linux-kernel - Re: [PATCH 3/3] serial: qcom-geni: fix receiver enable

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Message-ID: <ZulH0SZJBlgS4teO@hovoldconsulting.com>
Date: Tue, 17 Sep 2024 11:11:45 +0200
From: Johan Hovold <johan@...nel.org>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc: Jiri Slaby <jirislaby@...nel.org>,
	Douglas Anderson <dianders@...omium.org>,
	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org
Subject: Re: [PATCH 3/3] serial: qcom-geni: fix receiver enable

On Mon, Sep 16, 2024 at 07:26:42PM +0200, Johan Hovold wrote:
> The receiver should be enabled in the startup() callback and there is no
> need to stop it on every termios update.
> 
> Since commit 6f3c3cafb115 ("serial: qcom-geni: disable interrupts during
> console writes") the calls to manipulate the secondary interrupts, which
> were done without holding the port lock, can lead to the receiver being
> left disabled when set_termios() races with the console code (e.g. when
> init opens the tty during boot).
> 
> Fixes: 6f3c3cafb115 ("serial: qcom-geni: disable interrupts during console writes")
> Signed-off-by: Johan Hovold <johan+linaro@...nel.org>

Turns out the DMA implementation is broken and currently depends on
these bogus calls to stop and restart rx in set_termios().

I won't have time to look at this for a couple of weeks due to
conferences, so please hold off on merging these until I'm back.

Johan