Re: ns8250: UART FCR is broken

Reply: Matteo Riondato : "Re: ns8250: UART FCR is broken"
In reply to: Colin Percival : "Re: ns8250: UART FCR is broken"
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From: Colin Percival <cperciva_at_freebsd.org>
Date: Fri, 28 Oct 2022 21:49:28 UTC

>> On Mon, 24 Oct 2022 at 22:11, void <void@f-m.fm> wrote:
>>> this started appearing in dmesg
>>>
>>> ns8250: UART FCR is broken
>>> ns8250: UART FCR is broken
For the list: While I was correct that bhyve didn't emulate FCR_XMT_RST,
this warning was actually caused by a bug in my earlier commit.  It should
be fixed now:

> commit 5ad8c32c722b58da4c153f241201af51b11f3152
> Author:     Colin Percival <cperciva@FreeBSD.org>
> AuthorDate: 2022-10-28 04:42:44 +0000
> Commit:     Colin Percival <cperciva@FreeBSD.org>
> CommitDate: 2022-10-28 19:20:28 +0000
> 
>     ns8250: Fix sense of LSR_TEMT FCR check
>     
>     When flushing the UART, we need to drain manually if LSR_TEMT is
>     *not* asserted, aka. if the transmit FIFO is not empty.
>     
>     Reported by:    void <void@f-m.fm>
>     Fixes:          c4b68e7e53bb "ns8250: Check if flush via FCR succeeded"
>     Differential Revision:  https://reviews.freebsd.org/D37185

-- 
Colin Percival
Security Officer Emeritus, FreeBSD | The power to serve
Founder, Tarsnap | www.tarsnap.com | Online backups for the truly paranoid