You copied the Doc URL to your clipboard.

PMCR_EL0, Performance Monitors Control Register

The PMCR_EL0 characteristics are:

Purpose

Provides details of the Performance Monitors implementation, including the number of counters implemented, and configures and controls the counters.

Configuration

AArch64 System register PMCR_EL0 bits [31:0] are architecturally mapped to AArch32 System register PMCR[31:0] .

AArch64 System register PMCR_EL0 bits [7:0] are architecturally mapped to External register PMCR_EL0[7:0] .

This register is in the Warm reset domain. Some or all RW fields of this register have defined reset values. On a Warm or Cold reset these apply only if the PE resets into an Exception level that is using AArch64. Otherwise, on a Warm or Cold reset RW fields in this register reset to architecturally UNKNOWN values.

Attributes

PMCR_EL0 is a 64-bit register.

Field descriptions

The PMCR_EL0 bit assignments are:

6362616059585756555453525150494847464544434241403938373635343332
RES0
IMPIDCODENRES0LPLCDPXDCPE
313029282726252423222120191817161514131211109876543210

Bits [63:32]

Reserved, RES0.

IMP, bits [31:24]

Implementer code. This field is RO with an IMPLEMENTATION DEFINED value.

If this field is zero, then PMCR_EL0.IDCODE is RES0 and software must use the MIDR_EL1 to identify the PE.

Otherwise, this field and PMCR_EL0.IDCODE identifies the PMU implementation to software. The implementer codes are allocated by Arm. A non-zero value has the same interpretation as MIDR_EL1.Implementer.

IDCODE, bits [23:16]

When PMCR_EL0.IMP != 0x00:

Identification code. This field is RO with an IMPLEMENTATION DEFINED value.

Each implementer must maintain a list of identification codes that are specific to the implementer. A specific implementation is identified by the combination of the implementer code and the identification code.


Otherwise:

Reserved, RES0.

N, bits [15:11]

An RO field that indicates the number of event counters implemented. This value is in the range of 0b00000-0b111111. If the value is 0b00000 then only PMCCNTR_EL0 is implemented. If the value is 0b111111 PMCCNTR_EL0 and 31 event counters are implemented.

When EL2 is implemented and enabled for the current Security state, reads of this field from EL1 and EL0 return the value of MDCR_EL2.HPMN.

Access to this field is RO.

Bits [10:8]

Reserved, RES0.

LP, bit [7]

When ARMv8.5-PMU is implemented:

Long event counter enable. Determines when unsigned overflow is recorded by a counter overflow bit.

LPMeaning
0b0

Event counter overflow on increment that causes unsigned overflow of PMEVCNTR<n>_EL0[31:0].

0b1

Event counter overflow on increment that causes unsigned overflow of PMEVCNTR<n>_EL0[63:0].

If EL2 is implemented and MDCR_EL2.HPMN or HDCR.HPMN is less than PMCR_EL0.N, this bit does not affect the operation of event counters in the range [HDCR.HPMN:(PMCR_EL0.N-1)] or [MDCR_EL2.HPMN:(PMCR_EL0.N-1)].

Note

The effect of MDCR_EL2.HPMN or HDCR.HPMN on the operation of this bit applies if EL2 is implemented regardless of whether EL2 is enabled in the current Security state. For more information, see the description of MDCR_EL2.HPMN or HDCR.HPMN.

On a Warm reset, this field resets to an architecturally UNKNOWN value.


Otherwise:

Reserved, RES0.

LC, bit [6]

Long cycle counter enable. Determines when unsigned overflow is recorded by the cycle counter overflow bit.

LCMeaning
0b0

Cycle counter overflow on increment that causes unsigned overflow of PMCCNTR_EL0[31:0].

0b1

Cycle counter overflow on increment that causes unsigned overflow of PMCCNTR_EL0[63:0].

Arm deprecates use of PMCR_EL0.LC = 0.

In an AArch64 only implementation, this field is RES1.

On a Warm reset, this field resets to an architecturally UNKNOWN value.

DP, bit [5]

Disable cycle counter when event counting is prohibited. The possible values of this bit are:

DPMeaning
0b0

Cycle counting by PMCCNTR_EL0 is not affected by this bit.

0b1

When event counting for counters in the range [0..(MDCR_EL2.HPMN-1)] is prohibited, cycle counting by PMCCNTR_EL0 is disabled.

For more information about the interaction between the Performance Monitors and EL3, see 'Effect of EL3 and EL2' in the Arm® Architecture Reference Manual, Armv8, for Armv8-A architecture profile.

When EL3 is not implemented, this field is RES0:

  • When ARMv8.1-PMU is not implemented.
  • When ARMv8.1-PMU is implemented, only if EL2 is not implemented.

Otherwise this field is RW.

On a Warm reset, this field resets to an architecturally UNKNOWN value.

X, bit [4]

Enable export of events in an IMPLEMENTATION DEFINED event stream. The possible values of this bit are:

XMeaning
0b0

Do not export events.

0b1

Export events where not prohibited.

This field enables the exporting of events over an event bus to another device, for example to an OPTIONAL PE trace unit. If the implementation does not include such an event bus then this field is RAZ/WI, otherwise it is an RW field.

In an implementation that includes an event bus, no events are exported when counting is prohibited.

This field does not affect the generation of Performance Monitors overflow interrupt requests or signaling to a cross-trigger interface (CTI) that can be implemented as signals exported from the PE.

On a Warm reset, this field resets to an architecturally UNKNOWN value.

