/** @file
Copyright (c) 2008 - 2010, Apple Inc. All rights reserved.<BR>
+ Copyright (c) 2011, ARM Limited. All rights reserved.
This program and the accompanying materials
are licensed and made available under the terms and conditions of the BSD License
#include <Library/PcdLib.h>
#include <Library/IoLib.h>
#include <Drivers/SP804Timer.h>
-#include <ArmPlatform.h>
+
+#define SP804_TIMER_METRONOME_BASE ((UINTN)PcdGet32 (PcdSP804TimerMetronomeBase))
+#define SP804_TIMER_PERFORMANCE_BASE ((UINTN)PcdGet32 (PcdSP804TimerPerformanceBase))
// Setup SP810's Timer2 for managing delay functions. And Timer3 for Performance counter
// Note: ArmVE's Timer0 and Timer1 are used by TimerDxe.
VOID
)
{
- // Check if Timer 2 is already initialized
- if (MmioRead32(SP804_TIMER2_BASE + SP804_TIMER_CONTROL_REG) & SP804_TIMER_CTRL_ENABLE) {
+ // Check if the Metronome Timer is already initialized
+ if (MmioRead32(SP804_TIMER_METRONOME_BASE + SP804_TIMER_CONTROL_REG) & SP804_TIMER_CTRL_ENABLE) {
return RETURN_SUCCESS;
} else {
- // Configure timer 2 for one shot operation, 32 bits, no prescaler, and interrupt disabled
- MmioOr32 (SP804_TIMER2_BASE + SP804_TIMER_CONTROL_REG, SP804_TIMER_CTRL_ONESHOT | SP804_TIMER_CTRL_32BIT | SP804_PRESCALE_DIV_1);
-
- // Preload the timer count register
- MmioWrite32 (SP804_TIMER2_BASE + SP804_TIMER_LOAD_REG, 1);
+ // Configure the Metronome Timer for free running operation, 32 bits, no prescaler, and interrupt disabled
+ MmioWrite32 (SP804_TIMER_METRONOME_BASE + SP804_TIMER_CONTROL_REG, SP804_TIMER_CTRL_32BIT | SP804_PRESCALE_DIV_1);
- // Enable the timer
- MmioOr32 (SP804_TIMER2_BASE + SP804_TIMER_CONTROL_REG, SP804_TIMER_CTRL_ENABLE);
+ // Start the Metronome Timer ticking
+ MmioOr32 (SP804_TIMER_METRONOME_BASE + SP804_TIMER_CONTROL_REG, SP804_TIMER_CTRL_ENABLE);
}
- // Check if Timer 3 is already initialized
- if (MmioRead32(SP804_TIMER3_BASE + SP804_TIMER_CONTROL_REG) & SP804_TIMER_CTRL_ENABLE) {
+ // Check if the Performance Timer is already initialized
+ if (MmioRead32(SP804_TIMER_PERFORMANCE_BASE + SP804_TIMER_CONTROL_REG) & SP804_TIMER_CTRL_ENABLE) {
return RETURN_SUCCESS;
} else {
- // Configure timer 3 for free running operation, 32 bits, no prescaler, interrupt disabled
- MmioOr32 (SP804_TIMER3_BASE + SP804_TIMER_CONTROL_REG, SP804_TIMER_CTRL_32BIT | SP804_PRESCALE_DIV_1);
+ // Configure the Performance timer for free running operation, 32 bits, no prescaler, interrupt disabled
+ MmioWrite32 (SP804_TIMER_PERFORMANCE_BASE + SP804_TIMER_CONTROL_REG, SP804_TIMER_CTRL_32BIT | SP804_PRESCALE_DIV_1);
- // Enable the timer
- MmioOr32 (SP804_TIMER3_BASE + SP804_TIMER_CONTROL_REG, SP804_TIMER_CTRL_ENABLE);
+ // Start the Performance Timer ticking
+ MmioOr32 (SP804_TIMER_PERFORMANCE_BASE + SP804_TIMER_CONTROL_REG, SP804_TIMER_CTRL_ENABLE);
}
return RETURN_SUCCESS;
Stalls the CPU for at least the given number of microseconds.
