The Sticky Pipeline Advance bit in the DBGDSCR register enables the debugger to detect whether the processor is idle. The CPU does not implement accesses to DBGDRCR[3] via the debug APB interface, so the debugger is unable to clear the Sticky Pipeline Advance bit.
| Impact: | Minor. The Sticky Pipeline Advance bit concept is unusable. |
Work-around: | None. |
Configurations Affected: | Systems that use one or both ARM processors. |
Device Revision(s) Affected: | All. No plan to fix. Refer to (Xilinx Answer 47916) - Zynq-7000 SoC Silicon Revision Differences. |
Description Details
The Sticky Pipeline Advance register (bit 25 of the DBGDSCR register) enables the debugger to detect whether the processor is idle. This bit is set to 1 every time the processor pipeline retires one instruction. A write to DBGDRCR[3] clears this bit. The issue is that the Cortex-A9 does not implement any debug APB access to DBGDRCR[3] to clear the bit.
Impact Details
Minor. Due to the issue, the Sticky Pipeline Advance bit in the DBGDSCR cannot be cleared by the external debugger.
| Answer Number | Answer Title | Version Found | Version Resolved |
|---|---|---|---|
| 47916 | Zynq-7000 AP SoC Devices - Silicon Revision Differences | N/A | N/A |
| AR# 47557 | |
|---|---|
| Date | 05/23/2018 |
| Status | Active |
| Type | Design Advisory |
| Devices | |