Samsung S5PC110, Manual

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S5PC110_UM 1 DRAM CONTROLLER
1-11
1.2.5 QUALITY OF SERVICE
The Quality of Service (QoS) is defined for the controller to increase the arbitration priority of a master that
requires low latency read data. The QoS is determined if the control queue (Refer to Figure 1-1
Figure 1-1
)
receives the command through the AXI bus and the QoS count starts depreciating at this moment. If the count
reaches zero, this command becomes the highest priority among the other commands that are in the control
queue.
There are three types of QoS, namely:
•
qos_cnt
•
qos_cnt_f
•
default_qos
1.2.5.1 qos_cnt
There are 16 configurable QoSControls, which have independent qos_masks that masks the ARID/AWID from
one bit up to the ARID/AWID width. All 16 QoSControls are either enabled or disabled,
1. If the command is received via the AXI bus, the ARID/AWID is masked by the qos_masks
(
QoSConfig(n).qos_mask
) from the 16 QoSControls that are enabled.
2. The masked results are then compared to the qos_ids (
QoSConfig(n).qos_id
). If one of the result are equal,
the qos_cnt (
QoSControl(n).qos_cnt
) value is applied to the command and saved in the control queue.