Stalls the CPU for the number of microseconds specified by MicroSeconds.
+ The hardware timer is 32 bits.
+ The maximum possible delay is (0xFFFFFFFF / TimerFrequencyMHz), i.e. ([32bits] / FreqInMHz)
+ For example:
+ +----------------+------------+----------+----------+
+ | TimerFrequency | MaxDelay | MaxDelay | MaxDelay |
+ | (MHz) | (us) | (s) | (min) |
+ +----------------+------------+----------+----------+
+ | 1 | 0xFFFFFFFF | 4294 | 71.5 |
+ | 5 | 0x33333333 | 859 | 14.3 |
+ | 10 | 0x19999999 | 429 | 7.2 |
+ | 50 | 0x051EB851 | 86 | 1.4 |
+ +----------------+------------+----------+----------+
+ If it becomes necessary to support higher delays, then consider using the
+ real time clock.
+
+ During this delay, the cpu is not yielded to any other process, with one exception:
+ events that are triggered off a timer and which execute at a higher TPL than
+ this function. These events may call MicroSecondDelay (or NanoSecondDelay) to
+ fulfil their own needs.
+ Therefore, this function must be re-entrant, as it may be interrupted and re-started.
@param MicroSeconds The minimum number of microseconds to delay.
IN UINTN MicroSeconds
)
{
- UINTN Index;
+ UINT64 DelayTicks64; // Convert from microseconds to timer ticks, more bits to detect over-range conditions.
+ UINTN DelayTicks; // Convert from microseconds to timer ticks, native size for general calculations.
+ UINTN StartTicks; // Timer value snapshot at the start of the delay
+ UINTN TargetTicks; // Timer value to signal the end of the delay
+ UINTN CurrentTicks; // Current value of the 64-bit timer value at any given moment
+
+ // If we snapshot the timer at the start of the delay function then we minimise unaccounted overheads.
+ StartTicks = MmioRead32 (SP804_TIMER_METRONOME_BASE + SP804_TIMER_CURRENT_REG);
+
+ // We are operating at the limit of 32bits. For the range checking work in 64 bits to avoid overflows.
+ DelayTicks64 = MultU64x32((UINT64)MicroSeconds, PcdGet32(PcdSP804TimerFrequencyInMHz));
+
+ // We are limited to 32 bits.
+ // If the specified delay is exactly equal to the max range of the timer,
+ // then the start will be equal to the stop plus one timer overflow (wrap-around).
+ // To avoid having to check for that, reduce the maximum acceptable range by 1 tick,
+ // i.e. reject delays equal or greater than the max range of the timer.
+ if (DelayTicks64 >= (UINT64)SP804_MAX_TICKS) {
+ DEBUG((EFI_D_ERROR,"MicroSecondDelay: ERROR: MicroSeconds=%d exceed SP804 count range. Max MicroSeconds=%d\n",
+ MicroSeconds,
+ ((UINTN)SP804_MAX_TICKS/PcdGet32(PcdSP804TimerFrequencyInMHz))));
+ }
+ ASSERT(DelayTicks64 < (UINT64)SP804_MAX_TICKS);
+
+ // From now on do calculations only in native bit size.
+ DelayTicks = (UINTN)DelayTicks64;
+
+ // Calculate the target value of the timer.
- // Reload the counter for each 1Mhz to avoid an overflow in the load value
- for (Index = 0; Index < (UINTN)PcdGet32(PcdSP804FrequencyInMHz); Index++) {
- // load the timer count register
- MmioWrite32 (SP804_TIMER2_BASE + SP804_TIMER_LOAD_REG, MicroSeconds);
+ //Note: SP804 timer is counting down
+ if (StartTicks >= DelayTicks) {
+ // In this case we do not expect a wrap-around of the timer to occur.
+ // CurrentTicks must be less than StartTicks and higher than TargetTicks.
+ // If this is not the case, then the delay has been reached and may even have been exceeded if this
+ // function was suspended by a higher priority interrupt.
