linux-kernel - Re: [PATCH 2/8] serial: qcom-geni: fix false console tx restart

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Message-ID: <CAD=FV=UH8dLB6ebCXGeF2t5Bi5EhYrumLDnSV68fg7qzdPCQMg@mail.gmail.com>
Date: Wed, 4 Sep 2024 14:51:05 -0700
From: Doug Anderson <dianders@...omium.org>
To: Johan Hovold <johan+linaro@...nel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Jiri Slaby <jirislaby@...nel.org>, 
	Bjorn Andersson <andersson@...nel.org>, Konrad Dybcio <konradybcio@...nel.org>, 
	Nícolas F . R . A . Prado <nfraprado@...labora.com>, 
	linux-arm-msm@...r.kernel.org, linux-serial@...r.kernel.org, 
	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH 2/8] serial: qcom-geni: fix false console tx restart

Hi,

On Mon, Sep 2, 2024 at 8:26 AM Johan Hovold <johan+linaro@...nel.org> wrote:
>
> Commit 663abb1a7a7f ("tty: serial: qcom_geni_serial: Fix UART hang")
> addressed an issue with stalled tx after the console code interrupted
> the last bytes of a tx command by reenabling the watermark interrupt if
> there is data in write buffer. This can however break software flow
> control by re-enabling tx after the user has stopped it.
>
> Address the original issue by not clearing the CMD_DONE flag after
> polling for command completion. This allows the interrupt handler to
> start another transfer when the CMD_DONE interrupt has not been disabled
> due to flow control.
>
> Fixes: c4f528795d1a ("tty: serial: msm_geni_serial: Add serial driver support for GENI based QUP")
> Fixes: 663abb1a7a7f ("tty: serial: qcom_geni_serial: Fix UART hang")
> Cc: stable@...r.kernel.org      # 4.17
> Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> ---
>  drivers/tty/serial/qcom_geni_serial.c | 13 +++----------
>  1 file changed, 3 insertions(+), 10 deletions(-)

This seems reasonable. I guess this can end up causing a spurious
"done" interrupt to sometimes occur but that looks to be harmless.

Reviewed-by: Douglas Anderson <dianders@...omium.org>