Trace ATB Bridge

Some SoCs may have an Advanced Trace Bus (ATB) infrastructure to manage trace produced by other components. In such systems, it may be desired to route entire RISC-V trace stream to the ATB through an ATB Bridge. This module manages the interface to ATB, generating ATB trace records that encapsulate RISC-V trace produced by the Trace Encoder[s] and/or Trace Funnel[s]. There is a control register that includes trace on/off control and a field allowing software to set the ID to be used on the ATB bus. This ID allows software to extract entire RISC-V trace from the combined trace. This interface is compatible with AMBA 4 ATB v1.1.

Table 1. Register: trAtbBridgeControl: ATB Bridge Control Register (trAtbBridgeBase+0x000)
Bit Field Description RW Reset

0

trAtbBridgeActive

Primary activate/reset for the ATB Bridge. When 0, the ATB Bridge may have clocks gated off or be powered down, and other register locations may be inaccessible. Hardware may take an arbitrarily long time to process power-up and power-down and will indicate completion when the read value of this bit matches what was written. See Reset and Discovery chapter for more details.

RW

0

1

trAtbBridgeEnable

1: ATB Bridge enabled. Setting trAtbBridgeEnable to 0 flushes any queued trace data to ATB. See Enabling and Disabling chapter for more details.

RW

0

2

 — 

Reserved

 — 

0

3

trAtbBridgeEmpty

Reads 1 when ATB Bridge internal buffers are empty

RO

1

7:4

 — 

Reserved

 — 

0

14:8

trAtbBridgeID

ID of this node on ATB. Values of 0x00 and 0x70-0x7F are reserved by the ATB specification and should not be used.

RW

Undef

31:15

 — 

Reserved

 — 

0
Table 2. Register: trAtbBridgeImpl: ATB Bridge Implementation Register (trAtbBridgeBase+0x004)
Bit Field Description RW Reset

3:0

trAtbBridgeVerMajor

ATB Bridge Component Major Version. Value 1 means the component is compliant with this document.

RO

1

7:4

trAtbBridgeVerMinor

ATB Bridge Component Minor Version. Value 0 means the component is compliant with this document.

RO

0

11:8

trAtbBridgeCompType

ATB Bridge Component Type (ATB Bridge)

RO

0xE

14:12

trAtbBridgeAsyncFreq

0: Alignment synchronization (Async) packets disabled (may be the only choice for some protocols)
1-7: Different levels of alignment synchronization (bigger number, bigger distance).
Details should be defined the specification of each trace protocol.

WARL

Undef

23:15

 — 

Reserved for future versions of this standard

 — 

0

31:24

 — 

Reserved for vendor specific implementation details

 — 

SD

An implementation determines the data widths of the connection from the Trace Encoder or Trace Funnel and of the ATB port.

ATB Bridge may optionally insert ATB alignment synchronization packets (controlled by trAtbBridgeAsyncFreq field) allowing trace decoding software to detect ATB packet boundaries. Not all protocols may require it.