AR# 52756
14.3 EDK, axi_emc version 1.03a - Possible race condition when AWVALID and ARVALID assert at the same time
Description
There is a possible race condition when AWVALID and ARVALID assert at the same time.Solution
This issue appears when two AXI4 MASTERs access the S_AXI_MEM port of the controller version 1.03.a simultaneously.
AssemblyView.JPG
A specific sequence of AXI4 accesses to the EMC controller version 1.03a can cause the S_AXI_MEM interface to hang.
The sequence is:
READ_BURST of length 4 (from MASTER1)
followed by:
WRITE (from MASTER0) and READ_BURST (from MASTER1) where AWVALID and ARVALID are asserted at the same time. (Note: WVALID is only one cycle after.)
Following is a snapshot of a simulation that shows S_AXI_MEM hanging. In fact, WREADY and AWREADY never go HIGH, but BVALID pulses HIGH and this is a AXI VIOLATION because BRESP does not flag any error (always 0).
Sim_Bug.JPG
A tactical patch is included at the end of this answer record to apply on the 1.03.a core that comes with the 14.3 release of the tools.
| ar52756_EDK_14_3_Preliminary_rev1.zip |
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| AR# 52756 | |
|---|---|
| Date | 12/03/2012 |
| Status | Active |
| Type | Known Issues |
| Devices | |
| Tools | |
| IP | |