TimestampDxe

Overview

TimestampDxe implements the EFI_TIMESTAMP_PROTOCOL by calibrating the x86 Time-Stamp Counter (TSC) against a hardware reference counter at I/O port 0x508. It enables the TCO/REF counter via PCIe configuration space, performs a spin-wait calibration loop with interrupts disabled, computes TSC frequency in Hz, and publishes GetTimestamp and GetProperties protocol services. This driver is sourced from MdeModulePkg/Universal/TimestampDxe in the EDK II tree.

Key Functions

• ModuleEntryPoint -- Entry point; calibrates TSC frequency and installs EFI_TIMESTAMP_PROTOCOL
• CalibrateTscFrequency -- Core calibration routine using TIMESTAMP_CALIBRATION_PORT (0x508)
• GetTimestamp -- Returns the current TSC value from RDTSC
• GetProperties -- Returns timestamp counter properties (frequency, end value)
• DebugPrint -- Debug output via DebugLib protocol
• DebugAssert -- Assertion handler via DebugLib protocol
• GetHobList -- Locates HOB list from system configuration table
• LocateProtocol -- Wraps gBS->LocateProtocol()
• IsGuidEqual -- GUID comparison using two 64-bit unaligned reads

Dependencies

• UEFI Boot Services (gBS->LocateProtocol, gBS->AllocatePool)
• EFI_TIMESTAMP_PROTOCOL (published service)
• DebugLib Protocol ({36232936-0E76-31C8-A13A-3AF2FC1C3932})
• PCD Protocol
• I/O port 0x508: 32-bit free-running reference counter (masked to 24 bits)
• PCIe ECAM configuration space (TCO/REF counter enable)
• RTC CMOS index 0x4B: Platform identifier byte

Platform

• Architecture: x86-64 (PE32+)
• Machine: 0x8664
• Subsystem: EFI Boot Service Driver (0x000B)
• Toolchain: VS2015, X64 DEBUG
• Sections: 6 (.text, .rdata, .data, .idata, .reloc)
• Entry Point: 0x3E0