D, bit [3]

Clock divider. The possible values of this bit are:

DMeaning
0b0

When enabled, PMCCNTR_EL0 counts every clock cycle.

0b1

When enabled, PMCCNTR_EL0 counts once every 64 clock cycles.

In an AArch64 only implementation this field is RES0, otherwise it is an RW field. If PMCR_EL0.LC == 1, this bit is ignored and the cycle counter counts every clock cycle.

Arm deprecates use of PMCR_EL0.D = 1.

On a Warm reset, this field resets to an architecturally UNKNOWN value.

C, bit [2]

Cycle counter reset. This bit is WO. The effects of writing to this bit are:

CMeaning
0b0

No action.

0b1

Reset PMCCNTR_EL0 to zero.

This bit is always RAZ.

Note

Resetting PMCCNTR_EL0 does not change the cycle counter overflow bit.

P, bit [1]

Event counter reset. This bit is WO. The effects of writing to this bit are:

PMeaning
0b0

No action.

0b1

Reset all event counters accessible in the current Exception level, not including PMCCNTR_EL0, to zero.

This bit is always RAZ.

In EL0 and EL1:

  • If EL2 is implemented and enabled in the current Security state, and MDCR_EL2.HPMN is less than PMCR_EL0.N, a write of 1 to this bit does not reset event counters in the range [MDCR_EL2.HPMN:(PMCR_EL0.N-1)].
  • If EL2 is not implemented, EL2 is disabled in the current Security state, or MDCR_EL2.HPMN equals PMCR_EL0.N, a write of 1 to this bit resets all the event counters.

In EL2 and EL3, a write of 1 to this bit resets all the event counters.

Note

Resetting the event counters does not change the event counter overflow bits.

If ARMv8.5-PMU is implemented, the value of MDCR_EL2.HLP, or PMCR_EL0.LP is ignored and bits [63:0] of all affected event counters are reset.

E, bit [0]

Enable.

EMeaning
0b0

All event counters in the range [0:(PMN-1)] and PMCCNTR_EL0, are disabled.

0b1

All event counters in the range [0:(PMN-1)] and PMCCNTR_EL0, are enabled by PMCNTENSET_EL0.

This bit is RW.

If EL2 is implemented then:

  • If EL2 is using AArch32, PMN is HDCR.HPMN.
  • If EL2 is using AArch64, PMN is MDCR_EL2.HPMN.
  • If PMN is less than PMCR_EL0.N, this bit does not affect the operation of event counters in the range [PMN:(PMCR_EL0.N-1)].

If EL2 is not implemented, PMN is PMCR_EL0.N.

Note

The effect of MDCR_EL2.HPMN or HDCR.HPMN on the operation of this bit applies if EL2 is implemented regardless of whether EL2 is enabled in the current Security state. For more information, see the description of MDCR_EL2.HPMN or HDCR.HPMN.

On a Warm reset, this field resets to 0.

Accessing the PMCR_EL0

Accesses to this register use the following encodings:

MRS <Xt>, PMCR_EL0

op0op1CRnCRmop2
0b110b0110b10010b11000b000
if PSTATE.EL == EL0 then
    if !ELUsingAArch32(EL1) && PMUSERENR_EL0.EN == '0' then
        if EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TGE == '1' then
            AArch64.SystemAccessTrap(EL2, 0x18);
        else
            AArch64.SystemAccessTrap(EL1, 0x18);
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && MDCR_EL2.TPM == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && MDCR_EL2.TPMCR == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TPM == '1' then
        AArch64.SystemAccessTrap(EL3, 0x18);
    else
        return PMCR_EL0;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && MDCR_EL2.TPM == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && MDCR_EL2.TPMCR == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TPM == '1' then
        AArch64.SystemAccessTrap(EL3, 0x18);
    else
        return PMCR_EL0;
elsif PSTATE.EL == EL2 then
    if HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TPM == '1' then
        AArch64.SystemAccessTrap(EL3, 0x18);
    else
        return PMCR_EL0;
elsif PSTATE.EL == EL3 then
    return PMCR_EL0;
              

MSR PMCR_EL0, <Xt>

op0op1CRnCRmop2
0b110b0110b10010b11000b000
if PSTATE.EL == EL0 then
    if !ELUsingAArch32(EL1) && PMUSERENR_EL0.EN == '0' then
        if EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TGE == '1' then
            AArch64.SystemAccessTrap(EL2, 0x18);
        else
            AArch64.SystemAccessTrap(EL1, 0x18);
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && MDCR_EL2.TPM == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && MDCR_EL2.TPMCR == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TPM == '1' then
        AArch64.SystemAccessTrap(EL3, 0x18);
    else
        PMCR_EL0 = X[t];
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && MDCR_EL2.TPM == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && MDCR_EL2.TPMCR == '1' then
        AArch64.SystemAccessTrap(EL2, 0x18);
    elsif HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TPM == '1' then
        AArch64.SystemAccessTrap(EL3, 0x18);
    else
        PMCR_EL0 = X[t];
elsif PSTATE.EL == EL2 then
    if HaveEL(EL3) && !ELUsingAArch32(EL3) && MDCR_EL3.TPM == '1' then
        AArch64.SystemAccessTrap(EL3, 0x18);
    else
        PMCR_EL0 = X[t];
elsif PSTATE.EL == EL3 then
    PMCR_EL0 = X[t];
              


Was this page helpful? Yes No