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GICD_TYPER, Interrupt Controller Type Register

The GICD_TYPER characteristics are:

Purpose

Provides information about what features the GIC implementation supports. It indicates:

  • Whether the GIC implementation supports two Security states.
  • The maximum number of INTIDs that the GIC implementation supports.
  • The number of PEs that can be used as interrupt targets.

Configuration

This register is available in all configurations of the GIC. When GICD_CTLR.DS==0, this register is Common.

Attributes

GICD_TYPER is a 32-bit register.

Field descriptions

The GICD_TYPER bit assignments are:

ESPI_range field, bits [31:27]

When GICD_TYPER.ESPI == 1:

Indicates the maximum INTID in the Extended SPI range.

  • Maximum Extended SPI INTID is (32*(ESPI_range + 1) + 4095)


Otherwise:

Reserved, RES0.

RSS, bit [26]

Range Selector Support. Possible values are:

RSSMeaning
0b0

The IRI supports targeted SGIs with affinity level 0 values of 0 - 15.

0b1

The IRI supports targeted SGIs with affinity level 0 values of 0 - 255.

No1N, bit [25]

Indicates whether 1 of N SPI interrupts are supported.

No1NMeaning
0b0

1 of N SPI interrupts are supported.

0b1

1 of N SPI interrupts are not supported.

A3V, bit [24]

Affinity 3 valid. Indicates whether the Distributor supports nonzero values of Affinity level 3. Possible values are:

A3VMeaning
0b0

The Distributor only supports zero values of Affinity level 3.

0b1

The Distributor supports nonzero values of Affinity level 3.

IDbits, bits [23:19]

The number of interrupt identifier bits supported, minus one.

DVIS, bit [18]

Indicates whether the implementation supports Direct Virtual LPI injection.

DVISMeaning
0b0

The implementation does not support Direct Virtual LPI injection.

0b1

The implementation supports Direct Virtual LPI injection.

For GICv3, this field is RES0.

LPIS, bit [17]

Indicates whether the implementation supports LPIs.

LPISMeaning
0b0

The implementation does not support LPIs.

0b1

The implementation supports LPIs.

MBIS, bit [16]

Indicates whether the implementation supports message-based interrupts by writing to Distributor registers.

MBISMeaning
0b0

The implementation does not support message-based interrupts by writing to Distributor registers.

The GICD_CLRSPI_NSR, GICD_SETSPI_NSR, GICD_CLRSPI_SR, and GICD_SETSPI_SR registers are reserved.

0b1

The implementation supports message-based interrupts by writing to the GICD_CLRSPI_NSR, GICD_SETSPI_NSR, GICD_CLRSPI_SR, or GICD_SETSPI_SR registers.

num_LPIs, bits [15:11]

Number of supported LPIs.

  • 0b00000 Number of LPIs as indicated by GICD_TYPER.IDbits.

  • All other values Number of LPIs supported is 2^(num_LPIs+1) .

    • Available LPI INTIDs are 8192..(8192 + 2^(num_LPIs+1) - 1).

    • This field cannot indicate a maximum LPI INTID greater than that indicated by GICD_TYPER.IDbits.

When the supported INTID width is less than 14 bits, this field is RES0 and no LPIs are supported.

SecurityExtn, bit [10]

Indicates whether the GIC implementation supports two Security states:

When GICD_CTLR.DS == 1, this field is RAZ.

SecurityExtnMeaning
0b0

The GIC implementation supports only a single Security state.

0b1

The GIC implementation supports two Security states.

Bit [9]

Reserved, RES0.

ESPI, bit [8]

Extended SPI

ESPIMeaning
0b0

Extended SPI range not implemented.

0b1

Extended SPI range implemented.

CPUNumber, bits [7:5]

Reports the number of PEs that can be used when affinity routing is not enabled, minus 1.

These PEs must be numbered contiguously from zero, but the relationship between this number and the affinity hierarchy from MPIDR is IMPLEMENTATION DEFINED. If the implementation does not support ARE being zero, this field is 000.

ITLinesNumber, bits [4:0]

Indicates the maximum SPI INTID that the GIC implementation supports. If the value of this field is N, the maximum SPI INTID is 32(N+1)-1. For example, 00011 specifies that the maximum SPI INTID is 127.

The maximum SPI INTID an implementation might support is 1019 (field value 11111). Regardless of the range of INTIDs defined by this field, interrupt IDs 1020-1023 are reserved for special purposes.

A value of 0 indicates no SPIs are support.

Note

The value derived from this field specifies the maximum number of SPIs that the GIC implementation might support. An implementation might not implement all SPIs up to this maximum.

The ITLinesNumber field only indicates the maximum number of SPIs that the GIC implementation might support. This value determines the number of instances of the following interrupt registers:

The GIC architecture does not require a GIC implementation to support a continuous range of SPI interrupt IDs. Software must check which SPI INTIDs are supported, up to the maximum value indicated by GICD_TYPER.ITLinesNumber.

Accessing the GICD_TYPER

GICD_TYPER can be accessed through the memory-mapped interfaces:

ComponentOffsetInstance
GIC Distributor0x0004GICD_TYPER

This interface is accessible as follows:

  • When GICD_CTLR.DS == 0b0 access to this register is RO.
  • When IsAccessSecure() access to this register is RO.
  • When !IsAccessSecure() access to this register is RO.


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