ArmPlatformPkg/Library/SP804TimerLib/SP804TimerLib.c

   1 /** @file
   2
   3   Copyright (c) 2008 - 2010, Apple Inc. All rights reserved.<BR>
   4   Copyright (c) 2011, ARM Limited. All rights reserved.
   5
   6   This program and the accompanying materials
   7   are licensed and made available under the terms and conditions of the BSD License
   8   which accompanies this distribution.  The full text of the license may be found at
   9   http://opensource.org/licenses/bsd-license.php
  10
  11   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  12   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  13
  14 **/
  15
  16 #include <Base.h>
  17
  18 #include <Library/BaseLib.h>
  19 #include <Library/TimerLib.h>
  20 #include <Library/DebugLib.h>
  21 #include <Library/PcdLib.h>
  22 #include <Library/IoLib.h>
  23 #include <Drivers/SP804Timer.h>
  24
  25 #define SP804_TIMER_METRONOME_BASE    ((UINTN)PcdGet32 (PcdSP804TimerMetronomeBase))
  26 #define SP804_TIMER_PERFORMANCE_BASE  ((UINTN)PcdGet32 (PcdSP804TimerPerformanceBase))
  27
  28 // Setup SP810's Timer2 for managing delay functions. And Timer3 for Performance counter
  29 // Note: ArmVE's Timer0 and Timer1 are used by TimerDxe.
  30 RETURN_STATUS
  31 EFIAPI
  32 TimerConstructor (
  33   VOID
  34   )
  35 {
  36   // Check if the Metronome Timer is already initialized
  37   if (MmioRead32(SP804_TIMER_METRONOME_BASE + SP804_TIMER_CONTROL_REG) & SP804_TIMER_CTRL_ENABLE) {
  38     return RETURN_SUCCESS;
  39   } else {
  40     // Configure the Metronome Timer for free running operation, 32 bits, no prescaler, and interrupt disabled
  41     MmioWrite32 (SP804_TIMER_METRONOME_BASE + SP804_TIMER_CONTROL_REG, SP804_TIMER_CTRL_32BIT | SP804_PRESCALE_DIV_1);
  42
  43     // Start the Metronome Timer ticking
  44     MmioOr32 (SP804_TIMER_METRONOME_BASE + SP804_TIMER_CONTROL_REG, SP804_TIMER_CTRL_ENABLE);
  45   }
  46
  47   // Check if the Performance Timer is already initialized
  48   if (MmioRead32(SP804_TIMER_PERFORMANCE_BASE + SP804_TIMER_CONTROL_REG) & SP804_TIMER_CTRL_ENABLE) {
  49     return RETURN_SUCCESS;
  50   } else {
  51     // Configure the Performance timer for free running operation, 32 bits, no prescaler, interrupt disabled
  52     MmioWrite32 (SP804_TIMER_PERFORMANCE_BASE + SP804_TIMER_CONTROL_REG, SP804_TIMER_CTRL_32BIT | SP804_PRESCALE_DIV_1);
  53
  54     // Start the Performance Timer ticking
  55     MmioOr32 (SP804_TIMER_PERFORMANCE_BASE + SP804_TIMER_CONTROL_REG, SP804_TIMER_CTRL_ENABLE);
  56   }
  57
  58   return RETURN_SUCCESS;
  59 }
  60
  61 /**
  62   Stalls the CPU for at least the given number of microseconds.
  63
  64   Stalls the CPU for the number of microseconds specified by MicroSeconds.
  65   The hardware timer is 32 bits.
  66   The maximum possible delay is (0xFFFFFFFF / TimerFrequencyMHz), i.e. ([32bits] / FreqInMHz)
  67   For example:
  68   +----------------+------------+----------+----------+
  69   | TimerFrequency |  MaxDelay  | MaxDelay | MaxDelay |
  70   |     (MHz)      |    (us)    |   (s)    |  (min)   |
  71   +----------------+------------+----------+----------+
  72   |        1       | 0xFFFFFFFF |   4294   |   71.5   |
  73   |        5       | 0x33333333 |    859   |   14.3   |
  74   |       10       | 0x19999999 |    429   |    7.2   |
  75   |       50       | 0x051EB851 |     86   |    1.4   |
  76   +----------------+------------+----------+----------+
  77   If it becomes necessary to support higher delays, then consider using the
  78   real time clock.
