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PMLSR, Performance Monitors Lock Status Register

The PMLSR characteristics are:

Purpose

Indicates the current status of the software lock for Performance Monitors registers.

The optional Software Lock provides a lock to prevent memory-mapped writes to the Performance Monitors registers. Use of this lock mechanism reduces the risk of accidental damage to the contents of the Performance Monitors registers. It does not, and cannot, prevent all accidental or malicious damage.

Configuration

If ARMv8.3-DoPD is implemented, Software Lock is not implemented by the architecturally-defined debug components of the PE in the Core power domain.

If ARMv8.3-DoPD is not implemented, this register is in the Debug power domain.

Software uses PMLAR to set or clear the lock, and PMLSR to check the current status of the lock.

Attributes

PMLSR is a 32-bit register.

Field descriptions

The PMLSR bit assignments are:

313029282726252423222120191817161514131211109876543210
RES0nTTSLKSLI

Bits [31:3]

Reserved, RES0.

nTT, bit [2]

Not thirty-two bit access required. RAZ.

SLK, bit [1]

When Software Lock is implemented and ARMv8.3-DoPD is not implemented:

Software Lock status for this component. For an access to LSR that is not a memory-mapped access, or when Software Lock is not implemented, this field is RES0.

For memory-mapped accesses when Software Lock is implemented, possible values of this field are:

SLKMeaning
0b0

Lock clear. Writes are permitted to this component's registers.

0b1

Lock set. Writes to this component's registers are ignored, and reads have no side effects.

The following resets apply:

  • On a Cold reset, the value of this field is unchanged.

  • On an External debug reset, this field resets to 1.

  • On a Warm reset, the value of this field is unchanged.


Otherwise:

Reserved, RAZ.

SLI, bit [0]

Software Lock implemented. For an access to LSR that is not a memory-mapped access, this field is RAZ. For memory-mapped accesses, the value of this field is IMPLEMENTATION DEFINED. Permitted values are:

SLIMeaning
0b0

Software Lock not implemented or not memory-mapped access.

0b1

Software Lock implemented and memory-mapped access.

Accessing the PMLSR

PMLSR can be accessed through the memory-mapped interfaces:

ComponentOffsetInstance
PMU0xFB4PMLSR

This interface is accessible as follows:

  • When ARMv8.3-DoPD is not implemented or IsCorePowered() accesses to this register are RO.
  • Otherwise accesses to this register generate an error response.