The ICV_BPR1_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 virtual Group 1 interrupt preemption.
This register is part of:
AArch64 System register ICV_BPR1_EL1 is architecturally mapped to AArch32 System register ICV_BPR1.
ICV_BPR1_EL1 is a 32-bit register.
The ICV_BPR1_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.
If the GIC is configured to use separate binary point fields for virtual Group 0 and virtual 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. This is done as follows:
Binary point value | Group priority field | Subpriority field | Field with binary point |
---|---|---|---|
0 | - | - | - |
1 | [7:1] | [0] | ggggggg.s |
2 | [7:2] | [1:0] | gggggg.ss |
3 | [7:3] | [2:0] | ggggg.sss |
4 | [7:4] | [3:0] | gggg.ssss |
5 | [7:5] | [4:0] | ggg.sssss |
6 | [7:6] | [5:0] | gg.ssssss |
7 | [7] | [6:0] | g.sssssss |
Writing 0 to this field will set this field to its reset value, which is IMPLEMENTATION DEFINED and non-zero.
If ICV_CTLR_EL1.CBPR is set to 1, Non-secure EL1 reads return ICV_BPR0_EL1 + 1 saturated to 0b111. Non-secure EL1 writes are ignored.
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> | op0 | op1 | CRn | CRm | op2 |
---|---|---|---|---|---|
ICC_BPR1_EL1 | 11 | 000 | 1100 | 1100 | 011 |
When HCR_EL2.IMO is set to 0, execution of this encoding at Non-secure EL1 results in an access to ICC_BPR1_EL1.
The register is accessible as follows:
Control | Accessibility | ||||||
---|---|---|---|---|---|---|---|
FMO | IMO | TGE | NS | EL0 | EL1 | EL2 | EL3 |
x | x | x | 0 | - | ICC_BPR1_EL1 | n/a | ICC_BPR1_EL1 |
x | x | 1 | 1 | - | n/a | ICC_BPR1_EL1 | ICC_BPR1_EL1 |
x | 0 | 0 | 1 | - | ICC_BPR1_EL1 | ICC_BPR1_EL1 | ICC_BPR1_EL1 |
x | 1 | 0 | 1 | - | RW | ICC_BPR1_EL1 | ICC_BPR1_EL1 |
This table applies to all instructions that can access this register.
ICV_BPR1_EL1 is only accessible at Non-secure EL1 when HCR_EL2.IMO is set to 1.
When HCR_EL2.IMO is set to 0, at Non-secure EL1, the instruction encoding used to access ICV_BPR1_EL1 results in an access to ICC_BPR1_EL1.
The reset value is IMPLEMENTATION DEFINED, but is equal to the minimum value of ICV_BPR0_EL1 plus one.
An attempt to program the binary point field to a value less than the reset value sets the field to the reset value.
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, Non-secure accesses to this register from EL1 are trapped to EL1.
When SCR_EL3.NS==1 :
If ICH_HCR_EL2.TALL1==1, Non-secure accesses to this register from EL1 are trapped to EL2.
28/09/2017 08:24
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