The ICC_BPR0_EL1 characteristics are:
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.
This register is part of:
AArch64 System register ICC_BPR0_EL1 is architecturally mapped to AArch32 System register ICC_BPR0.
Virtual accesses to this register update ICH_VMCR_EL2.VBPR0.
ICC_BPR0_EL1 is a 32-bit register.
The ICC_BPR0_EL1 bit assignments are:
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 |
0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 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 |
This register can be read using MRS with the following syntax:
MRS <Xt>, <systemreg>
This register can be written using MSR (register) with the following syntax:
MSR <systemreg>, <Xt>
This syntax uses the following encoding in the System instruction encoding space:
<systemreg> | op1 | CRn | CRm | op2 |
---|---|---|---|---|
ICC_BPR0_EL1 | 000 | 1100 | 1000 | 011 |
When HCR_EL2.FMO is set to 1, execution of this encoding at Non-secure EL1 results in an access to ICV_BPR0_EL1.
The register is accessible as follows:
Control | Accessibility | ||||||
---|---|---|---|---|---|---|---|
FMO | IMO | TGE | NS | EL0 | EL1 | EL2 | EL3 |
x | x | x | 0 | - | RW | n/a | RW |
x | x | 1 | 1 | - | n/a | RW | RW |
0 | x | 0 | 1 | - | RW | RW | RW |
1 | x | 0 | 1 | - | ICV_BPR0_EL1 | RW | RW |
This table applies to all instructions that can access this register.
ICC_BPR0_EL1 is only accessible at Non-secure EL1 when HCR_EL2.FMO is set to 0.
When HCR_EL2.FMO is set to 1, at Non-secure EL1, the instruction encoding used to access ICC_BPR0_EL1 results in an access to ICV_BPR0_EL1.
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 ICC_CTLR_EL1.PRIbits and ICC_CTLR_EL3.PRIbits.
An attempt to program the binary point field to a value less than the minimum value sets the field to the minimum value. On a reset, the binary point field is UNKNOWN.
For a description of the prioritization of any generated exceptions, see section D1.13.2 (Synchronous exception prioritization) in the ARM® Architecture Reference Manual, ARMv8, for ARMv8-A architecture profile. Subject to the prioritization rules, the following traps and enables are applicable when accessing this register.
In both Security states, and not dependent on other configuration bits:
If ICC_SRE_EL1.SRE==0, accesses to this register from EL1 are trapped to EL1.
If ICC_SRE_EL2.SRE==0, accesses to this register from EL2 are trapped to EL2.
If ICC_SRE_EL3.SRE==0, accesses to this register from EL3 are trapped to EL3.
When SCR_EL3.NS==1 :
If ICH_HCR_EL2.TALL0==1, Non-secure accesses to this register from EL1 are trapped to EL2.
When EL3 is implemented and is using AArch64 and SCR_EL3.NS==0 :
If SCR_EL3.FIQ==1, Secure accesses to this register from EL1 are trapped to EL3.
When EL3 is implemented and is using AArch64 :
If SCR_EL3.FIQ==1, accesses to this register from EL2 are trapped to EL3.
When EL3 is implemented and is using AArch64 and SCR_EL3.NS==1 :
02/05/2017 15:43
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