One Possible Configuration For The Service Chains - Texas Instruments OMAP5910 Reference Manual

Figure 73.

One Possible Configuration for the Service Chains

High priority
Channel
0
Channel
1
Low priority
SPRU890A
Section 7.2.6.1 contains an example that shows a service chain configuration
applied to three ports.
High priority
Channel
2
The channels and the MPUI have a programmable priority level. Each
-
channel has a PRIO bit in DMACCR for selecting a high priority or a low
priority. The MPUI is assigned a high or low priority with the MPUI_PRIO
bit in DMAGCR. The DMA controller only services the low-priority items
when all the high-priority items are done or stalled. After a DSP subsystem
reset, all channels and the MPUI are low priority.
In the figure, channels 0, 2, and 5 are high-priority (in each of these
channels, PRIO = 1). DMA channels 1, 3, and 4 and the MPUI are low
priority (in each of these channels, PRIO = 0, and for the MPUI,
MPUI_PRIO = 0).
The channels and the MPUI have fixed positions in the service chain. The
-
port checks the channels and the MPUI in a repeating circular sequence:
0, 1, 2, 3, 4, 5, MPUI, 0, 1, 2, 3, 4, 5, MPUI, and so on. At each position
in the service chain, the port checks whether the channel/MPUI is ready
and able to be serviced. If the channel is ready to be serviced and a higher
priority request is not pending in another channel, it is serviced; otherwise,
the port skips to the next position. After a DSP subsystem reset, the port
restarts its circular sequence, beginning with channel 0.
Channel Channel
3 4
Low priority Low priority
DSP DMA
High priority
Channel
5
MPUI
Low priority
MPUI _EXCL = 0
DSP Subsystem 133