4.3.3. Multiprocessor Affinity Register

The MPIDR characteristics are:

Purpose

Provides an additional processor identification mechanism for scheduling purposes in a multiprocessor system.

Usage constraints

The MPIDR is only accessible in privileged mode.

Configurations

Available in all configurations. The value of the U bit, bit [30], indicates a multiprocessor or a uniprocessor configuration.

Attributes

See the register summary in Table 4.2.

Figure 4.3 shows the MPIDR bit assignments.

Figure 4.3. MPIDR bit assignments

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Table 4.20 shows the MPIDR bit assignments.

Table 4.20. MPIDR bit assignments

BitsNameFunction
[31]-Indicates the register uses the new multiprocessor format. This is always 1.
[30]U bit

Multiprocessing Extensions:

Set to 0

Processor is part of a multiprocessor cluster.

[29:12]ReservedSBZ.
[11:8]Cluster ID

Value read in CLUSTERID configuration inputs. It identifies a Cortex-R7 processor in a system with more than one Cortex-R7 processor present.

[7:1]ReservedSBZ.
[0]CPU ID

Indicates the processor number in the Cortex-R7 MPCore configuration:

0x0

Processor 0.

0x1

Processor 1.


To access the MPIDR, read the CP15 register with:

MRC p15,0,<Rd>,c0,c0,5; read Multiprocessor ID register
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