2 The Timer Library implementation which uses the Time Stamp Counter in the processor.
4 For Pentium 4 processors, Intel Xeon processors (family [0FH], models [03H and higher]);
5 for Intel Core Solo and Intel Core Duo processors (family [06H], model [0EH]);
6 for the Intel Xeon processor 5100 series and Intel Core 2 Duo processors (family [06H], model [0FH]);
7 for Intel Core 2 and Intel Xeon processors (family [06H], display_model [17H]);
8 for Intel Atom processors (family [06H], display_model [1CH]):
9 the time-stamp counter increments at a constant rate.
10 That rate may be set by the maximum core-clock to bus-clock ratio of the processor or may be set by
11 the maximum resolved frequency at which the processor is booted. The maximum resolved frequency may
12 differ from the maximum qualified frequency of the processor.
14 The specific processor configuration determines the behavior. Constant TSC behavior ensures that the
15 duration of each clock tick is uniform and supports the use of the TSC as a wall clock timer even if
16 the processor core changes frequency. This is the architectural behavior moving forward.
18 A Processor's support for invariant TSC is indicated by CPUID.0x80000007.EDX[8].
20 Copyright (c) 2009 - 2011, Intel Corporation. All rights reserved.<BR>
21 This program and the accompanying materials
22 are licensed and made available under the terms and conditions of the BSD License
23 which accompanies this distribution. The full text of the license may be found at
24 http://opensource.org/licenses/bsd-license.php
26 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
27 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
31 #include "TscTimerLibInternal.h"
33 /** Calculate TSC frequency.
35 The TSC counting frequency is determined by comparing how far it counts
36 during a 1ms period as determined by the ACPI timer. The ACPI timer is
37 used because it counts at a known frequency.
38 If ACPI I/O space not enabled, this function will enable it. Then the
39 TSC is sampled, followed by waiting for 3579 clocks of the ACPI timer, or 1ms.
40 The TSC is then sampled again. The difference multiplied by 1000 is the TSC
41 frequency. There will be a small error because of the overhead of reading
42 the ACPI timer. An attempt is made to determine and compensate for this error.
44 @return The number of TSC counts per second.
48 InternalCalculateTscFrequency (
59 // If ACPI I/O space is not enabled yet, program ACPI I/O base address and enable it.
61 if ((PciRead8 (PCI_ICH_LPC_ADDRESS (R_ICH_LPC_ACPI_CNT
)) & B_ICH_LPC_ACPI_CNT_ACPI_EN
) == 0) {
62 PciWrite16 (PCI_ICH_LPC_ADDRESS (R_ICH_LPC_ACPI_BASE
), PcdGet16 (PcdPerfPkgAcpiIoPortBaseAddress
));
63 PciOr8 (PCI_ICH_LPC_ADDRESS (R_ICH_LPC_ACPI_CNT
), B_ICH_LPC_ACPI_CNT_ACPI_EN
);
67 // ACPI I/O space should be enabled now, locate the ACPI Timer.
68 // ACPI I/O base address maybe have be initialized by other driver with different value,
69 // So get it from PCI space directly.
71 TimerAddr
= ((PciRead16 (PCI_ICH_LPC_ADDRESS (R_ICH_LPC_ACPI_BASE
))) & B_ICH_LPC_ACPI_BASE_BAR
) + R_ACPI_PM1_TMR
;
72 Ticks
= IoRead32 (TimerAddr
) + (3579); // Set Ticks to 1ms in the future
73 StartTSC
= AsmReadTsc(); // Get base value for the TSC
75 // Wait until the ACPI timer has counted 1ms.
76 // Timer wrap-arounds are handled correctly by this function.
77 // When the current ACPI timer value is greater than 'Ticks', the while loop will exit.
79 while (((Ticks
- IoRead32 (TimerAddr
)) & BIT23
) == 0) {
82 EndTSC
= AsmReadTsc(); // TSC value 1ms later
84 TscFrequency
= MultU64x32 (
85 (EndTSC
- StartTSC
), // Number of TSC counts in 1ms
86 1000 // Number of ms in a second
92 /** Stalls the CPU for at least the given number of ticks.
