Re: git: 09ef538713e0 - main - uart: Add primitive noise filtering on RX

On Wed, 27 Nov 2024 14:17:29 GMT
Justin Hibbits <jhibbits@FreeBSD.org> wrote:

> The branch main has been updated by jhibbits:
> 
> URL: https://cgit.FreeBSD.org/src/commit/?id=09ef538713e08a98584dbcf66ff80290cc1b41a2
> 
> commit 09ef538713e08a98584dbcf66ff80290cc1b41a2
> Author:     Justin Hibbits <jhibbits@FreeBSD.org>
> AuthorDate: 2024-11-20 17:08:26 +0000
> Commit:     Justin Hibbits <jhibbits@FreeBSD.org>
> CommitDate: 2024-11-27 14:17:09 +0000
> 
>     uart: Add primitive noise filtering on RX
>     
>     A long cable attached to the UART can act as an antenna if
> disconnected from the other end.  This can cause noise on the receive
> side, possibly as reflections from the transmit side, leading to an
> interrupt storm. Filter this by adding a threshold of received
> characters without TX ready, above which characters are dropped.
> This is disabled by default, but has been tested with a threshold of
> 1000+.  A high threshold is recommended to avoid dropping characters
> during, for instance, a large copy/paste from the other end.
>     
>     Sponsored by:   Juniper Networks, Inc.

Reviewed by:	imp
Differential Revision:	https://reviews.freebsd.org/D47685

- Justin