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Date:      Fri, 28 Oct 2022 14:49:28 -0700
From:      Colin Percival <cperciva@freebsd.org>
To:        freebsd-current@freebsd.org
Subject:   Re: ns8250: UART FCR is broken
Message-ID:  <aeafa1ce-3dcd-7201-932b-4cbe2132923a@freebsd.org>
In-Reply-To: <fa45b3cc-fa65-b5b9-49fa-a1dcbbddebc6@freebsd.org>
References:  <Y1dF0CvrJZubFizl@openbsd.local> <CAPyFy2CeWi2_ejv6%2BdKQB6Sa0KLpe0Kq8=p4QNS46HDkADCB9Q@mail.gmail.com> <fa45b3cc-fa65-b5b9-49fa-a1dcbbddebc6@freebsd.org>

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>> 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



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