Why does reconfiguration of the Hard Processor System (HPS) over JTAG fail for Intel Agilex® 7 and Intel® Stratix® 10 devices after a corrupted bitstream has been loaded through U-boot?

Description

Due to a known problem in the Intel® Quartus® Prime Pro Edition Software version 20.3, loading a corrupted bitstream through U-boot on Intel Agilex® 7 and Intel® Stratix® 10 devices will create an error state that prevents reconfiguration of the Hard Processing System (HPS) over JTAG.  You might see the following error messages when attempting to reconfigure the HPS over JTAG with a good bitstream:

Error (18939):  Unexpected error in JTAG server:  JTAG chain broken

Error (18947):  Device not responding

Resolution

If a corrupted HPS bitstream is loaded through U-boot, you can work around this problem by power cycling the device.  This will allow you to reconfigure the HPS over JTAG with a good bitstream successfully.

This problem is fixed starting with the Intel® Quartus® Prime Pro Edition Software version 20.4.