linux-kernel - Re: [PATCH] ARM: dts: at91: Reenable UART TX pull-ups

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Message-ID: <8e8dfc02-bdab-d6f1-f6e9-e1dba7e38bfd@axentia.se>
Date:   Tue, 3 Dec 2019 13:04:56 +0000
From:   Peter Rosin <peda@...ntia.se>
To:     Ingo van Lil <inguin@....de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
CC:     Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Ludovic Desroches <ludovic.desroches@...rochip.com>
Subject: Re: [PATCH] ARM: dts: at91: Reenable UART TX pull-ups

On 2019-11-28 11:06, Ingo van Lil wrote:
> Pull-ups for SAM9 UART/USART TX lines were disabled in 5e04822f.
> However, several chips in the SAM9 family require pull-ups to prevent
> the TX lines from falling (and causing an endless break condition) when
> the transceiver is disabled.
> 
> From the SAM9G20 datasheet, 32.5.1: "To prevent the TXD line from
> falling when the USART is disabled, the use of an internal pull up
> is mandatory.". This commit reenables the pull-ups for all chips having
> that sentence in their datasheets.
> 
> Signed-off-by: Ingo van Lil <inguin@....de>

Sounds reasonable, and sorry for the breakage. However, perhaps a proper
fixes tag (with the prescribed length of the commit hash) should be in
there somewhere?

Fixes: 5e04822f7db5 ("ARM: dts: at91: fixes uart pinctrl, set pullup on rx, clear pullup on tx")

Also, I think the same kind of change was made to the barebox bootloader
at about the same time. Is there a fix for that queued up as well?

Cheers,
Peter