DC CSW, Data or unified Cache line Clean by Set/Way

The DC CSW characteristics are:

Purpose

Clean data cache by set/way.

This System instruction is part of the Cache maintenance instructions functional group.

Configuration

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

Attributes

DC CSW is a 64-bit System instruction.

Field descriptions

The DC CSW input value bit assignments are:

6362616059585756555453525150494847464544434241403938373635343332
00000000000000000000000000000000
SetWayLevel0
313029282726252423222120191817161514131211109876543210

Bits [63:32]

Reserved, RES0.

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 DC CSW instruction

This instruction is executed using DC with the following syntax:

DC <dc_op>, <Xt>

This syntax uses the following encoding in the System instruction encoding space:

<dc_op> op0op1CRnCRmop2
CSW0100001111010010

Accessibility

The instruction is executable as follows:

Control Accessibility
E2HTGENSEL0EL1EL2EL3
xx0 - WO n/a WO
x01 - WOWOWO
x11 - n/a WOWO

This table applies to all syntax that can be used to execute this 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:

Traps and enables

For a description of the prioritization of any generated exceptions, see section D1.13.2 (Synchronous exception prioritization) in the ARM® Architecture Reference Manual, ARMv8, for ARMv8-A architecture profile. Subject to the prioritization rules, the following traps and enables are applicable when executing this System instruction.

When EL2 is implemented and is using AArch64 and SCR_EL3.NS==1 && HCR_EL2.E2H==0 :

When EL2 is implemented and is using AArch64 and SCR_EL3.NS==1 && HCR_EL2.E2H==1 && HCR_EL2.TGE==0 :




18/04/2017 17:00

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