source: rtems/c/src/lib/libbsp/arm/gba/timer/timer.c @ 3c7ed6b

4.104.114.84.9
Last change on this file since 3c7ed6b was 3c7ed6b, checked in by Joel Sherrill <joel.sherrill@…>, on Jul 6, 2005 at 6:46:04 PM

2005-07-06 Markku Puro <markku.puro@…>

  • .cvsignore, ChangeLog?, Makefile.am, README, bsp_specs, configure.ac, clock/clockdrv.c, console/conio.c, console/console.c, console/defaultfont.c, include/arm_mode_bits.h, include/asm_macros.h, include/bsp.h, include/bspopts.h.in, include/conio.h, include/gba.h, include/gba_registers.h, include/tm27.h, irq/bsp_irq_asm.S, irq/bsp_irq_init.c, irq/irq.c, irq/irq.h, irq/irq_asm.S, irq/irq_init.c, start/logo.S, start/start.S, startup/bspstart.c, startup/cpu.c, startup/cpu_asm.S, startup/exit.c, startup/linkcmds, timer/timer.c: New files.
  • Property mode set to 100644
File size: 3.7 KB
Line 
1/**
2 *  @file timer.c
3 *
4 *  GBA Timer driver.
5 */
6/*
7 *  RTEMS GBA BSP
8 *
9 *  Copyright (c) 2002 by Jay Monkman <jtm@smoothsmoothie.com>
10 *
11 *  Copyright (c) 2004  Markku Puro <markku.puro@kopteri.net>
12 *
13 *  The license and distribution terms for this file may be
14 *  found in found in the file LICENSE in this distribution or at
15 *  http://www.rtems.com/license/LICENSE.
16 *
17 *
18 * Notes:
19 *  This file manages the benchmark timer used by the RTEMS Timing Test
20 *  Suite.  Each measured time period is demarcated by calls to
21 *  Timer_initialize() and Read_timer().  Read_timer() usually returns
22 *  the number of microseconds since Timer_initialize() exitted.
23 *
24 *  It is important that the timer start/stop overhead be determined
25 *  when porting or modifying this code.
26 *
27 *  $Id$
28 */
29
30#include <rtems.h>
31#include <bsp.h>
32#include <irq.h>
33#include <gba.h>
34
35/*
36 * Set up the timer hardware
37 *    1 / 16.78Mhz  => 59.595 ns
38 *   64 / 16.78Mhz  =>  3.814 us
39 *  256 / 16.78Mhz  => 15.256 us
40 * 1024 / 16.78Mhz  => 61.025 us
41 */
42#define  __TimePreScaler      1
43#define  __TickTime_ns        ((1000000000L/__ClockFrequency)*__TimePreScaler)
44#define  __TickTime_us        ((1000000L/__ClockFrequency)*__TimePreScaler)
45
46#if (__TimePreScaler==1)
47 #define GBA_TM0CNT_PS    0x0000
48#elif (__TimePreScaler==64)
49 #define GBA_TM0CNT_PS    0x0001
50#elif (__TimePreScaler==256)
51 #define GBA_TM0CNT_PS    0x0002
52#elif (__TimePreScaler==1024)
53 #define GBA_TM0CNT_PS    0x0003
54#else
55 #define GBA_TM0CNT_PS    0x0003
56#endif
57
58rtems_boolean  Timer_driver_Find_average_overhead;
59
60/**
61 *  @brief Timer_initialize start TM0 and TM1
62 *
63 *  @param  None
64 *  @return None
65 */
66void Timer_initialize( void )
67{
68  GBA_REG_TM1CNT =  0x0000;                /* Stop Counters         */
69  GBA_REG_TM0CNT =  0x0000;
70  GBA_REG_TM1D   =  0x0000;                /* Reset Counters        */
71  GBA_REG_TM0D   =  0x0000;
72  /* Start Counters */
73  GBA_REG_TM1CNT =  0x0084;                /* Start Count Up timing */
74  GBA_REG_TM0CNT = (0x0080|GBA_TM0CNT_PS); /* Start Count           */
75}
76
77/*
78 *  The following controls the behavior of Read_timer().
79 *
80 *  AVG_OVEREHAD is the overhead for starting and stopping the timer.  It
81 *  is usually deducted from the number returned.
82 *
83 *  LEAST_VALID is the lowest number this routine should trust.  Numbers
84 *  below this are "noise" and zero is returned.
85 */
86
87#define AVG_OVERHEAD    3  /**< It typically takes 3 microseconds          */
88#define LEAST_VALID     1  /**< Don't trust a clicks value lower than this */
89
90/**
91 *  @brief Read_timer return timer countervalue in microseconds.
92 *
93 *  Used in Timing Test Suite.
94 *
95 *  @param  None
96 *  @return Timer value in microseconds
97 */
98uint32_t Read_timer( void )
99{
100  uint32_t  ticks;
101  uint32_t  total;
102
103  /* Stop Counters */
104  GBA_REG_TM0CNT =  0x0000;
105  GBA_REG_TM1CNT =  0x0000;
106  /* Read Counters */
107  ticks = (GBA_REG_TM1D<<16) | GBA_REG_TM0D;
108  if ( ticks < LEAST_VALID ) {
109      return 0;  /* below timer resolution */
110  }
111  /* convert to uS */
112  total = ((ticks * __TickTime_ns) / 1000);
113  if ( Timer_driver_Find_average_overhead == 1 ) {
114      return total;          /* in microseconds */
115  }
116  else {
117    if ( total < AVG_OVERHEAD ) {
118        return 0;
119    }
120    return (total - AVG_OVERHEAD);
121  }
122}
123
124/**
125 *  @brief Empty function
126 *
127 *  Empty function call used in loops to measure basic cost of looping
128 *  in Timing Test Suite.
129 *
130 *  @param  None
131 *  @return RTEMS_SUCCESSFUL
132*/
133rtems_status_code Empty_function( void )
134{
135   return RTEMS_SUCCESSFUL;
136}
137
138/**
139 *  @brief Set Timer_driver_Find_average_overhead flag.
140 *
141 *  Used in Timing Test Suite.
142 *
143 *  @param  find_flag boolean find_flag
144 *  @return None
145*/
146void Set_find_average_overhead(rtems_boolean find_flag)
147{
148   Timer_driver_Find_average_overhead = find_flag;
149}
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