ICC_BPR1

Defines the point at which the priority value fields split into two parts, the group priority field and the subpriority field. The group priority field determines Group 1 interrupt preemption.

Configuration

AArch32 System register ICC_BPR1 bits [31:0] (ICC_BPR1_S) are architecturally mapped to AArch64 System register ICC_BPR1_EL1[31:0] (ICC_BPR1_EL1_S).

AArch32 System register ICC_BPR1 bits [31:0] (ICC_BPR1_NS) are architecturally mapped to AArch64 System register ICC_BPR1_EL1[31:0] (ICC_BPR1_EL1_NS).

This register is present only when EL1 is capable of using AArch32 and GICv3 is implemented. Otherwise, direct accesses to ICC_BPR1 are UNDEFINED.

Attributes

Field descriptions

Bits [31:3]

BinaryPoint, bits [2:0]

If the GIC is configured to use separate binary point fields for Group 0 and Group 1 interrupts, the value of this field controls how the 8-bit interrupt priority field is split into a group priority field, that determines interrupt preemption, and a subpriority field. For more information about priorities, see 'Priority grouping' in ARM® Generic Interrupt Controller Architecture Specification, GIC architecture version 3.0 and version 4.0 (ARM IHI 0069).

Writing 0 to this field will set this field to its reset value.

If EL3 is implemented and ICC_MCTLR.CBPR_EL1S is 1:

Accesses to this register at EL3 not in Monitor mode access the state of ICC_BPR0.
When SCR_EL3.EEL2 is 1 and HCR_EL2.IMO is 1, Secure accesses to this register at EL1 access the state of ICV_BPR1.
Otherwise, Secure accesses to this register at EL1 access the state of ICC_BPR0.

If EL3 is implemented and ICC_MCTLR.CBPR_EL1NS is 1, Non-secure accesses to this register at EL1 or EL2 behave as follows, depending on the values of HCR.IMO and SCR.IRQ:

HCR.IMO	SCR_IRQ	Behavior
0b0	0b0	Non-secure EL1 and EL2 reads return ICC_BPR0 + 1 saturated to 0b111. Non-secure EL1 and EL2 writes are ignored.
0b0	0b1	Non-secure EL1 and EL2 accesses trap to EL3.
0b1	0b0	Non-secure EL1 accesses affect virtual interrupts. Non-secure EL2 reads return ICC_BPR0 + 1 saturated to 0b111. Non-secure EL2 writes ignored.
0b1	0b1	Non-secure EL1 accesses affect virtual interrupts. Non-secure EL2 accesses trap to EL3.

If EL3 is not implemented and ICC_CTLR.CBPR is 1, Non-secure accesses to this register at EL1 or EL2 behave as follows, depending on the values of HCR.IMO:

HCR.IMO	Behavior
0b0	Non-secure EL1 and EL2 reads return ICC_BPR0 + 1 saturated to 0b111. Non-secure EL1 and EL2 writes are ignored.
0b1	Non-secure EL1 accesses affect virtual interrupts. Non-secure EL2 reads return ICC_BPR0 + 1 saturated to 0b111. Non-secure EL2 writes are ignored.

This field resets to an IMPLEMENTATION DEFINED nonzero value.

Accessing ICC_BPR1

When the PE resets into an Exception level that is using AArch32, the reset value is equal to:

For the Secure copy of the register, the minimum value of ICC_BPR0 plus one.
For the Non-secure copy of the register, the minimum value of ICC_BPR0.

Where the minimum value of ICC_BPR0 is IMPLEMENTATION DEFINED.

If EL3 is not implemented:

If the PE is Secure this reset value is (minimum value of ICC_BPR0 plus one).
If the PE is Non-secure this reset value is (minimum value of ICC_BPR0).

An attempt to program the binary point field to a value less than the reset value sets the field to the reset value.

Accesses to this register use the following encodings in the System register encoding space:

MRC{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <CRn>, <CRm>{, {#}<opc2>}