- while (MmioRead32 (SP804_TIMER2_BASE + SP804_TIMER_CURRENT_REG) > 0) {
- ;
- }
+ TargetTicks = StartTicks - DelayTicks;
+
+ do {
+ CurrentTicks = MmioRead32 (SP804_TIMER_METRONOME_BASE + SP804_TIMER_CURRENT_REG);
+ } while ((CurrentTicks > TargetTicks) && (CurrentTicks <= StartTicks));
+
+ } else {
+ // In this case TargetTicks is larger than StartTicks.
+ // This means we expect a wrap-around of the timer to occur and we must wait for it.
+ // Before the wrap-around, CurrentTicks must be less than StartTicks and less than TargetTicks.
+ // After the wrap-around, CurrentTicks must be larger than StartTicks and larger than TargetTicks.
+ // If this is not the case, then the delay has been reached and may even have been exceeded if this
+ // function was suspended by a higher priority interrupt.
+
+ // The order of operations is essential to avoid arithmetic overflow problems
+ TargetTicks = ((UINTN)SP804_MAX_TICKS - DelayTicks) + StartTicks;
+
+ // First wait for the wrap-around to occur
+ do {
+ CurrentTicks = MmioRead32 (SP804_TIMER_METRONOME_BASE + SP804_TIMER_CURRENT_REG);
+ } while (CurrentTicks <= StartTicks);
+
+ // Then wait for the target
+ do {
+ CurrentTicks = MmioRead32 (SP804_TIMER_METRONOME_BASE + SP804_TIMER_CURRENT_REG);
+ } while (CurrentTicks > TargetTicks);
}
return MicroSeconds;
Stalls the CPU for the number of nanoseconds specified by NanoSeconds.
+ When the timer frequency is 1MHz, each tick corresponds to 1 microsecond.
+ Therefore, the nanosecond delay will be rounded up to the nearest 1 microsecond.
+
@param NanoSeconds The minimum number of nanoseconds to delay.
@return The value of NanoSeconds inputted.
IN UINTN NanoSeconds
)
{
- UINTN Index;
- UINT32 MicroSeconds;
+ UINTN MicroSeconds;
// Round up to 1us Tick Number
- MicroSeconds = (UINT32)NanoSeconds / 1000;
- MicroSeconds += ((UINT32)NanoSeconds % 1000) == 0 ? 0 : 1;
+ MicroSeconds = NanoSeconds / 1000;
+ MicroSeconds += ((NanoSeconds % 1000) == 0) ? 0 : 1;
- // Reload the counter for each 1Mhz to avoid an overflow in the load value
- for (Index = 0; Index < (UINTN)PcdGet32(PcdSP804FrequencyInMHz); Index++) {
- // load the timer count register
- MmioWrite32 (SP804_TIMER2_BASE + SP804_TIMER_LOAD_REG, MicroSeconds);
+ MicroSecondDelay (MicroSeconds);
- while (MmioRead32 (SP804_TIMER2_BASE + SP804_TIMER_CURRENT_REG) > 0) {
- ;
- }
- }
-
return NanoSeconds;
}
// Free running 64-bit/32-bit counter is needed here.
// Don't think we need this to boot, just to do performance profile
UINT64 Value;
- Value = MmioRead32 (SP804_TIMER3_BASE + SP804_TIMER_CURRENT_REG);
- ASSERT(Value > 0);
+ Value = MmioRead32 (SP804_TIMER_PERFORMANCE_BASE + SP804_TIMER_CURRENT_REG);
return Value;
}
{
if (StartValue != NULL) {
// Timer starts with the reload value
- *StartValue = (UINT64)0ULL;
+ *StartValue = 0xFFFFFFFF;
}
if (EndValue != NULL) {
- // Timer counts up to 0xFFFFFFFF
- *EndValue = 0xFFFFFFFF;
+ // Timer counts down to 0x0
+ *EndValue = (UINT64)0ULL;
}
return PcdGet64 (PcdEmbeddedPerformanceCounterFrequencyInHz);
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