TRBDEVAFF

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TRBDEVAFF, Device Affinity Register

Purpose

Reads the same value as the MPIDR_EL1 register for the PE that this trace buffer has affinity with.

Depending on the IMPLEMENTATION DEFINED nature of the system, it might be possible that TRBDEVAFF is read before system firmware has configured the trace buffer and/or the PE or group of PEs that the trace buffer has affinity with. When this is the case, TRBDEVAFF reads as zero.

Configuration

This register is present only when FEAT_TRBE_EXT is implemented. Otherwise, direct accesses to TRBDEVAFF are RES0.

Attributes

Field descriptions

Bits [63:40]

Aff3, bits [39:32]

Affinity level 3. See the description of Aff0 for more information.

This field has an IMPLEMENTATION DEFINED value.

Access to this field is RO.

Bit [31]

U, bit [30]

Indicates a Uniprocessor system, as distinct from PE 0 in a multiprocessor system.

The value of this field is an IMPLEMENTATION DEFINED choice of:

U	Meaning
0b0	Processor is part of a multiprocessor system.
0b1	Processor is part of a uniprocessor system.

Access to this field is RO.

Bits [29:25]

MT, bit [24]

Indicates whether the lowest level of affinity consists of logical PEs that are implemented using an interdependent approach, such as multithreading. See the description of Aff0 for more information about affinity levels.

The value of this field is an IMPLEMENTATION DEFINED choice of:

MT	Meaning
0b0	Performance of PEs with different affinity level 0 values, and the same values for affinity level 1 and higher, is largely independent.
0b1	Performance of PEs with different affinity level 0 values, and the same values for affinity level 1 and higher, is very interdependent.

Note

This field does not indicate that multithreading is implemented and does not indicate that PEs with different affinity level 0 values, and the same values for affinity level 1 and higher are implemented.

Access to this field is RO.

Aff2, bits [23:16]

Affinity level 2. See the description of Aff0 for more information.

This field has an IMPLEMENTATION DEFINED value.

Access to this field is RO.

Aff1, bits [15:8]

Affinity level 1. See the description of Aff0 for more information.

This field has an IMPLEMENTATION DEFINED value.

Access to this field is RO.

Aff0, bits [7:0]

Affinity level 0. The value of the MPIDR.{Aff2, Aff1, Aff0} or MPIDR_EL1.{Aff3, Aff2, Aff1, Aff0} set of fields of each PE must be unique within the system as a whole.

This field has an IMPLEMENTATION DEFINED value.

Access to this field is RO.

Accessing TRBDEVAFF

TRBDEVAFF can be accessed through the external debug interface:

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																								Aff3
RAO/WI	U	RES0					MT	Aff2								Aff1								Aff0