linux-kernel - Re: [PATCH 0/4] serial: qcom-geni: fix console shutdown hang

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Date:   Wed, 8 Mar 2023 14:27:15 +0000
From:   Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:     Johan Hovold <johan@...nel.org>,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Cc:     Johan Hovold <johan+linaro@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Andy Gross <agross@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Douglas Anderson <dianders@...omium.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/4] serial: qcom-geni: fix console shutdown hang



On 07/03/2023 17:03, Johan Hovold wrote:
> On Tue, Mar 07, 2023 at 05:47:27PM +0100, Bartosz Golaszewski wrote:
>> On Tue, 7 Mar 2023 at 17:44, Bartosz Golaszewski
>> <bartosz.golaszewski@...aro.org> wrote:
>>>
>>> On Tue, 7 Mar 2023 at 17:43, Johan Hovold <johan+linaro@...nel.org> wrote:
>>>>
>>>> This series fixes some of the fallout after a recent series adding
>>>> support for DMA transfers to the Qualcomm geni serial driver.
>>>>
>>>> Most importantly it fixes a hang during reboot when using a serial
>>>> console and the getty is stopped during reboot.
>>>>
>>>> Doug just posted an equivalent fix here:
>>>>
>>>>          https://lore.kernel.org/lkml/20230307073155.1.Iaab0159b8d268060a0e131ebb27125af4750ef99@changeid
>>>>
>>>> but the commit message only mentions the regression with respect to
>>>> kgdb, which is not as widely used serial consoles generally, so I
>>>> figured I'd post my version for completeness.
>>>>
>>>> Either version of that fix should address the immediate regression, but
>>>> fixing the underlying problems which have been there since the driver
>>>> was first merged is going to be a bit more involved.
>>>>
>>>> The rest of the series fixes a few bugs in the new DMA support that I
>>>> found while investigating the console regression.
>>>>
>>>> Johan
>>>>
>>>>
>>>> Johan Hovold (4):
>>>>    serial: qcom-geni: fix console shutdown hang
>>>>    serial: qcom-geni: fix DMA mapping leak on shutdown
>>>>    serial: qcom-geni: fix mapping of empty DMA buffer
>>>>    serial: qcom-geni: drop bogus uart_write_wakeup()
>>>>
>>>>   drivers/tty/serial/qcom_geni_serial.c | 11 +++++++----
>>>>   1 file changed, 7 insertions(+), 4 deletions(-)
>>>>
>>>> --
>>>> 2.39.2
>>>>
>>>
>>> Hey Johan,
>>>
>>> Douglas and Srini beat you to these fixes but thanks!
> 
>> Nevermind, I read your other message now. And also patch 3/4 looks right.
> 
> Heh, this hang has been in linux-next for over a month and I've
> actively tried to not spend time on investigating it in the hope that
> someone else would be beat me to it before I moved to 6.3-rc. :)
> 
> Obviously I may be a bit biased, but I prefer this series over the
> alternate fixes as the commit messages are a bit more complete and my
> version of the empty DMA buffer fix is a bit cleaner.

I don't mind, as long as the bugs are fixed.


--srini
> 
> Johan