94 Stalls the CPU for at least the given number of ticks. It's invoked by
95 MicroSecondDelay() and NanoSecondDelay().
97 @param[in] Delay A period of time to delay in ticks.
108 // The target timer count is calculated here
110 Ticks
= AsmReadTsc() + Delay
;
113 // Wait until time out
114 // Timer wrap-arounds are NOT handled correctly by this function.
115 // Thus, this function must be called within 10 years of reset since
116 // Intel guarantees a minimum of 10 years before the TSC wraps.
118 while (AsmReadTsc() <= Ticks
) CpuPause();
121 /** Stalls the CPU for at least the specified number of MicroSeconds.
123 @param[in] MicroSeconds The minimum number of microseconds to delay.
125 @return The value of MicroSeconds input.
131 IN UINTN MicroSeconds
137 InternalGetTscFrequency (),
146 /** Stalls the CPU for at least the specified number of NanoSeconds.
148 @param[in] NanoSeconds The minimum number of nanoseconds to delay.
150 @return The value of NanoSeconds input.
162 InternalGetTscFrequency (),
171 /** Retrieves the current value of the 64-bit free running Time-Stamp counter.
173 The time-stamp counter (as implemented in the P6 family, Pentium, Pentium M,
174 Pentium 4, Intel Xeon, Intel Core Solo and Intel Core Duo processors and
175 later processors) is a 64-bit counter that is set to 0 following a RESET of
176 the processor. Following a RESET, the counter increments even when the
177 processor is halted by the HLT instruction or the external STPCLK# pin. Note
178 that the assertion of the external DPSLP# pin may cause the time-stamp
181 The properties of the counter can be retrieved by the
182 GetPerformanceCounterProperties() function.
184 @return The current value of the free running performance counter.
189 GetPerformanceCounter (
196 /** Retrieves the 64-bit frequency in Hz and the range of performance counter
199 If StartValue is not NULL, then the value that the performance counter starts
200 with, 0x0, is returned in StartValue. If EndValue is not NULL, then the value
201 that the performance counter end with, 0xFFFFFFFFFFFFFFFF, is returned in
204 The 64-bit frequency of the performance counter, in Hz, is always returned.
205 To determine average processor clock frequency, Intel recommends the use of
206 EMON logic to count processor core clocks over the period of time for which
207 the average is required.
210 @param[out] StartValue Pointer to where the performance counter's starting value is saved, or NULL.
211 @param[out] EndValue Pointer to where the performance counter's ending value is saved, or NULL.
213 @return The frequency in Hz.
218 GetPerformanceCounterProperties (
219 OUT UINT64
*StartValue
, OPTIONAL
220 OUT UINT64
*EndValue OPTIONAL
223 if (StartValue
!= NULL
) {
226 if (EndValue
!= NULL
) {
227 *EndValue
= 0xFFFFFFFFFFFFFFFFull
;
230 return InternalGetTscFrequency ();
234 Converts elapsed ticks of performance counter to time in nanoseconds.
236 This function converts the elapsed ticks of running performance counter to
237 time value in unit of nanoseconds.
239 @param Ticks The number of elapsed ticks of running performance counter.
241 @return The elapsed time in nanoseconds.
246 GetTimeInNanoSecond (
255 Frequency
= GetPerformanceCounterProperties (NULL
, NULL
);
259 // Time = --------- x 1,000,000,000
262 NanoSeconds
= MultU64x32 (DivU64x64Remainder (Ticks
, Frequency
, &Remainder
), 1000000000u);
265 // Ensure (Remainder * 1,000,000,000) will not overflow 64-bit.
266 // Since 2^29 < 1,000,000,000 = 0x3B9ACA00 < 2^30, Remainder should < 2^(64-30) = 2^34,
267 // i.e. highest bit set in Remainder should <= 33.
269 Shift
= MAX (0, HighBitSet64 (Remainder
) - 33);
270 Remainder
= RShiftU64 (Remainder
, (UINTN
) Shift
);
271 Frequency
= RShiftU64 (Frequency
, (UINTN
) Shift
);
272 NanoSeconds
+= DivU64x64Remainder (MultU64x32 (Remainder
, 1000000000u), Frequency
, NULL
);