SPRZ452I july 2018 – may 2023 AM6526 , AM6528 , AM6546 , AM6548
UDMA-P: UDMA-P Host Packet Descriptor’s “0x3FFFFF” Packet Length Mode not Functional
AM65x SR 1.0
In the UDMA-P Host Packet Descriptor (PD Word 0), there is a 22-bit packet length field. This field is typically set to a value between 0x0 – 0x3FFFFE, representing the total byte length of the packet. If the packet length is less than the sum of the buffer length, the packet will be truncated to the size specified in the packet length field. Specifying a packet length that is greater than the sum of the buffers will result in an error.
Alternatively, the packet length field can be set to a special value, 0x3FFFFF, which disables truncation and allows the UDMA-P to transmit as much data as is specified in the Buffer Length fields. This “0x3FFFF” mode is not functional.
There is no workaround. A valid packet length field must be supplied. This only prevents a user from sending a packet larger than 0x3FFFFE bytes, which is more than large enough for any envisioned use case.