Interrupt Controller Binary Point Register 0
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 0 interrupt preemption.
AArch64 System register ICC_BPR0_EL1 bits [31:0] are architecturally mapped to AArch32 System register ICC_BPR0[31:0].
This register is present only when (GICv3 is implemented or FEAT_GCIE_LEGACY is implemented) and FEAT_AA64 is implemented. Otherwise, direct accesses to ICC_BPR0_EL1 are UNDEFINED.
Virtual accesses to this register update ICH_VMCR_EL2.VBPR0.
ICC_BPR0_EL1 is a 64-bit register.
| 63 | 62 | 61 | 60 | 59 | 58 | 57 | 56 | 55 | 54 | 53 | 52 | 51 | 50 | 49 | 48 | 47 | 46 | 45 | 44 | 43 | 42 | 41 | 40 | 39 | 38 | 37 | 36 | 35 | 34 | 33 | 32 |
| 31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | 22 | 21 | 20 | 19 | 18 | 17 | 16 | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| RES0 | |||||||||||||||||||||||||||||||
| RES0 | BinaryPoint | ||||||||||||||||||||||||||||||
Reserved, RES0.
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. This is done as follows:
| Binary point value | Group priority field | Subpriority field | Field with binary point |
|---|---|---|---|
| 0 | [7:1] | [0] | ggggggg.s |
| 1 | [7:2] | [1:0] | gggggg.ss |
| 2 | [7:3] | [2:0] | ggggg.sss |
| 3 | [7:4] | [3:0] | gggg.ssss |
| 4 | [7:5] | [4:0] | ggg.sssss |
| 5 | [7:6] | [5:0] | gg.ssssss |
| 6 | [7] | [6:0] | g.sssssss |
| 7 | No preemption | [7:0] | .ssssssss |
The reset behavior of this field is:
The minimum binary point value is derived from the number of implemented priority bits. The number of priority bits is IMPLEMENTATION DEFINED, and reported by:
On a reset, the binary point field is UNKNOWN.
Accesses to this register use the following encodings in the System register encoding space:
MRS <Xt>, ICC_BPR0_EL1
(op0 = 0b11, op1 = 0b000, CRn = 0b1100, CRm = 0b1000, op2 = 0b011)
if !((IsFeatureImplemented(FEAT_GICv3) || IsFeatureImplemented(FEAT_GCIE_LEGACY)) && IsFeatureImplemented(FEAT_AA64)) then Undefined(); elsif HaveEL(EL3) && !(EffectivelyAtEL0InHost() || EffectivelyAtEL0NotInHost() || PSTATE.EL == EL3) && EL3SDDUndefPriority() && SCR_EL3().FIQ == '1' then Undefined(); elsif PSTATE.EL == EL0 then Undefined(); elsif PSTATE.EL == EL1 then if IsFeatureImplemented(FEAT_GCIE_LEGACY) && (ICH_VCTLR_EL2().V3 == '0' || !EL2Enabled() || !(ICH_HCR_EL2().TALL0 == '1' || HCR_EL2().FMO == '1')) then Undefined(); elsif ICC_SRE_EL1().SRE == '0' then AArch64_SystemAccessTrap(EL1, 0x18); elsif EL2Enabled() && ICH_HCR_EL2().TALL0 == '1' then AArch64_SystemAccessTrap(EL2, 0x18); elsif EL2Enabled() && HCR_EL2().FMO == '1' then X{64}(t) = ICV_BPR0_EL1(); elsif HaveEL(EL3) && SCR_EL3().FIQ == '1' then if EL3SDDUndef() then Undefined(); else AArch64_SystemAccessTrap(EL3, 0x18); end; else X{64}(t) = ICC_BPR0_EL1(); end; elsif PSTATE.EL == EL2 then if IsFeatureImplemented(FEAT_GCIE_LEGACY) then Undefined(); elsif ICC_SRE_EL2().SRE == '0' then AArch64_SystemAccessTrap(EL2, 0x18); elsif HaveEL(EL3) && SCR_EL3().FIQ == '1' then if EL3SDDUndef() then Undefined(); else AArch64_SystemAccessTrap(EL3, 0x18); end; else X{64}(t) = ICC_BPR0_EL1(); end; elsif PSTATE.EL == EL3 then if IsFeatureImplemented(FEAT_GCIE_LEGACY) then Undefined(); elsif ICC_SRE_EL3().SRE == '0' then AArch64_SystemAccessTrap(EL3, 0x18); else X{64}(t) = ICC_BPR0_EL1(); end; end;
MSR ICC_BPR0_EL1, <Xt>
(op0 = 0b11, op1 = 0b000, CRn = 0b1100, CRm = 0b1000, op2 = 0b011)
if !((IsFeatureImplemented(FEAT_GICv3) || IsFeatureImplemented(FEAT_GCIE_LEGACY)) && IsFeatureImplemented(FEAT_AA64)) then Undefined(); elsif HaveEL(EL3) && !(EffectivelyAtEL0InHost() || EffectivelyAtEL0NotInHost() || PSTATE.EL == EL3) && EL3SDDUndefPriority() && SCR_EL3().FIQ == '1' then Undefined(); elsif PSTATE.EL == EL0 then Undefined(); elsif PSTATE.EL == EL1 then if IsFeatureImplemented(FEAT_GCIE_LEGACY) && (ICH_VCTLR_EL2().V3 == '0' || !EL2Enabled() || !(ICH_HCR_EL2().TALL0 == '1' || HCR_EL2().FMO == '1')) then Undefined(); elsif ICC_SRE_EL1().SRE == '0' then AArch64_SystemAccessTrap(EL1, 0x18); elsif EL2Enabled() && ICH_HCR_EL2().TALL0 == '1' then AArch64_SystemAccessTrap(EL2, 0x18); elsif EL2Enabled() && HCR_EL2().FMO == '1' then ICV_BPR0_EL1() = X{64}(t); elsif HaveEL(EL3) && SCR_EL3().FIQ == '1' then if EL3SDDUndef() then Undefined(); else AArch64_SystemAccessTrap(EL3, 0x18); end; else ICC_BPR0_EL1() = X{64}(t); end; elsif PSTATE.EL == EL2 then if IsFeatureImplemented(FEAT_GCIE_LEGACY) then Undefined(); elsif ICC_SRE_EL2().SRE == '0' then AArch64_SystemAccessTrap(EL2, 0x18); elsif HaveEL(EL3) && SCR_EL3().FIQ == '1' then if EL3SDDUndef() then Undefined(); else AArch64_SystemAccessTrap(EL3, 0x18); end; else ICC_BPR0_EL1() = X{64}(t); end; elsif PSTATE.EL == EL3 then if IsFeatureImplemented(FEAT_GCIE_LEGACY) then Undefined(); elsif ICC_SRE_EL3().SRE == '0' then AArch64_SystemAccessTrap(EL3, 0x18); else ICC_BPR0_EL1() = X{64}(t); end; end;
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