libffado/src/libieee1394/CycleTimerHelper.h

   1 /*
   2  * Copyright (C) 2005-2008 by Pieter Palmers
   3  *
   4  * This file is part of FFADO
   5  * FFADO = Free Firewire (pro-)audio drivers for linux
   6  *
   7  * FFADO is based upon FreeBoB
   8  *
   9  * This program is free software: you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License as published by
  11  * the Free Software Foundation, either version 2 of the License, or
  12  * (at your option) version 3 of the License.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17  * GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License
  20  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  21  *
  22  */
  23 #ifndef __CYCLETIMERHELPER_H__
  24 #define __CYCLETIMERHELPER_H__
  25
  26 /**
  27  * Implements a DLL based mechanism to track the cycle timer
  28  * register of the Ieee1394Service pointed to by the 'parent'.
  29  *
  30  * A DLL mechanism is performance-wise better suited, since it
  31  * does not require an OS call. Hence we run a thread to update
  32  * the DLL at regular time intervals, and then use the DLL to
  33  * generate a cycle timer estimate for the parent to pass on
  34  * to it's clients.
  35  *
  36  * The idea is to make reading the cycle timer real-time safe,
  37  * which isn't (necessarily)the case for the direct raw1394 call,
  38  * since it's a kernel call that could block (although the current
  39  * implementation is RT safe).
  40  *
  41  * This also allows us to run on systems not having the
  42  * raw1394_read_cycle_timer kernel call. We can always do a normal
  43  * read of our own cycle timer register, but that's not very accurate.
  44  * The accuracy is improved by this DLL mechanism. Still not as good
  45  * as when using the raw1394_read_cycle_timer call, but anyway.
  46  *
  47  * On the long run this code will also allow us to map system time
  48  * on to 1394 time for the current host controller, hence enabling
  49  * different clock domains to operate together.
  50  */
  51
  52 #include "libutil/Thread.h"
  53 #include "libutil/SystemTimeSource.h"
  54 #include "cycletimer.h"
  55
  56 #include "libutil/Functors.h"
  57 #include "libutil/Mutex.h"
  58
  59 #include "debugmodule/debugmodule.h"
  60
  61 class Ieee1394Service;
  62
  63 class CycleTimerHelper : public Util::RunnableInterface
  64 {
  65 public:
  66     CycleTimerHelper(Ieee1394Service &, unsigned int);
  67     CycleTimerHelper(Ieee1394Service &, unsigned int, bool rt, int prio);
  68     ~CycleTimerHelper();
  69
  70     virtual bool Init();
  71     virtual bool Execute();
  72
  73     bool setThreadParameters(bool rt, int priority);
  74     bool Start();
  75
  76     /**
  77      * @brief get the current cycle timer value (in ticks)
  78      * @note thread safe
  79      */
  80     uint32_t getCycleTimerTicks();
  81
  82     /**
  83      * @brief get the cycle timer value for a specific time instant (in ticks)
  84      * @note thread safe
  85      */
  86     uint32_t getCycleTimerTicks(uint64_t now);
  87
  88     /**
  89      * @brief get the current cycle timer value (in CTR format)
  90      * @note thread safe
  91      */
  92     uint32_t getCycleTimer();
  93
  94     /**
  95      * @brief get the cycle timer value for a specific time instant (in CTR format)
  96      * @note thread safe
  97      */
  98     uint32_t getCycleTimer(uint64_t now);
  99
 100     /**
 101      * @brief get the system time for a specific cycle timer value (in ticks)
 102      * @note thread safe
 103      */
 104     uint64_t getSystemTimeForCycleTimerTicks(uint32_t ticks);
 105
 106     /**
 107      * @brief get the system time for a specific cycle timer value (in CTR format)
 108      * @note thread safe
 109      */
 110     uint64_t getSystemTimeForCycleTimer(uint32_t ctr);
 111
 112     float getRate();
 113     float getNominalRate();
 114
 115     /**
 116      * @brief handle a bus reset
 117      */
 118     void busresetHandler();
 119
 120     void setVerboseLevel(int l);
 121
 122 private:
 123     bool readCycleTimerWithRetry(uint32_t *cycle_timer, uint64_t *local_time, int ntries);
 124     bool initValues();
 125
 126 #if IEEE1394SERVICE_USE_CYCLETIMER_DLL
 127     bool initDLL();
 128 #endif
 129
 130     Ieee1394Service &m_Parent;
 131     // parameters
 132     uint32_t m_ticks_per_update;
 133     uint32_t m_usecs_per_update;
 134
 135     float    m_avg_wakeup_delay;
 136
 137     // state variables
 138     double m_dll_e2;
 139
 140     double m_current_time_usecs;
 141     double m_next_time_usecs;
 142     double m_current_time_ticks;
 143     double m_next_time_ticks;
 144     bool m_first_run;
 145     ffado_microsecs_t m_sleep_until;
 146
 147     uint32_t m_cycle_timer_prev;
 148     uint64_t m_cycle_timer_ticks_prev;
 149
 150     double m_dll_coeff_b;
 151     double m_dll_coeff_c;
 152
 153     // cached vars used for computation
 154     struct compute_vars {
 155         uint64_t usecs;
 156         uint64_t ticks;
 157         double rate;
 158     };
 159
 160     #define CTRHELPER_NB_SHADOW_VARS 8
 161     struct compute_vars m_shadow_vars[CTRHELPER_NB_SHADOW_VARS];
 162     volatile unsigned int m_current_shadow_idx;
 163
 164     // Threading
 165     Util::Thread *  m_Thread;
 166     bool            m_realtime;
 167     unsigned int    m_priority;
 168     Util::Mutex*    m_update_lock;
 169
 170     // busreset handling
 171     Util::Functor* m_busreset_functor;
 172     bool            m_unhandled_busreset;
 173
 174 #ifdef DEBUG
 175     uint64_t m_last_loop_entry;
 176     int m_successive_short_loops;
 177 #endif
 178
 179     // debug stuff
 180     DECLARE_DEBUG_MODULE;
 181 };
 182 #endif