zephyr/src: Increase UART input buffer to 512 bytes and reduce latency.

There are two changes here:

1. Increase the UART input bufffer to 512 bytes.  That's necessary to get
   basic REPL reliability tests working, and helps improve `mpremote`
   usage, eg copying large files.

2. Remove `uart_sem` semaphore.  This is no longer needed because
   `zephyr_getchar()` should be fully non-blocking and have as low a
   latency as possible.  `mp_hal_stdin_rx_chr()` (which calls
   `zephyr_getchar`) already uses `MICROPY_EVENT_POLL_HOOK` to get
   an efficient wait, and doing an extra wait and check for the
   semaphore in `zephyr_getchar()` just introduces unnecessary latency and
   can lead to slower input, and potentially overflowing the UART input
   buffer.

Signed-off-by: Damien George <damien@micropython.org>

0 files changed, 0 insertions, 0 deletions