3.3.1. Control Override Register

The Control Override Register characteristics are:

Purpose

Additional control register that provides a fail-safe override for some CCI-400 functions, if these cause problems that you cannot otherwise work around.

Usage constraints

If you cannot avoid using them, only set them using non-bufferable transactions, and before barriers, shareable transactions, or DVM messages are issued into the CCI-400. This can be, for example, very early in the boot sequence, prior to the installation of any Secure OS. You can access the Control Override Register using Secure transactions only, irrespective of the programming of the Secure Access Register.

Configurations

Available in all CCI-400 configurations.

Attributes

Figure 3.1 shows the bit assignments.

Figure 3.1. Control Override Register bit assignments

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Table 3.2 shows the bit assignments.

Table 3.2. Control Override Register bit assignments

Bits

Reset

Access

Function

[31:6]

0b0

RAZ/WI

Reserved.

[5]0b0RW

Disable retry reduction buffers for speculative fetches:

0b0

Retry reduction buffers enabled.

0b1

Retry reduction buffers disabled.

[4]

RW

Disable priority promotion:

0b0

The CCI-400 uses ARQOSARBS inputs to promote the priority of earlier requests.

0b1

The CCI-400 ignores ARQOSARBS inputs.

[3]

0b0

RW

Terminate all barrier transactions.

0b0

Master interfaces terminate barriers according to the BARRIERTERMINATE inputs.

0b1

All master interfaces terminate barriers.

[2]

0b0

RW

Disable speculative fetches:

0b0

Send speculative fetches according to the Speculation Control Register. See Speculation Control Register.

0b1

Disable speculative fetches from all master interfaces.

[1]

0b0

RW

DVM message disable:

0b0

Send DVM messages according to the Snoop Control Registers. See Snoop Control Registers.

0b1

Disable propagation of all DVM messages.

[0]

0b0

RW

Snoop disable:

0b0

Snoop masters according to the Snoop Control Registers. See Snoop Control Registers.

0b1

Disable all snoops, but not DVM messages.


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