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GICR_CTLR, Redistributor Control Register

The GICR_CTLR characteristics are:

Purpose

Controls the operation of a Redistributor, and enables the signaling of LPIs by the Redistributor to the connected PE.

Configuration

Some or all RW fields of this register have defined reset values.

A copy of this register is provided for each Redistributor.

Attributes

GICR_CTLR is a 32-bit register.

Field descriptions

The GICR_CTLR bit assignments are:

313029282726252423222120191817161514131211109876543210
UWPRES0DPG1SDPG1NSDPG0RES0RWPRES0CESEnableLPIs

UWP, bit [31]

Upstream Write Pending. Read-only. Indicates whether all upstream writes have been communicated to the Distributor.

UWPMeaning
0b0

The effects of all upstream writes have been communicated to the Distributor, including any Generate SGI packets.

0b1

Not all the effects of upstream writes, including any Generate SGI packets, have been communicated to the Distributor.

Bits [30:27]

Reserved, RES0.

DPG1S, bit [26]

Disable Processor selection for Group 1 Secure interrupts. When GICR_TYPER.DPGS == 1:

DPG1SMeaning
0b0

A Group 1 Secure SPI configured to use the 1 of N distribution model can select this PE, if the PE is not asleep and if Secure Group 1 interrupts are enabled.

0b1

A Group 1 Secure SPI configured to use the 1 of N distribution model cannot select this PE.

When GICR_TYPER.DPGS == 0 this bit is RAZ/WI.

When GICD_CTLR.DS==1, this field is RAZ/WI. In GIC implementations that support two Security states, this field is only accessible by Secure accesses, and is RAZ/WI to Non-secure accesses.

It is IMPLEMENTATION DEFINED whether this bits affect the selection of PEs for interrupts using the 1 of N distribution model when GICD_CTLR.ARE_S==0.

This field resets to 0.

DPG1NS, bit [25]

Disable Processor selection for Group 1 Non-secure interrupts. When GICR_TYPER.DPGS == 1:

DPG1NSMeaning
0b0

A Group 1 Non-secure SPI configured to use the 1 of N distribution model can select this PE, if the PE is not asleep and if Non-secure Group 1 interrupts are enabled.

0b1

A Group 1 Non-secure SPI configured to use the 1 of N distribution model cannot select this PE.

When GICR_TYPER.DPGS == 0 this bit is RAZ/WI.

It is IMPLEMENTATION DEFINED whether this bits affect the selection of PEs for interrupts using the 1 of N distribution model when GICD_CTLR.ARE_NS==0.

This field resets to 0.

DPG0, bit [24]

Disable Processor selection for Group 0 interrupts. When GICR_TYPER.DPGS == 1:

DPG0Meaning
0b0

A Group 0 SPI configured to use the 1 of N distribution model can select this PE, if the PE is not asleep and if Group 0 interrupts are enabled.

0b1

A Group 0 SPI configured to use the 1 of N distribution model cannot select this PE.

When GICR_TYPER.DPGS == 0 this bit is RAZ/WI.

When GICD_CTLR.DS==1, this field is always accessible. In GIC implementations that support two Security states, this field is RAZ/WI to Non-secure accesses.

It is IMPLEMENTATION DEFINED whether this bits affect the selection of PEs for interrupts using the 1 of N distribution model when GICD_CTLR.ARE_S==0.

This field resets to 0.

Bits [23:4]

Reserved, RES0.

RWP, bit [3]

Register Write Pending. This bit indicates whether a register write for the current Security state is in progress or not.

RWPMeaning
0b0

The effect of all previous writes to the following registers are visible to all agents in the system:

0b1

The effect of all previous writes to the following registers are not guaranteed by the architecture to be visible yet to the all agents in the system as the changes are still being propagated:

Bit [2]

Reserved, RES0.

CES, bit [1]

Clear Enable Supported:

CESMeaning
0b0

The IRI does not indicate whether GICR_CTLR.EnableLPIs is RES1 once set.

0b1

GICR_CTLR.EnableLPIs is not RES1 once set.

Implementing GICR_CTLR.EnableLPIs as programmable and not reporting CES == 1 is deprecated.

Implementing GICR_CTLR.EnableLPIs as RES1 once set is deprecated.

When GICR_CLTR.CES == 0, software cannot assume that GICR_CTLR.EnableLPIs is programmable without observing the bit being cleared.

EnableLPIs, bit [0]

In implementations where affinity routing is enabled for the Security state:

EnableLPIsMeaning
0b0

LPI support is disabled. Any doorbell interrupt generated as a result of a write to a virtual LPI register must be discarded, and any ITS translation requests or commands involving LPIs in this Redistributor are ignored.

0b1

LPI support is enabled.

Note

If GICR_TYPER.LPIS == 0, this field is RES0. If GICD_CTLR.ARE_NS is written from 1 to 0 when this bit is 1, behavior is an IMPLEMENTATION DEFINED choice between clearing GICR_CTLR.EnableLPIs to 0 or maintaining its current value.

When affinity routing is not enabled for the Non-secure state, this bit is RES0.

When written from 0 to 1, the Redistributor loads the LPI Pending table from memory to check for any pending interrupts.

After it has been written to 1, it is IMPLEMENTATION DEFINED whether the bit becomes RES1 or can be cleared by to 0.

Where the bit remains programmable:

  • Software must observe GICR_CTLR.RWP==0 after clearing GICR_CTLR.EnableLPIs from 1 to 0 before writing GICR_PENDBASER or GICR_PROPBASER, otherwise behavior is UNPREDICTABLE.
  • Software must observe GICR_CTLR.RWP==0 after clearing GICR_CTLR.EnableLPIs from 1 to 0 before setting GICR_CTLR.EnableLPIs to 1, otherwise behavior is UNPREDICTABLE.
Note

If one or more ITS is implemented, Arm strongly recommends that all LPIs are mapped to another Redistributor before GICR_CTLR.EnableLPIs is cleared to 0.

This field resets to 0.

The participation of a PE in the 1 of N distribution model for a given interrupt group is governed by the concatenation of GICR_WAKER.ProcessorSleep, the appropriate GICR_CTLR.DPG{1, 0} bit, and the PE interrupt group enable. The behavior options are:

PSDPG{1S, 1NS, 0}EnablePE Behavior
0b00b00b0The PE cannot be selected.
0b00b00b1The PE can be selected.
0b00b1*The PE cannot be selected.
0b1**The PE cannot be selected when GICD_CTLR.E1NWF == 0. When GICD_CTLR.E1NWF == 1, the mechanism by which PEs are selected is IMPLEMENTATION DEFINED.

If an SPI using the 1 of N distribution model has been forwarded to the PE and a write to GICR_CTLR occurs that changes the DPG bit for the interrupt group of the SPI, the IRI must attempt to select a different target PE for the SPI. This might have no effect on the forwarded SPI if it has already been activated.

Accessing the GICR_CTLR

GICR_CTLR can be accessed through the memory-mapped interfaces:

ComponentFrameOffsetInstance
GIC RedistributorRD_base0x0000GICR_CTLR

This interface is accessible as follows:

  • When GICD_CTLR.DS == 0b0 accesses to this register are RW.
  • When IsAccessSecure() accesses to this register are RW.
  • When !IsAccessSecure() accesses to this register are RW.


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