uart device send fails to send beyond a threshold bytes at high baud rate with release optimization i

[pranav12321]

what

At high baud rate (4M tested in this case), the uart send implementation on device side (TM4C), fails to send beyond 22 bytes. It doesn't panic or crash. simply fails to send more than 22 bytes. Some messages (eg - get_registers and pc (23 byte response)) have relatively larger response packets.

steps to reproduce

• increase baud to 4M on device and host
• TUI crashes when invoking get_registers_and_pc
• Also isolated and tested a simple response of > 22 bytes and it caps off
• Happens only with release optimization (was ok when tested with isolated example without optimization). the full device implementation does not fit without optimization

where

device-support/rpc/transport/uart*

log with isolated test expecting a 33 byte response:

sending lc3_device_support::util::fifo::Fifo<u8> { 2, 3, 2, 42, 1,  } num bytes = 6Received some data: num bytes = 22
lc3_device_support::util::fifo::Fifo<u8> { 0, 1, 2, 3, 4, 5, 6, ..., 15, 16, 17, 18, 19, 20, 21 }
	


sending lc3_device_support::util::fifo::Fifo<u8> { 2, 3, 2, 42, 1,  } num bytes = 6Received some data: num bytes = 22
lc3_device_support::util::fifo::Fifo<u8> { 0, 1, 2, 3, 4, 5, 6, ..., 15, 16, 17, 18, 19, 20, 21 }

environment information

• rustc/cargo version: 1.61.0 (a028ae4 2022-04-29)
• OS: linux