1 /*
   2  * include/asm-arm/arch-ns9xxx/clock.h
   3  *
   4  * Copyright (C) 2007 by Digi International Inc.
   5  * All rights reserved.
   6  *
   7  * This program is free software; you can redistribute it and/or modify it
   8  * under the terms of the GNU General Public License version 2 as published by
   9  * the Free Software Foundation.
  10  */
  11 #ifndef __ASM_ARCH_CLOCK_H
  12 #define __ASM_ARCH_CLOCK_H
  13
  14 #include <asm/arch-ns9xxx/regs-sys.h>
  15
  16 #define CRYSTAL 29491200 /* Hz */
  17
  18 /* The HRM calls this value f_vco */
  19 static inline u32 ns9xxx_systemclock(void) __attribute__((const));
  20 static inline u32 ns9xxx_systemclock(void)
  21 {
  22         u32 pll = SYS_PLL;
  23
  24         /*
  25          * The system clock should be a multiple of HZ * TIMERCLOCKSELECT (in
  26          * time.c).
  27          *
  28          * The following values are given:
  29          *   - TIMERCLOCKSELECT == 2^i for an i in {0 .. 6}
  30          *   - CRYSTAL == 29491200 == 2^17 * 3^2 * 5^2
  31          *   - ND in {0 .. 31}
  32          *   - FS in {0 .. 3}
  33          *
  34          * Assuming the worst, we consider:
  35          *   - TIMERCLOCKSELECT == 64
  36          *   - ND == 0
  37          *   - FS == 3
  38          *
  39          * So HZ should be a divisor of:
  40          *      (CRYSTAL * (ND + 1) >> FS) / TIMERCLOCKSELECT
  41          *   == (2^17 * 3^2 * 5^2 * 1 >> 3) / 64
  42          *   == 2^8 * 3^2 * 5^2
  43          *   == 57600
  44          *
  45          * Currently HZ is defined to be 100 for this platform.
  46          *
  47          * Fine.
  48          */
  49         return CRYSTAL * (REGGET(pll, SYS_PLL, ND) + 1)
  50                 >> REGGET(pll, SYS_PLL, FS);
  51 }
  52
  53 static inline u32 ns9xxx_cpuclock(void) __attribute__((const));
  54 static inline u32 ns9xxx_cpuclock(void)
  55 {
  56         return ns9xxx_systemclock() / 2;
  57 }
  58
  59 static inline u32 ns9xxx_ahbclock(void) __attribute__((const));
  60 static inline u32 ns9xxx_ahbclock(void)
  61 {
  62         return ns9xxx_systemclock() / 4;
  63 }
  64
  65 static inline u32 ns9xxx_bbusclock(void) __attribute__((const));
  66 static inline u32 ns9xxx_bbusclock(void)
  67 {
  68         return ns9xxx_systemclock() / 8;
  69 }
  70
  71 #endif /* ifndef __ASM_ARCH_CLOCK_H */