  79
  80   During this delay, the cpu is not yielded to any other process, with one exception:
  81   events that are triggered off a timer and which execute at a higher TPL than
  82   this function. These events may call MicroSecondDelay (or NanoSecondDelay) to
  83   fulfil their own needs.
  84   Therefore, this function must be re-entrant, as it may be interrupted and re-started.
  85
  86   @param  MicroSeconds  The minimum number of microseconds to delay.
  87
  88   @return The value of MicroSeconds inputted.
  89
  90 **/
  91 UINTN
  92 EFIAPI
  93 MicroSecondDelay (
  94   IN  UINTN MicroSeconds
  95   )
  96 {
  97   UINT64    DelayTicks64;         // Convert from microseconds to timer ticks, more bits to detect over-range conditions.
  98   UINTN     DelayTicks;           // Convert from microseconds to timer ticks, native size for general calculations.
  99   UINTN     StartTicks;           // Timer value snapshot at the start of the delay
 100   UINTN     TargetTicks;          // Timer value to signal the end of the delay
 101   UINTN     CurrentTicks;         // Current value of the 64-bit timer value at any given moment
 102
 103   // If we snapshot the timer at the start of the delay function then we minimise unaccounted overheads.
 104   StartTicks = MmioRead32 (SP804_TIMER_METRONOME_BASE + SP804_TIMER_CURRENT_REG);
 105
 106   // We are operating at the limit of 32bits. For the range checking work in 64 bits to avoid overflows.
 107   DelayTicks64 = MultU64x32((UINT64)MicroSeconds, PcdGet32(PcdSP804TimerFrequencyInMHz));
 108
 109   // We are limited to 32 bits.
 110   // If the specified delay is exactly equal to the max range of the timer,
 111   // then the start will be equal to the stop plus one timer overflow (wrap-around).
 112   // To avoid having to check for that, reduce the maximum acceptable range by 1 tick,
 113   // i.e. reject delays equal or greater than the max range of the timer.
 114   if (DelayTicks64 >= (UINT64)SP804_MAX_TICKS) {
 115     DEBUG((EFI_D_ERROR,"MicroSecondDelay: ERROR: MicroSeconds=%d exceed SP804 count range. Max MicroSeconds=%d\n",
 116       MicroSeconds,
 117       ((UINTN)SP804_MAX_TICKS/PcdGet32(PcdSP804TimerFrequencyInMHz))));
 118   }
 119   ASSERT(DelayTicks64 < (UINT64)SP804_MAX_TICKS);
 120
 121   // From now on do calculations only in native bit size.
 122   DelayTicks = (UINTN)DelayTicks64;
 123
 124   // Calculate the target value of the timer.
 125
 126   //Note: SP804 timer is counting down
 127   if (StartTicks >= DelayTicks) {
 128     // In this case we do not expect a wrap-around of the timer to occur.
 129     // CurrentTicks must be less than StartTicks and higher than TargetTicks.
 130     // If this is not the case, then the delay has been reached and may even have been exceeded if this
 131     // function was suspended by a higher priority interrupt.
 132
 133     TargetTicks = StartTicks - DelayTicks;
 134
 135     do {
 136       CurrentTicks = MmioRead32 (SP804_TIMER_METRONOME_BASE + SP804_TIMER_CURRENT_REG);
 137     } while ((CurrentTicks > TargetTicks) && (CurrentTicks <= StartTicks));
 138
 139   } else {
 140     // In this case TargetTicks is larger than StartTicks.
 141     // This means we expect a wrap-around of the timer to occur and we must wait for it.
 142     // Before the wrap-around, CurrentTicks must be less than StartTicks and less than TargetTicks.
 143     // After the wrap-around, CurrentTicks must be larger than StartTicks and larger than TargetTicks.
 144     // If this is not the case, then the delay has been reached and may even have been exceeded if this
 145     // function was suspended by a higher priority interrupt.
