3.3.12. QoS Control Register

The QoS Control Register characteristics are:

Purpose

Controls the regulators that are enabled on the slave interfaces.

Usage constraints

Accessible using only Secure accesses, unless you set the Secure Access Register. See Table 3.4.

Configurations

Available in all CCI-400 configurations.

Attributes

Note

When outstanding transaction regulation is enabled or disabled for an interface, changes take effect only when there are no outstanding transactions in that interface.

Figure 3.11 shows the bit assignments.

Figure 3.11. QoS Control Register bit assignments

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Table 3.14 shows the bit assignments.

Table 3.14. QoS Control Register bit assignments

Bits

Reset

Access

Function

[31]

-

RO

Determines whether this CCI-400 implementation supports QoS regulation.

0b0

QoS regulation fully supported as described in this document.

See Quality of Service.

0b1

QoS regulation not supported, reads and writes to this register have no effect.

[30:22]

-

RAZ/WI

Reserved.

[21]

0b0

RW

Sets the mode for bandwidth regulation:

0b0

Normal mode.

The QoS value is stable when the master is idle.

0b1

Quiesce High mode.

The QoS value tends to the maximum when the master is idle.

[20]

0b0

RW

Configures the mode of the QoS value regulator for read transactions.

0b0

Latency mode.

0b1

Period mode, for bandwidth regulation.

[19:17]

-

RAZ/WI

Reserved.

[16]

0b0

RW

Configures the mode of the QoS value regulator for write transactions:

0b0

Latency mode.

0b1

Period mode, for bandwidth regulation.

[15:4]

-

RAZ/WI

Reserved.

[3]

0b0

RW

Enable regulation of outstanding read transactions for slave interfaces:

  • ACE-Lite interfaces only, for example S0, S1, and S2.

  • RAZ/WI for ACE interfaces, for example S3 and S4.

[2]

0b0

RW

Enable regulation of outstanding write transactions for slave interfaces.

  • ACE-Lite interfaces only, for example S0, S1, and S2.

  • RAZ/WI for ACE interfaces, for example S3 and S4.

[1]

0b0

RW

Enable QoS value regulation on reads for slave interfaces.

[0]

0b0

RW

Enable QoS value regulation on writes for slave interfaces.


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