coproc	opc1	CRn	CRm	opc2
0b1111	0b000	0b1100	0b1100	0b011

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if HaveEL(EL3) && EL3SDDUndefPriority() && !ELUsingAArch32(EL3) && SCR_EL3.IRQ == '1' then UNDEFINED; elsif HaveEL(EL3) && EL3SDDUndefPriority() && ELUsingAArch32(EL3) && PSTATE.M != M32_Monitor && SCR.IRQ == '1' then UNDEFINED; elsif EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T12 == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T12 == '1' then AArch32.TakeHypTrapException(0x03); elsif ICC_SRE.SRE == '0' then UNDEFINED; elsif EL2Enabled() && !ELUsingAArch32(EL2) && ICH_HCR_EL2.TALL1 == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && ELUsingAArch32(EL2) && ICH_HCR.TALL1 == '1' then AArch32.TakeHypTrapException(0x03); elsif EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.IMO == '1' then R[t] = ICV_BPR1; elsif EL2Enabled() && ELUsingAArch32(EL2) && HCR.IMO == '1' then R[t] = ICV_BPR1; elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && SCR_EL3.IRQ == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.AArch32SystemAccessTrap(EL3, 0x03); elsif HaveEL(EL3) && ELUsingAArch32(EL3) && PSTATE.M != M32_Monitor && SCR.IRQ == '1' then if EL3SDDUndef() then UNDEFINED; else AArch32.TakeMonitorTrapException(); elsif HaveEL(EL3) then R[t] = ICC_BPR1_NS; else R[t] = ICC_BPR1; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && EL3SDDUndefPriority() && !ELUsingAArch32(EL3) && SCR_EL3.IRQ == '1' then UNDEFINED; elsif HaveEL(EL3) && EL3SDDUndefPriority() && ELUsingAArch32(EL3) && SCR.IRQ == '1' then UNDEFINED; elsif ICC_HSRE.SRE == '0' then UNDEFINED; elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && SCR_EL3.IRQ == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.AArch32SystemAccessTrap(EL3, 0x03); elsif HaveEL(EL3) && ELUsingAArch32(EL3) && SCR.IRQ == '1' then if EL3SDDUndef() then UNDEFINED; else AArch32.TakeMonitorTrapException(); elsif HaveEL(EL3) then R[t] = ICC_BPR1_NS; else R[t] = ICC_BPR1; elsif PSTATE.EL == EL3 then if ICC_MSRE.SRE == '0' then UNDEFINED; else if SCR.NS == '0' then R[t] = ICC_BPR1_S; else R[t] = ICC_BPR1_NS;

MCR{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <CRn>, <CRm>{, {#}<opc2>}

coproc	opc1	CRn	CRm	opc2
0b1111	0b000	0b1100	0b1100	0b011

if PSTATE.EL == EL0 then UNDEFINED; elsif PSTATE.EL == EL1 then if HaveEL(EL3) && EL3SDDUndefPriority() && !ELUsingAArch32(EL3) && SCR_EL3.IRQ == '1' then UNDEFINED; elsif HaveEL(EL3) && EL3SDDUndefPriority() && ELUsingAArch32(EL3) && PSTATE.M != M32_Monitor && SCR.IRQ == '1' then UNDEFINED; elsif EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T12 == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T12 == '1' then AArch32.TakeHypTrapException(0x03); elsif ICC_SRE.SRE == '0' then UNDEFINED; elsif EL2Enabled() && !ELUsingAArch32(EL2) && ICH_HCR_EL2.TALL1 == '1' then AArch64.AArch32SystemAccessTrap(EL2, 0x03); elsif EL2Enabled() && ELUsingAArch32(EL2) && ICH_HCR.TALL1 == '1' then AArch32.TakeHypTrapException(0x03); elsif EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.IMO == '1' then ICV_BPR1 = R[t]; elsif EL2Enabled() && ELUsingAArch32(EL2) && HCR.IMO == '1' then ICV_BPR1 = R[t]; elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && SCR_EL3.IRQ == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.AArch32SystemAccessTrap(EL3, 0x03); elsif HaveEL(EL3) && ELUsingAArch32(EL3) && PSTATE.M != M32_Monitor && SCR.IRQ == '1' then if EL3SDDUndef() then UNDEFINED; else AArch32.TakeMonitorTrapException(); elsif HaveEL(EL3) then ICC_BPR1_NS = R[t]; else ICC_BPR1 = R[t]; elsif PSTATE.EL == EL2 then if HaveEL(EL3) && EL3SDDUndefPriority() && !ELUsingAArch32(EL3) && SCR_EL3.IRQ == '1' then UNDEFINED; elsif HaveEL(EL3) && EL3SDDUndefPriority() && ELUsingAArch32(EL3) && SCR.IRQ == '1' then UNDEFINED; elsif ICC_HSRE.SRE == '0' then UNDEFINED; elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && SCR_EL3.IRQ == '1' then if EL3SDDUndef() then UNDEFINED; else AArch64.AArch32SystemAccessTrap(EL3, 0x03); elsif HaveEL(EL3) && ELUsingAArch32(EL3) && SCR.IRQ == '1' then if EL3SDDUndef() then UNDEFINED; else AArch32.TakeMonitorTrapException(); elsif HaveEL(EL3) then ICC_BPR1_NS = R[t]; else ICC_BPR1 = R[t]; elsif PSTATE.EL == EL3 then if ICC_MSRE.SRE == '0' then UNDEFINED; else if SCR.NS == '0' then ICC_BPR1_S = R[t]; else ICC_BPR1_NS = R[t];

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RES0																													BinaryPoint

ICC_BPR1, Interrupt Controller Binary Point Register 1

Purpose