 146
 147     // The order of operations is essential to avoid arithmetic overflow problems
 148     TargetTicks = ((UINTN)SP804_MAX_TICKS - DelayTicks) + StartTicks;
 149
 150     // First wait for the wrap-around to occur
 151     do {
 152       CurrentTicks = MmioRead32 (SP804_TIMER_METRONOME_BASE + SP804_TIMER_CURRENT_REG);
 153     } while (CurrentTicks <= StartTicks);
 154
 155     // Then wait for the target
 156     do {
 157       CurrentTicks = MmioRead32 (SP804_TIMER_METRONOME_BASE + SP804_TIMER_CURRENT_REG);
 158     } while (CurrentTicks > TargetTicks);
 159   }
 160
 161   return MicroSeconds;
 162 }
 163
 164 /**
 165   Stalls the CPU for at least the given number of nanoseconds.
 166
 167   Stalls the CPU for the number of nanoseconds specified by NanoSeconds.
 168
 169   When the timer frequency is 1MHz, each tick corresponds to 1 microsecond.
 170   Therefore, the nanosecond delay will be rounded up to the nearest 1 microsecond.
 171
 172   @param  NanoSeconds The minimum number of nanoseconds to delay.
 173
 174   @return The value of NanoSeconds inputted.
 175
 176 **/
 177 UINTN
 178 EFIAPI
 179 NanoSecondDelay (
 180   IN  UINTN NanoSeconds
 181   )
 182 {
 183   UINTN  MicroSeconds;
 184
 185   // Round up to 1us Tick Number
 186   MicroSeconds = NanoSeconds / 1000;
 187   MicroSeconds += ((NanoSeconds % 1000) == 0) ? 0 : 1;
 188
 189   MicroSecondDelay (MicroSeconds);
 190
 191   return NanoSeconds;
 192 }
 193
 194 /**
 195   Retrieves the current value of a 64-bit free running performance counter.
 196
 197   The counter can either count up by 1 or count down by 1. If the physical
 198   performance counter counts by a larger increment, then the counter values
 199   must be translated. The properties of the counter can be retrieved from
 200   GetPerformanceCounterProperties().
 201
 202   @return The current value of the free running performance counter.
 203
 204 **/
 205 UINT64
 206 EFIAPI
 207 GetPerformanceCounter (
 208   VOID
 209   )
 210 {
 211   // Free running 64-bit/32-bit counter is needed here.
 212   // Don't think we need this to boot, just to do performance profile
 213   UINT64 Value;
 214   Value = MmioRead32 (SP804_TIMER_PERFORMANCE_BASE + SP804_TIMER_CURRENT_REG);
 215   return Value;
 216 }
 217
 218
 219 /**
 220   Retrieves the 64-bit frequency in Hz and the range of performance counter
 221   values.
 222
 223   If StartValue is not NULL, then the value that the performance counter starts
 224   with immediately after is it rolls over is returned in StartValue. If
 225   EndValue is not NULL, then the value that the performance counter end with
 226   immediately before it rolls over is returned in EndValue. The 64-bit
 227   frequency of the performance counter in Hz is always returned. If StartValue
 228   is less than EndValue, then the performance counter counts up. If StartValue
 229   is greater than EndValue, then the performance counter counts down. For
 230   example, a 64-bit free running counter that counts up would have a StartValue
 231   of 0 and an EndValue of 0xFFFFFFFFFFFFFFFF. A 24-bit free running counter
 232   that counts down would have a StartValue of 0xFFFFFF and an EndValue of 0.
 233
 234   @param  StartValue  The value the performance counter starts with when it
 235                       rolls over.
 236   @param  EndValue    The value that the performance counter ends with before
 237                       it rolls over.
 238
 239   @return The frequency in Hz.
 240
 241 **/
 242 UINT64
 243 EFIAPI
 244 GetPerformanceCounterProperties (
 245   OUT UINT64  *StartValue,  OPTIONAL
 246   OUT UINT64  *EndValue     OPTIONAL
 247   )
 248 {
 249   if (StartValue != NULL) {
 250     // Timer starts with the reload value
 251     *StartValue = 0xFFFFFFFF;
 252   }
 253
 254   if (EndValue != NULL) {
 255     // Timer counts down to 0x0
 256     *EndValue = (UINT64)0ULL;
 257   }
 258
 259   return PcdGet64 (PcdEmbeddedPerformanceCounterFrequencyInHz);
 260 }