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DCCISW, Data Cache line Clean and Invalidate by Set/Way

The DCCISW characteristics are:

Purpose

Clean and Invalidate data or unified cache line by set/way.

Configuration

AArch32 System instruction DCCISW performs the same function as AArch64 System instruction DC CISW.

This instruction is present only when AArch32 is supported at any Exception level. Otherwise, direct accesses to DCCISW are UNDEFINED.

Attributes

DCCISW is a 32-bit System instruction.

Field descriptions

The DCCISW input value bit assignments are:

313029282726252423222120191817161514131211109876543210
SetWayLevelRES0

SetWay, bits [31:4]

Contains two fields:

  • Way, bits[31:32-A], the number of the way to operate on.
  • Set, bits[B-1:L], the number of the set to operate on.

Bits[L-1:4] are RES0.

A = Log2(ASSOCIATIVITY), L = Log2(LINELEN), B = (L + S), S = Log2(NSETS).

ASSOCIATIVITY, LINELEN (line length, in bytes), and NSETS (number of sets) have their usual meanings and are the values for the cache level being operated on. The values of A and S are rounded up to the next integer.

Level, bits [3:1]

Cache level to operate on, minus 1. For example, this field is 0 for operations on L1 cache, or 1 for operations on L2 cache.

Bit [0]

Reserved, RES0.

Executing the DCCISW instruction

If this instruction is executed with a set, way or level argument that is larger than the value supported by the implementation then the behavior is CONSTRAINED UNPREDICTABLE and one of the following occurs:

  • The instruction is UNDEFINED
  • The instruction performs cache maintenance on one of:
    • No cache lines.
    • A single arbitrary cache line.
    • Multiple arbitrary cache lines.

Accesses to this instruction use the following encodings:

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

coprocopc1CRnCRmopc2
0b11110b0000b01110b11100b010
if PSTATE.EL == EL0 then
    UNDEFINED;
elsif PSTATE.EL == EL1 then
    if EL2Enabled() && !ELUsingAArch32(EL2) && HSTR_EL2.T7 == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HSTR.T7 == '1' then
        AArch32.TakeHypTrapException(0x03);
    elsif EL2Enabled() && !ELUsingAArch32(EL2) && HCR_EL2.TSW == '1' then
        AArch64.AArch32SystemAccessTrap(EL2, 0x03);
    elsif EL2Enabled() && ELUsingAArch32(EL2) && HCR.TSW == '1' then
        AArch32.TakeHypTrapException(0x03);
    else
        DCCISW(R[t]);
elsif PSTATE.EL == EL2 then
    DCCISW(R[t]);
elsif PSTATE.EL == EL3 then
    DCCISW(R[t]);


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