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CCSIDR2, Current Cache Size ID Register 2

The CCSIDR2 characteristics are:

Purpose

When ARMv8.3-CCIDX is implemented, in conjunction with CCSIDR, provides information about the architecture of the currently selected cache.

When ARMv8.3-CCIDX is not implemented, this register is not implemented.

Configuration

AArch32 System register CCSIDR2 bits [31:0] are architecturally mapped to AArch64 System register CCSIDR2_EL1[31:0] .

This register is present only when ARMv8.3-CCIDX is implemented. Otherwise, direct accesses to CCSIDR2 are UNDEFINED.

The implementation includes one CCSIDR2 for each cache that it can access. CSSELR and the Security state select which Cache Size ID Register is accessible.

Attributes

CCSIDR2 is a 32-bit register.

Field descriptions

The CCSIDR2 bit assignments are:

313029282726252423222120191817161514131211109876543210
00000000NumSets

Bits [31:24]

Reserved, RES0.

NumSets, bits [23:0]

(Number of sets in cache) - 1, therefore a value of 0 indicates 1 set in the cache. The number of sets does not have to be a power of 2.

Accessing the CCSIDR2

If CSSELR.Level is programmed to a cache level that is not implemented, then on a read of the CCSIDR2 the behavior is CONSTRAINED UNPREDICTABLE, and can be one of the following:

  • The CCSIDR2 read is treated as NOP.
  • The CCSIDR2 read is UNDEFINED.
  • The CCSIDR2 read returns an UNKNOWN value.

Accesses to this register use the following encodings:

MRC{<c>}{<q>} <coproc>, {#}<opc1>, <Rt>, <CRn>, <CRm>{, {#}<opc2>}

opc1opc2CRncoprocCRm
0b0010b0100b00000b11110b0000
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T0 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T0 == '1' then
        AArch32.TakeHypTrapException(0x03);
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TID2 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TID4 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HCR.TID2 == '1' then
        AArch32.TakeHypTrapException(0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HCR2.TID4 == '1' then
        AArch32.TakeHypTrapException(0x03);
    else
        return CCSIDR2;
elsif PSTATE.EL == EL2 then
    return CCSIDR2;
elsif PSTATE.EL == EL3 then
    return CCSIDR2;
              


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