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GT Block,
Server Base System Architecture (SBSA) Generic Watchdog.
GTDT table structure
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SW Status
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ACPI table defined in UEFI:
| Code Block |
|---|
typedef struct {
UINT32 Signature;
UINT32 Length;
UINT8 Revision;
UINT8 Checksum;
UINT8 OemId[6];
UINT64 OemTableId;
UINT32 OemRevision;
UINT32 CreatorId;
UINT32 CreatorRevision;
} EFI_ACPI_DESCRIPTION_HEADER;
///
/// Generic Timer Description Table definition.
///
typedef struct {
EFI_ACPI_DESCRIPTION_HEADER Header;
UINT64 PhysicalAddress;
UINT32 GlobalFlags;
UINT32 SecurePL1TimerGSIV;
UINT32 SecurePL1TimerFlags;
UINT32 NonSecurePL1TimerGSIV;
UINT32 NonSecurePL1TimerFlags;
UINT32 VirtualTimerGSIV;
UINT32 VirtualTimerFlags;
UINT32 NonSecurePL2TimerGSIV;
UINT32 NonSecurePL2TimerFlags;
} EFI_ACPI_5_0_GENERIC_TIMER_DESCRIPTION_TABLE; |
SW Status
Generic timer work well on i.MX8MP.
Code for ACPI
GTDT table for i.MX8MP:
| Code Block |
|---|
# ARM Architectural Timer Interrupt(GIC PPI) numbers
gArmTokenSpaceGuid.PcdArmArchTimerSecIntrNum|29|UINT32|0x00000035
gArmTokenSpaceGuid.PcdArmArchTimerIntrNum|30|UINT32|0x00000036
gArmTokenSpaceGuid.PcdArmArchTimerHypIntrNum|26|UINT32|0x00000040
gArmTokenSpaceGuid.PcdArmArchTimerVirtIntrNum|27|UINT32|0x00000041
#define GTDT_GLOBAL_FLAGS_MAPPED EFI_ACPI_5_0_GTDT_GLOBAL_FLAG_MEMORY_MAPPED_BLOCK_PRESENT
#define GTDT_GLOBAL_FLAGS_NOT_MAPPED 0
#define GTDT_GLOBAL_FLAGS_EDGE EFI_ACPI_5_0_GTDT_GLOBAL_FLAG_INTERRUPT_MODE
#define GTDT_GLOBAL_FLAGS_LEVEL 0
// Note: We could have a build flag that switches between memory mapped/non-memory mapped timer
#ifdef SYSTEM_TIMER_BASE_ADDRESS
#define GTDT_GLOBAL_FLAGS (GTDT_GLOBAL_FLAGS_MAPPED | GTDT_GLOBAL_FLAGS_LEVEL)
#else
#define GTDT_GLOBAL_FLAGS (GTDT_GLOBAL_FLAGS_NOT_MAPPED | GTDT_GLOBAL_FLAGS_LEVEL)
#define SYSTEM_TIMER_BASE_ADDRESS 0xFFFFFFFFFFFFFFFF
#endif
#define GTDT_TIMER_EDGE_TRIGGERED EFI_ACPI_5_0_GTDT_TIMER_FLAG_TIMER_INTERRUPT_MODE
#define GTDT_TIMER_LEVEL_TRIGGERED 0
#define GTDT_TIMER_ACTIVE_LOW EFI_ACPI_5_0_GTDT_TIMER_FLAG_TIMER_INTERRUPT_POLARITY
#define GTDT_TIMER_ACTIVE_HIGH 0
#define GTDT_GTIMER_FLAGS (GTDT_TIMER_ACTIVE_LOW | GTDT_TIMER_LEVEL_TRIGGERED)
EFI_ACPI_5_0_GENERIC_TIMER_DESCRIPTION_TABLE Gtdt = {
ARM_ACPI_HEADER(
EFI_ACPI_5_0_GENERIC_TIMER_DESCRIPTION_TABLE_SIGNATURE,
EFI_ACPI_5_0_GENERIC_TIMER_DESCRIPTION_TABLE,
EFI_ACPI_5_0_GENERIC_TIMER_DESCRIPTION_TABLE_REVISION
),
SYSTEM_TIMER_BASE_ADDRESS, // UINT64 PhysicalAddress
GTDT_GLOBAL_FLAGS, // UINT32 GlobalFlags
FixedPcdGet32 (PcdArmArchTimerSecIntrNum), // UINT32 SecurePL1TimerGSIV
GTDT_GTIMER_FLAGS, // UINT32 SecurePL1TimerFlags
FixedPcdGet32 (PcdArmArchTimerIntrNum), // UINT32 NonSecurePL1TimerGSIV
GTDT_GTIMER_FLAGS, // UINT32 NonSecurePL1TimerFlags
FixedPcdGet32 (PcdArmArchTimerVirtIntrNum), // UINT32 VirtualTimerGSIV
GTDT_GTIMER_FLAGS, // UINT32 VirtualTimerFlags
FixedPcdGet32 (PcdArmArchTimerHypIntrNum), // UINT32 NonSecurePL2TimerGSIV
GTDT_GTIMER_FLAGS // UINT32 NonSecurePL2TimerFlags
}; |
External timer
For external timer (also called as SoC timer), different SoC vendor may design their SoC timer, there have many difference in register layout and timer logic. So we see there have many platform timer driver in the kernel “drivers/clocksource/“.
How to support one new SoC timer ? Currently, it can use Device scope and DSD can match the platform driver requirement.