Stratix® 10 Hard Processor System Technical Reference Manual

ID 683222
Date 8/15/2024
Public
Document Table of Contents

4.5.5.1. Quality of Service

You can program an 8-bit QoS weight value for each bridge.

In a weighted allocation policy, the CCU divides the resource bandwidth among all contending flows based on a pre-programmed set of weights.

You can set a higher weight for more important masters by programming the QoS Profile Data register (*p_n) for that master.

For example, if master_0 has a weight set to X for a slave access and master_1 has a weight set to Y, master_0 receives X/(X+Y)% of the total available bandwidth at the slave. This calculation assumes that all other masters that can access the CCU are idle.

Similarly, master_1 receives Y/(X+Y)% of the total available bandwidth at the slave.
Note: The default value of the QoS profile in the QoS Profile Data register is 3 and the maximum value you can program for this field is 255.

The coherency interconnect uses dynamic weight adjustment algorithms that are fully distributed and provides full end-to-end weighted fairness.

The CCU uses round-robin arbitration when masters that share the same QoS priority and weight are simultaneously accessing the same slave.

Note: Changing the QoS level while commands are outstanding can momentarily stall a channel if the change reorders the command to a slave.