Debug SBA: Don't reset sbState if dmactive is set to 0 #2265
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rmac-sifive
approved these changes
Jan 21, 2020
mwachs5
approved these changes
Jan 21, 2020
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Related issue:
Type of change: bug report
Impact: no functional change
Development Phase: implementation
Release Notes
sbState tracks the progress of a TileLink transaction initiated by the debug module SBA interface. When a read transaction is initiated by the DM, sbState progresses from Idle to SBReadRequest to SBReadResponse and back to idle. The states control what is driven onto the TL interface, including driving d.ready to 1 when sbState is in the SBReadResponse state.
If there is a TL transaction in progress and the debugger sets dmactive to 0, sbState is immediately returned to Idle, thereby forcing d.ready to 0. This can potentially hang TileLink.
This PR disconnects sbState from dmactive so that any transaction started by the DM is followed to completion even if the DM is subsequently disabled.