1 | /* timer.c |
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2 | * |
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3 | * This file manages the interval timer on the PowerPC 405. |
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4 | * We shall use the bottom 32 bits of the timebase register, |
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5 | * |
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6 | * NOTE: It is important that the timer start/stop overhead be |
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7 | * determined when porting or modifying this code. |
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8 | * |
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9 | * Author: Andrew Bray <andy@i-cubed.co.uk> |
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10 | * |
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11 | * COPYRIGHT (c) 1995 by i-cubed ltd. |
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12 | * |
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13 | * To anyone who acknowledges that this file is provided "AS IS" |
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14 | * without any express or implied warranty: |
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15 | * permission to use, copy, modify, and distribute this file |
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16 | * for any purpose is hereby granted without fee, provided that |
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17 | * the above copyright notice and this notice appears in all |
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18 | * copies, and that the name of i-cubed limited not be used in |
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19 | * advertising or publicity pertaining to distribution of the |
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20 | * software without specific, written prior permission. |
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21 | * i-cubed limited makes no representations about the suitability |
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22 | * of this software for any purpose. |
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23 | * |
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24 | * Derived from c/src/lib/libcpu/hppa1.1/timer/timer.c: |
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25 | * |
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26 | * COPYRIGHT (c) 1989-2007. |
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27 | * On-Line Applications Research Corporation (OAR). |
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28 | * |
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29 | * The license and distribution terms for this file may be |
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30 | * found in the file LICENSE in this distribution or at |
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31 | * http://www.rtems.com/license/LICENSE. |
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32 | * |
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33 | * Modifications for PPC405GP by Dennis Ehlin |
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34 | * |
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35 | * Further mods for PPC405EX/EXr by Michael Hamel |
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36 | * |
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37 | * $Id$ |
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38 | * |
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39 | */ |
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40 | |
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41 | #include <rtems.h> |
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42 | #include <libcpu/powerpc-utility.h> |
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43 | |
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44 | extern uint32_t bsp_timer_least_valid; |
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45 | extern uint32_t bsp_timer_average_overhead; |
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46 | |
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47 | static volatile uint32_t startedAt; |
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48 | static rtems_boolean subtractOverhead; |
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49 | |
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50 | void Timer_initialize() |
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51 | { |
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52 | /* We are going to rely on clock.c to sort out where the clock comes from */ |
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53 | startedAt = ppc_time_base(); |
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54 | } |
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55 | |
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56 | int Read_timer() |
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57 | { |
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58 | uint32_t clicks, total; |
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59 | |
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60 | clicks = ppc_time_base(); |
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61 | total = clicks - startedAt; |
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62 | if ( ! subtractOverhead ) |
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63 | return total; /* in XXX microsecond units */ |
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64 | else if ( total < bsp_timer_least_valid ) |
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65 | return 0; /* below timer resolution */ |
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66 | else |
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67 | return (total - bsp_timer_average_overhead); |
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68 | } |
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69 | |
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70 | rtems_status_code Empty_function( void ) |
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71 | { |
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72 | return RTEMS_SUCCESSFUL; |
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73 | } |
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74 | |
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75 | void Set_find_average_overhead( rtems_boolean find_flag) |
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76 | { |
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77 | subtractOverhead = find_flag; |
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78 | } |
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