DCCSW, Data Cache line Clean by Set/Way

The DCCSW characteristics are:

Purpose

Clean data or unified cache line by set/way.

Configuration

AArch32 System instruction DCCSW performs the same function as AArch64 System instruction DC CSW.

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

Attributes

DCCSW is a 32-bit System instruction.

Field descriptions

The DCCSW input value bit assignments are:

313029282726252423222120191817161514131211109876543210
SetWayLevelRES0

SetWay, bits [31:4]

Contains two fields:

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 DCCSW 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:

Accesses to this instruction use the following encodings:

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

coprocopc1CRnCRmopc2
0b11110b0000b01110b10100b010

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 DCCSW(R[t]); elsif PSTATE.EL == EL2 then DCCSW(R[t]); elsif PSTATE.EL == EL3 then DCCSW(R[t]);




01/07/2020 15:57; 80324f0b9997bede489cc15ad1565345720bcd2a

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