When prefetch is enabled and the prefetch offset is equal to 23 (0x17), then the L2 cache controller prefetches across a 4 KB address boundary. This can cause system issues because those cache line-fills can target a new 4 KB page of memory space, regardless of page attribute settings in the L1 MMU.
The offset values for the prefetch unit can be set from 0 to 31, but to avoid prefetching across the 4 KB boundary, it must never be set to 23. The default value is 0 and enables the next cache line to be prefetched.
Impact: |
Trivial. The issue is easily avoided. |
Work-around: |
The offset for the Prefetch (which can take a value between 0 and 31) should never be 23. The default value is 0 which enables the next catch line to be Prefetched. |
Configurations Affected: |
Systems that use the processors L2 cache with prefetching enabled. |
| Device Revision(s) Affected: | All. No plan to fix. Refer to (Xilinx Answer 47916) - Zynq-7000 AP SoC Silicon Revision Differences. |
This problem occurs when both of the following conditions are met:
* One of the Prefetch Enable bits (bits [29:28] of the Auxiliary or Prefetch Control Register) is set.
| Answer Number | Answer Title | Version Found | Version Resolved |
|---|---|---|---|
| 47916 | Zynq-7000 AP SoC Devices - Silicon Revision Differences | N/A | N/A |
| AR# 47563 | |
|---|---|
| Date | 06/06/2013 |
| Status | Active |
| Type | Design Advisory |
| Devices |
|